I found his battery desulfater and it explains how it works. It got me to thinking that with all the stuff we work on this forum it would be easy to make a battery chrager that does not need to be plugged in. Just hook it to the battery to charge it. it could draw a small current from the battery to trigger a radiant spike that then is pulsed int oth battery to charge it. thi battery desulfater already does that to some degree and maybe with a little modification or increase in robustness it could work as a chrager as well as a desulfator. then if you have a bank of batteries you just have one of these boxes sitting on top of each battery and it continuosly charges them. Just an idea ,I don't have the circuit design skill to actually do it but maybe some of you do.

battery desulphater