Low voltage in the 12V battery means the electric car won’t go
Software fix available at dealers, OTA coming
Owners of the first Ford Mustang Mach-E EVs could run into a problem with starting their vehicles, says a new report. The issue is said to come not from the full-size battery back, but from the 12-volt old-school battery that is still found in every EV running the parts that the high-voltage system can’t.
The problem, says The Verge, is in how the 12V battery is being charged from the larger pack. Because using conventional 12V systems for things like lighting, radios, and other smaller electrical features is easier and cheaper than designing all-new, EVs have a 12V system that is charged up as needed from the main battery pack to run those systems.
According to multiple owner reports, the report says, when drivers have their vehicles plugged in to charge the main pack, the 12V battery stops charging. So owners using the 12V accessories, especially in cold weather areas, can see the 12V battery drop to a voltage too low to run the vehicle. When this happens, the EV won’t “start” and can’t be driven.
Ford acknowledged the issue in a Technical Service Bulletin filed with the NHTSA, saying that “some 2021 Mustang Mach-E vehicles built on or before 3-Feb-2021 may exhibit the 12-volt battery becoming discharged while the vehicle is plugged in during the high voltage charging process.” The fix is a reprogramming of certain modules involved in the process and charging the 12V battery from an external source to get the vehicle running again.
At this time, The Verge said, Ford says the fix will require a dealer trip, but that an OTA fix is coming. Another short-term solution for drivers who find themselves stranded (aside from Ford roadside assistance) is to jump the 12V battery. A process that requires the front trunk to be boosted, then a panel removed to access the 12V battery.