Starting/charging advice

[karl1171]

I've just been looking at a\ 93 525, manual, aircon and sunroof - a rare spec here in the UK

The car has a starting problem: It has been stood for a couple of weeks and now it will only start when jumped from another car/battery. The car has recently had a new battery, there's a bill to prove. So although the car has been driven a short distance, the battery does not appear to be charging.

I'm guessing this is most likely the alternator although the charge light does not remain on when the engine is running.

Could there be anything else causing a drain on the battery?

[whiskychaser]

I've just been looking at a\ 93 525, manual, aircon and sunroof - a rare spec here in the UK

The car has a starting problem: It has been stood for a couple of weeks and now it will only start when jumped from another car/battery. The car has recently had a new battery, there's a bill to prove. So although the car has been driven a short distance, the battery does not appear to be charging.

I'm guessing this is most likely the alternator although the charge light does not remain on when the engine is running.

Could there be anything else causing a drain on the battery?

The warning light will go out even if you havent got the correct charging voltage. Should be 12.6V for a full charged battery (key off) and about 13.8V with engine running.When you say looking at I take that to mean you havent got the car yet so I'd suggest this is resolved before you get it

[Ferret]

It could be the alternator is shot or the battery has just been deep discharged E34's will only stand a few weeks without running the battery into the ground. If you keep a load on a lead acid battery after it's gone flat, it'll self destruct internally and never charge again.

Check the charging voltage - it may well be that the battery has just been run into the ground and will not recover.

If it's a current drain, the E34 has so many systems on it that it'll be a complete arse to find it. Put a current meter in the battery loop while the key's out of the ignition and start pulling fuses.

[karl1171]

I bought the car, now to find the problem!

I drove home, about 30 miles, and the car started fine the following day, and the day after, I then left it for 2 days and the battery was flat...

It appears the battery is charging, but will not hold the charge

I've checked the charging voltage, it was 13.7v

I put an ammeter in the battery loop, with all interior lights off, stereo out, key out, clock out(!) its pulling around 200mA.

I then did this test on my old car, a 91 525, and it pulls a similar amount of current: That sat for a week untouched about 2 months ago (with the alrm on), starting on first turn when I tried it.

I've had it suggested to me the rectifier on the alternator may be faulty and draining the battery, but I would have thought this would show up on the ammeter reading?

I have noticed the physical size of the battery in the new car is smaller than the old one, if its not the correct one could this cause these symptoms?

[dukester]

I would suggest hooking a proper 10 amp or better trickle charger up to the battery and charging it for a period of 8 to 10 hours. This will charge the battery up to full capacity. Alternators are not designed or capable of charging a completely dead battery in a short time, they will maintain and top up the battery while in normal usage. From your description, all systems sound like they should be working OK other than the dead battery.