On my 1997 GMC Yukon the ammeter shows a continued discharge, about two
ticks below the 14 mark. It used to stay right on the 14 mark. Two days ago
I did leave the dome light on and it took almost 12 hours to charge the
battery with a 10 amp auto battery charger. I have also totally discharged
the battery several times in the past. Could the battery be causing the
ammeter to show a low charging rate. The battery is a 1000 amp warm 800 cold
and about eight months old.
Is it discharging at 12 volts or just not up to 14 volts while charging?
Most starting batteries are not designed to deep discharge very often. The
batter may be toast or about to be. You can try trickle charging it slowly
to see if it will get back up to a full charge. You can also go to
http://batteryminder.com/faqbw.cfm#q7 to get some additional answers.
According to the ammeter it is discharging while running because it is below
the 14 mark. I plugged a volt meter in the cigar lighter and it says 13.8
while running at sixty miles an hour, but I don't think these things are
accurate. I think I have discharged the battery too many times. I believe
the charging system is OK because there is a red light that does not come
on. I will try charging the battery real slow with an automatic battery
charger and see what happens. I found a site on the internet that says a
steady discharge can indicate a battery going bad.
you don't have an ammeter, it's a voltmeter. 13.8 is fine if you have a
load (like the lights on or the a/c Blower going). anything above 12 volts
is charging, over 14.4 volts is frying your battery.
buy or borrow a mutlimeter... (they make some decent cheap ones at
radio shack)... check voltage across teh battery terminals while
truck is running. It must be over 12 volts to be charging the battery.
Normal voltage while the truck is running should be around 13 volts or
better. It you have 13 volts or better while truck is running then
you have a problem with the battery. If you don't have 13 volts or
better whille truck is running your problem is the alternator.
having deeply discharged (deep cycled) a normal lead acid battery, its very
likely that you've damaged at least one of the plates inside and the battery
it will continue to give you problems until you replace the battery
outright. have the autoparts store load-test the original battery to
confirm its "damaged plate" condition.
there is a reason that deep cycle batteries (which are designed to be deeply
discharged over and over) are much more expensive!! :-)
Car Audio, Security & Performance
Interesting. most autoparts stores around here use the same wall-mounted
battery tester/analyzer that most shops use. so how could they not do the
same job as a shop??
I agree that if they use one of those bullshit handheld deals, the test will
not be accurate. but here's a test for yourself:
drive the vehicle for a bit to bring it up to warm, and park it. open one
of the doors to put the interior light on, and leave it. come back in 1/2
hr and start the vehicle. if the engine even hesitates for a moment to
crank, the battery is weakened/damaged....you should be able to leave that
domelight on for hours before ANY noticable drain. we see it in the shop
all the time....doors open for a remote start or stereo, and a battery
SOOOOO dead that it won't even power the vehicle.
our policy is to put the powerpack on a car that will have the doors open
any length of time....this prevents ME from being annoyed by a dead battery
Car Audio, Security & Performance
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