Originally Posted by seanblee
The batteries are either lead calcium or AGM. The E9x has IBS (Intelligent Battery System) that theoretically needs to be told when you replace the battery, even if it's like-for-like - this takes about 2 minutes with INPA or Tool32. Some people replace without telling the car, but I've seen stories that this kills the new battery as the system doesn't recalibrate the charging voltage - sounds a bit like urban myth to me, but up to you if you want to take the risk!
If you replace with a different capacity or type, this needs recoding (ideally through an update to the vehicle order), which takes probably 5-10 minutes with NCS). Codeable battery options are:
E B046 BATT_46AH //46 Ah-Batterie
E B055 BATT_55AH //55 Ah-Batterie
E B070 BATT_70AH //70 Ah-Batterie
E B080 BATT_80AH //80 Ah-Batterie
E B090 BATT_90AH //90 Ah-Batterie
E A070 BATT_AGM_70AH //70 Ah-AGM Batterie
E A080 BATT_AGM_80AH //80 Ah-AGM Batterie
E A090 BATT_AGM_90AH //90 Ah-AGM Batterie
To tell what type of battery you have now, check the top of the casing. The capacity will be marked on it; lead calcium batteries are white and AGM batteries are black.
FTR, BMW don't make batteries. The standard batteries are made by a variety of manufacturers - I've seen Exide standard and Banner AGM, so these are both safe bets.
Partly urban myth.
If you change the battery TYPE and/or CAPACITY then you need to code it to the car.
If its EXACTLY the same spec, then there is no need to do the coding.
All the coding does is teach the car computer the capacity, and therefor its expected and optimal charge/discharge rates.
Charge voltage for a L/A or SLA battery is constant, the current and charge time will change with different capacities.