Dead 12V battery

[Trielectric]

While towing my 2012 FFE home on a front wheel dolly I had the FFE 4 way flashers on. When I noticed the flashers were barely flashing I stopped and tried to open the door with the electronic key. No good. I used the mechanical key to open the door. The 4 way flashers would not turn off, apparently because there was little or no power to the switch. I disconnected the 12V battery and continued home in the dark. Upon arriving home I placed the 12V battery on a normal 12 charger for an hour, disconnected the charger, then reconnected the 12V battery. The 4 way flashers were still flashing and I still could not turn them off. The electronic key still did not work and no buttons in the car worked. As a last resort I plugged in the 120V main battery charger to see if that worked. Bingo, the alarm sounded, the remote worked, every thing lit up and life was great again since I still had to get the FFE off the trailer.

 

[Evocus]

Thanks for detailing your debugging steps. There aren't very many of us FFE owners and this information is really valuable.

I believe there is a DC/DC charger that charges the 12V battery from the main battery, so I'm surprised the 12V would go flat.

Was your main battery flat?
Perhaps this charger is only engaged when the main battery is charged?

 

[Trielectric]

My 300v battery was fully charged at the beginning of the trip and at the end of the trip. It appears that the 12 volt battery only gets charged from the main battery when the Stop/Start button has been depressed for the Start(run)(ignition?) mode. There is a note in the owners manual referencing something similar to this but it doesn't quite match up with the symptons I had.

 

[Econenviro]

The Prius and the Chevy volt also work this way. The car has to be on for it to keep the 12 volt battery charged.

 

[dwf123]

Thanks for the interesting info on the 12v battery. In keeping with this discussion, does anyone know exactly what the 12v battery runs? Does the main Lithium battery constantly charge the 12v, or does it only charge when the car is plugged in. Are there any power saving tips to be gained. For example are the seats heated by the 12v or the main battery. What I am looking for are ways to reduce the power drain during the cold weather. My range with the heaters has been dramatically reduced.

 

[Ram]

My previous electric vehicle was a 2000 Ford Ranger EV. Ford made these from 1999 to 2001 as lease only. Most got crushed. About 200 slipped under the radar and still are on the road. We also had a similar problem with the 12 volt battery. If the 12V battery went dead, the truck was dead and would not charge. You would have to charge up with a 12V charger or replace the 12V battery to even get the truck to charge. I am not sure how much technology they took from the Ranger but it was a fantastic vehicle.

 

[Econenviro]

The seat heaters are 12volt. But are much more efficient than the cabin heaters. If you drive an hour a day with the seat heat heaters on max, they might use a fifth of a kwh. Or less than a mile of range.

 

[dwf123]

If you drive an hour a day with the seat heat heaters on max, they might use a fifth of a kwh. Or less than a mile of range.

Have you really tried that??? Makes for a pretty warm arse.... :lol:

 

[dwf123]

So, I went away for a week, I left the FFE fully charged and plugged in to my ChargePoint Level 2 charger. 24 hours out I started getting these messages about plugging in because the 12 volt battery needs to be charged.

I called my bride and asked her to check the car. She told me the key would not allow her entry and had to take out the metal entry key to open the car. Nothing was working. I asked her to remove the plug, reattach to the ChargePoint, swipe the card and reinsert into the car. Nothing happened. At that point and thanks to this forum, I realized the 12 volt was dead. So she left it alone. (Thankfully, I took my gasser to the airport.)

Upon returning, I disconnected the 12 volt battery terminals and attached my trickle charger. As soon as the battery was charged, I reattched the terminals and bingo everything lit up. I started the car and the main battery was fully charged.

My question is - Why did this battery lose it's charge? I drive this car everyday. I charge it twice per day. There are no gauges showing 12v battery charge, no indication of a low charge other then the text messages I received, too late to address the problem. What if I had taken it to the airport? How do I prevent this in the future? I read the owner's manual and found no information other that how to jump start the battery. Really... Jump start an 8 month old car????

 

[Evocus]

Wood,

I've left my FFE at the airport for more than 2 weeks without any issues with the 12V or other problems. Easiest explanation is that you probably have something unexpected draining your 12V.

Tim

 

[dwf123]

Tim,
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.
Wood

 

[mountaineer]

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.

 

[user 3729]

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.

 

[SolarSteve]

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.

 

[hybridbear]

TSB 13-9-19 calls for reprogramming the PCM if the customer is experiencing a dead 12V battery.