Additional Battery Fault

Aly Diagnostician Congo City, Congo Posted   Latest  
2016 Mercedes-Benz G550 4.0L (178.980) 7-spd (722.9)
Instrument Warning Message


i have this fault code on mercedes G class (B11C118:the additional battery is faulty,the limit value for current is not attained,)

i remove the additional battery and i measure voltage it gives 12,5V.

Anybody facing this problem before?


Albin Diagnostician
Leavenworth, Washington
Albin Default

That was the OCV on the battery, what voltage did it have under a load, such as a carbon pile load test?

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Samuel Technician
Somers Point, New Jersey
Samuel Default

Great question....when in a rush we often pass over the load test....load testing the circuit to me is the best test for overall circuit integrity

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Ray Diagnostician
Wichita, Kansas
Ray Default

You will have to check it under load since the computer is telling you "current", not "voltage"

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George Diagnostician
Burnaby, British Columbia
George Default

Load test that acucilary battery you probably find it will fail a sign is the start and stop will be working intermittently best way to load test is while stating from start stop action

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Zachary Mobile Technician
Austin, Texas
Zachary Default

Aly, As others have stated you'll want to load test that battery. Open circuit voltage isn't a clear indication of battery health. Much like voltage drop testing circuit with no current flowing. I'm also curious what pids are available for the auxiliary battery system. Chances are you can monitor battery voltage and current on the scan tool during attempted start-stop as well as charging system…

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Eric Mechanic
Chapel Hill, North Carolina
Eric Default

If it's any help I just replaced an additional battery in a '15 GL450. According to the iScan the internal resistance of the battery is 60 ohms (new battery). Had code B 11c11b. Neither the code nor the message returned.

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Hollis Technician
Boulder, Colorado
Hollis Default

Do you have access to repair manuals for this car ? If you're not familiar with Stop/Start Systems, here's a link to an explanation. You might want to do some further reading for your specific make. Stop/Start batteries from some manufacturers have different recommended testing methods. aa1car​.​com/library/stop-s… I would test the auxilly battery & system according to…

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Osundeyi Technician
Lagos, Nigeria
Osundeyi Default

Since the circuit is live, why not disconnect the battery totally and test for voltage at the charging terminals and see how the voltage behaves, I've got an issue like that before, ad and the problem was that one of the wire was have an intermittent contact with ground. So it was really difficult to notice, I have to connect a voltmeter and then wiggle the wires around that area before I could…

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Aly Diagnostician
Congo City, Congo
Aly Resolution

Solved,battery replaced with new one. Thank you for your assistance.

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