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The Beginner’s Complete Guide to RV Solar Battery Chargers

The Beginner’s Complete Guide to RV Solar Battery Chargers

 RV solar battery chargers are a great way to power your recreational vehicle’s electrical system while on the go. These systems rely on a combination of components to convert the sun’s energy into usable electricity. In this article, we will discuss the different components of an RV solar system and how they work together to provide you with reliable energy. From the solar panels that capture the sun’s energy to the charge controllers that regulate the flow of electricity, we will explore each component in detail and explain how they fit into the overall system.

I am an electrical engineer, RV Tech, and solar installer. I have written this article to cover the basics of RV solar battery charging systems. Whether you’re a seasoned RVer or just considering adding solar to your RV, this article will provide you with the knowledge you need to make informed decisions about your solar setup.

What Is an RV Solar Battery Charger?

An RV solar battery charger is a system that charges your RV batteries with solar power. In fact, this refers to practically any RV solar system you hear about. At their core, every single system has one basic function: to charge your RV batteries.

Unless you plug into a power source (i.e. shore power or generator), your RV batteries supply all the power to your RV. Without a battery charger, your fridge, furnace, lights, and any other electronics will not work. All RVs have chargers that run when plugged into shore power or run a generator. When disconnected from shore power, many people seek to utilize the sun’s energy to charge their RV batteries practically anywhere. 

Of course, RV solar systems can come in a variety of sizes, created for specific uses. There are three primary ways you can set up such a solar battery-charging system:

1. RV Solar Battery Tenders

Have you ever got to your RV (or car) after it sat for a long time and the battery was dead? For vehicles sitting outside, the sun is an amazing source of energy that anyone can harness to help make batteries last longer. RV solar battery tenders “tend” your batteries, which means keeping them charged and healthy even when you’re away from the RV.  These systems do not provide enough power for running appliances, just enough to keep the battery from draining when not in use.

2. Portable Solar Panel Kits

You can hook up your RV batteries to a Portable Solar Panel kit to charge. Portable solar panel kits are commonly sized in the 50-200 watt range. These kits can meet basic electrical needs. These are all-in-one solutions that do not require any special installation or knowledge.

3. Large RV Solar Systems

Large RV solar systems rely on a combination of solar panels, charge controllers, batteries, and inverters installed in the RV to convert the sun’s energy into usable electricity. Of course, like other solar systems, the large versions still charge your batteries. However, they can also serve as primary power sources. Large systems are not for the novice and are built into the vehicle. Its required to have an understanding of electricity to safely install a larger RV solar power system.  Its is possible, however to learn what’s required to know to safely install a system yourself. Here on our website, we have many articles covering these types of systems including some examples.

What Can RV Solar Battery Chargers Do?

Depending on the type of RV solar battery charger system you go with, you can achieve several different results. Moreover, your end goal will vary based on your RVing style and power needs and will help determine which system you’ll need.

Trickle Charge: 10-50 Watt Chargers

Ordinarily, batteries discharge a bit, even without usage. A battery charger can be used to trickle charge, topping off the battery at a small rate to make sure the battery is kept full.  Depending on the battery type, if it is discharged too deeply, it can significantly damage it and lessen its life.  All three types of solar chargers mentioned above can trickle charge batteries. This keeps them healthy and lasting as long as possible when you’re not using the RV.

Provide Power for Light Use: 50-100 Watt Chargers

With a small solar battery charger, you can expect to use the battery lightly while the solar makes up the power you use, keeping the battery full. For example, solar does not work at night. So, the battery will provide you with power overnight and then the solar system will charge the battery back up the next day.  “Light use” means powering energy-efficient lights, charging a cell phone or camera batteries, and running small electronics. Portable solar panels or a small system are great for this application. Unfortunately, TVs or computers can not be run on these systems and require a generator for use.     

Medium Power Use: 100-600 Watt Chargers

With medium-sized RV solar battery charger systems, you can expect to run your RV’s lights and DC appliances, like the furnace, water heater, and fridge. You can even run a smaller inverter for some light AC applications, like running a computer or TV.  Often, these systems are paired with a generator but will significantly lessen generator runtime.      

Power Everything: 600 – 4000 Watt chargers

Unlike the previous systems, this one includes running an inverter, which converts the power to AC. Like in your home, you can run computers, TVs and other high-power appliances.  The limit to how much you can power is based on the size of the RV’s roof, the space and weight limits of the RV, as well as cost restrictions. With a large enough system, it’s possible to even run the air conditioner or charge an electric car. Generators are also rarely needed with a well-designed large solar system, as the solar makes up most of the energy needs.   

These large systems are very useful when camping away from electrical providers. They give you enough energy to boondock in the wilderness or stealth camp in the city without the need for a generator.  If you are trying to figure out how much solar power you need, we put together a detailed article and calculator to help you determine the right amount of solar, so you don’t waste money.

How Do RV Solar Battery Chargers Work?

All RV solar systems are off-grid RV solar chargers. This means their primary function is to charge a battery. Furthermore, solar battery chargers consist of a minimum of two parts, the solar panels, and a solar charge controller.  Solar panels collect power, and the charge controller modulates the power to properly charge the battery.

RV solar charger diagram

Solar Panels: Solar panels are what collect energy from the sun and convert it into electricity. There are a few different types of solar panels, but most are made of silicon crystals encased in glass. Additionally, it is possible to get flexible or foldable solar panels for portability.    

Solar Charge Controller: Once the solar panels have generated electricity, the electricity needs to be converted into something the battery can accept.  Batteries require a very specific voltage and current to properly charge. The charge controller (per its name) controls the charge for the battery, prevent overcharging, and maintains battery health. 

Charge controllers can be independent units (in larger systems) or are sometimes built directly into the solar panels (in small, portable setups).  The charge controllers will also stop charging the batteries when they are full to prevent damage.         

This is a single-charge controller in a large RV solar system

The RV can use power directly from the charge controller and the battery at the same time. Also, the batteries will store additional solar charge for use at night or when there is not enough sun to power the RV, like on cloudy days.

Charge controllers watch both the voltage of the batteries and solar panels to match the power. If the battery is full, it will sense when you are using the battery and provide the power from the solar, so the battery does not drain.

There are a few different types of solar charge controllers and lots more to learn about them, so I highly suggest you dive into these components in our article all about RV solar charge controllers.

RV Battery Type Considerations

Since we now know that RV solar systems are all battery chargers, let’s take a look at the different types of batteries that can be used in RV’s. 

Lead-Acid Batteries

For the longest time, lead-acid batteries were the only feasible energy storage device for cars and RV’s. These batteries use a chemical reaction between an acid electrolyte and metal (lead) to store and release electrons to be used. There are two main subsets of these types of batteries: flooded and AGM. Let’s briefly take a look at these two types. 

Flooded Lead-Acid: These are the most common type of batteries and are what most cars use to start their engines. To make sure their electrolyte is kept full, flooded lead-acid batteries need to be maintained regularly. Additionally, they release corrosive and flammable gasses when charging and need to be kept in ventilated spaces where you will not breathe the fumes.  

AGM (Absorbed Glass Mat): AGM are lead-acid batteries with the added benefit of not needing any maintenance. What’s more, they do not release toxic gases, so AGM can be installed in enclosed spaces or in living quarters.  However, they are more expensive than flooded lead-acid batteries.  

Generally, lead-acid batteries are relatively cheap but have very specific charging needs to keep them healthy.  With regular use, a set of lead-acid batteries will last around 1-3 years for most RVers.  One very important thing to note about lead-acid batteries is you can only discharge them partially each time you use them. Otherwise, they get damaged from deep discharges.  It is also very important to charge them each day fully. Unfortunately, this frequently does not happen with a solar charger, so a generator may need to be used. Flooded cells also need regular equalization that boosts the voltage to balance out the cells.    

Overall I never recommend using lead acid batteries with solar systems because they are not a good match for solar generation compared to lithium batteries.

Lithium Batteries

Lithium-based batteries are the newest technology for energy storage in an RV and have major benefits over lead-acid. These batteries will typically last 5 to 10 times longer than lead-acid and can store about 4 times more power for the same amount of weight.  Equally important, they do not have rigorous charging requirements, can be discharged as low as needed, and do not need to be recharged every day. 

These are by far the best type of batteries for use in a solar charger system. However, they cost more upfront. Luckily, one lithium battery can usually replace 4 lead acids, and will last much much longer! These batteries will cost less and save you headaches in the long run.  We recommend Battle Born Batteries for their high quality and excellent customer service.

PRO TIP – Read why we have chosen Battle Born Batteries for our RV’s 3 times in a row in our article about the real reason we used Battle Born batteries.

Battery Energy Ratings: Deep cycle batteries for RVs are rated in amp hours for capacity.  This rating is based on how many amps the battery should be able to discharge in one hour.  However, comparing battery capacity is not apples to apples. This is because a lithium battery can provide all of its power, while a lead-acid will only give you 50-60% of its rating if you stop discharging them sooner to prolong their life.  

What Are Advantages of an RV Solar Battery Charger

There are many advantages to having an RV solar battery charger and taking free energy from the sun. 

  1. RV solar battery chargers work just about everywhere there is sunlight!
  2. They can help to provide power in places where standard electricity isn’t readily available.
  3. They help to protect lead-acid and AGM batteries by topping off the voltage. These types of batteries will self-discharge, even without use, and need to have a charger on them for longevity. A dead battery is particularly bad in cold weather as dead lead-acid batteries can freeze up and be destroyed. Likewise, lithium batteries should be stored with a good charge when it’s cold.  
  4. Many are very lightweight and can be carried anywhere. Some small setups have a panel that can even be strapped to a backpack, so you can use your solar battery charger to provide power away from the RV, too.
  5. If camping without hookups, RV solar battery chargers provide silent power, versus the sound of a generator. 
Learn more about flexible solar panels like this in our article about them

What Are the Disadvantages To RV Solar Chargers

As with any system, there can be some drawbacks and limitations. Here are some considerations to keep in mind when thinking of getting an RV solar battery charger:

  1. They must have sunlight to work. Using a trickle charger in a garage won’t be possible (unless you have a long extension cord!).
  2. Solar won’t charge your batteries overnight or if it’s a cloudy or rainy day. Climate and time of year have a big effect on solar charging.
  3. RV Solar battery chargers can be expensive, depending on what size you go with. They also cost more when compared to a plug-in battery charger. 
  4. The smaller chargers can be slow to charge your batteries. However, large solar systems can be faster.

Get Started With RV Solar Battery Charging

Personally, we are big fans of utilizing solar energy to power our adventures and lifestyle. We hope you’re now more comfortable taking some steps into the world of RV solar battery charging. 

If you’re interested in charging your smaller electronic devices with portable solar panels, check out our Portable Solar Panels blog for more information on this option.

Last but not least, you may want to look into our Ultimate Off-Grid Solar System article. Or, watch this YouTube video, especially if you are interested in building a large RV solar system to enjoy off-grid boondocking and run everything in your rig.


Start Your Solar Journey!

Thinking about adding solar to your RV? Start here with our solar calculator to get an idea of what might be right for you!

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Tom & Caitlin Morton of Mortons on the Move gave up the stationary life for one where they are constantly on the move. They are full-time travelers, television hosts, and digital media producers.
They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
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Alan

Thursday 24th of March 2022

I have an E-Pro Trailer with a Solar Panel. It was stored over the winter without a cover. It is the first year I had it. Now the batteries are dead. Is it best to disconnect and store the batteries in my garage during winter months? I live in Colorado, if that makes any difference.

Mortons on the Move

Friday 15th of April 2022

Its always best to store batteries with a trickle charger on them, particularly in cold climates. If they discharge all the way they can actually freeze but not if kept charged. If needed pulling them and keeping them in the garage with a battery tender on them is best practice. If that is not possible, at least fully charging them and fully disconnecting them (lift the negative terminal) will usually be ok for up to six months. More than that without charge and they can still get damage.

Mark2459

Saturday 24th of April 2021

I was excited at your comment that "one lithium battery can usually replace 4 lead-acids" but I also realize that I need some cryptic math to understand if that will work meet or needs, based on our usage. We don't boondock a lot, but we occasionally have two consecutive days of driving and an overnight without access to shore power. So the needs are pretty basic, keep the residential fridge functioning and run the CPAPs at night. Does someone have a spreadsheet where we can input the devices, and their usage so we can see determine battery needs so we can start designing a system? Is there a service that does this?

Mortons on the Move

Sunday 25th of April 2021

Because appliances vary so much in their power needs there is no good estimating tool that I know of that will get you close. If you take a look at our how much solar article we have a section about power measurement. https://www.mortonsonthemove.com/how-much-solar-power-do-you-need/ My best recommendation is to install a battery monitor and get actual power usage from your appliances.

Jeff Ireland

Saturday 30th of January 2021

I have purchased Renogy 100 watt flexible panels for a good price from a local classified. I have hopes of a new rv in the future but currently have a 24.5 Arctic Fox 5th wheel. Looking for your recommendation on a solar charger/controller. Eventually for a medium size system in the end with lithium batteries. Thank you in advance Jeff Ireland

Mortons on the Move

Sunday 31st of January 2021

I would most recommend any programmable MPPT unit. My favorite is the Victron 50A MPPT smart solar. Its more expensive but super easy to program and will work with a larger system and many different battery types.https://amzn.to/3crTUFu

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