help. battery bad?

[Kaz117]

Hi all,

I bought my Z3 roadster from Wales a week ago, where it was around 5C when I picked it up, however I live in Scotland.

Conveniently its gotten REALLY COLD in Scotland these past few days!

Consistently -6C in the morning, barely going maybe 1 or 0.5 Celsius during mid day (the hottest time of day).

So I have done a few cold starts since having it for a few days, and they were perfectly fine: only 1 or 2 revolutions then she fires right up.

This morning at 6:45am ish I started it, at -6C outside. She started with a few turns but seemed plenty healthy.

I finished work at 4pm, went to start my car at -2C outside, and she wouldn't turn.
Ignition worked, electronics worked perfectly, just classic cold battery no turn.

So I jump started her, and she ran alright. (High quality NOCO jumpstarter)
I thought maybe it would be a 1 off, so I went to the fuel station instead of home.

Again (at fuel station) when I went to start the car, no turn. So I jumpstarted her again. But after turning the lights on, the TCS and ABS started to flicker. Those 2 lights (only those 2) flickered on and off, but were being on more of the time the longer she idled. They went away after the slightest bit of revs.

So I started going back to my house, in a bit of a hurry before she died completely out, just a few streets away.

When I stopped for a junction of course the 2 ABS and TCS lights came back on. I managed to park up at home, and when I switched my lights off, the idle went maybe 50 revs higher and the 2 dash lights went away (after they were on since I was stopped).

Then I measured the battery voltage:

11.3V while running.

11.5V while off.

So yeah. I won't be driving it until I fix this LOL

Can someone advise please please if this is just the battery?

 

[Duncodin]

When the engine is running just abive idle you should have near 13.5 or 14v I think - the alternator should be putting that out when it's running.

 

[Kaz117]

When the engine is running just abive idle you should have near 13.5 or 14v I think - the alternator should be putting that out when it's running.

ahahahha b*******s I'll need a new alternator probably!

 

[ChrisD]

Hi all,

I bought my Z3 roadster from Wales a week ago, where it was around 5C when I picked it up, however I live in Scotland.

Conveniently its gotten REALLY COLD in Scotland these past few days!

Consistently -6C in the morning, barely going maybe 1 or 0.5 Celsius during mid day (the hottest time of day).

So I have done a few cold starts since having it for a few days, and they were perfectly fine: only 1 or 2 revolutions then she fires right up.

This morning at 6:45am ish I started it, at -6C outside. She started with a few turns but seemed plenty healthy.

I finished work at 4pm, went to start my car at -2C outside, and she wouldn't turn.
Ignition worked, electronics worked perfectly, just classic cold battery no turn.

So I jump started her, and she ran alright. (High quality NOCO jumpstarter)
I thought maybe it would be a 1 off, so I went to the fuel station instead of home.

Again (at fuel station) when I went to start the car, no turn. So I jumpstarted her again. But after turning the lights on, the TCS and ABS started to flicker. Those 2 lights (only those 2) flickered on and off, but were being on more of the time the longer she idled. They went away after the slightest bit of revs.

So I started going back to my house, in a bit of a hurry before she died completely out, just a few streets away.

When I stopped for a junction of course the 2 ABS and TCS lights came back on. I managed to park up at home, and when I switched my lights off, the idle went maybe 50 revs higher and the 2 dash lights went away (after they were on since I was stopped).

Then I measured the battery voltage:

11.3V while running.

11.5V while off.

So yeah. I won't be driving it until I fix this LOL

Can someone advise please please if this is just the battery?

Very possible it’s just the battery. Batteries are a service item and only last a few years so no major issue replacing it. It make be taking no charge/ creating a huge current draw (best case) or you may indeed have an alternator problem. I’d throw a new battery on anyway.

 

[Duncodin]

Very possible it’s just the battery. Batteries are a service item and only last a few years so no major issue replacing it. It make be taking no charge/ creating a huge current draw (best case) or you may indeed have an alternator problem. I’d throw a new battery on anyway.

I'd agree with ChrisD. But look at the battery. If the previous owner has been struggling with a bad charging system he may have already put a new battery in there hoping it would fix it. If the battery doesn't look brand new then I'd replace it. Then check that running voltage again.

 

[Kaz117]

I'd agree with ChrisD. But look at the battery. If the previous owner has been struggling with a bad charging system he may have already put a new battery in there hoping it would fix it. If the battery doesn't look brand new then I'd replace it. Then check that running voltage again.

the battery is some off brand thing "Accucharge". The alternator was squeaking also, which I didn't think much of when I bought the car.

 

[colb]

Sounds very much like your alternator has gone bad with that low voltage when running. Its probably the diode pack in the rear of the alternator thats gone bad and not regulating the amount of charge the car requires. Since you say it was also making noise the bearings inside may also be on their way out so replacement alternator would be the way to go rather than putting a new regulator into the rear of the alternator. Whilst your in there put a new drive belt on and keep the old one in the boot as a spare.

 

[ktnez99]

Sounds very much like your alternator has gone bad with that low voltage when running. Its probably the diode pack in the rear of the alternator thats gone bad and not regulating the amount of charge the car requires. Since you say it was also making noise the bearings inside may also be on their way out so replacement alternator would be the way to go rather than putting a new regulator into the rear of the alternator. Whilst your in there put a new drive belt on and keep the old one in the boot as a spare.

Can you charge a battery in-situ without taking it off or will this create a problem elsewhere?

 

[colb]

When taking the Alternator out you MUST disconnect the battery in the boot. Take the Negative connection off the battery and and wrap it with a rag so it cannot connect to the battery terminal or the bodywork. Once disconnected it is safe to disconnect the alternator connections and get it out.

 

[Pond]

Sounds very much like your alternator has gone bad with that low voltage when running. Its probably the diode pack in the rear of the alternator thats gone bad and not regulating the amount of charge the car requires. Since you say it was also making noise the bearings inside may also be on their way out so replacement alternator would be the way to go rather than putting a new regulator into the rear of the alternator. Whilst your in there put a new drive belt on and keep the old one in the boot as a spare.

Agreed. If getting 11.5v at the battery posts whilst running, the alternator ain't pushing anything. Should see 14v at the posts even at idle.

The only anomaly is that the battery light should flicker with a dodgy alternator, not the ABS and TCS.

If it were me I would change the battery first (as it's easier and cheaper and can't hurt), with a view to getting a new alternator if a battery doesn't help.

 

[Duncodin]

As for the ABS etc lights. I wouldn't worry about them (yet). If the diagnostics codes were read it would almost certainly report low voltage and a whole host of other errors logged.

Problem is with a low voltage all manner of other errors appear simply because so many sensors rely on a steady >12v circuit and get confused when it's low or erratic and you can see all kinds of errors popping up. So sort out the battery/alternator before worrying about the abs and other warning lights.

As a new z3 owner you might want to invest in a simple diagnostic scanner that will help you track down weird goings on. (ie 'after' sorting your current problem)

 

[Trevor /chedder]

I had similar. And ended up changing the alternator, wasn't hard to do. Made the engine bay look nice

 

[Fender2004]

Can you charge a battery in-situ without taking it off or will this create a problem elsewhere?

Yes I do it all the time and I’ve had no problems, but use the connections in the engine compartment.

 

[Pingu]

Yes I do it all the time and I’ve had no problems, but use the connections in the engine compartment.

You should connect directly to the battery, because you should disconnect the earth, as you can create problems elsewhere. The most common is overloading the alternator.

Alternators don't expect to see 14.5 volts (or more) when they are not running, and can go pop. It sounds like yours has already gone pop, though.

DO NOT disconnect, or even worse connect the charger when it is switched on - the battery can explode.

 

[RickyBobby]

Most companies that sell batteries offer a free testing service and usually give you or at least show you the associated test results.

I've used this service a few times and more often than not the battery was fine even though on a couple of occasions it was flat when I took it for testing.

Point is before investing in a new battery get the existing one tested

 

[Pond]

You should connect directly to the battery, because you should disconnect the earth, as you can create problems elsewhere. The most common is overloading the alternator.

That's a new one on me.
I was under the impression that ALL BMWs should be charged via the engine bay connections, not the battery directly.

 

[Pingu]

That's a new one on me.
I was under the impression that ALL BMWs should be charged via the engine bay connections, not the battery directly.

It's a general mechanicking rule.

It will never go wrong if you do the same for every car.

Disconnect the earth and charge the battery directly on the poles. I always remove the battery, but that's because it's easier for me to take the battery to the charger than vice versa. If I had a portable charger I could plug into the car, I'd do it on the car.

Ideally, you would remove the battery, charge it in a battery room with exhaust extraction and fire suppression, with the battery inside a box that could reduce the effects of an explosion, all whilst wearing an apron, gloves and galoshes that can be quickly removed if acid is spilt. Not forgetting the mask and goggles.

Obviously, I like to cut a few corners

 

[petecossie]

I've used the under bonnet connections on my Z3 M Coupe for jump starting and using my Ctek battery conditioner for the last 12 years without any problems. The battery isn't in the engine bay on my car but buried under the boot floor so is not readily accessible.

 

[ktnez99]

I've used the under bonnet connections on my Z3 M Coupe for jump starting and using my Ctek battery conditioner for the last 12 years without any problems. The battery isn't in the engine bay on my car but buried under the boot floor so is not readily accessible.

Same here: battery under the carpet in the boot.

I’m no wiser as to whether it is safe to charge a battery while it is still on the car in the boot and connected but using the under bonnet connectors instead. My question is, is it safe to charge the battery from inder the bonnet connectors? I’m reading that it could affect the alternator.

 

[RickyBobby]

According to the manual charging / conditioning should be done under the bonnet using the jump-start terminal