mbusafan

What should be the optimal resting voltage of the 12V battery on GLB35? Is 12.6V the cutoff? I got a critical 12V battery warning from Mercedes Me and said I need to drive it for 30 to 60 minutes continuously. So I took it out on a back road and did some spirited driving for 30 minutes. Now the resting voltage reads 12.34V on a multimeter. Should I get an AC charger and put it on charge? Thanks.

Odd Piggy

Battery voltage is somewhat temperature dependent. It’s winter, so voltage could be lower. What’s the temperature where the battery has been sitting?

mbusafan

Indoor garage in SoCal with ambient temperature in the 50s at the lowest. The car has been sitting idle for 2-3 weeks.

Odd Piggy

12.34V is low for those conditions. If the car sits unused for more than 7 days, a 2 amp battery maintainer might be a good idea.

goditas

You may have done this, but if your car is going to sit for at least seven or more days, you can activate Standby Mode. You can find in MBUX under the Settings -> Vehicle menu. It is suppose to help save your battery if the car is expected to sit.

benz_driver

IMHO yes. Portland area '21 GLB 35 owner. A week or so before the cold weather hit us the MMe service was informing me of the critical status of the battery, the day before snowmaggedon I picked up my E550 from a service (and a new battery for it, it was time) and bought an MB 5A trickle charger. I connected the charger to the GLB and it showed an "OK" status (green light) but with a 50% charge level and IMHO the most important status - the "Fault" indicator was not illuminated. I left the charger connected for 8 days while the weather was in the teens and 20s, it took 5 days to get to 75% status and on day 9 the charger indicated a 100% charge and I disconnected it. The error messages were being sent out while the garage was in generally in the upper 40s to lower 50s.

Two days ago I drove the GLB about 125 miles and yesterday about 40 miles. Out of curiosity I hooked up the charger a couple of hours ago and the charge status showed an amber color at 50%, it's still amber but now at 75%. The temp in the garage is again in the mid-40s. The Fault light is still not illuminated. My takeaway from this is that I'm aware the GLB's battery is just over 3 years old and the system isn't charging it fully - it's due for a B1 service in the next couple of weeks and, despite not showing a Fault I'm going to have a new battery installed and not wait for a fault to leave me stranded. Do look into getting an MB trickle charger, my 2¢.