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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 batteries are at the heart of your RV’s electrical system. Indeed, few things can operate without them – even if you’re plugged into shore power! Today, we’re talking about how to use solar power to keep your RV batteries charged and healthy with RV solar battery chargers, also known as RV solar systems. 

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. While RV solar systems can be intimidating, 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 proper battery charge, your fridge, furnace, lights, and any other electronics will not work. Since it is critical to keep batteries charged, 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 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, whic means keeping them charged and healthy even when you’re away from the RV. 

2. Portable Solar Panel Kits

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

3. Large RV Solar Systems

Large RV solar systems are complete with solar panels, charge controllers, wiring, and batteries that are integrated into your RV. Of course, like other solar systems, the large versions charge your batteries. However, they can also serve as primary power sources. Not for the novice, these complicated systems are built into the vehicle and require an understanding of electricity to install.  

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.  

Consequently, these 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.  

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.  

RV solar charger diagram

Solar Panels: Solar panels are what collect energy from the sun and convert it into electricity. There are 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 take a proper charge. The charge controller (per its name) controls the charge for the battery. These 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.         

The RV can use power as the batteries charge. Also, the batteries will store the solar charge for use at night or when there is not enough sun to power the RV, like on cloudy days. When a device that requires electricity is plugged into the batteries, the stored current is transferred to that device. The voltage in the battery drops as it’s used and the charge controller will know that it needs to recharge the battery using power from the sun.  

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.  It is very important to fully charge them each day. 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.    

Lithium Batteries

Lithium-based batteries are the newest technology for energy storage in an RV and have many 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.

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.  

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. 

Disadvantages / Considerations

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. Meaning, using a trickle charger in a dark garage won’t be possible (unless you have a long extension cord!). It also won’t charge your batteries overnight, or if it’s a cloudy or rainy day. 
  2. 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. 
  3. 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.


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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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