[T2] Aux Battery

[MUTS]

I have a class B Roadtrek- they use an isolator that sends current only 
after starting and when alternator is running current through 50 amp 
breaker fuses to the spare battery over wire nearly as thick as the 
battery wire. . I saw them even in a napa store for about $50.  Mine 
broke (would not let battery charge) and I put in a $6 battery switch 
that manually lets me hook both batteries together when driving and can 
separate them when parked.
The Hella relay sold for the Westfalia with about a 4 amp electric 
fridge has a small wire that does not allow a lot of charging current to 
pass, so it takes longer for a recharge which may not be enough time for 
weekend camping.  The external charger (use at home or in campground) 
should be a smart charger, so it automatically tapers the charge not to 
overcharge (causing gas release) or undercharge (must be over 14v and 
step down to allow a resting voltage of 12.7 volts.  I'd get a 35-45 amp 
charger for a single wet cell battery of about 90 amp hours; Trojan is 
very good.
MUTS  = Michael's Ultimate Thumb Saver oboe, clarinet support
93 Chevy Roadtrek 210P
78 VW Westfalia Camper