Battery problem?

[Andrew H.]

Can anybody help? (1991 S3 owner for 3 weeks)

Do I simply have a faulty (new!) battery or is there something more seriously wrong?

Out for a run over the weekend, stalled the engine and was unable to restart, fortunately opposite a garage! A helpful chap with a battery booster soon had the engine running again, although it did cut out after a minute or two and had to be restarted with the booster. All o/k for the rest of the weekend.

This evening, moved car out of garage (trying to tidy up!) engine started o/k and left running for ten minutes to warm up, I switched the lights on and engine cut out - not what you would usually expect to happen once the engine is running even with a poor battery!


When the engine is running the volt meter initially shows 11 volts and seems to take a long time to get up to around 12/13, so I assume the alternator is charging o/k. Reading Steve H's book I understand this is normal?

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quote:

This evening, moved car out of garage (trying to tidy up!) engine started o/k and left running for ten minutes to warm up, I switched the lights on and engine cut out - not what you would usually expect to happen once the engine is running even with a poor battery!

Actually I would. If the battery is severely discharged any additional heavy load like lights can cause a problem. So either you have a duff battery, a duff alternator or both.

quote:
When the engine is running the volt meter initially shows 11 volts and seems to take a long time to get up to around 12/13, so I assume the alternator is charging o/k. Reading Steve H's book I understand this is normal?

If you read the book a bit more it should state that the revs have to go above 2200 rpm ish before the alternator will start charging. This is normal.

I would recharge the battery and then see how you get on. It might simply be that. If not you could have a duff cell in the battery . Fault finding alternator and battery faults needs pretty hefty meters and stuff so a few minutes at a friendly garagre can save you a lot.... providing the car will start and you can drive there! Always the problem with these type of faults.

Steve
www.tvrbooks.co.uk

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quote:Can anybody help? (1991 S3 owner for 3 weeks)

Do I simply have a faulty (new!) battery or is there something more seriously wrong?

Out for a run over the weekend, stalled the engine and was unable to restart, fortunately opposite a garage! A helpful chap with a battery booster soon had the engine running again, although it did cut out after a minute or two and had to be restarted with the booster. All o/k for the rest of the weekend.

This evening, moved car out of garage (trying to tidy up!) engine started o/k and left running for ten minutes to warm up, I switched the lights on and engine cut out - not what you would usually expect to happen once the engine is running even with a poor battery!


When the engine is running the volt meter initially shows 11 volts and seems to take a long time to get up to around 12/13, so I assume the alternator is charging o/k. Reading Steve H's book I understand this is normal?

Alternators usually charge on light load at 13V - 14.5V dependent upon demand. If the battery was drained down low, it could show lower than this however 11V is a bit too low and the alternator should at least be able to maintain 12V on full load. (current is inversely proportional to voltage, which means current drawn is high, voltage is low).
It IS possible, however unlikely, that the new battery is at fault. You can check the charge voltage with a voltmeter on the battery terminals while the engine is running which is far more accurate than the TVR gauge. ALTERNATively (pardon the pun!) you can get the alternator checked at any auto electrical specialist which may be the best bet, they can also test the battery to see if it holds a charge as well.

Jas.