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#299334 - 12/06/2007 03:51 Dead battery
tanstaafl.
carpal tunnel

Registered: 08/07/1999
Posts: 5546
Loc: Ajijic, Mexico
I went out to my car this morning to find the battery totally dead. I strongly suspect that the empeg was the culprit.

Last night I changed the oil and filter, then started the car and ran it just long enough to back down off the ramps, then shut it off before the empeg had finished booting.

When you do this, the empeg continues the boot process, and goes into play mode (not standby).

My car is wired so that the amplifiers receive power only when the ignition is on (or the key is switched to accessory) so no sound was being produced.

It doesn't seem reasonable that the empeg by itself, drawing less than one amp, could have killed the battery in just 12 hours. That battery was stone cold dead -- it wouldn't even give a glimmer of dash lights when I switched on the ignition. I know that the empeg will shut itself down when battery voltage drops to 10-11 volts, so I don't see how it could have completely drained the battery. In fact, the empeg requires more voltage to keep going than my starter motor does. I can play my stereo until the empeg drops out, and still have enough battery left to start the engine!

So... did the empeg kill my battery? If so, how did it do it? If not, what might have done it?

tanstaafl.
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"There Ain't No Such Thing As A Free Lunch"

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#299335 - 12/06/2007 09:37 Re: Dead battery [Re: tanstaafl.]
pca
old hand

Registered: 20/07/1999
Posts: 1102
Loc: UK
It seems very unlikely that the empeg could have drained a functioning battery completely in such a short time. It does present a very small load even when off, due to the linear regulator for the 5v analogue line, but this is on the order of a couple of mA. A good battery should sustain that for weeks.

It sounds like your battery is either faulty (low acid in one or more cells?) or you have another load on it somewhere. The last time this sort of thing happened to me it took ages to track down, and eventually turned out to be a faulty alternator. It was putting a 5A load across the battery when in the right position! I suspect it was a faulty diode in the rectifier.

pca
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Experience is what you get just after it would have helped...

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#299336 - 12/06/2007 22:56 Re: Dead battery [Re: pca]
tanstaafl.
carpal tunnel

Registered: 08/07/1999
Posts: 5546
Loc: Ajijic, Mexico
Quote:
It sounds like your battery is either faulty (low acid in one or more cells?) or you have another load on it somewhere.


Battery is known to be good. I can run the stereo with engine off for hours (and that's with five amplifiers feeding 11 speakers!) before the voltage drops enough to shut down the empeg -- and even then, there's enough left to start the car.

Charging system seems to be fine, the battery always stays fully charged regardless of load, has done for years.

I think you're right, there must have been another load on the battery, maybe something wacky like a relay stuck and the rear window defroster came on or something. But it does seem an odd coincidence that the empeg was in the process of booting when I turned off the ignition, and it would have stayed running all night under the circumstances. But as you said, no way could it draw enough power to totally discharge the battery. In any case it would have turned itself off when battery voltage dropped to 10-11 volts.

Just one of life's little mysteries, I guess.

tanstaafl.
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"There Ain't No Such Thing As A Free Lunch"

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#299337 - 13/06/2007 15:38 Re: Dead battery [Re: tanstaafl.]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31596
Loc: Seattle, WA
Quote:
In any case it would have turned itself off when battery voltage dropped to 10-11 volts.

I'll bet it would have kept dropping in and out of "showing the battery icon" mode a whole bunch of times at the cusp...
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Tony Fabris

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