So long story short .... I managed to put a Deka ETX16 battery (19ah_AGM) into my R61 .... Everything worked fine. Now I need to code this battery through Bimmercode.

The lowest pre-set option for battery in Bimmercode is 40ah_AGM, corresponds to Hex value (0x0B), which is still two times the value of the installed battery. There is also a choice to enter custom hex value but all other custom values I put in returns "Unassigned Value" as result. So it seems 40ah is the lowest I can get.

Does anyone know if it is possible to write a valid custom value through Bimmercode?


Preset Value

Custom Value Menu




Installed Deka Etx16 Battery

 

I know it's MINI, but 19Ah sounds too small for any car. I personally wouldn't use anything lower than about 50Ah.

 

I ended up getting a DieHard 40ah H3 battery from advanced auto part. Its about 27lbs which is 10lbs more than Deka (17lbs) but still way lighter than the old battery I have (45.5lbs). Only problem being it is $160 more expensive than the Deka battery ...... I was told 40ah_agm is the lowest setting the ECU can "officially" accept, but there are BMW and R56 folks out there running lightweight batteries (Maybe they just registered with whatever the lowest setting given? Not sure). Anyhow, extra 10lbs for peace of mind is definitely worth it!

 

Glad you found a good compromise on extra weight.
And something to think about regarding extra cost: lower capacity battery will likely go through its lifetime cycles faster requiring replacement much sooner. This would negate or at least significantly offset the extra cost of larger battery.