BMW 320i New-ish battery not holding charge

KevArno

Hi guys,

I have a 2000 BMW 320i and battery went last year so got a new one. Problem is its dead again 6 months later. Got it jumped and it charged up no problems but two days later it was gone again and actually lost power while trying to jump it. No lights on dash or anything.
Battery has a warranty but I have lost the receipt, so before I go trawling through online banking for the transaction is there anything else that might be causing this other than a dodgy battery?

Thanks for any help...I'm pretty clueless here!!

bazz26

Could be a few things:

1. The battery could be faulty, get it tested.
2. Something electrical is draining juice from the battery.
3. Your alternator is goosed and the battery is not getting a proper charge.

KevArno

Cheers for the reply!

Just curious, but when it was jumped it seemed to charge up and ran perfectly fine until it was left sit over night...in that case could it still be the alternator?

Supertoucher

Could be a alternator or it could be a drain as Bazz mentioned. If you have a multimeter it's probably easiest to check the latter first - see here:

http://www.popularmechanics.com/cars/how-to/repair/how-to-stop-car-battery-drains

HJL

Is your blower/heater playing up? The 'hedgehog' final stage resistor can drain the battery when switched off if it needs replacing as far as i remember.

KevArno

Could be a culprit right here...Coolant light came on when I switched on the heater, went and bought some and car died that night. Haven't actually even put the coolant in yet as a result!

delly

Coolant wouldn't make an impact on the battery, unless your engine is toasted from overheating. Even without the engine running you should still get something on the display, unless the final stage resistor has caused it to drain completely. A telltale sign would be your fan pulsating quiet a bit, so you would notice it.

If you do manage to get it started again, you don't need a multimeter as the E46 has a voltage meter built in to test the battery voltage, and if the alternator is outputting the 14v. See the video below.

https://www.youtube.com/watch?v=UGuMXU3SkLs

langdang

Also, I suspect that the car should have been "told" it had a new battery for proper charging. That's the case for some, not sure of all, versions of those Intelligent Batteries. Not sure if that's done through a set of menus in the car, or on a laptop.

rebel.ranter

HJL wrote: »

Is your blower/heater playing up? The 'hedgehog' final stage resistor can drain the battery when switched off if it needs replacing as far as i remember.

This is the most likely culprit. They are a very common fault on that era of BMW 3 & 5 Series. They can affect the car in a few ways including erratic heating control issues & battery drain,.

langdang wrote: »

Also, I suspect that the car should have been "told" it had a new battery for proper charging. That's the case for some, not sure of all, versions of those Intelligent Batteries. Not sure if that's done through a set of menus in the car, or on a laptop.

You don't need to register a battery in a 2000 3 Series (e46). It is only the 2005 on (e90/91/92) that have this requirement.

KevArno wrote: »

Could be a culprit right here...Coolant light came on when I switched on the heater, went and bought some and car died that night. Haven't actually even put the coolant in yet as a result!

I would think this is a coincidence, a separate issue that would need to be investigated also.