12V discharging problems on the Ford Focus Electric

I just made the last payment on my Ford Focus Electric (FFE). I’ve had it now for five mostly-wonderful years. But there’s been an occasional problem related to the 12V battery and I’ve finally figured out (most) of the details about it. If you have an FFE, you probably want to read this.

There are two batteries in the FFE: the big 325V 24kWh drive battery and the standard automative 12V (approximately 0.4kWh). The 12V gets recharged from the drive battery via a DC to DC converter because unlike a standard car there’s no alternator (and no engine to drive an alternator). In normal operation, the 12V’s charging cycle goes something like this:

• Push Start button – 12V provides power to the computers and systems that turn the car on.
• While the car is on, the DC to DC converter keeps the 12V battery charged similar to how an alternator would.
• When you shut the car off, the 12V battery stops being charged, and it’s used to keep power trickling to the car’s computers and electronics in sleep mode.
• When you plug in to charge the drive battery, the 12V usually doesn’t get charged unless it’s low – in which case the DC to DC converter will charge it just like when the car is on (I wrote more on this in an earlier post).

Typically the drain on the battery when the car is shut off is pretty minimal. I’ve had my car sit in long-term parking at the airport for a week or so and start up with no problems. But, sometimes the FFE can get into a bad state where it will drain the 12V battery at a much higher rate while the car is off. When in this state, the 12V will run down in approximately 48 hours, or less depending on the age and condition of your 12V battery. When this happens, you’ll come out to a dead car – the power door locks won’t work and the start button won’t work. When you charge up the battery with a trickle charger, it will start up fine and it will no longer be in the bad state! (To add insult to injury, when the car restarts it will then send you an email saying that the 12V battery is low!) Complete loss of power resets the electronics and clears up that bad state. So now you can drive it around just like normal and leave it unplugged for days and you’re fine – until the next time it gets into that bad state.

What I’ve finally figured out after years of having this problem crop up occasionally is that the trigger seems to be parking the car where it can’t get online and communicate with the cloud. For example, parking on the second basement level in my office garage means I can’t get satellite radio and there’s also no way for my car’s TCU (telematics control unit) to reach the online servers at Ford. Once that happens, the TCU or some related part of the electronics gets stuck in some state where it’s draining a lot of power. Once it’s in that state, if you let it sit for a day or two, the 12V will likely be dead. You can prevent this by disconnecting the 12V for a minute or so and then reconnecting it. That will reset things just like it does when the battery totally dies.

There are a few ways to tell when your car gets into this bad state:

1. It will stop sending you emails about charge state (e.g. the one that tells you charge has completed).
2. The MyFord Mobile app won’t be able to sync with the car anymore. It has a “Last updated at” field on the main screen – that will stay frozen at whatever date your car got into the bad state.
3. If you park somewhere that your car should go into “Value Charge” mode when you turn it off, it won’t – it will be stuck on “Charge Now” and you won’t be able to change it.

This all seems pretty simple and straightforward as I write this up, but it took me five years and several dead-car incidents to figure all this out. Now I carry a lithium-ion jump starter in my car in case it happens again, and I’m very proactive about doing the disconnect/reconnect thing whenever it gets into the bad state. (Plus I don’t park on B2 anymore!)

I had hoped that software upgrades would fix this problem. I had my dealer perform TSB 16-0024 which updated the software on the PCM, ABS, BECM, SOBDM, and TCM. The problem still happens after all those upgrades. They also updated the APIM (Sync) to 3.10 and that didn’t make a difference either.

While I’m glad I’ve figured this out and I expect that going forward I’ll be able to manage this and never wind up with a dead car again, I am very disappointed that the 12V battery is the weakest link in the whole FFE platform. I love the car in general. It’s loaded with high tech components and systems. And yet the most mundane part – the 12V lead-acid battery that’s been part of automobiles for 100 years – that’s the one that causes the biggest problems, and even their latest updates haven’t fixed it. I hope they will deliver a fix for it someday but I’m not optimistic, as the FFE doesn’t seem to get much of Ford’s attention. If only that would change….