Excessive Battery Discharge at start-up

B

BatmanReturns

Member
Hi All,
I am getting "excessive battery discharge" message when I first start my Z4 (aka The Batmobile). In addition, I see an image of a car on a car lift appear on my iDrive. Both messages disappear at the same time; within a minute after starting the car, so I'm assuming they are related. I checked the battery level and it reported a good charge, but I had driven it the day before. I'm currently letting it sit for a few days, in the bat cave, and will check it again over the weekend. Assuming I need to replace the battery, is there anything in particular I should be aware of? I understand I need to ensure the battery I buy into is coded for my car (not 100% sure what that means, but I'm sure the battery shop can help with that), but is there anything else that I need to be aware of?

Thanks in advance,
BatmanReturns
 
Definitely sounds like a failing battery, if you replace it with a like for like amperage then it needs registering to the car so it knows it’s new and can charge it accordingly, if you fit a different amperage then that needs coding so the car knows how much charge it can take.
 
The battery must be of the AGM type. If you get one of a different capacity (e.g. 80Ah instead of 70Ah), then it needs to be coded, not registered (or is it the other way round?), so the car knows that as well, for optimum charging.

Any owner of these cars is well advised to invest in an OBDII code reader, which attaches to the port in the driver's footwell. Buy a decent one and you can do the above yourself. The (not cheap) gold standard appears to be BimmerGeeks' ProTool; it runs only on an Andriod phone and you will need a suitable Bluetooh adapter or cable. Do NOT leave a Bluetooth adapter in the socket as it is permanently live and will kill (not just drain) the battery in a few weeks -don't ask how I know :wink:

As the battery is so critical to these cars, you can fit something like this https://www.amazon.co.uk/dp/B08VHMJYXY?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1 and leave it permanently in place to monitor the battery health.

If you decide to get one of these, you could do that first, to be certain that the battery itself is the issue.
 
As discussed if the battery is old / unsure of its previous life it’s prudent to replace it ..however..

That error message is often associated with one or more sub systems not closing down, often due to physical failures or coding related changes..

The gold standard is to monitor the current from the battery after the car is shut down…it should settle to around 7ma-10ma..obviously need a suitable test meter..

Comfort access failing, Bluetooth module failing are two common examples
 
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