But when you went to start your van and leave the campsite, the Hella
> relay/fuse will make sure that the aux battery recharged at a controlled
> rate of about 15 amps,

Ron,
It does no such thing. The only job the relay does is to connect the two
batteries when the ignition is on. The only thing the 15 amp fuse does is to
allow the connection to continue as long as the amperage is below 15
amps.... it does not assure a controlled 15 amp rate of charging... Read the
post again... it is the wire size that controls the rate of charge...  In
fact, one of the limitations of the Hella Kit is that the small wiring
basically restricts the charging rate to something like 8 or 10 amps. Which
means it will take 8 or 10 or 12 hours (or running the engine) to charge a
65 amp hour battery rather than say 3 or 4 hours with a system that uses a
larger wire size.

rather than dumping a ton of amperage into the now > nearly dead battery
(which, as Beckett points out, is a good thing

Good thing if you like to take more time rather than less time to charge
your battery ...

The Optima will take a fast charge. Perhaps some others won't.... check your
battery specifications.

Bill