Battery drain

[Shahzaib]

Hello All,

I have a problem with my 2003 Audi A3 8P 2.0 TDi with a BKD engine, where the battery loses charge overnight. Not enough to stop it starting but enough to make the starting rough. I have a new Bosch silver battery and it seems to charge and work fine if I charge it away from the car or with the car.

The alternator seems to work fine. I get around 14.5 volts when its running and there doesn’t seem to be any loss of voltage getting to the battery.

Although all the connectors seemed look clean. I removed and cleaned them just to be sure.
I have spent many weekends with the ammeter connected in series with the battery and monitoring the current drawn. After all the circuits power down I see 30 milliamps to 10 milliamps.
I suspect that there is something which stays on but only in a condition where I drive the car, park-up, switch it off and leaving and when I remove the battery terminal do test I disturb this.
On the other hand there could be something that is time based.
The question I would really appreciate someone helping me with is:

Does this car have any time based circuits?
Any known common issues that could be causing the battery drain?
Any recommendation on when I could do to find the offending circuit?
Also most helpful thing for me to know would be what current drain should I expect on this car?

Thank you for taking the time to read my questions and I would really appreciate any help you can offer as this is just driving me crazy.

[Guest 2]

Do you have anything plugged into the 12v socket?

[zollaf]

disconnect the battery and leave it overnight , reconnect it in the morning and see what happens.

[rehash_lyrics]

A drain less than 50 milli amps should be fine and should not drain a healthy battery.
A typical car battery of 80Ah should last for 80 amps for one hour, or divisions of.
A 40 milliamp load would take 80000/40 which is 2000 hours (80 Ah/40mAh = over 80 days).

It might be that your battery charger is not fully charging your battery, most only work of a voltage measure, but a decent charger will go through a sulphation or de-sulphate stage first then a charge stage then a maintain or top up stage.

I would check all doors and boot and bonnet in case a dodgy switch is leaving a interior light or glove box light on etc.
next would be remove the fuses for radio/nav and then any unnecessary items and test again overnight.

also if possible just lock the doors with the alarm off for a test as if the alarm is going off it could drain it.

good luck

[Geraldy212]

Two ideas: Firstly, I would get the battery load-tested. A garage should be able to do this for you. They should have equipment that puts the battery under a high current drain for a few
seconds. If it does not pass, it should be under warranty. Secondly, I would suspect the starter motor, or possibly the starter motor 12v connections. I believe that a starter motor problem
is common on the older BKD engines. Good luck.

[touranasurus]

HI,I had this a couple of years ago, it was the "diode" in the alternator, draining to earth when the engine was off, take the plug out of the alternator overnight and see if that stops the battery draining, good luck.

[Shahzaib]

Thank you for all the helpful replies.

A6_Chris: Not that i know off. I've disconnected the 12v socket, glove box light and the boot light just to illuminate them anyway.

zollaf: I've done that in the past and all works fine and the battery holds charge fine when disconnected from the car.

rehash_lyrics: I have a cheap Halfords maintenance charger but when I use it everything work well its just when the battery is left connected overnight that causes problems.
I disconnected the feed for the interior components and still the same. Strangely it seems as tho the alarm is armed even if I use the key although it is off if I disconnect it so I don't think that is the problem.

Geralday212: Battery passes a load test with flying colors. I thought it was a connection problem too but Ive been through all the connection on the starting/charging circuit cleaned them, although they looked fine. When you say the 12v connection do you mean for the started solenoid or the motor? I removed the started and had a tested by a local recon place and they said it worked fine, but it could still be a possibility, I might try a new one if all else fails.

touranasurus: I think you may be onto something there but then again I disconnected the live feed from the alternator to the fuse box as one of my tests. Could it still be causing a drain in this condition?

Another thing I've read a little about is the ignition switch. Has anyone had any experience of it causing such issues? Also I know how to get to it but can't remove it?

Thank you all.

[Crasher]

I have had this a lot with Bosch Silver batteries, they discharge internally, I had one that got hot on top.

[Shahzaib]

Hi Crasher,

Mine doesn't seem to exhibit any of those characteristics and I did have a cheap no branded battery before that which was also new and I only used it for 3 months before deciding it could be just a cheap battery and invested in the Bosch one from ECP. Any experience of returns or exchange with ECP and batteries?

[Shahzaib]

I guess the question I should also be asking is how do I go about proving its bad to ECP?