Z4Battery Drained - any ideas?

[Z4MCSL]

So during lockdown 1 my MOT ran out - I ended up putting off getting it sorted and just drove my clio 182 around instead.

Then I went back to my Z4 Coupe and the battery was 100% flat. It had been at most 2 weeks so I was pissed off.

I tried charging it with an old battery charger thing I had but that didnt work as it was a cheap halfords charger id bought ages ago and was useles.s

The car had a pretty budget battery in it so I thought Id upgrade and got a decent bosch batttery.

Fitted the battery and the car was fine. I few beeps and resets on the trip compiter etc but otherwise fine.

Took it to get some petrol, 3 mile drive.

Left the car overnight - then next evening drove to the shop and back, 1 mile round trip - all fine.


When I got back I realised I had parked a little out from the curb after getting out the car so literally 30 seconds after turning the engine off I went to start again and nothing.

battery was flat.

It had a little power and lights were trying to come on but it couldnt turn the motor at all.

Took the keys out and went to the boot to detach the battery and it was clicking away and internal lights sort of pulsing,

I am guessing something is draining the battery even when the keys are not in.

Any ideas?

I am hoping it will somehow have enough charge if left a while to start the car and drive to the garage (is that wishful thiking) but any ideas on what the issue is?



Its a Z4C E86 in otherwise good nick

Thanas

[RUSSELLM]

Is the battery getting charged when the engine is running ?

Edit... in fact, if it’s that flat so quickly after being drove, I’d be fairly confident it isn’t getting charged.

Edited by RUSSELLM on Sunday 10th January 19:24

[Z4MCSL]

But would that be enough to drain a new battery, I mean I don't know how charged it was when it arrived but I've barely driven it.

[Doofus]

Old batteries degrade.

Once batteries go completely flat, they often won't hold a charge any longer.

Buy a new battery.

[rob_golfgti]

If I remember correctly from when I had mine, the Z4’s either has a common problem with the glovebox or armrest cubby hole light staying on.

[Z4MCSL]

Doofus said:

Old batteries degrade.

Once batteries go completely flat, they often won't hold a charge any longer.

Buy a new battery.

Yeah I did, it's a brand new battery that has drained jn about 30 hours since fitting and about 2-3 miles of driving

[RUSSELLM]

Check the voltage at the battery, ideally being new, it should be 12.6v. If it is, then you’ve a starter related problem or bad connection at battery terminals, bad earth, dodgy mega fuse, etc etc

If it’s significantly lower than that, charge the battery up or jump it from another vehicle.

Once your car is running, remove the jump leads, grab a multimeter, set it to DC volts and see if you’re getting 13.2v or higher across your battery.

If you’re not getting that voltage or higher, the battery isn’t getting charged.

If it is getting 13.2v or higher, with the same multimeter, your can disconnect a lead, set the meter to DC Amps, and see what the car is drawing.

Edited by RUSSELLM on Sunday 10th January 22:51

[Doofus]

Z4MCSL said:

Doofus said:

Old batteries degrade.

Once batteries go completely flat, they often won't hold a charge any longer.

Buy a new battery.

Yeah I did, it's a brand new battery that has drained jn about 30 hours since fitting and about 2-3 miles of driving

Sorry. I missed that.

[Mave]

If it's discharged, it's not going to be more likely to start the car just by leaving it. If there's a drain, then it'll just make it less likely you'll be able hey some charge into it, so really you need to do the checks suggested by an earlier poster sooner rather than later.

Edited by Mave on Tuesday 12th January 18:55

[davejf]

Could be a number of things, if it’s quick then it could be alternator gone bad and draining the battery. I seem to remember seeing that when mine went bad after I’d left it a week while I was away with work. Jumped it after leaving connected to a running car for 20 minutes before it had enough juice to fire!
I’ve seen the lights as mentioned above but easy to check.
Mine went flat in just over 24 hours. Couldn’t find the cause and took it to a specialist. They couldn’t find it and took it to a proper auto electrician who finally managed to find the Bluetooth module had gone bad (just like that). Sourced a secondhand one off eBay for £150 as the £700 new from BMW was a bit eye watering! After diagnosis time it was still a total Bill of around £1k!
But the Z4 Coupes worth it as it still puts a smile on my face every time I drive it and I’ve had it 6 years now!