My solar contributes to the alternator's amps up until the house batteries reach 14.5.
My solar is programmed to hold 14.5 for 90 minutes, yet my vehicles voltage regulator likes to prematurely drop back to 13.7.
After the vehicles voltage regulator decides 13.7 is plenty, and if the solar has not seen 90 minutes at 14.5, then the solar then contributes again, and several times I have seen the solar actually powering a portion of the vehicles electrical demands.
But in general it makes little difference. I like quenching my depleted house batteries with 60+ alternator amps in the morning, even if short lived. They seem to like it.
This time of year I often don't even bother bringing the alternator into the house battery loop.
I like how quickly my engine starts when 3 batteries are cranking the starter, but I don't want the fridge compressor to be running when I crank the starter with assist from the house batteries. With my manual switch, I feel safer just leaving the 2 banks separate.
