battery drain

[johnrr]

Does anybody know what a 'normal' current drain on the battery should be on a 2001 model year Octavia TDI?
My battery went flat after about a week of not being used. If I use it every day it's fine. The battery was replaced about a year ago with a 72AH Varta. When I connected an ammeter between the battery negative and the disconnected negative battery cable there was a current draw of about 15 Ma with everything switched off, doors closed etc and after a couple of minutes when everything had settled down. Is this a normal sort of current? Surely a good battery shoudn't go flat after 7 days?
There's no information in the Haynes manual on this, but the manual I have for another car suggests a max current drain with everything switched off of around 2or 3 Ma!
Any ideas anyone?

[Lummox]

0.2 to 0.3 amps maximum drain.

[mbames]

My 2001 TDi sat on the driveway for about 2 weeks (while waiting for a new windscreen and then an MoT - as it had expired), started straight away.... sounds like like your battery may be on the way out (or have a couple of dodgy cells)

[cheezemonkhai]

You say you have already had a new battery and certainly on the dervs i have run they were good for about 10 years. Obviously it is worth checking the water levels in the cells mind

15mA is approximately 0.015A, so if that is your drain it is well below the 0.2-0.3A the car can drain. I may be used to oldercars, but 72AH doesn't seem especially high for a derv engine and they do take a hell of a lot of cold cranking amps to start.

Other thing i would do is get a fully automatic battery charger, top the cells up (not to the lid, just so the lead is covered) with water and charge it until the thing is on the maintain cycle and see how it goes. You could just have a battery that never quite fully recharges, especially if you do a lot of short trips.

[mbames]

And to top up battery water levels, you are meant to use distilled water (I tend use water from a dehumdifier)...

[johnrr]

Thanks guys. Lummox do you mean 0.2 to 0.3 amps or 2 to 3 milliamps?, because The reading I'm getting is around 15 milliamps. ie fifteen hundredths of an amp. The battery was replaced at my local dealer about 16 months ago, its the so-called magic eye type, although I have removed the cell caps and checked the water level. The battery capacity of 72AH is the one specified for the car, and with the engine running and everything switched on there's around 14 volts across the terminals so it seems to be charging on the car.
Another strange thing I discovered while doing the testing, after i'd removed the 5amp fuse which protects the instrument panel, the warning light for door open started working for the first time! However it stopped working again after I turned the key. It seems to re-set itself every time I take out, then replace the fuse!! Everything else appears to work properly.

[sparky2]

It could be your boot or glove box light staying on intermitantly or maybe a relay sticking on causing the battery to go flat ? to check the battery if you go into a garage/battery shop they will do a battery check with a twin probe device which will take a large amount of amps from the battery and show the voltage at the same time, if one of the cells bubbles then it shows that individual cell has a high resistance and the battery is duff, hope this helps as winter is coming up and weak batterys dont like the cold.

[johnrr]

Thanks guys, took the car to a local auto electrician last Sat. They reckon there was around quarter on amp drain with everything switched off, doors closed and locked. Wasn't interior light, hands free holder or glove locker light. Suggested bring car back monday for further tests. Monday they found only about 30 milliamps (0.030) drain well within spec. Did all the obvious things to reproduce the fault without success. Did some testing of my own with borrowed fluke meter and found that opening and closing any door left current drain of arounf 0.08 amps. Disconnecting and reconnecting meter and battery resets something and current drain returned to 0.030 amps! Also noticed that 'door open' warning light only works after battery reconnected. Once I've turned the key to start or even just to 'lights on' position, the door open light no longer works. Pulling out fuse 15 - instrument panel and replacing it seems to reset something and the 'door open' warning works again! Could the problem be something to do with the convenience control unit?