The Three Parts of a Motorhome Solar Battery Charging System

The solar PV module

The panel is the part everyone specifies first, and the part that gets the most attention. In this range that means a module between 5 W and 45 W, in 12 V or 24 V nominal, multicrystalline or monocrystalline, with full electrical data published — open circuit voltage, short circuit current, optimum operating voltage and current.

The solar charge controller or regulator

The regulator is there to prevent damage to the battery from over-charging. It used to be thought that you did not need a regulator, and if the capacity of the battery is large compared with the output of the solar PV modules you may not need one. On any installation you intend to leave unattended, fit one.

The battery

In a solar system you will always need a battery. The panel produces when the sun is on it; the loads are there when they are there. The battery is what reconciles the two. Anything advertised as solar powered and needing no battery is only useful in bright sunlight.

Sizing the three together

Check the module's open circuit voltage against the controller's maximum input rating — 22.1 V on the BSM045P, 41.3 V on the 24 V BSM020P-N. Check the short circuit current against the controller's rating and your fusing. The mono modules publish a series fuse rating directly: 10 A on the BSM020M and 12 A on the BSM030M.