<VV> Re: backup electrical system 2 methods

[N2VZD at aol.com]

i run an extra battery thru an isolator (like marine) on my rampy so i can  
leave a marine chest type refridgerator running without running the main 
battery  down.it works well. i put a 30 amp circuit breaker before the feed to the 
extra  battery off the isolator for a "safety " valve. when we travel we put 
the  refridge in the truck bed to carry wine,meat and cheese etc that we pick up 
in  vt.. this has worked out well several times.so the secret really is a 
diode to  isolate your extra circuit. you can use a large diode or buy an isolate 
from n a  p a or marine catalogs.it is 2 diodes , fed by alternator (  i run 
a heavy  one!)  with a lead to each battery. another way is to run a heavy 
constant  duty relay off the key to shut the extra battery from the rest of the 
vehicle if  not charging (on).
regards, windy tim colson