Saab: Need Some Advice on Charging System Saab 9000

On Sat, 17 Jan 2004 19:07:32 GMT, in alt.autos.saab you wrote:
 

If that's before cranking, then something is a bit wrong, although 12
volts is the nominal voltage, it's really happier at a bit more than
that. 

Bet this was in a nice warm shop, wasn't it?
 


So no alternator problems, although I think the voltage is a bit high,
but not by much. 14.2 volts is about 2.36 volts/cell, and that's just
fine for charging, but it's trying to charge. (normal rest voltage is
about 2.2 volts/cell for floating, iirc). That's where the 13.8 volts
for mobile radio equipment comes in.

 

I suspect that you might be having a temperature problem with the
battery. I'd take an analog voltmeter (unless yours can measure and
hold a minimum) and then measure the voltage:

1) open circuit without the key in the ignition.

2) key in, off position

3) key in, run position

4) key in, start position

Voltage on the average battery under those circumstances can be as
little as about 8 to 9 volts while cranking.


 

If the battery goes down by 0.5 volts on a 15 to 20 amp load, that's
perhaps a bit much, although it might be average. That says that the
internal resistance is about .0333 ohms, which will drop 5 volts
(assuming nothing else drops anything) at 150 amps. However much the
starter is rated at, will give you an idea. That would get you from
12 down to 7, or the nominal 13.8 down to 8.8.

I'm thinking that the battery has a cold problem.

If you can, measure the specific gravity in the morning, which will
also tell you if you are getting a full charge. Get something with a
gauge on it, not the silly little balls.

If all else fails, you can get a battery tester at Harbor Freight
(only if on sale)... or go to an autozone or battery store which often
has a battery checker. Of course, you don't want to be driving the
car there...

In removing the battery, always remove the - lead first, that way, the
only thing you have to worry about is touching the - terminal with the
wrench. If you try to remove the + lead first, touching the engine
with the wrench will short out the battery.

Hope that this helps.

Harvey.
 

Well I made it through the night without detecting any appreciable drain
from the battery ( stayed steady at 50 milliamps as expected). The temp hit
a crispy low of -16. This morning when I turned the key, the in-dash volt
momentary flashed at 12.3 and instantly dropped to 11.8. When I cranked the
engine it dropped to 9.5 and did not sound too happy about it. All these
slow grinding starts cant be good for my starter, unless it is part of the
problem. Tomorrow I will return to my garage and grovel for a new
replacement battery. Wish me luck.

"Radar166" <com> wrote in message
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