On Sun, Dec 12, 2010 at 7:39 AM, Dennis Haynes <d23haynes57@hotmail.com>wrote:

> Don't bother unless you do both sides. If that wire shorts out the
> auxiliary
> battery will have no problem smoking it. Only real protection for the wire
> is to fuse both sides. Since the real power source for charging is the
> alternator that is really where the charge line should start or at least
> upgrade the wiring from the alternator to the main battery cable.
>
> Dennis
>
> Thanks, yes I see now the fuse would only work when the engine is running.

  At the Aux Batt. end of the charging wire I have a mechanical relay.
Powered up (completes the circuit to the aux batt) when the engine is
running, only.   So this means, now that I think it through a bit more, that
when the engine is running, that cross-van power supply wire IS still
hot...all I am doing with a fuse at the main (starter) battery is protecting
that wire when the motor is off...because with the motor off, the relay is
'closed' and there is no current path back to the starter batt. if there is
a fuse at that end....right?

   So I should probably put one of the fuses at each end...then the wire
would be 'fused' with the motor running and the both batteries charging.

   If indeed this reasoning is correct, then is this fuse I found (175A  32v
"Slo-Blo") at Shucks Auto Parts anywhere near the correct 'range' to not
blow under a full load?  Would this range fuse actually stop the current in
a timely manner,  in the event that the charging wire between the two
batteries gets in contact with the body somehow?   I have good access to the
ends of the wire in the battery boxes under the seats, but not to the whole
wire as it crosses under the chassis and right near the gas tank....I don't
want to remove the gas tank, a major project, to mount and shield the
charging  wire so that it will be 1000% unable to wear thought somehow...so
I thought the fuse...and now I see one at each end is required...would be
another way to make sure I don't explode or burn up.