Brand new battery gone flat overnight

[jblakes]

Morning all,

Driving car (audi a3 2010) yesterday and battery light came on, then msg flashed up saying battery charging while driving. Car then died, so pulled over and found battery to be flat as a pancake. It was 8year old so replaced with a new boshh one, fitted all fine. Dash code still there (battery light, esp/abs) I assumed they would ****** off after driving round. Used it this morning all fine again (apart from dash codes), then come to use it again and nothing is happening when key switched on just hear a clicking.

Any idea what the hell this could be ‍?

Kind regards
James

 

[Darren92]

Battery light usually means your alternator has failed, not the battery.

 

[jblakes]

I had a feeling that might be the case. Surely a new battery shouldn't go flat overnight though?

 

[Darren92]

If you’ve been driving your car without it being charged, then it will drain quickly.

you could also have a parasitic drain.

 

[jblakes]

OK, so any idea how I check for either?

Kind regards
James

 

[Darren92]

You can see if your battery is being charged with a multimeter and a garage can do a parasitic drain test.

 

[Garrett 69]

If you can pop a charged battery in the car, start the engine and measure the voltage across the battery terminals. It should read between 14.0v and 14.6v if the alternator is producing.

 

[desertstorm]

Probably the alternator diode pack has an issue. Faulty diodes in the bridge will cause current to flow from the battery to the alternator when the engine isn't running.

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[Garrett 69]

Probably the alternator diode pack has an issue. Faulty diodes in the bridge will cause current to flow from the battery to the alternator when the engine isn't running.

Are the diode packs replaceable on Audi alternators? A lot of brands don't offer diode packs as a repair item, very few offer replaceable brush packs either.

 

[desertstorm]

You can get diode packs if you find the part number. The voltage regulator is replaceable on almost any VAG alternator. Replacing a Diode pack isn't straightforward as thay are usually soldered to the stator windings. Best thing to do if the issue is a diode pack is probably replace the alternator. You can get a second hand item off Fleabay for £30-£40.

 

[Garrett 69]

That's worth knowing, cheers.

Anyway, I'd echo the above and just replace the whole alternator. So much easier. Just be aware that tightening up the belt too much can damage the bearings. You should tension it so that you can turn a section of belt by around 70-80 degrees in your fingers.

 

[jblakes]

Would not coding the battery cause it to not charge properly?

Of so can I use autocom /delphi?

Kind regards
James

 

[aqibi2000]

Would not coding the battery cause it to not charge properly?

Of so can I use autocom /delphi?

Kind regards
James

No, classic case of throwing money at a car

 

[Garrett 69]

Would not coding the battery cause it to not charge properly?

Of so can I use autocom /delphi?

Kind regards
James

I doubt it on a 2010 car.

 

[ch1z64]

What i have found out is when i put a new Tanya battery in mine meant to be the correct 1 for an S3 8P i found it would only hold 12.54volts when car hadn't been run for a day or 2 . Now not sure myself if thats what the S3 battery should hold .
I fid notice a drain on battery when my Magic pro for Dashcam was in parking mode .

Sent from my SM-G970F using Tapatalk

 

[Garrett 69]

A static voltage of 12.54v is fine. With engine running you should see around 14.4v.

 

[aqibi2000]

What i have found out is when i put a new Tanya battery in mine meant to be the correct 1 for an S3 8P i found it would only hold 12.54volts when car hadn't been run for a day or 2 . Now not sure myself if thats what the S3 battery should hold .
I fid notice a drain on battery when my Magic pro for Dashcam was in parking mode .

Sent from my SM-G970F using Tapatalk

You do understand a 12.6V is a 100% charged lead acid battery!?