Rowland Carson wrote --
> I believe that a voltmeter which gives good resolution can be useful
> on its own, and I'd want one even if I already had an ammeter.
Resolution and accuracy. The needle versions will be approximate,
even if accurate. Especially on recombinant gas batteries, small
changes in voltage produces large changes in charging current. Equals
temperature. The RG battery people specify various voltages in
50-100mV.
LCD digital panel meters, some quite small and with decorative bezels,
are on the surplus market for as little as $10. Just add two
resistors, maybe a Zener diode, and read, with 1% accuracy, down to 10
mV. For ammeter use, a few more circuit issues besides the shunt.
> 'Lectric Bob suggests a simple capacity test that you can carry out
> at intervals if you want to avoid throwing out a battery that still
> has some good life left.
His is a clever design and is better than nothing if you can't read
specific gravity. But the current is way less than the 50-100A
consumer-type testers, and they're about $40. Repair shops use (up
to) 1,000A cranking capacity testers, as recommended by battery
mfr's. They have huge carbon-pile resistors, cost about $1,000 for
the simple models. Long ago when I worked in auto repair, we had a
modest current tester, but often it would suggest only a battery
charge was required. One week later a jump start, and a pissed off
customer.
Regards,
Fred F.
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