Deep Cycle Batteries for Solar: A Beginner’s Guide

Introduction to Deep Cycle Batteries

Embarking on an off-grid RV adventure is an exhilarating experience, made even more liberating with the addition of a solar power system. It offers you freedom from the constraints of traditional power sources and paves the way for sustainable and eco-friendly adventures.

However, the heart of any efficient RV solar power system lies in its batteries, and that’s where deep-cycle batteries come into play.

Deep cycle batteries are specifically designed to provide a steady amount of current over a long period, making them the ideal choice for your RV solar system. They are the powerhouse behind your solar setup, storing the energy harnessed by your solar panels and delivering it when you need it.

There are several types of deep-cycle batteries available, each with its own strengths and considerations. The most common ones include:

  • AGM (Absorbed Glass Mat) batteries,
  • Lithium-Iron Phosphate batteries (LiFeP04), and
  • Traditional Lead-Acid flooded batteries.

Choosing the right battery for your RV is crucial, as it directly impacts the efficiency and longevity of your solar power system.

In this guide, we will help demystify these battery types, enabling you to make an informed decision about the best fit for your solar-powered RV. We’ll delve into the pros and cons of each battery type, helping you understand their performance, maintenance needs, and cost implications.

Types of RV Solar Batteries and How They Work

Choosing the right type of battery is crucial for your RV solar system. The main types of batteries suitable for this purpose include flooded lead-acid, AGM (Absorbed Glass Mat), and lithium-iron phosphate deep cycle batteries. Each of these types has distinct characteristics, working principles, and suitability for various needs. Let’s delve into each of them:

Flooded Lead-Acid Batteries

Flooded Lead-acid batteries have been around for more than a century and are commonly used in a variety of applications, including RV solar systems. They work through a chemical reaction between lead plates and sulfuric acid, which produces electricity. As they discharge, the acid reacts with the lead plates to form lead sulphate. When recharging, the process is reversed.

These batteries are popular due to their affordability and reliability. They’re a solid choice for many RV owners, especially those on a budget or those who prefer a tried-and-true solution. However, they do require regular maintenance and have a shorter lifespan compared to AGM and lithium batteries. It’s important that they are stored on the outside of a vehicle, not inside.

AGM (Absorbed Glass Mat) Batteries

AGM batteries, a subtype of lead-acid batteries, are a more modern and sophisticated option. They operate through the same basic chemical process as lead-acid batteries. However, instead of having a freely flowing electrolyte solution, AGM batteries contain a thin fibreglass mat saturated with the electrolyte. This design makes them spill-proof and virtually maintenance-free.

AGM batteries are great for RV solar systems as they offer excellent performance and a longer lifespan than traditional lead-acid batteries. They are sealed and do not require topping up.

They handle high charge and discharge rates well, and they are less likely to be damaged by deep discharging. Although AGM batteries tend to be more expensive, their benefits often outweigh the cost in the long run.

Lithium-iron phosphate Deep Cycle Batteries

Lithium-iron phosphate deep cycle batteries, specifically Lithium-iron Phosphate (LiFePO4), are the newest and most advanced option for RV solar systems. They work through a different chemical process, involving lithium ions moving between positive and negative electrodes during charging and discharging.

These batteries are significantly lighter and more compact than both lead-acid and AGM batteries. They also have a remarkably longer lifespan, can handle deeper discharges without damage, and require no maintenance.

The primary downside is their initial cost, which is generally higher than the other options, and often other electrical equipment within the RV has to be modernized to accept the profile charge of lithium. However, given their longevity, increased efficiency and performance, they are a much more cost-effective solution over time.

In conclusion, the choice between a lead-acid, AGM, or lithium-iron phosphate deep-cycle battery will largely depend on your budget, the amount of maintenance you’re willing to do, and your power needs. By understanding the workings of each battery type, you can make an informed decision that best suits your RV solar system.

Choosing the Right Battery for Your Solar Needs

Choosing the right battery for your RV solar system is a crucial decision that requires careful consideration of several factors. It’s not just about picking the most advanced or expensive option; it’s about finding a balance between your power needs, budget, and maintenance capabilities. Here are some critical factors to consider:

Your Energy Consumption

The first step to choosing the right battery for your RV solar system is understanding your energy needs. This will be dependent on the type and number of appliances you use, as well as how frequently and how long you use them.

Once you have a good grasp of your daily energy consumption, you can choose a battery with the necessary capacity to meet your needs.

At Motorhome Solar, we understand that there’s no “one size fits all” solution when it comes to energy consumption. That’s why we offer a free energy assessment and recommendations tailored to your unique situation.

We take into account various factors like your current solar setup, the make and model of your vehicle, the number of people travelling, your off-grid duration, and the area lived in and travelled to.

We aim to provide enough power to keep your batteries as happy as we can for as long as we can.


Your budget plays a significant role in your choice of battery. Lead-acid batteries are the most affordable upfront but require regular maintenance and have a shorter lifespan. On the other hand, AGM batteries have a higher upfront cost but require less maintenance and typically last longer. Lithium-iron phosphate batteries are the most expensive initially but can offer the best value over time due to their long lifespan and superior performance.


If you’re not interested in regularly maintaining your batteries, then sealed options like AGM or lithium-iron phosphate batteries would be a better fit. These are virtually maintenance-free, unlike lead-acid batteries, which require regular topping up of the electrolyte levels and periodic equalization charges.


The lifespan of a battery is a significant factor to consider. Lithium-iron phosphate batteries last the longest, followed by AGM, and then lead-acid batteries. Choosing a battery with a longer lifespan may cost more upfront, but it could save you money in the long run as you won’t have to replace the batteries as frequently.

Size and Weight Constraints

The physical dimensions and weight of the battery are also important, especially in an RV where space is at a premium. Lithium-iron phosphate batteries are the lightest and most compact, making them a great choice if space and weight are key considerations.

Navigating the world of RV solar batteries can be daunting, especially with the assortment of specifications and terminologies. Let’s shed some light on the key terms and specifications, focusing on battery brands FullRiver, ALLiON, and RELiON batteries.

Deep Cycle Battery:

A deep cycle battery, like the FullRiver AGM battery, is designed to provide sustained power over a long period. It can be repeatedly discharged and recharged (or cycled) to a high degree without damaging the battery’s performance. Hence, a deep cycle battery is an excellent choice for RV solar systems, delivering reliable power for your off-grid adventures.

AGM Battery:

AGM stands for Absorbed Glass Mat. It’s a type of sealed lead-acid battery that offers superior performance and longevity compared to traditional lead-acid batteries. In an AGM battery, the electrolyte is absorbed into a mat of fine glass fibers, making it spill-proof and maintenance-free. For instance, AGM batteries are known for their exceptional durability and resistance to vibration, making them a suitable choice for rugged RV travels.

Lithium Deep Cycle Battery:

Lithium deep cycle batteries, like those from RELiON, are the gold standard in RV solar batteries. They offer a superior cycle life, high energy density, and excellent charge efficiency. Despite a higher upfront cost, a lithium deep cycle battery offers the best long-term value for your RV solar system.

Ampere Hours (Ah):

Ampere hours, commonly seen as ‘100Ah deep cycle battery’ or ’12V 100Ah AGM deep cycle battery,’ is a measure of the battery’s capacity. It tells you how much electric charge the battery can deliver over time. For example, a 100Ah battery can deliver 5 amps for 20 hours. Understanding amp hours helps you estimate the battery’s ability to power your RV appliances for your desired period.

Battery Charger:

Proper charging is crucial to maintain an AGM battery’s health and longevity. An AGM battery charger is designed to deliver the right charging profile, ensuring the battery is charged safely and efficiently. Lithium-iron phosphate requires a charger that will turn completely off and goes into storage mode, which is also a healthy choice for an AGM.

Battery Voltage:

Battery voltage, like ’12V deep cycle battery’ or ’12V flooded deep cycle battery,’ indicates the electric potential difference within the battery. A higher voltage doesn’t necessarily mean more power, but it allows the electrical current to be carried more efficiently over long distances.

Internal Resistance:

Internal resistance in AGM batteries impacts their efficiency and lifespan. A lower internal resistance, like in a FullRiver AGM battery, means less energy is lost as heat, leading to better battery performance.

Get in touch with us today to maximise your RV solar power system.

We’ll help you find the perfect battery for your needs, so you can enjoy off-grid adventures with confidence.

Why You Need To Maintain Your Batteries

Maintaining your RV solar batteries is essential for ensuring optimal performance and lifespan. Neglecting your battery’s maintenance leads to reduced capacity, shorter lifespan, and even battery failure. Given that the battery is the most expensive part of the solar system, it just makes sense to follow a few simple maintenance tips to keep your batteries in good condition and avoid having to buy new ones.

AGM Battery Charging Procedure

Charging an AGM battery correctly is crucial to its performance and longevity. Here are some general steps to follow:

Initiate Bulk Charge:

The first step in the AGM battery charging process is the bulk charge, where the charger delivers a constant current to the battery. Typically, this stage recovers about 80% of the battery’s capacity.

Absorption Charge:

Once the voltage reaches a predetermined level, the charger switches to an absorption mode, reducing the current while maintaining a constant voltage. This stage fills up the remaining 20% of the battery’s capacity.

Float Charge:

In the final float stage, the charger maintains a lower voltage to prevent overcharging, while compensating for the battery’s self-discharge.

Remember, an AGM battery charger is designed to deliver the correct charging profile for AGM batteries. Using a non-AGM charger could potentially damage your battery.

Charging AGM Batteries with an Alternator

Charging your AGM battery with an alternator is a common practice when on the move. However, it’s essential to ensure that your alternator can deliver the correct charging voltage for your AGM battery.

Most AGM batteries prefer a charging voltage in the range of 14.4 to 14.6 volts from the alternator. We recommend checking with your battery manufacturer for specific guidelines.

Understanding Depth of Discharge (DoD)

Depth of Discharge refers to how much of a battery’s capacity has been used. Different batteries can handle different DoDs. For instance, a typical AGM battery should only be discharged to about 20% of its capacity, meaning 80% of its capacity remains unused (12.4V maximum discharge).

However, not all AGM batteries are the same. FullRiver batteries, for instance, can handle a higher DoD of up to 50% (12.1V maximum discharge). This means you can use more of the FullRiver battery’s capacity without negatively impacting its longevity.

Understanding your battery’s DoD is vital in managing its use and extending its lifespan.
Remember, proper usage/maintenance of your RV batteries ensures their optimal performance and longevity, allowing you to enjoy your off-grid adventures without worrying about power shortages.

Recommended Battery Brands for Your RV

Trusted battery brands for your RV Solar Battery

Long-Lasting Battery Solutions for Your Motorhome Solar System

The Top Battery Brands We Recommend

When it comes to powering your RV, you need a reliable, durable solution that suits your specific needs. For this reason, we recommend considering three superior brands known for their quality and performance:

  • FullRiver,
  • ALLiON, and
  • RELiON.

FullRiver, ALLiON, and RELiON are all premium quality battery brands that are ideal for applications requiring sealed batteries, with a proven track record for heavy-duty cycling capabilities or power supply.

Fullriver batteries are designed to be charged and recharged hundreds of times and range from a true deep cycle battery to a battery with better starting performance.

Renowned for their quality, FullRiver offers AGM deep-cycle batteries designed for consistent, reliable power.

A standout feature of FullRiver batteries is their ability to handle a higher Depth of Discharge (DoD) than many AGM options.

With FullRiver, you can utilise up to 50% of the battery’s capacity without impacting its longevity – perfect for long off-grid adventures.

ALLiON provides high-quality deep cycle batteries, celebrated for their sturdy construction and reliable performance.

With consistent power output, ALLiON batteries are an ideal choice for powering your RV’s various systems and appliances.

They can be discharged 100% of their capacity. Boasting 4000 cycles at 50% DoD. Most of the Allion range also offer Bluetooth monitoring.

ALLiON’s Lithium Iron Phosphate (LiFePO4) cells, compared to other lithium technologies, provide superior thermal and chemical stability.

For a more advanced solution, consider RELiON’s high-performance lithium deep-cycle batteries. Known for their lightweight design, high energy density, and long lifespan, RELiON batteries offer a modern, efficient power option for your RV.  Boasting 13,000 cycles at 50% DoD

Each of these brands offers unique advantages, but all are committed to quality, reliability, and performance. When choosing the right battery, consider your energy needs, the frequency of your off-grid travels, and the specifics of your RV setup.

RELiON batteries are designed to provide reliable power for renewable energy applications.

Don't let limited battery capacity hold you back on your off-grid adventures

Contact us today for expert guidance on choosing the right RV solar battery, and explore our range of trusted battery brands and comprehensive guides to find the perfect fit for your rig.

How Does Victron Energy Fit In?

At Motorhome Solar, we prefer to use Victron power products to maintain your RV solar batteries. Victron is the frontrunner in terms of quality and technology. They offer a range of accessories that can help you monitor and maintain your batteries, including battery monitors, charge controllers, and inverters.

Victron Energy inverters allow you to convert DC power from your batteries into AC power for your  domestic appliances. This can help you get the most out of your batteries by enabling you to use your appliances more efficiently.

Victron Energy Logo

Maintaining your RV solar batteries is essential for ensuring optimal performance and lifespan.

By following a few simple procedures and using Victron Energy power products, you can keep your batteries in good condition and avoid costly replacements.

Let’s Talk Solar Battery Capacity

The capacity of an RV solar battery refers to the amount of energy it can store. It is measured in ampere-hours (Ah), which represents the number of amps a battery can supply over time.

For example a 100Ah battery can deliver 5 amps for 20 hours. We use 20 hours as most batteries use a 20 hour rating method.

Determining the Right Battery Capacity for Your Motorhome

Selecting the right battery capacity for your RV is crucial for ensuring that your solar system meets your power needs while off-grid. The capacity required will depend on various factors, such as the size of the vehicle, the number of appliances and devices used, and the length of time spent off-grid.

To calculate the battery capacity required, you will need to determine how much power you will need each day. This can be done by adding up the power consumption of all the appliances and devices you plan to use, and multiplying this by the number of hours you plan to use them.

For example, if you plan to use a 12V fridge that consumes 4 amps per hour for 8 hours per day, you will need a battery capacity of at least 32Ah (4 amps x 8 hours).

Understanding your power needs is critical when selecting the right battery capacity for your RV. Battery capacity is measured in Ampere-hours (Ah), representing the amount of current a battery can supply over a given period. Let’s walk through how to estimate the right battery capacity for your motorhome, with references to capacities like ‘100Ah deep cycle battery’ and ‘105Ah deep cycle battery’.

Estimate Your Daily Power Consumption

Start by listing all the electrical appliances in your RV and their power ratings (in watts). Consider everything from your lights and refrigerator to your phone charger and entertainment system.

Calculate Ampere-Hours (Ah) Usage

To convert your total daily power consumption from watts to Ah (which batteries use), divide your total wattage by your system’s voltage (usually 12V for RVs).

Consider Battery DoD

Remember that different battery types have different recommended Depths of Discharge (DoD). For example, an AGM battery from FullRiver can handle a 50% DoD, while others may only recommend a 20% DoD. This means you’ll need a larger capacity to ensure you’re not discharging your battery beyond the recommended DoD.

Choose Your Battery

Based on your calculations and considerations, you can now choose your battery. If your daily consumption is around 50Ah daily and you’re opting for an AGM battery with a 50% DoD, a 100Ah deep cycle battery might be suitable. For slightly higher consumption, a 105Ah deep cycle battery could be a better fit.

While these steps provide a general guide, determining the right battery capacity involves many variables, including your unique usage patterns and the specific energy requirements of your appliances.

For an accurate assessment tailored to your needs, consider Motorhome Solar’s free energy audit. Our experts can help ensure you’re getting the right battery capacity to meet your needs without straining your battery or leaving you without power.

The Importance of Accurate Energy Assessments: Navigating the Solar Landscape with Confidence


As a leader in New Zealand’s solar industry, Motorhome Solar has seen firsthand the issues and expense that can arise from ‘cowboy’ quotes. These quotes often overlook the specifics of your RV setup, resulting in improperly installed systems that need costly repairs.

That’s why we offer free energy audits. We aim to arm you with the knowledge you need to confidently navigate the solar landscape. Our audit provides a personalised understanding of your RV’s power needs, helping you avoid potential pitfalls and expensive oversights.

Whether you opt for us to carry out the installation or not, our primary goal is to ensure you’re well-informed and prepared. Contact us to book your free energy audit. With the right knowledge, you can ensure your journey into solar is a safe, efficient, and rewarding one.

Battery Capacity Calculation Examples

Scenario 1:

Small RV with Basic Appliances

Suppose you have a small RV with basic appliances like a 3-way gas fridge, LED lights, and a water pump. In that case, you may only need a battery capacity of around 100Ah. This will allow you to power your appliances.

Scenario 2:

Large RV with High Power Demands

Suppose you have a larger RV with high power demands, such as a microwave, and multiple TVs. In that case, you will need a much larger battery capacity. A battery capacity of 400Ah or more may be required to meet your power needs.

Scenario 3:

Weekend Getaway

Even if you are in the weekend getaway mode. It is important that your battery bank is suited to your needs so you can enjoy your getaway without worrying about running out of energy. For example, a battery capacity of 200Ah may be sufficient for powering basic appliances for a weekend.

It’s important to note that these are just examples. Your power needs may vary depending on your specific RV setup and usage patterns.

Common Questions About RV Solar Batteries

As you navigate the world of deep cycle batteries for RV solar, you might encounter some recurring questions. Here, we’ll address a few common queries to help clarify your understanding. Remember, always consult with professionals when dealing with your solar system’s installation or significant changes to avoid safety hazards.

Should I upgrade to
Lithium-iron Phosphate?

Given their numerous advantages, you might be wondering if it’s worth upgrading to lithium-iron phosphate batteries. In many cases, the answer is yes. If you live in, or frequently use your RV, especially for extended off-grid adventures, the superior efficiency, lifespan, and maintenance-free nature of lithium batteries can be a game-changer. However, if your usage is minimal or you’re on a tight budget, AGM or even lead-acid batteries might suffice.

Ultimately, the right battery for your RV solar system is the one that meets your specific needs and circumstances. Weigh these considerations carefully to make the best choice for your off-grid adventures.

Can I replace an AGM battery with a lead-acid battery in my RV?

Yes, technically, you can replace an AGM battery with a flooded lead-acid battery as they both use similar technology. However, it’s essential to note that there are significant differences between the two.

AGM batteries are sealed, maintenance-free, and generally safer for use inside a motorhome, while flooded lead-acid batteries require regular maintenance, including topping up with distilled water. They also vent gases, which can be hazardous if the battery is installed inside your RV.

Therefore, we generally recommend sticking with AGM or switching to lithium batteries for most RV applications.

How do I hook up solar panels to my RV batteries?

Connecting solar panels to your RV batteries involves a process that, although not overly complex, should be carried out with caution.

The panels typically connect to a charge controller, which regulates the power going into the battery. The charge controller then connects to the battery itself.

While we can’t provide a detailed step-by-step guide due to safety considerations, we highly recommend seeking professional help for this process. Incorrect installation can result in poor system performance and potential safety risks.

Looking to maximise your RV solar power system and prolong your battery's lifespan?

Contact us today for personalised advice and support, and find the perfect battery brand, capacity, and maintenance plan to match your needs and usage patterns.

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Talk To Us

We can help. Our advice is freely available, with no obligation from you. Book your free assessment today.

We’re committed to helping you find the right RV solar battery for your needs and providing you with the knowledge and support to enjoy off-grid adventures with confidence.

At Motorhome Solar, we offer a range of battery capacities to suit different RV setups and usage patterns, so you can find the correct battery for your needs.

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