Jfaret

Have always stored my car with a C-tek Trickle charger attached to the convenience battery (rear). One day I came out, I found the car with almost flat battery, and a warning on the c-tek

I believe the BNS (battery controller) has failed for some reason.
The error can not be erased by the Mercedes workshop, and I get error code B1E74. The scan says that BNS no longer transmits via CAN bus.
I assume that the battery control unit with partnr 2305400945 has failed.

What happened ? The C-Tek fried it ?

Will the error disappear if I replace the unit ?

Is it recommended to disconect all power when replacing it ?

Any other items that must be replaced at the same time ?

Anyone know if parts# 2305400945 is replaced by 2305401045 ?

Help ;-)!