Posts: 100
Joined: Sat Mar 10, 2012 8:04 am

Re: Dead 12V battery

Wed Jan 23, 2013 6:13 am

Leaving something on was my assumption also. No lights on, doors tightly closed. It is a mystery to me. My next test is to simply leave it in the barn for several days and see if it dies again.
2012 Ford Focus Electric. Delivered 5/29/2012

Posts: 51
Joined: Sun Dec 23, 2012 4:17 pm
Location: western Colorado
Contact: Website

Re: Dead 12V battery

Sat Mar 16, 2013 9:53 am

I just killed my 2013 FFE (inadvertently) by getting out at my office in the morning without turning it off. I thought I had turned it off, but that didn't work because I wasn't in Park. The car doubtless beeped at me but I was in a hurry and ignored the signal. By the end of the afternoon, the car was completely dead because the 12V battery was depleted by the various controls and a seat heater that didn't know to turn off. I jumped it with a portable miniature lead-acid battery we keep for this purpose, and after 2 minutes' 12V charge it was fine. A good lesson in making sure, when you get out of your car, that it's REALLY off.

However, I'm puzzled that the nearly-full traction battery didn't use its DC-DC converter to recharge the 12V battery so the car would start. I seem to recall another post's saying that this works only when the car is being recharged. I don't see the rationale for that requirement. Of course the designers don't want to run out of traction energy, but it's unusable anyway if the 12V battery is dead. Maybe Ford could change the software so that if the 12V battery has seen a long steady load but no driving activity, it could hypothesize that the driver simply forgot to turn off the car and could recharge the 12V battery from the traction battery even if the car isn't plugged in.

Site Moderator
Posts: 81
Joined: Tue Jan 29, 2013 9:08 pm
Location: Houston

Re: Dead 12V battery

Sat Mar 16, 2013 1:39 pm

This is one of those teething issues that will get worked out eventually.

I think eventually the 12V batteries will go away entirely. IIRC, the Model S doesn't have one.

Posts: 12
Joined: Sun Mar 24, 2013 7:59 pm

Re: Dead 12V battery

Sun Apr 28, 2013 9:56 pm

I think the very inefficient 12 volt lead acid battery should go! The VW Jetta hybrid runs everything from the traction battery via a dc to dc converter.

Posts: 1425
Joined: Mon Apr 07, 2014 12:46 pm
Location: Minneapolis

Re: Dead 12V battery

Fri Jun 12, 2015 1:52 pm

TSB 13-9-19 calls for reprogramming the PCM if the customer is experiencing a dead 12V battery.
2013 Ford Focus Electric - Ice Storm - leased through 8/15/16
Replaced by a 2016 Tesla Model S 60D

Return to “Technical Discussions”