RV solar and alternator charging can be used, but it does not work as simply or as well as users expect. It is complex on post-2014 vehicles.

A sunset - background picture.

How caravan and motorhome battery charging works

A caravan or motorhome battery charges by connecting it across it a source that has a voltage that is higher than that battery has at the time. That battery neither knows nor cares whether that charge is from one source or even several. Those sources must all be closely similar voltage. Ideally, they are identical. If not, the battery draws mostly from that with the highest voltage. Charging becomes complicated, however, once the battery/s approach full charge.

What happens then is that the controllers associated with each charging source mistake each other’s voltage for the battery. This may cause damaging overcharging. This is particularly so with AGM and LiFePO4 batteries. This applies also to simultaneous solar and generator charging. Do not attempt to do this yourself unless you know how. That is, however, is explained in our book Caravan & Motorhome Electrics.

Suitable controllers for caravan and motorhome battery charging.

Some controllers sold for both solar and alternator charging, monitor both solar and alternator input but do not combine them. They switch to whichever has the higher input at the time. Solar Books recommends RV solar users to do likewise. This is particularly so with most vehicles made since 2010 or so and virtually all since 2014. 

Our books, Solar That Really Works! and Caravan & Motorhome Electrics explain all.

You can now buy our books in digital and print formats. You can buy the digital version (right now) from this website. Just click on Bookshop

Our print editions can be bought from all the 50 plus branches of Jaycar Electronics in Australia and New Zealand, ordered from any bookshop or via email from booktopia.com