Here is how i charge my batteries when the sun is not shining. this is a 12hp motor attached to a modified electric motor, which has 3 phase rectifier attached to make DC from AC. it has n50 permanent magnets in it. i bought it on eBay.
the DC current is fed directly into the outback charger where the solar dc goes into it, this is how i regulate the voltage. these outback charger controllers do an excellent job of controlling the charge on the batteries . i love my outback.