Battery died

[colb]

Battery finally died today, last run out was a week ago in the dark so lights on.
Went to start today and zilch, just a click from under the bonnet, checked the voltage and just showing 11volts so gave it a jump start using my mains powered starter/charger and started, volts show 13v+ with engine running so deduced battery was toast. Not sure of the age of the Battery it was a Bosch Silver.
Bought a Halfords 3 year guarantee battery and put it on, interesting to note that the ABS light which had been activated when I jump started it went out with the new battery fitted. I deduced the ABS system requires a good voltage in order to self test which it wasn't getting with the failed battery.

Colb

[pingu]

A battery usually isn't toast if it is on 11v. It indicates that you left something on. Check your boot light.

A good charger can usually recover a battery that shows 11v.

13v is also strange as it indicates that you are charging, but just not enough. You should get >14v from your alternator. Did you leave the engine running for a few minutes before testing the charging voltage? Did you rev the engine above 2000rpm before testing the charging voltage? If not, that would explain the low charging voltage, as some alternators don't start to put out their full voltage for a few minutes or until a certain rpm has been reached.

[peter2b]

had some thing like that on my zed, had to charged the battery engine (not run for 3 weeks)started fine for 2 days then flat took her for a mot but had to recharge the battery first poped into get some fuel restarted ok, mot chap started her again ok to get into the garage but had to jump start, battery flat again , new battery fitted no more problems
peter2b

[pingu]

A new battery would cure the fault, but I'm just saying that it might not have been needed.

It depends on whether you want to buy a new one now or next summer. I have just bought a new one for my van. It started to fail (similar symptoms) about 12 months ago. I'll keep the old one, empty the electrolyte, use distilled water to flush-out all the crud and try to kick-start it again, but I don't hold out much hope. It may come back or it may not.

If not, I can still get £5 from the scrappy's for it .

[colb]

Must admit I didn't run it long when I checked the voltage after fitting the new battery, just at tick over which gave me the +13 volts, will check it tomorrow at higher revs to check the output.
Not the first time I have had a flat battery, happened once before, jump start and a run plus a period on a battery charger solved it the last time.
Last weeks longish run in the dark led me to think battery was suspect having had headlights on, normally its a weekend car used in the daylight.
The old battery has no date on it so I don't know how old it is, I have had the car just over two years.
Will also check the boot light using my mobile phone to video the inside when closed to see if the light is going off.

Colb

[colb]

Had another look this morning and checked the alternator output a little closer which revealed charging to be 13.63 at 2k revs.
Further check with full beam headlights gave a range of 13.61 - 13.52volts.
Switched off the new battery read 12.95v.

It would appear alternator not putting out enough voltage, new one ordered, will report back when fitted.

Have put old battery on charge to see if it recovers.

Colb

[BladeRunner919]

Did you check alternator output at the alternator itself or at the battery?

[colb]

Checked at battery and at terminals under bonnet

Colb

[BladeRunner919]

You need to check the actual voltage at the alternator as well. No point spending on a new one if it's just a dirty contact.

[colb]

Will check that out whilst waiting for the replacement to arrive either way I will keep it as a spare if it is dirty connections.

Colb

[BladeRunner919]

One test is to put your voltmeter between the positive terminal of the alternator and the positive terminal of the battery (or, more easily, the positive post under the bonnet). Probably sounds like an odd test, but if you register a voltage then that indicates a voltage drop between the alternator and the battery circuit.

[Hairyscreech]

Do the Z3 alternators have replaceable regulators/brushing packs like the older BMW alternators?

If so its quite common that low alternator output can come from failing regulators or worn/failing brushings, on the older alternators the brushing pack and regulator is ~£14 and will restore a weak (12-13v) alternator back up to the full 14.2V and takes about 20mins to fit.

Always worth pursuing that before going for a whole alternator.

[colb]

Checked out the voltage at the alternator this morning which shows 13.5v, also checked voltage inside the car whilst running using cigar lighter socket, with headlights on plus heater fan and heated seats all on volts drop and recover to 13.5 at 2k revs so looks like alternator is failing to produce enough.
Will put on new alternator when it arrives and recheck.

[colb]

Now sorted, despite a hiccup with the wrong alternator being supplied, see other post "Alternator wiring question".

Correct alternator supplied by Euro Car Parts and fitted this afternoon, volts now restored to 14.4V and gives a healthy figure with everything switched on. Seems my earlier battery replacement was not needed, never mind I will keep it as a standby.

Colb