Charging is a common concern with electric vehicles. But some owners of the brand-new Mustang Mach-E have run into a peculiar problem: their electric SUVs won’t start even when the main battery pack is full.
That’s because, The Verge has learned, there’s a problem with some early Mustang Mach-E SUVs that involves how the much smaller 12-volt battery gets charged. It’s the latest in a growing line of small issues that have come to light during the rollout of Ford’s first long-range electric car.
As is the case in other electric cars, the Mustang Mach-E keeps its 12-volt lead-acid battery topped up by essentially sipping power from the much larger lithium-ion battery pack. Based on owners’ accounts across multiple forum threads, including one who spoke to The Verge, the problem is this stops happening whenever the Mustang Mach-E is plugged in to charge up the larger battery pack.
That is especially an issue for owners in areas with cold weather, as Ford encourages them to leave their Mustang Mach-Es plugged in so the SUVs can use power from the grid to warm up before driving.
The 12-volt battery powers many of the Mustang Mach-E’s systems (since the larger battery pack is high-voltage), and so when it dies, the electric SUV cannot be started. When this happens, owners have reported the FordPass app says the vehicle is in “deep sleep” mode. Some forum members have started referring to it as the “electric brick” problem.
Ford recently filed a technical service bulletin with the National Highway Traffic Safety Administration that confirms the problem has to do with the software on the powertrain control module. Ford wrote that this only affects Mustang Mach-E SUVs built on or before February 3rd, meaning it’s possible that dozens are affected. (Ford would only say that a “small number” of the nearly 7,000 Mustang Mach-Es delivered in the first three months of the year have the issue.)
Right now, those owners cannot get the fix via an over-the-air update. The company said in a statement that they’ll have to bring their Mustang Mach-Es to a dealer:
We are aware that a small number of Mustang Mach-E owners have had their 12V battery reach a low voltage condition. We proactively worked with early owners experiencing this issue to identify the root cause and a fix. In the rare instances where this still occurs, customers can now contact their local EV-certified Ford dealer to have the matter resolved.
Ford did tell The Verge that the problem will be fixable via wireless update “later this year” and that Mustang Mach-Es currently coming off the line should not be affected.
It is possible to jump the 12-volt battery, just as you would jump-start an internal combustion car. But it’s not nearly as straightforward, especially because the battery is located behind the Mustang Mach-E’s front trunk, and the hood’s electronic latch is powered by the low-voltage battery.
To first open the front trunk then, owners have to open a panel in the front bumper that contains two leads, which can be used to jump the front trunk’s electronic hood latch. Then they have to pull back a panel underneath the hood to find the battery — though even at this point, some owners have had trouble accessing the leads on the 12-volt battery and have cut through the vinyl to more easily jump-start the battery.
Ford offers free roadside assistance with the Mustang Mach-E, too, so owners have this as an option if they need to get their electric SUVs towed to a dealer. The roadside assistance is also supposed to include 12-volt battery jump starts, according to the owner manual.
Update April 8th, 5:48PM ET: Clarified in the tenth paragraph that owners have discussed on Mustang Mach-E forums cutting through the trunk panels to more easily access the battery, rather than out of necessity.