i have a massive BMW battery that powers my sub pump and when i use the van mount ( it really is big, i will check the amp tomorrow for you all ), this is solar charged
then i have 2 smaller everyday car batteries for my cart, when 1 is on charge ( solar in the van ) the other is being used ) for a while now i have not put a battery on charge from electricity ( another green plus )
they are thrown out as them might not hold the charge for starting a car, but dont forget thats a hefty hit, we only slowly discharge them, if you charge every night ( or solar ) then they are ideal
some will not take or hold charge, when you find them, take them to the recycling center, no harm they were going to end up down there anyways