Battery Drain Help asap please

Thu Nov 12, 2009 6:20 pm

Have got a battery drain issue, takes less than 24 hours to flatten so im guessing something large shorting out.

Just sorted my other problem with reverse light switch wire being fraid.

Anybody point me in direction of common causes??
Cheers

Thu Nov 12, 2009 6:22 pm

Have you tested the battery to make sure it's ok?

Thu Nov 12, 2009 6:24 pm

Have you recently put a heavyweight sound system into your car, or a new alarm?

Thu Nov 12, 2009 6:30 pm

recently just put a sub n amp in, but thats been in for about 2 weeks and has been ok

. Battery i belive is ok, always lasted a day atleas with music on without engine running with no prob startin up.
What current should be drained with the ignition off, like for the clock and stereo off?
cheers for quick responses

Thu Nov 12, 2009 7:28 pm

Disconnect the battery feed to your amp etc. and see what happens. The current drained should be very little with everything off.

Thu Nov 12, 2009 8:13 pm

Check all interior lights - glovebox, boot etc all go off

If your battery has gone very flat it might never recharge fully - they tend to die after they go flat.

Get someone with a multi meter to check for current drains and that your charging system is working.

Thu Nov 12, 2009 9:25 pm

No guesswork needed! Just get an ammeter in series with the negative battery lead, take the small wires off of the + terminal one at a time, and see which one the excess current is disappearing down. If it's the one that feeds the fusebox, pull fuses one at a time until you find it.
Normal current drain for an E30 with everything off is around 30mA, up to a maximum of around 90mA.

Mon Nov 16, 2009 6:12 pm

Had another qick look, its not draining though any of the four small wires on my batt, but the 2 main power 1s. Pulled a few fuses but no joy as yet. No boot light on or glovebox. In volts it goes down about 0.1 every 10 or so seconds

. Whats the best way to see if its the alternator? i know it charges it still though.
Cheers

Mon Nov 16, 2009 7:04 pm

It's current you're supposed to be measuring, not volts!
There should be only one 'main power' lead from the battery +.

Wed Nov 18, 2009 11:54 am

you are running your amp with the "remote" connected on the amp and connected to the blue remote wire on the back of the stereo? to make it switch on and off?
if not have you put a switch in to turn the amp off manually?

if you havent done either of those things, then your amp is permenantly on. draining your battery. can take a little while to drain a battery,

i just had a problem with a draining battery, replaced the alternator (did have battery lights on the dash on constantly),
and put a new battery in there (battery was going).

it turned out there was a dodgy earth wire connecting the new alternator, i was getting current readings of 14.4v out the alternator, and 12.4v at the battery, so obviously it would not charge the battery. i had that new battery lose 50% charge in 1 day.

got the alternator re-earthed (now reads out 14.4v at alternator, 13.8v constant at battery, fully loaded or not) and no problems with battery drain since.

Wed Nov 18, 2009 7:04 pm

how did u get the alternator re-earthed ??

thanks.

Wed Nov 18, 2009 7:28 pm

k13 wrote:how did u get the alternator re-earthed ??

thanks.

Some versions of the E30 have the alternator mounted in rubber bushes, and these have a seperate earth lead for the alternator, hidden away underneath.
Even alternators which are bolted metal to metal can still occasionally give problems, when corrosion forms at the junction of the two different metals, in spite of all bolts being tight.

Thu Nov 19, 2009 3:47 pm

Brianmoooore wrote:
k13 wrote:how did u get the alternator re-earthed ??

thanks.
Some versions of the E30 have the alternator mounted in rubber bushes, and these have a seperate earth lead for the alternator, hidden away underneath.
Even alternators which are bolted metal to metal can still occasionally give problems, when corrosion forms at the junction of the two different metals, in spite of all bolts being tight.

yup looks like that was exactly the problem i had. i had a different alternator on there which died, and was bolted metal to metal
put on a reconditioned BMW bosch one which had rubber bushes on, and a seperate earth output on it. which i didnt realise at the time. ran a wire from that output and earthed that. plus ran a seperate one just in case from the back of the alternator (off the voltage regulator) to a seperate earthing point on the car