How to I set up storing solar energy in a spare car battery?

My girlfriend and I have just bought a camper van, and we would like to hook up some roll up solar panels to a spare car battery so we can store energy in it to use with small electrical appliances.

I have no idea about how this could be done, if it is even possible. I would be very grateful for any help on how I might achieve this.

Thanks for all your replies! 🙂

The plan is to use the other battery to run small electrical appliances, phone charger, music etc, not to charge the actual car battery. I should have made that clearer to start with, I apologise. But your replies are still all helpful! 🙂

I was thinking of using the roll up solar panels that are available, does anyone know where I could buy a kit online that would contain the right battery and other components that are necessary?

Thanks for all your help! 🙂


6 thoughts on “How to I set up storing solar energy in a spare car battery?”

  1. You can do this in many ways.

    You can use thin film modules or Flat panel modules.

    We use 2 100 watt modules mounted on top of a trailer. It is hooked to a C35 charge controller, It charges two deep cycle batteries that is hooked to a Mono wave 750 watt inverter. We use it to run the air compresser, Charge hand tool batteries, a radio and other items as needed.

    100 watt Solar modules can be found here.

    C35 charge controller

    Get your batteries from a local Trojan battery dealer for the best priceing. Or you can get some top of the line batteries here.

    Pick an inverter you like from here. I think you should get a Prosine model because it is Pure Sine Wave the 2000 watt and larget models will allow you to charge your batteries from a camp ground or any AC outlet if needed.

    Good luck

  2. Look at any major boat supply like West Marine. They have small flexible panels for this purpose. I used one for years on my sailboat. Easy to set up.

  3. i had one arco solar panel on the roof of my land rover already 15 years ago in Africa ,

    I had an extra battery to charge ,
    at night i could run the video and music until the battery was flat ,making sure that the car was parked with the panels facing the sun
    i had enough juice to start up after one hour of morning sun.

    So two extra car batteries would be better for appliances
    and two panels facing oposite directions and you will have plenty of power for TV,Radio,Tape,satnaff,computor

    the panels are wired to a voltage regulator straight onto the batteries wired in series.

  4. Martin you are starting with the wrong kind of battery. You really need a deep cycle battery for a solar panel system. A car battery is designed to give a high current over a short time and not to give a modest current over a long time. But it will work for a while.

    For a nominally 12 volt system you will need a solar panel that can put out about 16 -17 volts when new. After some use, the voltage drops, so you have to allow for that. The size of the panel you need will depend on the expected load. You will have to calculate the total current drawn by each appliance in amps and multiply by the number of hours you will be using it, then add all the products together.

    Since you can only get about 3/4 of the power out of a battery that you put in, the solar cells have to be able to supply the battery with about 1.4 or so times the amp hours of the demand. So If you take 10 amp hours every night, you need to put in 14 amp hours (or so) every day. This can be 1.4 amps over 10 hours or 2.8 amps over 5 hours. These are rough estimates, not to be taken as gospel, you understand.

    To avoid overcharging the battery, the solar cells must have some kind of regulator between them and the battery. This recognises when the battery is fully charged by it’s voltage and cuts the current from the cells to a trickle. Conversely, if the battery voltage is low, it allows more current in.

    A solar system is really only good with a camper van if you are going to stay in one place with no mains power for long periods of time. In those sorts of situations it’s best to think about alternatives to electricity like kerosene or gas lamps etc just in case you get cloudy weather which will reduce the output from the cells.

    You can set the battery up in the van with a line to the ordinary charging system which is perfectly capable of charging a deep cycle battery and running a small fridge during daytime driving.

    Such a system needs a diode arrangement to prevent the deep cycle battery attempting to start the engine and burning out its wiring. It may also need its own special voltage regulator. This sort of thing is easily installed by a car electrician and it may already be installed in a fitted out van.

    I have looked into this a while ago but never done it and I had a bit to do with solar cells in the late 1980s but not recently. You might check some of the 4WD and camper van sites for more details. Overland is one site I know of.

  5. I recommend that you purchase a kit designed for this purpose, unless you are very good at tinkering with electronics.

    I have seen kits designed for this purpose available for sale at some camping supply stores and truck stops.

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