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Jack
I've had the same experience with jumper cables but I suspect most
of the problem is from the resistance in the cables. If you were to
disconnect
the dead battery and try to start the car using the cables from the other
car's
good battery you might still have problems. Fast idling with the cables
connected partially charges the dead battery and then it does help enough
to get the stalled car started. I'd bet that you wouldn't have this problem
if your jumper cables were #2/0 or #3/0. Most are just #2 or #4 and junk.
A battery that is severely discharged and measures only 10 volts or so
won't help crank anything although it probably doesn't hurt much either.
I think you are correct about overcharging a small starting battery when
it is connected to a large house battery bank that has been discharged
substantially. Starting batteries usually get discharged only 5 or 10%, if
that. The bulk and acceptance voltages will charge and then overcharge
the starting battery. I doubt this would be a problem if the charging
source is an engine alternator and "dumb" regulator. The starting
battery wouldn't get overcharged but the house battery would take
forever and probably never get properly charged.
In the unlikely case your starting battery and large house battery
bank were both discharged the same percent it might be ok to
connect them in parallel to the same 3 stage "smart" charger so
long as they are all the same type. Flooded cell, gel and agm all
have different charging characteristics.
Jim Fidler "Fiddlesticks"
----------------------------------------------------------------------------
----
Jack wrote:
I've been told it helps, but my experience
jumping cars is that the discharged battery impedes starting.
snip
I have often heard, and Calder mentions a couple of times, that paralleling
unlike battery banks (ie, a small starting battery and a large bank of deep
cycle batteries) will likely result in overcharging the smaller battery
and/or undercharging the house bank.
snip
Jack
sadly not boating
Minneapolis
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