The 12 Best Deep Cycle Battery Chargers to Buy In 2021

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Every driver knows the most basic fact that without the batteries, a vehicle would not go anywhere. Needless to say, you should pay attention to the type of battery and together with it, the charger, that suits your vehicle as well as how to take care of them to ensure smooth driving. This is especially important when you’re camping in your RV, since the best RV battery charger, or specifically the best deep cycle battery charger, will ensure you can power your electrical appliances and enjoy life on the road to the fullest. Having the best deep cycle battery charger can save you time and money as well.

Deep cycle batteries, which are well suited for camping applications, are very different from regular starter batteries or cranking batteries used in most vehicles you see on the street. Naturally they require a different charging mechanism for optimal charging as well as lifespan.  This comprehensive guide will also help you learn the unique features and benefits of deep cycle batteries and deep cycle battery chargers, in addition to our own handpicked list of the very best battery charger for deep cycle batteries on the market.

To make your purchase experience as effortless as possible, we explains in this article everything you need to know in easy-to-understand terms, including how deep cycle batteries work and how their charger works, the different types of deep cycle batteries and deep cycle battery chargers, important buying criteria and the most prestigious manufacturers of deep cycle battery chargers, safe charging instructions and tips, as well as useful answers to frequently asked questions.

Best Deep Cycle Battery Chargers Comparison Chart

NoBest Deep Cycle Battery ChargersVoltageAmperageOur Ratings
1Black+Decker BC2WBD12V2Amp*****
2NOCO Genius GEN112V10Amp*****
3Battery Tender Plus 021-012812V1.25Amp*****
4Schumacher SC12816/12V6/2Amp*****
5Black+Decker BM3B6/12V1.5Amp***
6NOCO Genius G1500012/24V15Amp****
7BatteryMINDer 150012V1.5Amp*****
8Schumacher SE-1-12S6/12V1.5Amp*****
9Optima Digital 40012V4Amp*****
10TecMate OptiMATE 612/24V5/2.5Amp*****
11Ampeak CGUFB202512V2/10/25Amp****
12Jethax JET-191112V4Amp*****

Deep Cycle Battery Charger Basics

What Is A Deep Cycle Battery Charger?

As the name suggests, a deep cycle battery charger is a purpose-design charger used to charge deep cycle batteries. Deep cycle batteries are very different from regular “starter” batteries or “cranking” batteries that are used for cranking your engine. Therefore, deep cycle batteries require to be charged by a specifically designed deep cycle battery charger for optimal charging and optimal battery lifespan. 

Understanding the difference between these two types of batteries and how deep cycle battery charging works will help you better choose the battery and the charger that best meets your camping needs.

Why Deep Cycle Battery?

The first question that many potential buyers of battery chargers ask is, “why do I need a “deep cycle battery charger” for my deep cycle batteries? Can’t I charge them with just any regular charger?” Or maybe, “why would I need deep cycle batteries?”, if you’re not well-informed about this area. 

Many vehicle and boat owners specifically choose deep cycle batteries for their intended applications for a number of reasons. Deep cycle batteries offer unique benefits, which directly relate to how they discharge and recharge, and thus they require special chargers to deliver the optimal charging, as well as maximizing the battery’s life. 

Before we explain why you absolutely must get a deep cycle battery charger to efficiently charge your deep cycle batteries, not any regular charger, it will be easier to understand going forward if you grasp the basic differences between regular automotive starting batteries and deep cycle batteries. 

If you’re confident with your knowledge on automotive batteries, skip further down for how deep cycle battery chargers work and their benefits, or the next few sections for important buying criteria and our selected list of the best deep cycle battery chargers. 

Slow and Deep Discharge

The most common type of batteries most vehicles are equipped with are starting batteries or cranking batteries, also sometimes called “SLI” batteries, which stands for starting, lighting, ignition. Their purpose is to start and run a vehicle’s engines and to do this job, they typically deliver a very large starting current for a very short time in order to crank the engine. 

As a result, only a small part of the starting battery is discharged, typically a shallow depth of discharge of only about 2% to 5% of the battery’s capacity. In normal starting use, starting batteries are designed to last for thousands of such shallow-discharge cycles. They are not designed for deep discharging and recharging, thus they will only last between 30 to 150 deep-discharge cycles. 

In contrast, a deep cycle battery is a battery designed to handle many thousands of cycles of deep discharge and recharge over its lifetime. The capacity of the battery can be almost used up each time, without permanent damage to the battery, to a certain extent. 

In addition to the depth of discharge, another key difference in comparison with starting batteries is the speed of discharge. Deep cycle batteries are also designed to discharge slowly, thereby providing steady power for several hours at a time instead of delivering an instant surge of high voltage for a very short time. This feature makes deep cycle batteries ideal for camping applications.  

A typical cycle for a deep cycle battery would start at 100% capacity, followed by a deep discharge of between 20% and 50% of its capacity, and then recharge back to full capacity. While technically, it is possible to cycle the battery down to 20% without “killing” the battery right away, it is recommended by professionals and full-time campers to keep the average maximum discharge at around 45% to 50% to maximize the lifespan of the battery. Remember that the lifetime of your batteries will be influenced by their typical depth of discharge.

A battery with frequent cycles of 50% depth of discharge maximum will last longer than a battery that is often pushed to a greater depth of discharge. As a rough comparison, if a battery is discharged to about 50% every day, it will last about twice as long as if it is cycled to 80% depth of discharge.

While 50% is the safe lower limit, at the same time, there is also a safe upper limit. Note that for a deep cycle battery, repeated shallow discharge, that is around 5-10%, also shortens the battery lifespan, since it is not designed for such shallow cycles. At very shallow cycles, the lead dioxide tends to build up in clumps on the positive plates of the battery instead of forming an even film. This uneven build-up will continue after each recharging cycle and gradually will deteriorate the battery’s capacity to store a full charge and eventually cause premature replacement. 

Structure

In terms of design or structure, the main difference between a deep cycle battery and a regular cranking battery is in their plates. In order to deliver short, high-current bursts to crank the engine, starting batteries have a large number of thin plates for maximum surface area with the electrolyte, and thus the electrolyte can penetrate the plates in a shorter time span for almost instant power. For maximum surface area, the lead plates are also made similar to a very fine foam sponge in appearance.  

Meanwhile, deep cycle batteries have thicker active plates and thicker separators, or the insulating material in between the positive and the negative plates. The alloys used to create the plates in deep cycle batteries have more antimony than cranking batteries. 

The benefit to having thicker plates is that they better resist a common problem called “positive grid corrosion” typically caused by extensive charge and discharge cycles. Such corrosion ranks among the top three reasons for battery failure. In other words, the thickness of the plates is directly related to the battery life. With all things being equal, the thicker the plates are, the longer the battery will last. 

Charging Efficiency

In addition, the typical charging efficiency in a deep cycle battery is 85-95%, the very best can even approach 98%, which is much higher than that of regular starting batteries. The higher efficiency is a result of the lower internal resistance of the battery, which causes most of the loss in charging efficiency.  Such loss manifests itself as heat, which is why batteries get warm when they’re being charged.

Therefore, lower internal resistance is more desirable for a battery’s efficiency. Much of the loss of battery efficiency is due to higher internal resistance at higher amperage rates, which occur with fast discharge and recharge. Therefore, as they are designed to discharge and recharge at a much slower rate, deep cycle batteries have up to 5 times lower internal resistance than standard starting batteries. 

How Deep Cycle Battery Chargers Work

It should come as no surprise that a deep cycle battery would require slightly different charging technologies compared to regular starter batteries to achieve optimum charging capacity as well as optimal lifespan. 

A deep cycle battery charger, also called a deep cell battery charger, is recommended to maintain the cycle of deep discharge and recharge of a deep cycle battery.

Charging Speed & The Resulting Heat

The biggest difference between regular battery chargers and deep cycle chargers is the speed at which they charge.  Firstly, using a regular battery charger to charge a deep cycle battery is not recommended, since a regular charger will charge the battery quickly at higher amperage rates, and as noted above, will result in high internal resistance and low charging efficiency.

High internal resistance will manifest itself as excessive heat, which is detrimental to the health and lifespan of a deep cycle battery not designed to handle such heat. A deep cycle battery may never reach full capacity when charged with a regular charger. Instead, it will show that it is fully charged long before it actually reaches full capacity. 

Secondly, a fast charge will not allow the battery a sufficient amount of time for the electrolyte to penetrate the thicker plates of a deep cycle battery. Meanwhile, a deep cycle battery chargers are designed to charge batteries at a much lower rate, thus allowing enough time for the battery acid to penetrate the plates while not damaging them.

In contrast, a slow charge is ideal for charging deep cycle batteries because it minimizes internal resistance, prevents excessive heat buildup and ensures optimal charging capacity and thus allowing the battery to effectively reach its full capacity. 

In addition, the slow charging process of the best deep cycle battery charger will maximize the battery lifespan. It does this by avoiding overheating the deep cycle battery, which can cause various problems such as internal materials slowly breaking down, fluctuating charging times and operational times, and ultimately shorter battery lifespan.

Charging Phases

Regular battery charge batteries from start to finish in one go and the charging current remains essentially constant throughout the process. Once max capacity is reached, regular battery chargers would automatically shut down.

In contrast, a deep cycle battery charger charges the battery in three distinct stages and each requires a different optimal charging current. This stepped model allows more current to flow to the battery when it is deeply discharged in the first stage, and then in the later stages, slowly tapers off the charging speed as the battery reaches full capacity. This serves to optimize charging time while maximizing the life of the battery in the long run.

In addition, once full capacity is reached, deep cycle battery chargers go into float mode to tackle self-discharge. That is why deep cycle battery chargers could keep batteries at full charge for a longer time.

Overcharging

Overcharging is needless to say harmful for both charging efficiency and the battery’s lifespan. The best deep cycle battery charger will also help protect against overcharging, so you can leave the charger plugged in 24/7 without worry of damaging the battery.

Price

On average, deep cycle battery chargers often cost more than regular battery chargers due to the use of dedicated circuitries. 

As you can see, while deep cycle batteries deliver unique benefits for your camping applications, you need to make sure you are using and maintaining them properly by investing in the best deep cycle battery charger. Using just any regular battery charger will only squeeze out suboptimal performance from your battery while killing it prematurely.

Benefits of Deep Cycle Battery Charger

Extend The Lifespan Of Batteries

Premature battery death is annoying, and replacing an old battery can be a time-consuming process. That said, although nothing lasts forever, you will enjoy optimal efficiency as well as a maximized lifespan from your deep cycle batteries if you charge your batteries with the best deep cycle battery charger. 

Keep Electrical Appliances Running

With a quality deep cycle battery charger by your side while traveling off-grid, you should have an easy time keeping the battery bank of your RV fully charged and powering all your electrical appliances. After all, there is no need to sacrifice basic amenities and comfort while you’re in the wild. 

Keep Electrical Parts Healthy

When you have a depleted battery, your vehicle ends up putting additional stress on the charging system, that is the alternator and the starter motor, by drawing excessive voltage to compensate for the lack of battery power. This can cause these electrical parts to malfunction–typically without warning. Therefore, having the best deep cycle battery charger at hand, as well as a simple toolI–a voltmeter, will allow you to regularly test and charge your batteries as needed and avoid expensive repairs.

Battery Conditioning

Another critical function of a quality 12 volt deep cycle battery charger is battery conditioning. This maintenance process helps keep your deep cycle battery extra healthy while it is plugged into the charger. Better yet, you can look for a smart charger that includes testing lights so that you can visually monitor your battery’s condition during charging. 

Meanwhile, a traditional battery charger may not be set up with the right technology for this job. 

Easy Charging 

Having the best deep cycle battery charger will help you save time and money in the long run, since you won’t have to bring your battery to a shop to have a professional mechanic safely recharge it. 

Open Up New Travel Options

Since you can recharge the batteries anywhere, anytime without having to bring it to a shop, you don’t have to plan your route to include locations that offer charging services. Such a reasonable investment not only brings you comfort but also the freedom to explore the outdoors however you like to.


Reviews On Best Deep Cycle Battery Chargers

Without further ado, let’s dive right into our delicious handpicked list of the very best deep cycle battery charger on the market. Rest assured that all of these units are the most well-rounded with key important buying criteria in mind, so that they will deliver reliable performance for many years down the road. Their functionality and durability have been sworn by verified purchases and in-depth deep cycle battery charger reviews, so these are the safest bets that you can make on your money. 

There is something for every camper in this list. That said, if you’re yet to know what to look for in a solid portable deep cycle battery charger for camping, jump to the next section to learn about key purchasing criteria.

1. Black+Decker BC2WBD – Best Of The Best

Black+Decker BC2WBD Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 5.13 x 3.60 x 8.25 Inches
  • Weight: 1.5 Pounds
  • Voltage: 12V
  • Ampere: 2Amp

Why This Is The Best:

Owing to its sealed housing, Black+Decker BC2WBD is good at resisting dust, oil, moisture, … which let it maintain stable operation in various environments. The 12V deep cycle battery charger of Black+Decker happens to be quite light as well so RVer could move it around quickly and effortlessly. In addition to that, BC2WBD offers up to three connection methods: DC accessory plug, terminal ring and battery clamps. Because of that, Black+Decker BC2WBD is deemed to be the best deep cycle battery charger for standard rigs.

As BC2WBD is an automatic battery maintainer, you may leave it connected to the battery bank of your vehicle for long periods of time. With built-in circuit protection, the Black+Decker model is secured against overcharge, short-circuit, reverse-polarity and so on. Interestingly, Black+Decker BC2WBD has low-voltage compensation and that is why it’s able to deliver maximum charge once paired with extension cords. Packing a combination of hanging hook and magnetic backing, BC2WBD also proves to be a breeze to set up.

Available at a reasonable price, the battery charger made by Black+Decker suit the budget of the average RVing enthusiast. To reassure customers, Black+Decker willingly backs BC2WBD with a one-year manufacturer warranty that brings peace of mind.

I use this charger almost everyday on a vehicle with dual batteries. At times the rig does not get driven for days and in the past the computer would drain the cranking battery pretty quickly. This charger allows me to keep both batteries topped off. The magnet on the back works great for mounting the unit on the side of a car or on a hood. Also the unit has preformed well in the rain without tripping any barkers.

Shared by Paul S.

Pros:

  • Affordable
  • Light and compact
  • Resilient construction

Cons:

  • Customer service could use some work
  • Users notice charging difficulty in cold climates

2. NOCO Genius GEN1 – Editor’s Choice

NOCO Genius GEN1 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 10.2 x 9.2 x 5.8 Inches
  • Weight: 3.8 Pounds
  • Voltage: 12V
  • Ampere: 10Amp

Why It’s An Editor’s Choice:

By employing innovative charging technologies, Genius GEN1 of NOCO provides charge twice as fast as traditional deep cycle battery chargers. Therefore, with the NOCO charger on your rig, you don’t have to wait too long for the battery bank to get to full charge. Since it could stabilize the chemistry of cells, Genius GEN1 lengthen the battery change interval. Moreover, if NOCO Genius GEN1 detects sulfation, lost capacity and alike, it would promptly apply high-voltage charges to restore the quality of the cells.

Rated at IP68, Genius GEN1 remains perfectly operational even after being submerged deep underwater for multiple hours so water intrusion is going to be inconsequential. Aside from that, with a low-profile build, the battery charger made by NOCO occupies a negligible amount of space. As a result, for owners of small recreational vehicles that travel around the year, Genius GEN1 of NOCO is the best deep cycle battery charger. Genius GEN1 is protected against an assortment of issues from sparks to thermal runaways too.

In terms of installation, NOCO Genius GEN1 could be set up and mounted onto plenty of applications in mere moments. The battery charger of NOCO requires basic care compared to most of its competitors nowadays so keeping Genius GEN1 in working order should be just a walk in the park.  

I have this charger installed under my hood in my truck connected to shore power. It does a nice job of bringing the voltage up to around 14 and keeping it level when the battery goes down. I plug my truck in to this every time I park in my garage and it keeps things fully topped off for me.

Shared by Tucker M.

Pros:

  • Nice handling
  • High endurance
  • Sublime charging rate

Cons:

  • A few units arrive defective
  • Reports about boiled batteries show up intermittently

3. Battery Tender Plus 021-0128 – Editor’s Choice

Battery Tender Plus 021-0128 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 4.75 x 2.75 x 2.75 Inches
  • Weight: 4.3 Pounds
  • Voltage: 12V
  • Ampere: 1.25Amp

Why It’s An Editor’s Choice:

Robust and simple to use,  Battery Tender Plus 021-0128 is held in high esteem by numerous RVers from novices to veterans. Capable of automatically changing to float mode as the max capacity is reached, Plus 021-0128 could keep deep cycle batteries at full charge without overcharging them. Also, the battery charge from Battery Tender is designed with top-notch temperature compensation so its charging rate should stay consistent regardless of ambient temperature. Possessing a lightweight body, Battery Tender Plus 021-0128 is portable too.

Thanks to the colored LED lights on the housing, determining the stage of charge with Plus 021-0128 is child’s play. Additionally, if the battery voltage drops under load for some reason, the  Battery Tender model would switch to ISM adaptive charging and resume full output. Similar to other modern-day battery chargers, Battery Tender Plus 021-0128 boasts integrated protection which leads to increased level of safety. Since Plus 021-0128 is a low-maintenance deep cell battery charger, RVing enthusiasts don’t have to give it special attention.

About post-purchase support, Battery Tender backs its unit with a solid ten-year warranty. In the case that you want to have an insurance policy while buying things, Plus 021-0128 is the best deep cycle battery charger you could get.

I have a pickup that I use mostly for towing and RV. It sits a lot and I was having problems of the battery draining. I figured it would be better to keep the battery charged than to ruin the battery. This unit is small and easy to use. It comes with two ways of connecting to the battery. One has battery clips and the other has ring terminals so that you leave it attached to the battery and just unhook the charger with the quick disconnect. I used the cable with the ring terminals and stuck the cable out the front of the truck. I now can hook up the charger without opening the hood. When I first hooked it up it took a couple hours to charge the battery and now light stays green all the time. This is a great unit and easy to use. I am glad I bought it.

Shared by JKR789

Pros:

  • Setup process is intuitive
  • Dependable and reliable
  • Outstanding resistance

Cons:

  • Less than ideal quality control
  • Get hot now and then

4. Schumacher SC1281

Schumacher SC1281 Deep Cycle Battery Charger
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Specifications:

  • Dimensions:  7.25 × 10.75 × 11.13 Inches
  • Weight: 12.65 Pounds
  • Voltage: 6/12V
  • Ampere: 6/2Amp (continuous), 30/100 Amp (boost)

Why We Love It:

As it incorporates a microprocessor that regulates power output, Schumacher SC1281 steadily optimizes charging time and maintains charges of the batteries at the same time. The multi-stage nature of its charging process means SC1281 excels at increasing the lifespan of the battery bank too. Thus, the charger made by Schumacher is considered to be the best deep cycle battery charger for those that care about the integrity of batteries. With Schumacher SC1281, your batteries should last through many seasons before they must be replaced.

Being compatible with typical batteries used in recreational vehicles, the Schumacher unit could charge AGM, gel and deep cycle batteries. That is why SC1281 works pretty well on a wide range of battery banks that contain batteries of various types. Furthermore, as Schumacher equip SC1281 with voltage detection, it’s able to tell 6V and 12V batteries apart upon hookup. Besides that, if the battery charger from Schumacher notices reversed clamps, it would refuse to operate until RVing enthusiasts put the clamps on correct polarities.

Since it utilizes a straightforward interface with LED display and start/stop push button, SC1281 earns positive remarks from countless deep cycle battery charger reviews for its ease of use. By taking a glance at the interface, you could grasp key details about the charging and proceed to react accordingly.

 Light weight and works well

The charger works as advertised. As with any charger it is important to remove any latent surface charge from the battery so the charger can read an accurate voltage. I found this charger read accurate battery charge. If you find it was at say 70% while charging, you disconnect and reconnect and it says 100% that is the surface charge. Turn your headlight on for 30 seconds before connecting the charger the second time and it will read accurately.

Shared by Christopher Moberg

Pros:

  • Versatile
  • Fair cost
  • User-friendly control

Cons:

  • People complain about loosed parts
  • Readings may be imprecise

5. Black+Decker BM3B

Black+Decker BM3B Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 8.00 x 3.00 x 2.00 Inches
  • Weight: 1.2 Pounds
  • Voltage: 6/12V
  • Ampere: 1.5Amp

Why We Love It:

Despite its low price, Black+Decker BM3B is loaded with virtually everything RVers need to recharge deep cycle batteries. Engineered with a voltage sector, the battery charger from Black+Decker could be used to charge 6V and 12V batteries. In addition, as the batteries get fully charged, BM3B would stop charging and switch to float charge by itself. Because of that, Black+Decker BM3B is the best deep cycle battery charger at its price range for RVing enthusiasts that wish to keep batteries of stored rigs at max capacity in off-seasons.

Since the housing of BM3B is made from enduring plastic, it’s rather light and handles physical shocks superbly. With mounting brackets, setting up the charger of Black+Decker is essentially a piece of cake in usual vehicle layouts. As for battery connection, BM3B of Black+Decker offers RVing enthusiasts two methods: battery clips and O-ring terminals. Hence, you should have an easy time matching BM3B to the battery bank of your rig which is a big plus if you don’t exactly have much time.

Like its cousins, the Black+Decker battery charger has low voltage compensation to make up for voltage loss in use. As a result, BM3B could still deliver full rated charges if connected to deep cycle batteries through extension cords.

Pros:

  • Economical
  • Marvelous portability
  • Structural strength is splendid

Cons:

  • Owner’s manual is poorly written
  • Some users report chargers arriving rusted

6. NOCO Genius G15000

NOCO Genius G15000 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 14.10 x 4.80 x 2.80 Inches
  • Weight: 6.5 Pounds
  • Voltage: 12/24V
  • Ampere: 15Amp

Why We Love It:

Built as an all-purpose smart deep cycle battery charger, Genius G15000 of NOCO is capable of meeting the charging needs of practically every RVer. With the ability to charge multiple types of batteries from lead-acid to deep cycle, Genius G15000 proves to be unrivaled in terms of adaptability. Aside from that, the NOCO charger is a fully automatic model so when plugged in, it would monitor and maintain batteries without requiring outside interaction. Spark proof and reverse-polarity protected, NOCO Genius G15000 is very safe to use too.

In the usual cases, the battery charger of NOCO should provide batteries with charge and keep them at max capacity. But if necessary, RVers could use Genius G15000 to bring heavily sulfated batteries back to life and save a couple of bucks on battery replacements. Therefore, for full-time RVers that like to cut down expenses in the long run, NOCO Genius G15000 is the best deep cycle battery charger. As the NOCO unit carries LED indicators, it’s a breeze to determine the stage of charge at any time.

Regarding installation, NOCO Genius G15000 features a combination of external mounting holes and a non-slipping rubberized base so securing it is a cakewalk. The charger made by NOCO is sold alongside battery clamps with detachable terminals so you may put it to use the moment it leaves the packaging.

Pros:

  • Sturdy and stable
  • Output is top-notch
  • Undemanding mainteance

Cons:

  • High-priced
  • Wiring should be overhauled

7. BatteryMINDer 1500

BatteryMINDer 1500 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 3.93 x 2.55 x 1.18 Inches
  • Weight: 3.0 Pounds
  • Voltage: 12V
  • Ampere: 1.5Amp

Why We Love It:

Effective and efficient, BatteryMINDer 1500 gives a good account of itself in plenty of environments and that earn it recommendations from many RV battery charger reviews. Fitted with a sensitive temperature sensor, the BatteryMINDer deep cycle battery charger makes precise voltage compensation based on ambient temperatures. That is why maintaining charge to batteries of recreational vehicles is a simple matter to 1500. By using BatteryMINDer 1500 to charge your batteries, it’s possible to increase the lifespan of the cells by several times.

As 1500 works with an assortment of batteries (flooded, sealed, AGM, deep cycle, …), you don’t have to worry about compatibility. In use, the battery charger made by BatteryMINDer can simultaneously charge and maintain up to four batteries in parallel if paired with a Y-connector. Additionally, with over-temperature,  reverse polarity and short-circuit protection, BatteryMINDer 1500 guarantees risk-free operation. Boasting LED indicators, 1500 keep users informed about the charging process as well as associated issues.

One interesting thing about the charger from BatteryMINDer is that it automatically desulfate batteries using a range of high frequencies. Thus, 1500 is particularly good at repairing sulfated deep cycle batteries that have seen substantial use. Since it comes at a highly affordable price, BatteryMINDer 1500 is the best deep cycle battery charger for budget-minded RVers. The BatteryMINDer unit is backed with a five-year warranty.

Pros:

  • Well-made and rugged
  • Tech support is responsive
  • Nice values for the price

Cons:

  • Inconsistencies between chargers
  • Corrosion resistance is kind of limited

8. Schumacher SE-1-12S

Schumacher SE-1-12S Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 2.00 x 8.00 x 9.00 Inches
  • Weight: 2.5 Pounds
  • Voltage: 6/12V
  • Ampere: 1.5Amp

Why We Love It:

Designed for stored and cold weather applications, Schumacher SE-1-12S could keep deep cycle batteries at full charge as long as it’s plugged in. Since its operation is controlled by an advanced microprocessor, SE-1-12S could adjust amperage rates to suit variable charging settings. Moreover, the battery charger from Schumacher charges the batteries in stages so it enhances safety level and preserves the quality of the batteries as well. Featuring LED indicators,  SE-1-12S of Schumacher permits RVers to easily monitor the charging process.

With the presence of a durable molded plastic case, the Schumacher model resists water, oil, solvents and so on well. As a result, the reliability of SE-1-12S is superior to that of the average chargers for deep cycle batteries. Schumacher SE-1-12S is also a universal installation charger that could be attached anywhere from fender wells to battery trays. Accompanied by double-sided adhesive and cable tie, the deep cycle battery charger of Schumacher only takes moments to set up in ordinary recreational vehicles.

Thanks to the reverse-polarity protection, SE-1-12S is going to remain undamaged even if you mess up the polarities. Besides that, as it automatically detects voltage upon connection, the charger made by Schumacher can identify 6V and 12V batteries.

Pros:

  • Reasonable price
  • Endurance is first-class
  • Compact and long-lasting

Cons:

  • Certain people complain about receiving flawed units
  • Quality control still leaves something to be desired

9. Optima Digital 400

Optima Digital 400 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 7.10 x 3.90 x 2.70 Inches
  • Weight: 5.0 Pounds
  • Voltage: 12V
  • Ampere: 4Amp

Why We Love It:

So portability happens to be your main concern while shopping for deep cycle battery chargers? If that is the case, it’s strongly recommended that you check out Optima Digital 400. Utilizing a lightweight space-saving design, the deep cycle battery charger made by Optima could be moved into position in a blink of an eye. In addition to that, Digital 400 comes with a versatile hook and tilt stand which allows it to adapt to a wide range of battery arrangements.

Since it employs a microprocessor for intelligent charging, Digital 400 is able to maximize charging current and augment the performance of batteries at the same time. The Optima battery charger contains advanced protection against spark, reverse-polarity and overcharging, hence, it owns a sublime safety record. As for the interface, Optima Digital 400 has a flush LCD display and lots of built-in indicators for charging statuses. Digital 400 integrates backlighting as well so working with it in low-light conditions would be a walk in the park.

In terms of price, the unit of Optima is a bit expensive compared to standard chargers for deep cycle batteries. That being said, considering its solid values, Digital 400 is nevertheless a good buy for those that have money to spend. As proof of confidence, Optima backs its deep cycle charger with a three-year warranty. If your Optima Digital 400 fails due to manufacturing defects then you could claim a replacement.

Pros:

  • Decent warranty
  • Fast recharges
  • Straightforward installation

Cons:

  • Slightly costly
  • Shipping requires improvements

10. TecMate OptiMATE 6

TecMate OptiMATE 6 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 3.9 x 2.80 x 2.40 Inches
  • Weight: 3.1 Pounds
  • Voltage: 12/24V
  • Ampere: 5/2.5Amp

Why We Love It:

Carrying the latest microprocessor controlled circuitry, TecMate OptiMATE 6 automatically diagnoses the characteristics of connected batteries and sets suitable charging currents. Aside from that, OptiMATE 6 makes compensations for temperature: it raises the voltage when hot and drops the voltage when cold. Therefore, the charger of TecMate could quickly get batteries to full charge in adverse weather. TecMate OptiMATE 6 is capable of preventing cells from self-discharging over time too so it’s a splendid battery maintainer.

Engineered to charge typical batteries (AGM, gel, deep cycle,…) in 12V and 24V, OptiMATE 6 is a must-have for people that have multiple battery banks and don’t want to manage too many battery chargers. To use the TecMate model, all you need to do is to select the desired voltage then plug it in. If it notices a disparity between the voltage you choose and the voltage of your batteries, OptiMATE 6 of TecMate immediately displays warnings and refrains from charging. Also, the charger made by TecMate would cease operation if the connection is severed.

If you opt to get OptiMATE 6, TecMate is going to provide you with battery clips as well as lead cable. Because of that, if you need to charge your battery bank on the go, TecMate OptiMATE 6 should be the best battery charger for deep cycle batteries you could grab nowadays. The battery charger from TecMate is backed with a three-year warranty that covers defects.

Pros:

  • Robust body
  • Impressive compatibility
  • Excellent delivery service

Cons:

  • Confusing owner’s manual
  • Chargers draining batteries is reported

11. Ampeak CGUFB2025

Ampeak CGUFB2025 Deep Cycle Battery Charger
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Specifications:

  • Dimensions: 10.91 x 7.05 x 4.47 Inches
  • Weight: 5.21 Pounds
  • Voltage: 12V
  • Ampere: 2/10/25Amp

Why We Love It:

With comprehensive temperature protection, Ampeak CGUFB2025 performs as expected in extreme settings which make it the all-time favorite of RVers that enjoy off-roading. Furthermore, the microprocessor of the charger from Ampeak constantly monitors the status of connected batteries and refine the charging cycle based on data it gathers. As a result, CGUFB2025 could accelerate the charging process while preventing overheat, overcharge, short-circuit, … The front-mounted display lets RVers determine the current situation with just a single glance.

As it packs a smart detect system, CGUFB2025 instantly recognizes the voltage of batteries and that helps it come up with the ideal charging rates. Once the max capacity is reached, the battery charger of Ampeak would switch to float mode to maintain the charge. Besides that, owing to its small build and ergonomic handle, CGUFB2025 of Ampeak proves to be very simple to manipulate. CGUFB2025 is distributed with output cable so you don’t have to make separate purchases to set it up.

To reverse the damages sustained by batteries that have been left uncharged for a long time, the Ampeak battery charger possesses an advanced recondition mode. Thus, if you have CGUFB2025, restoring severely depleted batteries should be a piece of cake. In times of need, it’s possible to use Ampeak CGUFB2025 to get low-capacity to batteries to start engines using the start aid function.

Pros:

  • Easy to install
  • Cable included
  • Fantastic ruggedness

Cons:

  • Barely acceptable packaging
  • Unresponsive support

12. Jethax JET-1911

Jethax 12V 4A Smart Battery Charger
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Specifications:

  • Dimensions: 6.0 x 4.0 x 3.2 Inches
  • Weight: 0.9 Pounds
  • Voltage: 12V
  • Ampere: 4Amp

Why We Love It:

Basic and practical, Jethax JET-1911 is well-liked by RVing enthusiasts that wish to get a no-nonsense battery charger. Being a three-in-one model, JET-1911 charges, repairs and maintains deep cycle batteries depending on the requirements of users. The deep cycle battery charger made by Jethax is also designed and tested to address overheat, overcharge, reverse-polarity, spark, …. That is why Jethax JET-1911 is widely considered to be one of the leading battery chargers in terms of safety.

Equipped with both heavy-duty alligator clips and ring terminals, the Jethax battery charger only takes moments to set up. Since it supports nearly every type of battery, JET-1911 is compatible with an assortment of battery banks used by RVers. The charging process offered by Jethax JET-1911 consists of multiple stages so the lifespan of batteries would be extended too. Using ambient temperature as references, the battery charger from Jethax automatically changes between summer and winter operating mode to deliver appropriate charges to the batteries.

Since it’s constructed with top-notch ABS plastic, JET-1911 is relatively light but it could withstand bumps and hits. Regarding the interface, the charger from Jethax has a handy display that shows the voltage, charge level and operating mode. Hence, it’s a breeze to monitor the charging process if you use Jethax JET-1911.

Pros:

  • Highly affordable
  • Durable and portable
  • Adaptable charging

Cons:

  • Many units without instructions
  • Get slightly hot on occasions

Deep Cycle Battery Chargers Buying Guide

Since the world of trailer battery charger is vast and diverse, you should first determine your priorities and decide on shortlisted models that best suit your budget and needs. Making sure your battery is properly and optimally charged is essential in securing a pleasant camping experience and in maximizing the lifespan of your expensive battery bank, thus under no circumstances should you blindly opt for a model, even if it receives relatively positive reviews. 

In order to get the best out of your money, get familiar with the most important buying criteria when looking for the deep cycle battery chargers for your rig. 

Power Capability, or Amps-Per-Bank

In layman’s terms, the output of a charger, or its power capabilities, is the amount of electricity that it provides to the batteries which determines how fast the batteries get to full charge. This rating is measured in amps-per-bank, or how many amps the charger can deliver to a battery bank.

Finding a deep cycle battery charger that is able to adapt to fit your specific battery is a must. Not all vehicle batteries operate at the same amperage or amp hours, so the charger has to be able to discern what amps it needs to properly charge a specific battery. 

Automatic battery chargers or smart chargers have the ability to detect the required amps and distribute the necessary voltage, making the charging process safer and easier. The best deep cycle battery chargers also have distinct charging phases that can read and adapt to the battery and adjust the charging mode accordingly.

In addition, to calculate the ideal output for your charger, it’s important that you consider the power consumption of your rig. If you don’t need a lot of power to keep the appliances on your RV running, a standard charger is going to be adequate. On the other hand, if you happen to own a power-hungry rig, you have to prioritize high-output chargers.

Do note that larger rating for amps-per-bank means a faster charge, which usually makes a charger more expensive. To choose a  charger with a suitable amps-per-bank number for your needs, consider this example:

An RV has a cranking battery and a deep cycle battery. Since you have two batteries, you should opt for a 2-bank charger.

Between a charger with a 5 amp-per-bank output and another with 10 amps per bank, the more economical choice is the charger with 5 amp per bank. But if you want faster recharge speed and are willing to pay for that, you can go for the 10 amp-per-bank model.

In another example, your vehicle has a starting battery and a set of three deep cycle batteries. Four batteries means you would need a 4-bank charger. A 4-bank charger would offer outputs of 10 or 15 amps-per-bank, which ensure rapid charging times even in case of deep battery discharge and low input line voltage. As above, a 15 amps-per-bank charger would deliver shorter charging time than a 10 amps-per-bank model.

Endurance

Equipment on recreational vehicles, including battery chargers, tend to be exposed to bumps and shocks as RVers move between locations. Because of that, while assessing deep cycle chargers available for purchase, it’s key that you pay attention to endurance. You should be able to tell if a particular battery charger could hold together by taking a close look at its material, construction and alike. Besides making direct evaluations, it’s a good idea to read reviews written by fellow RVers to gather relevant details.

Space

It’s common knowledge among RVing enthusiasts nowadays that space is a luxury on recreational vehicles so you need to think it through prior to adding anything to your rig. The last thing you want to pick up is an oversized battery charger that your RV is incapable of accommodating. Overall, to avoid wasting money on potentially unsuitable products, you must use the free space on your rig as references. That would help you reduce the number of battery chargers you have to check out.

Safety

It’s impossible to be too careful if electricity is involved and that is why you should give the safety features of the chargers some thoughts. Deep cycle battery chargers for recreational vehicles often pack protection against overheat, overcharge, reverse-polarity, … Before committing to a purchase, you need to make sure that the safety features of the chosen charger could keep you and your batteries secured. If your charger is loaded with proper features, you can casually enjoy your experience without having to worry about the integrity of the battery bank.

Charge Time

Charge time might be an important consideration for some campers. You can estimate charging time by dividing the battery’s capacity by the charger’s rating, and a good rule of thumb is to add about 10% for the extra time to totally top off the battery. For instance, It would take a 10-amp charger about 11 hours to recharge a dead 100 ampere-hour deep cycle battery to near 100% full charge at room temperature: 100AH ÷ 10A × 110% = 11 hours.  

As noted above, a charger with a larger rating for amps-per-bank will charge a depleted battery to a full charge faster, so if fast charging time is your priority, you should opt for a 10 amps-per-bank charger instead of a 5 amps-per-bank model, which should typically costs less.

Other Features

To ensure you get adequate and continuous power supply, you should get deep cycle battery chargers that double as power supplies for RV use, and while you’re at it, get a multi-bank charger for charging multiple batteries simultaneously. In the example above, based on your specific needs for power, you might have more than two batteries, including one starting battery for cranking your engine and more than one deep cycle battery.

In addition, as mentioned above, the best deep cycle battery chargers have an auto-stop feature that will stop charging when a full charge is reached, so you can leave the charger plugged in 24/7 without worry of damaging the battery.

Other useful additional features include waterproofness, which can be handy when you’re camping out in the open, since it’s recommended that you should charge your batteries in a well-ventilated area where the gas from the battery can escape through a window or door.  chargers for those times when you’re out in the elements

Ease of Use

Hooking up a battery charger shouldn’t be a difficult process. Generally, you just clamp on the positive and negative clamps, plug the charger into an outlet, and let it run. However, on some chargers, you may have to do some additional settings beforehand. If that is not your forte, you can opt for an automatic charger that can adjust accordingly to the battery to save you time and let you enjoy a faster charge.

Price

Unless you have certain requirements, there is no need to spend big bucks to get high-end premium-grade chargers. The market contains plenty of decent models that also come at reasonable prices so it’s unnecessary to empty your wallet on expensive battery chargers. However, as price is linked to quality, it’s widely advised that you stay away from dirt-cheap battery chargers. Though buying such models lets you save some buck, they usually break down after a short period of time and force you to buy replacements.

Below is a rough price guide for your reference:

  • $50 and under: This range covers budget chargers that typically don’t offer much in terms of extra gadgets and deliver lower voltage outputs, so they might not be adequate for charging large vehicles.
  • $50-$100: This standard range offers larger voltages plus extra features and accessories.
  • $100 and above: For $100 and upward, which is not a substantial investment, you get a high-end charger with more voltage plus the added bonus of extra safety features that will better ensure charging efficiency and will keep your battery healthy for longer.

Types of Deep Cycle Battery

A basic understanding of the different types of deep cycle batteries and what type you have is useful in selecting a well suited charger and in ensuring proper charging, since you need to set the charger to the specific type of battery in your vehicle and certain types of deep cycle batteries require additional maintenance charge.

There are two broad categories: flooded and sealed. Both categories work under the same concept: one lead plate and one lead oxide plate are submerged in an electrolyte solution of water and sulfuric acid. The sulfuric acid will trigger a reaction on the lead dioxide plate, causing the plate to produce ions and lead sulphate. The ions produced by the lead dioxide plate react to the adjacent plate to produce hydrogen and lead sulphate.

The result is a chemical reaction that produces electrons. The electrons race around the plates and generate electricity. The electricity flows out of the battery terminals to start your engine and power electrical devices.

“Flooded” Batteries, or Flooded Lead Acid (FLA) Batteries

This type of deep cycle battery, also called wet-cell batteries, requires two important maintenance processes. Firstly, flooded lead-acid batteries lose water during the charge cycle. They must be refilled regularly with distilled water every 2-4 weeks as needed to function properly and stay healthy.

Note that you should only use distilled water since non-distilled water, like tap water, has small particles and contaminants, which weakens the battery chemistry.

Secondly, flooded lead acid batteries should be equalized occasionally to make sure each cell is equally charged. You can do this by applying a controlled overcharge once every 30-90 days. More on the instructions for a controlled equalizing charge in the Frequently Asked Questions at the end of this guide.

Another distinct feature is that flooded batteries produce gas when overcharging. This gas must escape to avoid damage to the battery via some type of ventilation, which is why this type of battery is sometimes called vented cell battery.

“Sealed” Batteries, or Valve-Regulated Lead-Acid (VRLA) Batteries

Sealed batteries are also lead-acid batteries like the flooded type, however, as they are “sealed”, they eliminate the hazards associated with acid spills or leaks and they allow for a maintenance free design.

Easier to maintain, sealed batteries do not require water refilling and equalizing charge. They require very little maintenance other than the occasional check-up on the battery’s state of discharge using a multimeter or a voltmeter to read the voltage of the battery.

Gel

Gel batteries are absolutely spill-proof and almost maintenance free. Their cells contain acid that has been turned into a solid mass by adding Silica Gel, so it is impossible for them to spill acid even if broken. 

However, gel batteries have several disadvantages. One is that they must be charged at a lower voltage than the other three types of deep cycle batteries. If overcharged, voids can develop in the gel which will never heal by themselves, causing a loss in the battery’s capacity. In extremely hot climates, water loss can cause premature battery death in 2-4 years. 

Secondly, they will be permanently damaged if they are fast charged using a regular charger. Such fast charging will generate excess gas that can damage the cells, since these batteries produce gas when overcharged just like flooded batteries. 

AGM (Absorbed Glass Mat)

AGM batteries are also sealed, spill-proof, maintenance-free and will not leak acid even if broken. Being the most recent and advanced invention and offered at about the same price point of the gel type above, AGM batteries offer significant advantages over both the traditional flooded batteries and gel batteries, making them the battery of choice for countless campers and anglers. 

In particular, the best AGM battery charger has the highest charging efficiency, tolerates a much deeper depth of discharge than flooded batteries, can very well withstand low temperatures, and are much more resistant to vibration and impact. This makes them ideal for a greater number of camping applications.


Types Of Deep Cycle Battery Chargers

Using operational characteristics, it’s possible to split RV deep cycle battery chargers into three types: charger, restorer and maintainer

Deep Cycle Battery Chargers: Basic and practical, battery chargers simply deliver power to the batteries and get them back to full charge, even if it is completely out of juice. These are the most common types of battery chargers, and their universal fit makes them capable of providing the correct amperage to your vehicle no matter if it has a marine battery, AGM battery, gel battery, or any other type of battery. Being highly adaptable, models of the type consistently give a splendid account of themselves in a wide range of arrangements.

Deep Cycle Battery Restorers: As a more expensive type of charger, restorers are seen more in professional garages or shops than in the homes. Engineered to break up accumulations of foreign contaminants in the battery cells, which obstructs the flow of charge, the best deep cycle battery restorer can clear the cell block out and bring power to your battery once again. Battery restorers prove to be excellent choices for well-used batteries.

Deep Cycle Battery Maintainers: Batteries are prone to the problem called natural discharge or self-discharge, in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. With the ability to keep power in the cells from self-discharging, battery maintainers could keep batteries at full charge for a long time. Naturally, models of the type get a shower of praise from RVers that travel extensively. They work best as quick fixes and may help extend the battery life.


Top Deep Cycle Battery Charger Brands

Deep cycle battery chargers for RV come from many manufacturers but when it comes to reputability, several names stand out.

Black+Decker: As a long-established brand of power tools and associated accessories, Black+Decker is the top choice for those that seek stable and consistent chargers. In addition to that, Black+Decker produces highly versatile models that could be put to use in various power setups.

NOCO: Owing to a combination of innovative mindset and applications of the latest technologies, NOCO ensures that its battery chargers would be both adaptable and resilient. So if all you need is a robust deep cycle battery charger for RV, you should keep an eye out for units made by NOCO.

Battery Tender: Known to be one of the leading manufacturers of battery chargers, Battery Tender constantly reviews and optimizes the design of its products for modern standards. Needless to say, Battery Tender is held in high esteem by people that want to grab an up-to-date charger for deep cycle batteries.

best deep cycle battery charger
Photo: Tender

How to Charge A Deep Cycle Battery Properly

You don’t have to be a battery expert to charge a deep cycle battery, however there are a number of things you must not ignore. Follow the steps down below and you would be able to safely and efficiently bring your battery to full charge as well get more life out of your battery pack. 

Initial Programming for The Charger

The first time you bring your system online, depending on the model, you might need to program your chargers to the proper charging settings best suited for your battery bank. These settings dictate parameters like charging voltage and current. Refer to the manuals for your batteries and chargers for these specific settings.

Initial programming is crucial, since this is how you program “voltage set points”, or the different charging voltages that the battery will receive during each stage of the charging cycle. It is important to note that batteries typically charge in 3 stages—bulk, absorb, and float. Each stage requires the charger to be set at a specific voltage for optimal charging, which is based on the requirements of your specific battery pack:

  • Bulk: The first stage is characterized by a faster charge rate to bring voltage up as quickly as possible, so that a depleted battery will receive high current to quickly replenish. The battery will be recharged up to 80% of its capacity. 
  • Absorb: The battery will continue to be recharged to its full state of charge with a slower charge rate.
  • Float: After full capacity is reached, the batteries will receive a trickle charge to maintain this full state of charge. In other words, the charge rate in the float stage is equal to the battery’s natural self-discharge rate.

As such, programming the voltage set points accurately for these three charging stages is absolutely critical to ensuring your batteries’ ability to hold a full charge, its overall long-term health and lifespan. Setting the wrong parameters will make your batteries charge at suboptimal conditions, thus inevitably shortening their lifespan.

There are also other important values to set during the initial programming, which are different for every battery and charger. Check the manuals for your batteries and chargers to find the specific values for each setting:

  • Max charge rate or charge current limit: Maximum charging current, either expressed as maximum charging amps or a percentage of the charger output. This setting is used to make sure your batteries are not overcharged with too much current, which will cause overheating and shorten battery lifespan.
  • Temperature compensation: The best deep cycle battery chargers include a battery temperature sensor and allow for adjustments for operation in various temperature ranges. 
  • Absorb time: The amount of time the charger spends in the absorb phase.
  • AC input amps: The maximum input current from the generator is dependent on generator size, and ensures that the combined current from the battery charger and loads doesn’t exceed the rating of the generator. 

The Safe & Proper Charging Process

Step 1 – Preparation

Put on goggles and protective gloves for protection, since sulfides might escape from the battery during the charging process.

Safety first: Disconnect the battery from your boat’ or RV’s system and bring it to a well-ventilated space to avoid a surge or electrical damage. Be aware of gas release by the battery. It is best to inspect and charge the battery where the gas can safely dissipate outdoors.

Step 2 – Inspect water level

Most deep cycle batteries have water within their construction. Before you begin with a charging session, regularly inspect the battery for proper electrolyte levels for that battery type. 

Use a screwdriver to remove the covers of the cells to check the liquid level and add distilled water if needed. While you’re at it, also inspect to see if there are cracks on the outside housing.

Step 3 – Clean battery terminals

The buildup of sulfuric acid residue naturally occurs over time and may leave behind a yellow-ish powder on the battery terminals. Next, you should clean the battery terminals before attaching the clamps using a wire brush to make sure you get a good clean charge without interference. 

Afterward, spray the terminals with an anti-corrosion spray. Only plug in the battery charger when the spray is completely dry, or else this might ignite the battery.

Step 4 – Check state of discharge

Before actually starting charging, you must check the current state of discharge of the battery. The state of discharge on a battery that’s been under a load for most of the day would typically be between 25% and 30% full. 

Use a voltmeter with the battery detached from the system to read the voltage of the battery. This state of discharge will partly decide how long you should be charging deep cycle battery components. Refer to your battery manual for a chart that estimates the battery’s state of discharge based on the voltage readings.

To get the most accurate voltage reading, your batteries should be tested in a resting state, that is no charging or discharging, for at least 2 hours before using the voltmeter. Using the voltmeter when batteries are being charged or discharged is going to result in a misleading higher or lower voltage, depending on the load.

Getting the best deep cycle battery chargers is convenient regarding this matter along with others: a smart charger will determine the current charge and the right timing to top it off, so there’s no need to determine the state of discharge and the right charging time.

Step 5 – Set a timer

In case you don’t own a smart charger, it’s crucial that you set a timer for the charging session to avoid overcharging. Overcharging will overheat the battery, thus diminishing their charging capacity and lifespan. 

The time it takes to properly charge a battery depends on its current state of discharge as well as your charger’s amperage specification, which can be found in the manuals. For easy calculations, refer to the charts provided by your battery and charger’s manufacturer, either in the manuals or on their websites.

As stated above, a charger with a higher amps output will deliver a faster charge. As a rough comparison, a charger with 15 amps will take about two hours to fully charge a battery at a 25% state of discharge, while one with only 5 amps will need six hours to do the job.

Step 6 – Charging

Set the charger to match the type, that is flooded, gel or AGM, and characteristics of your battery. Next, connect the cables of the chargers to the terminals of the battery: Clip the red clamp to the positive terminal (+ symbol), then clip the black clamp to the negative terminal (- symbol).

After connecting the cables, connect the charge to the power outlet (110-120 volts AC). Turn on the charger and start the charging. 

Step 5: Once the battery is fully charged, the charger would display some kind of notification. Remove the cables and check the voltage of the battery. If all is well and the battery is fully charged, you may reinstall the battery in your RV or boat.

If your batteries fail to approach full charge, they are likely defective, damaged, or have simply reached old age and require replacement.

Safety Tips

  • Before starting your charging sessions, always make sure to remove the key from the ignition and switch off all lights and electrical circuits connecting the battery charger.
  • Never put on a battery charger while the battery or the terminals are wet. This can ignite the battery or cause a spark.
  • Do not clamp the positive cable to the negative battery terminal or vice versa. They are color-coded with corresponding symbols for easy identification.
  • Keep the battery and charger away from extreme heat or cold, as both aren’t ideal for the battery’ and the charger’s components. You may notice fluctuations in charging times when it’s too hot or cold. 
  • Note: While you do get a small short charge with a jumpstart and can leave the engine running for a time with a jump, it won’t be a permanent solution, and not the optimal choice considering the health and lifespan of your batteries. Invest in the best deep cycle battery chargers to save yourself time and money on troubleshooting, repair and battery replacement later on.

FAQs About Deep Cycle Battery Chargers For RV

Do deep cycle batteries need a special charger?

A deep cycle battery is not designed to handle such excess heat generated during the rapid charging of regular chargers. Such overheating can cause various problems, such as internal materials slowly breaking down, fluctuating charge and operational times, and ultimately shorter battery lifespan.

Furthermore, deep cycle batteries have thicker active plates than regular starter batteries. A regular battery charger is not suited for these thicker plates. Since such a charger charges a battery rapidly, it doesn’t allow enough time for the battery acid to penetrate the thicker plates of a deep cycle battery.

Therefore, using a traditional battery charger to recharge your deep cycle battery is not optimal. the battery may never reach full capacity, although the charger might display notifications that the battery has reached full charge when it is actually not. 

In short, due to having thicker plates and low tolerance for overheating, a deep cycle battery requires a different charging mechanism, that is slow charging, provided for by a deep cycle battery charger. 

What’s the best way to charge a deep cycle battery? Why should we use a deep cycle charger?

In contrast to starter batteries that deliver high-current, short bursts for cranking the engine, deep cycle batteries are designed to be deeply discharged and then recharged, they have thicker active plates and cannot handle the excessive heat associated with the fast charging by regular chargers. Therefore, the best way to charge deep cycle batteries is a slow charging process using a deep cycle battery charger. 

While a starter battery typically discharges only 2% to 5% of its full capacity in normal starting operations, a typical deep cycle battery will discharge 45-75% of its capacity, although this figure can vary depending on the battery’s construction and the manufacturer. While it is possible to cycle the battery down to 20%, it is considered best practice to keep the maximum discharge at around 45% to maximize the lifespan of the battery.

A deep cycle battery charger is recommended to efficiency maintain this deep-discharge and recharge cycle. A deep cycle battery chargers use a stepped model which allows more current to flow to the battery when it is deeply discharged, and then slowly tapers off the charging speed as the battery reaches full capacity. This serves to optimize charging time while avoiding overheating and thus maximizing the battery lifespan in the long run.

The best deep cycle battery charger will also help protect against overcharging, so you can leave the charger plugged in 24/7 without setting the timer and worrying about damaging the battery.

What amp should you charge a deep cycle battery?

Always refer to the manuals to check your battery and charger’s specifications for the accurate proper charge rate. In general, it is typically better to charge a deep cycle battery at a higher charge rate like 6-amps, 10-amps or 15 amps. 

There are times when charging a battery quicker is desirable. This is possible to do by increasing the amperage charge up to 20 amps from 10-15 amps that it starts at.

However, be aware that anything out of the ordinary specified in the manuals will shorten the useful life of your deep cycle battery. If you prioritize fast charging time, you can invest in the best deep cycle battery charger that has improved circuitry; this can manage current in an optimal way for a faster charge without deteriorating the battery in the long run.

What voltage should you charge a deep cycle battery?

This depends on the type of deep cycle battery your vehicle has and the specific model, so always read the manual carefully to properly charge your battery and take care of your charger.

If you use a charge voltage that is too high, the battery will overheat, leading to premature death. In addition, excessive current will flow into the battery after it has reached 100%, causing decomposition of water in the electrolyte and premature aging. 

Also remember that each of the three charging stages of a deep cycle battery requires a different voltage, which you must set during the initial programming phase. 

For instance, flooded deep cycle batteries require a recharging voltage of 2.43 to 2.45 volts per cell. This is 14.6/14.7 volts for a 12 volt nominal installation and 29.2/29.4 volts in a 24 volt site.

Meanwhile, AGM batteries should be charged using a charger with current limited to 20% or 0.2C of the batteries capacity at a charging voltage of between 14.6 – 14.8 volts following deep cycle use, or 13.6 – 13.8 volts for standby use.

How long does it take to charge a deep cycle battery?

The time required to charge your deep cycle battery system will depend on the number of battery banks that need to be charged, and the number of amps-per-bank that your charger can output. The atmospheric temperature also slightly affects charging time; charging time can noticeably fluctuate in extremely hot or cold weather.

You can estimate charging time by dividing the battery’s capacity by the charger’s rating, and a good rule of thumb is to add about 10% for the extra time to totally top off the battery. For instance, It would take a 10-amp charger about 11 hours to recharge a dead 100 ampere-hour deep cycle battery to near 100% full charge at room temperature: 100AH ÷ 10A × 110% = 11 hours.  

In general, many experts recommend charging the battery slowly over a 10-20-hour period at a moderate room temperature of 70°F or 21°C, given that your charger has damage protections in place and can be left plugged in 24/7. This way, the acid has plenty of time to penetrate the thicker active plates while also putting far less stress on the plates..

Sometimes, when you’re in a hurry and need to reduce charging time, one way is to only charge the battery up to 90%. This is because getting from 90% to a 100% full charge takes considerably longer than getting from 80% to 90%, extending the total charging time by a lot. However, do note that it is optimal for battery life to discharge down to 45% then recharged to full capacity, so charging to only 90% often will surely shorten your battery life.

Is it OK to fast charge a deep cycle battery?

Sometimes when needed, you can fast charge a deep cycle battery by increasing the amperage charge up to 20 amps from the typical and recommended 10-15 amps that it starts at. However, be aware that doing anything out of the ordinary will most likely shorten the useful life of your deep cycle battery, so only do this when circumstances absolutely require.

How often should you charge a deep cycle battery?

Deep cycle batteries should be recharged when they indicate a 45-50% charge, but the best practice is to never let them get lower than 20% to ensure a long life, although deep cycle batteries are technically designed to withstand a 80% depth of discharge. Use a multimeter or a voltmeter to regularly check the state of discharge of your battery, or how many voltages your battery is currently holding.

Depending on your power consumption, you will need to regularly check the voltage of your battery using a voltmeter to determine when you need to charge your battery and estimate for yourself the average time that it takes for your battery to cycle down to 45% of its full capacity.

Do note that all types of deep cycle batteries are lead-acid batteries, thus they run the risk of sulfation if left uncharged for too long. Sulfation, the process of lead sulfate crystals building up on a battery cell, is a natural process that happens with every battery over time. However, rapid sulfation happens when deep cycle batteries are stored in a discharge state, or left on the shelf for too long, and it is undesirable. The battery will accept far less current than normal. 

When rapid sulfation occurs, during a charging session, the battery will usually start to accept increasing amounts of current until a normal current level is reached. If there is no response even to higher charge voltages than recommended levels, the battery may have been in a discharged state for too long to recover and thus needs to be replaced.

How do you tell if a deep cycle battery is fully charged?

The best deep cycle battery charger will have some form of notification to tell you when the battery is fully charged and ready to be reinstalled and used. Otherwise, you can use a voltmeter or a multimeter to measure the current voltage the battery is holding to check whether it has reached 100% charge. 

 A 12­-volt deep cycle battery has 6 individual cells, and thus each cell holds approximately 2 volts. Interestingly, a fully charged 2-­volt cell has a voltage of approximately 2.15 volts while a fully discharged 2­ volt cell has a voltage of 1.9 volts. 

That’s only a difference of 0.25 volt per cell between fully-charged to fully-discharged states. In other words, a 12-­volt battery will measure at about 12.9 volts when it’s fully charged and about 11.4 volts when it is fully discharged. The exact fully-charged voltage and fully-discharged voltage will be slightly different depending on the specific type of the battery and its age.

To check if a 12 volt deep cycle battery charger has charged a battery to 100% charge, follow these steps:

  • Let the vehicle rest for at least two hours, or best overnight, before you use the multimeter to test the battery’s state of charge. If the vehicle has recently been running, the battery is likely to produce a higher misleading number on the multimeter. 
  • Insert the red lead for the voltmeter into the connector identified as “volts”, and the black lead into the connector marked as “com”.
  • Turn the switch on the meter to the position of “DC volts.” Set your multimeter to 20 DC voltage.
  • Connect the multimeter with the battery: Touch the red lead (positive, marked “+”)  with the red (positive) battery terminal. Touch the black lead (negative, marked “-”) with the black (negative) battery terminal.
  • Read the DC-volt value on the multimeter’s display.

Can you overcharge a deep cycle battery?

Batteries typically charge in 3 phases—bulk, absorb, and float—and each stage requires the charger to be set at a specific voltage, which is based on the requirements of your battery. Refer to the manuals for your battery to check for these specific voltage points. 

Optimal charging and optimal battery’s lifespan can be achieved if the charger delivers the correct voltage to the battery at a given phase of a charging cycle. Either undercharging— charging at a voltage lower than what is required during a charging phase, or overcharging—charging at a voltage too high, will result in inefficient charging and can shorten the battery’s lifespan in the long term. 

In the case of undercharging, the low voltage will essentially make the current flow stop before the battery is fully charged. This allows some of the lead sulfate to remain on the electrodes, which will eventually reduce the battery’s capacity to hold a charge.

In the case of overcharging with a charge voltage that is too high, excessive current will flow into the battery, after reaching full charge, causing decomposition of water in the electrolyte and premature aging. 

At high rates of overcharge a battery will overheat and as it gets hotter, it will accept more current, heating up even further. This is called “thermal runaway” and it can completely kill a battery in a few hours.

Do note that sometimes a controlled overcharged is desired as a means of battery maintenance. While this is not required for sealed deep cycle batteries, flooded lead acid batteries should be equalized occasionally to make sure each cell is equally charged. You can do this by applying a controlled overcharge once every 30-90 days, or whenever individual batteries are imbalanced, that is they are reading a different voltage. 

The process for an equalizing controlled overcharge is as follows:

  • Check water level before initiating an equalize charge.
  • Turn off any loads.
  • Set your charger at the Equalize voltage specified in your battery manual.
  • Start the Equalize charge. Gassing and bubbling is normal during this process.
  • Stop charging and take specific gravity readings every hour. The EQ process is complete when the specific gravity stops rising.

How do you charge a deep cycle battery with a battery charger?

Again, using a regular battery charger to charge your deep cycle battery is not at all recommended, however if you must, the process is the same. Do note that your deep cycle battery would not reach a full charge.

  • Put on goggles and protective gloves for protection.
  • Disconnect the battery from your boat or RV’s system and bring it to a well-ventilated space, so the gas released by the battery can safely dissipate outdoors.
  • a screwdriver to remove the covers of the cells and check the electrolyte level. If the electrolyte level appears to be low, proceed to add distilled water. 
  • To make sure you get a good clean charge without interference, before attaching the clamps, you should clean away any sulfuric acid residue from the terminals using a wire brush. Then, spray them with an anti-corrosion spray. Wait until the spray is dry.
  • If your charger is not a smart charger with an auto-stop function that will top it off when the battery is full, check the current state of discharge of the battery by using a voltmeter to read the battery’s voltage. The state of discharge will dictate how long you should be charging. Refer to online charts provided by your battery and charger’s manufacturer to calculate charging time. Then, set a timer.
  • Set the charger to match the type of your deep cycle battery. Next, connect the red clamp of the chargers to the positive terminal (+ symbol) of the battery, then clip the black clamp to the negative terminal (- symbol).
  • Connect the charge to the power outlet. Turn on the charger. 
  • Even if the charger notifies you that the battery is fully charged, a deep cycle battery will not reach a full charge with a regular charger. Remove the cables and reinstall the battery

You can also find our guides on how to choose the best RV battery, best lithium battery for RV, best AGM battery, best RV battery box, best RV surge protector, best RV generator, best solar-powered generator for RV, best solar panels for RV, best RV converter, best RV inverter, best trickle chargers, best RV battery monitors, best solar charge controller for RV with detailed reviews in RV Electrical category. In these reviews, we only include and recommend the best products with the highest ratings among highly sold products on the market.

Last Updated on June 25, 2021

Chris Coleman is an interesting travel blogger and outdoor photographer with a great sense of humor. He owns an RV Accessories shop in New York City so he has the knowledge necessary to provide thorough reviews and give advice on how to choose the right products for RV travel. He puts all that RV knowledge and experience to good use in his sharing posts. Besides product buying guides/reviews, Chris also writes informative articles, how-to articles and RV camping guide in his own interesting viewpoint. Chris’s blog is one of the most reliable information sources for RV campers no matter if you're an expert or a determined beginner.

1 Comment
  1. My three wheel Sport Rider scooter is specked out at 2-100amp, 12 volt deep cycle batteries.
    Along with the scooter came the TE battery charger model E20116227LJ, 24 volt, 8amp for 26-75 rechargeable batteries.

    On 9/2/19 Interstate sold me 2-75 amp, 12 volt batteries that I kept charged but they became worthless within 12 months. By worthless I mean my scooter would not climb a slight incline at the end of my block nor make it around the block.

    I intend to install 2 new 100amp batteries but feel the charger is inadequate. I purchased a 2- bank ProMariner 12 charger like found on tournament fishing boats. But the clamp connections meant I had to remove the seat and shroud to get to the batteries for charging.
    Instead, I mounted same gauge ring to plug in leads for both the batteries. Then I changed the clamp leads from the charger to plug in leads. Now I can plug in the charger leads to the plug leads connected to the batteries without removing the seat and shroud.

    But it won’t work, dam charger is in error mode.

    What do you think…am I on to something with double bank charger rather than what was sent with scooter? Wonder why the correctly installed plug in leads won’t friggin work?

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