Sorry for the delay in getting back to you. It's snowbird season here in SW FL and I've been putting in 12+ hour days. There are several brands of charge rate monitors that are 'smart chargers' for use with a solar system. I'll check into them as soon as I have a minute and get back to you. BTW, one way to avoid the maintenance issue on your batteries is to go AGM. A bank of 4, 6-volt golf cart AGM's connected in series/parallel will way out perform a similar sized pair of 12 volt
batteries, and you can even discharge them to 80% depth once in a while. That would kill an ordinary battery. PM me if you like.