"Wayne.B" wrote in message
...
On Sun, 7 Nov 2004 18:10:25 +1030, "BruceM"
wrote:
Once under way for several minutes when amp meter drops to zero switch to No
2 but AWAYS go in direction of No1 to BOTH to No2 so (like he said) you
always have current to alternator.

===================================

I consider switching batteries with the engine running to be a high
risk regardless of whether or not the switch is claimed to be
"make-before-break". Contacts and switch wipers can become worn or
corroded creating switching transients that can toast the alternator
in a heart beat. It happens all the time. If you have to switch with
the engine running for some reason, I'd recommend doing it only at
dead slow idle speed, and never switching it to the off position.

Or you could get a "zap-stop" for $30.



For what it's worth, here's what I do if the #2 has become run down.
Start the engine on #1 and let it warm up so that it will restart
easily. Shut down and restart on "both". In the "both" position the
charge will flow to the battery that needs it.

Periodiaclly test #2 by trying to start the engine with it. If it
will not crank and start a warm engine it is shot and should be
replaced. Ideally it should be capable of starting a cold engine also
but that may be asking a lot if it has been frequently deep cycled.

If it won't start the engine its pretty far gone. I've always taken it as axiomatic
that there should be two independent starting systems. I suppose it depends on the
engine, but every one I've used would start in a few seconds. Any reasonable battery
should be able to start a small engine even if age has diminished it's capacity a bit.