E30 318i convertible battery drain

Post Sat Nov 16, 2013 7:35 am

So I have a battery drain that seems to kill my battery its happened twice now both times at night.

I'm gonna be out with the multi meter today trying to find the drain but any help or ideas of where to start would be much appreciated

the most recent additions to my car are HID lights and an alarm although I'm fairly sure I have isolated the alarm now so my first port of call is the HID headlights, has anyone else had an issue with HID's causing battery drain??

Battery seems to be creating alot of sparks when connected too so I'm thinking bare wire somewhere

with a fresh battery charge my car seems to last about a week before the battery needs a charge again and as above both times its died on me have been at night.

No sign of the battery light before it fails either

Post Sat Nov 16, 2013 7:59 am

Turn everything off on the car electric wise. Remove the negative battery lead, then connect your multi meter to the neg terminal, and the lead which should be on it. Set your multi meter to a high amp scale to begin with(you can come down to get more resolution), keys out of the ignition, and dont turn anything on as the electrical circuit is running through your meter.

On the meter you will now have displayed the "parasitic draw" on the battery, you are looking for no higher than 0.05A.

If it is higher than that, start removing fuses while watching the meter. If you pull one out and the amps drop to a good level, then you have located the circuit that the drain is on.

Post Sat Nov 16, 2013 4:50 pm

So turns out it wasn't a battery drain but the cables that connect to the positive battery terminal were so badly corroded they only had about 2 strands of wire still connected and not giving a good connection to the starter motor.

thanks for the pointers anyway

Post Sat Nov 16, 2013 5:51 pm

pac1982 wrote: Battery seems to be creating alot of sparks when connected too

Don't celebrate too soon! A small spark is normal, but if you really do have bigger sparks, then you may still have a fault.

Post Sun Nov 17, 2013 10:36 am

Just having a few wire strands going to the battery has nothing to do with battery drain.

It will affect the charging rate however so your original problem was probably poor charging.

As Brian says....you should not get major sparks when connecting the battery up...just minor ones from the ECU and clock/radio draw.

Post Sun Nov 17, 2013 11:21 am

Brianmoooore wrote:
pac1982 wrote: Battery seems to be creating alot of sparks when connected too
Don't celebrate too soon! A small spark is normal, but if you really do have bigger sparks, then you may still have a fault.

its not done the big spark thing again since so not really sure what could be causing this.

I did test the system quite in-depth and the multi meter showed no signs of any draw with everything turned off.

Billwill wrote:Just having a few wire strands going to the battery has nothing to do with battery drain.

It will affect the charging rate however so your original problem was probably poor charging.

As Brian says....you should not get major sparks when connecting the battery up...just minor ones from the ECU and clock/radio draw.

the cable in question was the one that goes from the battery to the starter motor, this is why I thought it was battery drain, as my car would not turn over simply click due to the connection being poor but i thought it was down to lack of power in the battery.