[cristian920]

Hi forum dwellers

Recently I coded a bigger battery (105Ah AGM) instead of the factory 90Ah AGM battery and noticed there was not a lot to almost no information on the G20 as coding procedure. I had some discussions with shawnsheridan ( and with this occasion I would like to give a huge thumbs up and thank you for all the help ) and got some hints. In the end I decided to make a post here on the operation and what I did. Of course others are welcome to add more information if available as I did what I could and managed to find/understand.

So lets get to it:

Before everything some background info on the car as this might not apply to all G series in the same way. The car is an M340i xDrive from 2019 with 2021 I-Level at the time of coding. The car has all the possible options (Laser Headlights, MGU High, all pro assistance options, etc) from the factory. Also the car has DSS (Dual Storage System) with one 90Ah AGM battery in the back and one 10Ah Li-Ion battery in the front right side (not the 48V system its a 12V battery for additional energy capacity).


Only the rear AGM battery was changed the 10Ah one in the front was not changed.

DISCLAIMER: This DIY does not make me responsible for any damages or issues that can happen. Please make sure that you follow this guide if you have some basic skills and experience on this topic if not go to an authorized/proffessional service for this operation. Do this at your own risk by attempting a DIY!

The procedure to replace the main/rear battery is quite easy, check

as its the same for G20 as well.

After this if ISTA+ programming is not an option or not desired since original capacity is 90Ah and 105Ah is now mounted on the car then Esys + Bimmer Utillity is the way to go.

Make sure that you have the latest pszdData (same or higher then the vehicle I-Level). Open Esys, connect to the car, read FA, save it, and then click FZAuftrag -> Type -> E-Wort and it will be from factory something like A070/A080/A090/A105. Edit the value to your new desired capacity (Use A105 for AGM 105Ah and B105 for normal lead acid battery 105Ah). I know that recent M cars have Li-Ion in the back as well, not sure what they use instead of A/B, maybe someone can let us know here on the forum.

After changing the E-Wort right click on FA and calculate FP and it should work with no errors. If you have errors check the value you changed as it might be wrong.

(This step is only needed if you want the car to be considered as factory option with the new battery capacity) Now in expert mode in VCM down at the bottom load the modified FA in Vehicle Order and then click Master tab and write FA FP (again make sure that FP is calculated with no errors).

Now all that remains is to code the DME/DDE (can also code BDC_BODY if you want but I personally did not find any battery capacity parameters in BODY) by reading ECUs and then right click and Code. Take into consideration that Code writes default coding based on VO and will remove all previous coding done to the vehicle.

If you have a lot of coding on BODY or DME and dont want to redo it then you can just FDL code the following:
In DME CAFD 2742:
fEPM_Basisbordnetz_Batterienennkapazitaet from 70Ah/80Ah/90Ah to 105Ah or whatever new capacity you want.
Additionally if you did not change from AGM battery, you can leave
fEPM_Basisbordnetz_Batterietyp to Wert_02 for AGM. Not sure which Wert is for Normal lead acid battery but I would assume its the other option if you have just 2.
Now save the CAFD and press CODE NCD.

shawnsheridan also suggested in BDC_BODY CAF 17BD to change the following:
VCM_AEP_BATTERY_CLASS but I did not find it. I only found VCM_* values for engine type like 6cylinders, chasis name = G20, paint type, etc but nothing related to batterie. I checked the other CAFD's in BODY as well but nothing with *Batterie*. A few had some parameters with fEPM(which stands for flexible Energy and Power Management) but nothing related to a battery type.

After this is done the last step is to register the same battery with ISTA+:
Open ISTA+ and connect to vehicle and then go to Service Functions -> Body -> Voltage Supply -> Change battery and when asked choose same capacity not a higher/lower capacity. Careful for cars with DSS since you also have the option in ISTA+ to register a new 10Ah front battery for the dual storage system. If the small battery in the front was not changed as well only register the AGM battery.

Hope this will help and put some information on G20 as its quite sparse on the internet for this topic. If there is any additional info please add it as I might not covered everything and possibly missed a module or parameter in an ECU.

Side note, everything looked ok in ISTA and the 105Ah battery was registered successfully with no issues and recognized as 105Ah AGM. The car works with no issues and the DTC in the DME about old battery and OTA updates stopped dissapeared.