RE: Onboard Charger
You can get a good 30 or 40 amp charger for less money than the biggest they
show (20 amp)
http://www.progressivedyn.com/power_converters.html
and with the 1315 separator get the same thing, first charge one battery,
then the other.
BTW there are competing products out there, the link I provided is to the
products I've been using and am familiar with.