How to Hook Up Solar Panels to RV Batteries [NEW]

dr Drashco
dr Drashco Solar Panels

Today I'm going to show you how to hook up solar panels to RV batteries and build your first solar RV heating in less than two hours.

The are several ways how to hook up solar panels:

  • The first (and absolutely the best) option to connect the solar panel to a camper battery is through a 12-volt charge controller. The controller will take care not to overcharge the battery, and it will also make sure not to allow discharge or reverse current flow from the battery toward solar panel when there is no sun.
  • The second option is to connect solar panels directly to a battery using one diode per solar panel. Be careful, as this option does not provide overcharge control. Use it only in case when the total power capacity of hooked up solar panels is significantly lower than the battery capacity. That way, you can top-up the RV battery without overcharging it.

IMPORTANT: Before you decide to hook up a solar panel directly to a camper battery (without a charge controller), make sure your solar panel(s) came with an attached diode.

You might be asking: why is this important?

Well, a diode is a simple electronic component that allows electric current to flow only in one direction.

For example, if you directly connect solar panels to charge an RV battery without a diode, solar panels will charge a camper battery when there is enough sun.

However, during the night when there is no sun, the electric current will start to flow in the opposite direction - RV battery will begin supplying electricity to your solar panel!

Which will eventually drain the battery, and potentially damage the solar panel. By adding a diode into the solar charging circuit, you can easily prevent this unwanted behavior.

See also: What is a solar powered outlet?

12 volt RV Solar Heater

Maybe you are wondering why I would want to build a 12 volt RV heater?

Well, PV solar panels can only charge the camper battery but cannot provide RV heating when it is cold.

It might be a good idea to start with small RV DIY projects first.

RV solar panel

Especially if you're interested in building a portable 12volt RV heater or want to start with a large homemade solar project, but you have doubts regarding Solar Powered Heater efficiency.

You can quickly build a miniature prototype. With this down-scaled version of the solar heating unit, you can test the "proof of concept" and see how the system will perform in real conditions.

Besides demonstration purposes, a mini solar panel can preheat your RV cabin, car, or boat. You only need to bring the solar panel inside the vehicle, put it onto a windshield.

Have in mind to park the RV in the correct spot and direction, with the windshield facing the east side where the sun will come out in the morning. And there you have it, a simple but extremely efficient solar heating device for car, RV, truck or boat cabin!

Solar RV Heating DIY Project: Parts specification

  • 15 beer cans, preferably larger (0.5 liters)
  • Few cardboard boxes, preferably with thicker sides
  • Piece of glass, Lexan or plexiglass
  • 12 Volt Cooler fan recovered from an old PC power supply
  • 12 Volt DC plug to supply the fan (cooler), or
  • 12 Volt PV solar panel if you're going to preheat your car with automatic on/off function

Here is some cool picture of this unique, cheap, and simple sun collector for solar powered RV heater. All material and parts come from the re-used junk. Something that would most probably end up in the trash if there wasn't the opportunity to use all that to build our Do-It-Yourself solar panels.

solar panel for solar RV heating

It is an extraordinary feeling when you find out that your mini solar panel works! As you can see from the picture, this small solar thermal panel heated the air to 88ºC / 190ºF after barely half an hour under the sun! You can only imagine the amount of heating power produced by regular-sized solar thermal panels sitting in the sun all day.

People think that you have to live in southern or tropical areas to use solar energy and build DIY RV solar panels.

In fact, solar thermal panels work very well in southern parts and on an overcast day.
Usually, it is sufficient to have some sunlight or at least diffuse light.

Of course, more direct sunlight translates into more energy for harvesting by our RV solar panel...


Common FAQs

Can I connect solar panel directly to battery?

Connecting the solar panel directly to a car or RV battery may work, but it's not recommended. Without a charge controller or at least a diode, the difference in voltage between the 12 volts required for the battery and actual 20 volts being generated by the solar panel can result in more amps flowing into the battery.

How long does it take to charge a 12v battery with a solar panel?

Cca 8 hours - Depending on the battery's size and its state of charge, it will take between 6 to 8 hours to fully charge a 12-volt deep cycle battery with a 100-watt solar panel that can produce around 8 amps. For an efficient charge, you need to ensure that the panel is not partially shaded.

How long does it take a 100 watt solar panel to charge a battery?

Cca 8 hours - the 100-watt solar panel can produce around 8 amps of electric current. So 1 hour charges the battery by 8 amp-hours. Depending on the size of the battery and its state of charge, it will take between 6 to 8 hours to fully charge a 12-volt deep cycle battery with a 100-watt solar panel. For an efficient charge, make sure that the panel is oriented south and directly facing the sun.