The Best AGM and Lithium RV Deep Cycle Battery

Deep cycle batteries for recreational vehicles (RVs) have a very important purpose - they power onboard electronics and electrical devices while the vehicle's main motor is not working while being off the grid.

RV deep cycle batteries must tolerate deep discharge conditions and cyclic use, but they also must be resistant to vibrations, high and low temperatures, no usage for a long time (sometimes for months), etc.

Since these batteries are far from cheap, it is really important to choose them properly, according to individual needs and requirements.

Note that RV deep-cycle batteries often have very similar requirements to marine deep-cycle batteries, which are often used interchangeably.

Updated: July 31, 2024.

RV Deep Cycle Battery vs. RV Dual Purpose Battery

For RVs using a single battery system, a dual-purpose battery or battery pack is recommended. For RVs using a dual battery system, a deep cycle battery is recommended for 'house' applications, while a classic cranking battery is used for starting the vehicle.

Dual-purpose batteries have good deep discharge characteristics and are able to provide large currents for starting a vehicle. However, for deep discharge applications, they are not as good as deep discharge batteries and as cranking batteries, they are not as good as starting batteries.

But, using one single battery (or single battery pack) greatly simplifies the electrical system of RVs.

A single battery electrical system can be found on smaller RVs, not intended for longer use without the starting of the main engine or without the mains power available.

But, some people combine even smaller RVs with a single battery with solar panels and wind turbines and achieve longer "off the grid/no engine turned on" periods of time.

Deep-cycle RV batteries or battery packs are used in dual-battery electrical systems, where the starting battery and alternator are isolated from a larger deep-cycle battery or, more often, a battery pack.

Deep cycle batteries tolerate deep cyclic discharges (down to 20% of their capacity) without adverse effects on their longevity and reliability. However, their starting characteristics are often rather modest (to say the least) and in such situations, a dedicated starting battery is used.

Both batteries share common ground, but the deep cycle battery (or battery pack) is used for powering various electric and electronic devices, while the cranking battery is used for starting the RV and perhaps for the vehicle's lights.

While the dual-battery electrical system is more complicated than a single-battery system, it uses the best features of the available batteries in order to achieve the best performance.

Regardless of what kind of system you have, it is vital to use the same or better batteries than they were recommended by the RV's manufacturer. If you are unsure, ask for a professional electrician/mechanic to help you choose the proper battery for your vehicle.

Lithium RV Batteries

SLA AGM, gel cell, and lead-flooded cells were common RV batteries that were slowly being phased out by lithium RV batteries.

Lithium-ion batteries come in many versions and chemistries, some of them are:

• IMR batteries feature LiMn₂0₄ (Lithium Manganese Oxide) chemistry. Their nominal voltage is 3.6 - 3.7 V per cell, with a maximum recommended charging voltage of 4.2 V. IMR batteries commonly have a smaller capacity but are capable of delivering larger currents.
• INR batteries feature LiNiMnCoO₂ (Lithium Manganese Nickel) chemistry. These batteries are very similar to IMR batteries since they can provide plenty of currents, with slightly lower capacity.
• IFR batteries feature LiFePO₄ (Lithium Iron Phosphate) chemistry. Their nominal voltage is 3.2 - 3.3 V per cell, with the maximum recommended charging voltage of 3.5 - 3.6 V.
• ICR batteries feature LiCoO₂ (Lithium Cobalt Oxide) chemistry. Their nominal voltage is 3.6 - 3.7 V per cell, with the maximum recommended charging voltage of 4.2 V. They commonly have higher capacities, but maximum allowed currents are often limited to just a few C.

Note: there are other chemistries on the market too, including hybrid technologies like Lithium Nickel Cobalt Oxide (LiNiCoO₂), Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO₂), etc.

The most popular lithium battery chemistry for large, deep-cycle batteries is Lithium Iron Phosphate (LiFePO₄) battery chemistry.

All lithium batteries, Lithium Iron Phosphate (LiFePO₄) batteries included, must have a built-in Battery Management System that monitors the battery, preventing unwanted events like high/low temperatures, high/low voltages, high charging/discharging currents, and similar.

That is why lithium deep cycle batteries are commonly used in dual-battery systems where the lead-acid battery is used only for cranking the engine, and lithium battery (or battery pack) is used for powering all other devices.

12V Lithium RV Batteries

The following comparison table lists some of the most common and reliable 12V lithium LiFePO₄ batteries suitable for RV applications:

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In order to speed up the transition from AGM and other lead-acid batteries, many lithium-ion batteries come with built-in electronics and are designed to be in-place replacements for lead-acid batteries - such lithium-ion batteries are designed to be used requiring no changes to the RV's electrical system.

Note: Lithium batteries MUST be recharged using lithium battery chargers or with advanced lead-acid battery chargers with dedicated lithium battery charging mode.

The main features of lithium batteries are their lightweight design (3-4x lighter when compared with lead-acid batteries), which leads to the reduction in the total weight of the vehicle and their higher number of charging/discharging cycles (4-6x times more charging/discharging cycles when compared with lead-acid batteries).

On the other hand, lithium batteries do cost more than lead-acid batteries, making their initial purchase more expensive. But thanks to their longevity, their actual price during the use of the vehicle is in the range of the price of lead-acid batteries.

Note: like lead-acid batteries, some lithium batteries are designed to be used as starting batteries, and other batteries are designed to be used for deep discharge/cycling operations.

In order to provide larger capacities and/or larger voltages, some lithium batteries are designed to be connected in parallel and/or series - lithium batteries may be connected in parallel and/or series only if explicitly allowed by their manufacturer.

12V lithium batteries that are allowed to be connected in series can be used to create 24V, 36V, and 48V battery packs. Larger voltages decrease the required current for the same power levels, increasing energy efficiency when the same cables and wires are used.

Or one can simply use 24V lithium batteries for 24V electric systems.

24V Lithium RV Batteries

The following comparison table lists some of the most popular 24V lithium batteries with their most important features and specifications:

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Some 24V lithium batteries are allowed to be connected in series in order to create 48V battery packs - two 24V batteries in series feature three times (3x) fewer cables than four 12V batteries connected in series to create a 48V battery pack.

However, if your RV uses a 36V system, you can either connect 12V batteries in series, or you can keep things simpler and just use 36V batteries.

36V Lithium RV Batteries

The following comparison table lists some of the most popular 36V lithium batteries with their most important features and specifications:

However, many newer RVs use 48V instead of 36V - higher voltage allows the transfer of more energy with less energy losses.

48V Lithium RV Batteries

The following comparison table lists some of the most popular 48V lithium batteries with their most important features and specifications:

Obviously, lithium batteries are developing rapidly and offer more and more features with every new generation of batteries on the market.

Note: 36V and 48V DC systems are not to play with, especially if the person is sweaty or wet, so be very careful around them.

Lead-Acid RV Batteries

Due to their weight, lead-acid batteries are mostly used as starting/cranking batteries.

But, for people who don't cycle their batteries often, it is perhaps still more cost-effective to buy deep-cycle lead-acid batteries instead of lightweight lithium batteries.

The following chart lists some of the most popular 8D deep cycle lead-acid and lithium RV batteries, with their most important features and specifications:

Unlike lithium batteries, lead-acid batteries can freely be connected in series/parallel as long as the same batteries of the same age from the same manufacturer are used.

Although the 8D batteries are designed as deep cycle batteries, some of them are nonetheless able to crank really large engines, especially when several of such batteries are connected in parallel.

But, when large deep cycle batteries are discharged, their ability to provide strong(er) currents is reduced. In many situations, having separate starting and house batteries is a better and safer option.

Dual battery RV electric systems feature dedicated starting batteries - due to their size, RVs very often use one or more car starting batteries, sometimes even larger BCI Group 31 batteries for cranking their engines.

Note: Amazon affiliate links in the table open in the new windows, feel free to check them for the most up-to-date offers and prices.

Due to their size, many dual-purpose group 31 batteries feature 800-900 Amps CCA rating, while some of the best group 31 batteries feature CCA rating above 1100 Amps ... and that is a lot of current ...

How to Take Care of Deep Cycle RV Batteries

Taking care of deep-cycle AGM (Absorbent Glass Mat) and deep-cycle LiFePO₄ (Lithium Iron Phosphate) RV batteries is essential to ensure their longevity and optimal performance.

Both types of batteries have unique characteristics and maintenance requirements that should be carefully followed.

Deep-Cycle AGM Battery Maintenance

• Regular Charging: AGM batteries should be kept fully charged whenever possible. Regularly check the battery voltage and ensure it remains within the recommended range, typically between 12.6V and 12.9V, when at rest. Avoid deep discharges below 50% capacity to prolong battery life.
• Clean Connections: Ensure that the battery terminals and connections are clean and free from corrosion. Use a mixture of baking soda and water to clean any corrosion, and apply a thin layer of petroleum jelly or terminal protectant spray to prevent future buildup.
• Proper Storage: When storing AGM batteries, especially during the off-season, make sure they are fully charged and stored in a cool, dry place. It's advisable to check the battery charge every month and recharge if necessary to prevent self-discharge and sulfation. Or, use good battery maintainers to keep the batteries fully charged all the time.

Deep-Cycle LiFePO₄ Battery Maintenance

• Balanced Charging: LiFePO₄ batteries require balanced charging to ensure all cells are equally charged. Use a charger specifically designed for LiFePO₄ batteries or a lead-acid battery charger with LiFePO4 battery charging mode. Avoid using AGM chargers since they can damage the Battery Management System (BMS) or even battery cells.
• Temperature Considerations: LiFePO₄ batteries perform best in moderate temperatures. Avoid exposing them to extreme heat or cold, as it can affect their performance and lifespan. When charging in colder temperatures, ensure the battery is within the manufacturer's recommended temperature range.
• Regular Use: Unlike some other battery types, LiFePO₄ batteries benefit from regular use. Keeping them in a partially charged state is better than leaving them fully charged for extended periods. This practice helps maintain the battery's health and efficiency.

Both AGM and LiFePO4 batteries are excellent choices for RV applications, offering reliable power and long lifespans when properly maintained - just be aware of their pros and cons.

For short: When replacing old RV batteries, check the compartment size, and type/size/brand of old battery/batteries. First of all, new batteries must fit into your battery compartment and must be as good as or better than old batteries.

Some vehicles use flooded-cell lead-acid batteries, but IMHO, AGM/gel cell batteries should be used - they are spillproof and almost maintenance-free.

Lithium batteries are a great alternative to lead-acid batteries, but they are still rather expensive. However, their much larger number of charging/discharging cycles means that, in the end, they are not as expensive as they look at first sight :)

Note: Before switching from lead-acid to lithium batteries, check with your RV manufacturer (send them an email) if that switch is recommended/supported.