PV battery connection
If you are not worried about efficiency or the life of the batteries, a buck regulator with a decent size capacitor on the PV side would do. Set to 13.8V to float charge the batteries.

Bare in mind that lead acid batteries can deliver 100's of amps, so are a potential fire hazard when things go wrong if not suitably fused.

To do it properly, find a commercial maximum power point tracking (MPPT) solar controller