I would like to setup a solar charged/battery storage system for an RV/small camper environment.

Initially with one solar panel, one matched battery pair; but also allow the battery(ies) to be charged from 120VAC and/or auto alternator when available. I expect to add additional batteries and solar panels matched appropriately.

I expect to use only 12VDC powered devices in the RV, so no need for an inverter. I do not expect to try to power lots of gear at once.

I see lots of solar/battery setups, but none seem to include recharging by 120VAC and auto alternator in addition to solar, nor 12VCD loads exclusively.

Are there any special requirements for wire sizes depending on run length from solar panel to batteries? to charge controller? etc?

  • Many products (such as Goal Zero or West Mountain) offer multiple charging options. Few seem to offer only one output (excepting some ham radio products), perhaps because many folks want USB or 120V for something or other. Frankly, you likely will too at some point, so you might rethink that one...
    – Jon Custer
    Aug 14, 2018 at 22:52
  • 2
    I feel this question would be more suited in electronics.stackexchange.com
    – Gabriel
    Aug 15, 2018 at 12:32

3 Answers 3


Charge controllers are your friend here.

A good charge controller will monitor the circuit such that the battery gets the appropriate charging current at all times. This allows you to set up all your charging circuits independently, each with its own charge controller hooked up to the battery, with the load circuit running through one of the charge controllers.

Running the load circuit out this way acts to prevent you from overdraining the battery, as that is another function the charge controllers have.


I have a setup like this in my VW campervan.

The vehicle was originally equipped with a charge controller that receives input from both the vehicle alternator and a 240V mains hookup and charges either the main or leisure battery as necessary.

I fitted solar panels - with their own charge controller. These were purchased from a closing down sale (Maplin) so I can't necessarily recommend the same make.

This charge controller is typical in that it connects directly to the leisure battery terminals. Thus sits in parallel with the other charge controller. In my case the solar panels are not permanently wired (at least not yet), they are connected only when the vehicle is stationary. The leisure battery happily charges from either charge controller and each charge controller is protected against reverse feeding current.

As to the wiring and fuse sizes, my solar panels came with specific instructions regarding these. I would suggest that all panels would do the same. Different panels have different current output and so would have different requirements.

For wiring length, all guides that I have seen just recommend keeping the length of wire from the panel to the controller as short as possible. This will minimise voltage drop.

  • I was unaware that I could connect two charge controllers to the battery setup. Nice information. thank you Aug 15, 2018 at 14:28

I bought a complete set, containing a foldable solar panel, the charge controller and the cabling from https://www.phaesun.com/ about 4 years ago for my boat. Setup was very easy: Connect solar panels to charge controller, connect charge controller to battery. The set even included a cable to directly connect it to the cigarette plug.

The connections from the engine alternator and the shore power supply to the battery are completely independent. The charge controller that was included contains a setting to tell it whether all discarge would also go trough the controller or not. In the later case (which applies in this setup), the battery level display on the controller is not as precise, but that's a minor issue.

The main problem I got with my set (and which could apply to others as well), is that the solar panel enclosure isn't waterproof. And since rain is nothing unusual in outdoor activities, always having to put it away in rain is not an option. The solar panels themselves are not the problem, but the wiring is - in my case - very susceptible to (salt)water. I already had to replace the wiring inside the normally closed panel enclosure several times. Copper wires just tend to desintegrate in humid environments.

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