Starter Battery Charge Level
Thread Starter
Junior Member
Joined: Jul 2023
Posts: 15
Likes: 3
'10 C300 4Matic, '24 C43 AMG
Starter Battery Charge Level
Has anyone else been getting "the state of charge of your vehicles starter battery is critical"? I'll drive around it's go away for a couple days but then return. I've gotten it probably 5 times in the last two weeks.
Junior Member
Joined: Aug 2023
Posts: 71
Likes: 14
W206 C43
Dealership will likely say the battery passes their tests. The critical battery issue is due to the car getting an interrupted sleep cycle, which causes one of the pumps (I forget which, possibly coolant pump) to continue to run instead of shutting off after 15 minutes or so. The result is both the 48V mild hybrid battery and the 12V starter battery becoming depleted. You can see from the workshop menu that both batteries discharge when this happens.
Junior Member
Joined: Aug 2023
Posts: 71
Likes: 14
W206 C43
An update on this issue for others. I've had numerous low/critical battery alarms over the past year, and asked my dealership to look at this issue (for the second time) during a recent vehicle service, and they appear to have fixed it.
The issue relates to the door control unit software remaining active, which keeps the vehicle from going into full sleep mode and runs the battery flat. Software has been updated on all 4 door control units, and my battery was also replaced as it failed a test (likely the battery was damaged due to being fully discharged multiple times in 12 months because of the software issue.)
The full notes for the issue from the dealership below:
Owner reported critical battery alarm keeps popping up.
Please check & report.
Internal battery fault and door control unit software issue.
Complaint confirmed, quick test, EZS fault code, (B1FCB97) tips #GI54.10-P-076868.
Battery test, failed.
R/R and replaced battery, updated all four door control unit software.
Cleared faults, function test after repair, in order, complaint rectified.
The issue relates to the door control unit software remaining active, which keeps the vehicle from going into full sleep mode and runs the battery flat. Software has been updated on all 4 door control units, and my battery was also replaced as it failed a test (likely the battery was damaged due to being fully discharged multiple times in 12 months because of the software issue.)
The full notes for the issue from the dealership below:
Owner reported critical battery alarm keeps popping up.
Please check & report.
Internal battery fault and door control unit software issue.
Complaint confirmed, quick test, EZS fault code, (B1FCB97) tips #GI54.10-P-076868.
Battery test, failed.
R/R and replaced battery, updated all four door control unit software.
Cleared faults, function test after repair, in order, complaint rectified.
Newbie
Joined: Aug 2025
Posts: 3
Likes: 0
An update on this issue for others. I've had numerous low/critical battery alarms over the past year, and asked my dealership to look at this issue (for the second time) during a recent vehicle service, and they appear to have fixed it.
The issue relates to the door control unit software remaining active, which keeps the vehicle from going into full sleep mode and runs the battery flat. Software has been updated on all 4 door control units, and my battery was also replaced as it failed a test (likely the battery was damaged due to being fully discharged multiple times in 12 months because of the software issue.)
The full notes for the issue from the dealership below:
Owner reported critical battery alarm keeps popping up.
Please check & report.
Internal battery fault and door control unit software issue.
Complaint confirmed, quick test, EZS fault code, (B1FCB97) tips #GI54.10-P-076868.
Battery test, failed.
R/R and replaced battery, updated all four door control unit software.
Cleared faults, function test after repair, in order, complaint rectified.
The issue relates to the door control unit software remaining active, which keeps the vehicle from going into full sleep mode and runs the battery flat. Software has been updated on all 4 door control units, and my battery was also replaced as it failed a test (likely the battery was damaged due to being fully discharged multiple times in 12 months because of the software issue.)
The full notes for the issue from the dealership below:
Owner reported critical battery alarm keeps popping up.
Please check & report.
Internal battery fault and door control unit software issue.
Complaint confirmed, quick test, EZS fault code, (B1FCB97) tips #GI54.10-P-076868.
Battery test, failed.
R/R and replaced battery, updated all four door control unit software.
Cleared faults, function test after repair, in order, complaint rectified.
