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Flat battery, help needed...


Discofan
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I have a 300tdi. When used every day there is no problem but if it left for a week and a half or two weeks without running, the battery although it has power, hasn't enought to start the engine. Jump leads immediately start it , no problem, Any ideas??

Cheers

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Battery drain would be my guess, check the discharge with everything off. If it's a few tens of milliamps that is normal, if it's a lot more then you have a problem. Doesn't sound like a lot but 0.5 amps x 24 hours = 12 Ah x 7 days = a completely flat 80Ah+ battery.

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A few simple checks (assuming you have a volt/multimeter!):

What is the battery voltage before starting after being off overnight?

What is the battery voltage immediately after starting (within 30s)?

Immediately after starting, what is the voltage with positive lead on alternator casing, and negative lead on negative battery terminal?

Post up some voltages and we can help further :-)

Chris

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A few simple checks (assuming you have a volt/multimeter!):

What is the battery voltage before starting after being off overnight?

What is the battery voltage immediately after starting (within 30s)?

Immediately after starting, what is the voltage with positive lead on alternator casing, and negative lead on negative battery terminal?

Post up some voltages and we can help further :-)

Chris

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Hi There,

Mine was doing the same, and I did all the checks, but it was in the colder weather. A new battery fixed it, though the old battery is still good enough to jump start other cars with. I did however create a problem, jump starting it every day made the srs lights come on, and they are still on today. Take care.

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Sounds like one or more of the 6 battery cells are shot. Each cell gives off 2 Volts. 10 volts may start the engine but any less than that wont. Battery posts becoming hot under load is a common sign and bubbling of the battery after attempting to start the engine.

You could do no harm by topping the battery up with distilled water. It may be just low.

Good luck !

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