Something is draining the battery...

[ryan_george]

Well I've been having trouble with my battery lately. It doesn't seem to hold a charge. If the car is sitting for more than about half an hour, there's not enough juice left to start it up.
Once I get a boost, it stays running with no problems.

I have checked the brushes on the altenator, and they are due for a change, but I also noticed that there are some things drawing power when everything is off and doors are closed.

I went through the fuse box and found the following currents:

Fuse_____________Current (mA)
4__________________0.172
6__________________0.08
10_________________0.06
12_________________0.256
21_________________12.9
27_________________1.814

How much is too much? Like, how much power does the OBC, radio, ECU, etc. require to keep memory?

The ones I have in bold seem pretty high, but I'm not sure what's normal.

-Ryan

[BahnE30]

just had same problem, changed alternator and it's fine.... your alternator is only putting out enough charge to run the car and not charge the battary.... i've got one somewheres if you want it... pm me for a price

[DaN]

Your current values, are they all in mA? or seems weird to say .08mA.
If you have 12.9 amps running through fuse 21, the fuse should blow. It's a 7.5A isnt it?

[ryan_george]

all currents are in mA.

[chuckybob]

imho, if 21 and 27 arent required for running and youre not picky about a/c or radio, pull that shit and see if your battery lasts. if it dies again, its something else, if its fine, you know where to troubleshoot from.

[E304life]

bmw spec for e30s is 30 milliamps max.

[Vass325es]

Only way to know for sure that your alternator is bad or good. Turn the engine on and running. Then unplug the battery postive cable. If the engine still running that mean your alternator is good. If not that mean your alternator is no good.

[arsevader]

Only way to know for sure that your alternator is bad or good. Turn the engine on and running. Then unplug the battery postive cable. If the engine still running that mean your alternator is good. If not that mean your alternator is no good.

This has been covered a million times before, there are so many things wrong with this test. This is a good way to fry your ECU etc. This test was ok for older cars with limited electronics but newer cars is a big no no.

Also Alternators are not designed to run without a battery connected and if your alternator was good before this test can ruin it.

Use the correct tools (a multimeter) and check the voltage with the car running. You need about 14.5 Volts to charge the battery and run the accessories.

[DaN]

Yea, definitely do NOT disconnect the battery with it running. :tsk:

Check total current draw at the battery by disconnecting the negative terminal and clamping your meter leads between the terminal and the battery. Make sure all the lights are out, disconnect the trunk lamp. Nothing running off the access. outlet, etc.