Randall wrote:
>>All kidding aside and someone please correct me if I am wrong, but isn't
>>the volt gauge designed to measure the condition of the battery
>
> Nope. Depending on the failure mode, the voltmeter will look just fine
> when the battery is junk.
I agree completely. The volt meter tells you if your charging system is
producing enough voltage to run the electrics and keep the battery
topped off, not if the battery itself is dead or dying. Both gauges
have their strengths but if I only have a hole for a single gauge to
monitor the electrical system, my personal preference is for one that
tells me if the charging system is functioning correctly and producing
enough voltage to keep up with the load. Randall seems to prefer
monitoring the battery. Its a matter of individual preferences.
>>Whereas, the
>>ammeter will indicate charging capability of the charging system, shorts,
>>major power drains from a particular electrical sources (on our cars like
>>when activiating aux lights, air horns, electrical brakes from from the 24'
>>double wide you are towing, etc.) and the capacity to maintain adequate
>>battery charging.
A volt meter will tell you these things as well. IF the load is larger
than the charging system can handle, the voltage will decrease. So any
decrease or fluxuation indicates a load that exceeds the charging system
capabilities to handle. A volt meter reading 14V or slightly higher
indicates that the charging system is working fine can is capable of
handling the load plus keep the battery fully charged. It the voltage
goes up there is a problem with the voltage regulating system. If the
voltage goes down then you are drawing more current than your charging
system can handle. An ammeter at zero tells you that the charging
circuit is handling the electrical load but it doesn't tell you if it is
maxed out and can not generate enough voltage to keep the battery
fully topped up. You need a charging system that produces a higher
voltage than your battery produces to fully top up a battery amd to get
maximum service life out of it.
It is hard to see a one or two amp discharge in a 30 amp meter. It is
quite possible to be drawing just a tad more than your charging system
can handle and slowly discharge your battery over a long drive. Most
people don't run head lamps, heater and wiper motors at the same time on
a long drive in their TRs so don't over tax their generator long enough
to drain the battery. I had that happen in the Land Rover once. Drove
all day in a cold storm with everything on. The ammeter said everything
was fine but there was not enough juice left to start the Land Rover
next morning. A volt meter would have alerted me that the charging
system was not keeping up with the load by indicating a lower voltage level.
> It will also tell you when you've left the lights on, whether the brake lights
> work,
A volt meter will not show that. Also the ammeter reacts to changes
much faster than a car volt meter does (Lucas & Smiths volt meters have
very slow movements) A ammeter will catch a momentary short if your
eyes are on the meter at that instant. A car voltmeter can not react
that quickly.
> and when the engine idle rpm is too low to keep up with the electrical
> load.
A volt meter is very good doing the same, plus if the load is too much
for the cahrging circuit to handle and produce the 14.X volts needed to
keep a battery fully charged.
> BTW, that car had a voltmeter, that said everything was hunky-dory. But I
>could
> tell the engine was cranking slower than normal, even after driving 1/2 hour
> with the voltmeter reading 14.4.
A volt meter will not measure the battery's condition, just the
condition of the charging system and warn you if the electrical load is
exceeding the capabilities of the charging system. Once the engine is
running you could unplug the battery and the volt meter would not notice
unless the charging system did.
Different people prefer to monitor different things. I prefer to
monitor the charging system and load on the charging circuit. Randall
seems to prefer to monitor the battery and the load on the battery, and
as a bonus he can glance at his ammeter as a reminder to turn the
headlamps off.
TeriAnn
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