Ryno:Ideally it should be wired to charge off of the towing vehicle.
I have had exactly zero luck doing this. It always shorts on one side or the other and it inevitability causes an entire rewire of the trailer.
My battery charger has a few settings - one of them is a small/gel setting. I've used that with no problems.
Rob Leone
'07 Solstice GXP in AS
'87 Toyota Corolla in EP
ex - '91 MR2 Turbo in SM2 <- If you can't set a good example, serve as a horrible warning.