Sam Krahn 
Typically, the only fear electric vehicle owners have is running out of battery charge. But for a few select 2021 Ford Mustang Mach-E owners, they are having issues when their vehicle is fully charged. The Verge was the first to report a small percentage of early Mach-E owners were unable to start their vehicle when it was fully charged, a huge issue for Ford’s first mass-market EV. Luckily, Ford is addressing the issue and affected owners will soon have a fix in their local dealer, according to their National Highway Traffic Safety Administration filing. And it isn’t a recall, but rather a “technical service bulletin.”
The problem stems from balancing the charge of the main battery and the smaller, 12 volt battery. In the Ford Mustang Mach-E, like most EVs, the main lithium-ion battery pack keeps the 12 volt lead-acid battery topped up. It works in a similar way to an internal combustion engine charging a battery while driving. But in some Mach-Es, that process can be interrupted during charging the main battery, and the 12 volt unit loses its charge.
As is the case with other EVs, the main battery is high voltage, and isn’t actually used for many vehicle functions. On the Ford Mustang Mach-E, this includes starting the vehicle, and that’s why some owners are left with a fully charged electric vehicle that also manages to have a dead battery.
Luckily, it’s only a small number of 2021 Mustang Mach-E units affected, according to Ford. The service bulletin says it’s only affecting vehicles built on or before February 3, 2021. But even though this is a software glitch, and Ford touts their over the air updates should let most Mustang Mach-E do the majority of maintenance from their garage, affected customers have to go to the dealership for this fix.
Having a dead battery issue on fully charged electric vehicles is rather ironic, so hopefully this is the last time Ford has to deal with this problem.
the problem still plagues the new Mach-E, ours built in Sept 2021 has a bad battery from the factory and sat at the dealer for over a month waiting on a ford 12v battery before the dealer would release the unit to us.
Ford has yet to fix/replace the 12v battery, but we wanted the car before 2022…
2yrs from the reservation to delivery date was too long.
More growing pains for Ford and their electric car rollout I guess. 🙁
It’s a Ford thing. Look at the teething issues seen with the Bronco launch, the new F-150 launch, the Explorer launch from 2019… all this is to say going for the first model year probably isn’t the best move.