On Sat, 06 Sep 2003 13:15:31 +0100, Alaric B Snell wrote:
Gary Coffman wrote:
On Fri, 05 Sep 2003 22:19:00 GMT, Gunner wrote:

Yep. Got to any autoparts store or RV dealer for a "battery isolator".
Its used to charge more than one battery from a common source, but
only allow the battery to be drained from its respective loads. And
put a proper fuse on the line going to the trailer G. I think they
are only around $20 or so.

BTW..I believe the isolator is nothing more than a diode bridge, but I
cannot think how the diodes are oriented at the moment. Im sure the
very good bunch of electron plumbers we have here will be able to give
you chapter and part number G


Ok, ASCII art schematic follows, switch to a fixed pitch font now.

diode 1
x----|-------BAT 1-------Loads
|
Alternator+ ----x
|
x----|-------BAT 2-------Loads
diode 2

Hmmm, that only seems to involve one power rail, and puts the load in
series with the battery... you sure about that?

I'd say that it would be more like running several diode bridges off of
the alternator rails, then having the output of the bridge in parallel
with battery and load.

AC1 and AC2 are connections to the alternator:

AC1 --------+-----|------+-----------------------\
| | |
| | |
- - |
^ ^ |
| | |
| | |
+------|-----+--------- AC2 |
| |
| |
+--------------| |--------------------+ - smoothing
| | capacitor
| - + |
+-------------BATT--------------------+
| |
| |
\--------- - LOAD + ------------------/

Connect as many of those as you like to the same alternator by joining
the AC1 and AC2 inputs together. The smoothing capacitor may not be
necessary, the battery itself may smooth the output more than enough -
I'm not sure if a high ripple current into a battery does it any good,
though.

The output of an auto alternator is DC (the rectifiers are internal).
The loads, and the alternator negative in my diagram are, as is normal
in automotive practice, returned via the chassis. I didn't bother to
sketch that in since ASCII art is difficult enough without all that extra
detail.

Gary