Lost 4% Battery Without Driving

mamejunkie

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I doubt this is normal. Didn't drive the car all day yesterday, started at 90% charged and last night I noticed it was at 86% via the FordPass app. What would cause a drop like this? Did go out and check that it wasn't on or on some weird mode. Was locked. Strange it didn't unlock when I approach with the fob.





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mark360

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I doubt this is normal. Didn't drive the car all day yesterday, started at 90% charged and last night I noticed it was at 86% via the FordPass app. What would cause a drop like this? Did go out and check that it wasn't on or on some weird mode. Was locked. Strange it didn't unlock when I approach with the fob.
Was it at 86% this morning? That would sound about normal depending on if your car, most cars lose about 2% of battery per 24hr period.
 

mark360

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If it's cold outside the car will use power to keep the battery a certain temp as well, so there are some external factors to look at.
 

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Mine does not lose anything overnight (so far) - parked in a garage heated to 50F.
 
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In SoCal, outside low is 48. The MME is in the garage and its about 68.
 

TheVirtualTim

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Was the car plugged in? When the car is not plugged in it will use the big battery to maintain the little battery. 4% sounds like a lot in 24
Mine does not lose anything overnight (so far) - parked in a garage heated to 50F.
Do you leave your car plugged in?

Phantom drain is normal ... but probably not 4% in a day.

When the car is shut off, a lot of computer modules are put to sleep. But there are some modules that have to stay awake the whole time and those are always drawing power from the 12v battery.

There's a module that monitors the charge state of the 12v battery and it will periodically decide the 12v needs a charge. If the car is plugged in then it will draw power from your charger (AC power). If the car is not plugged in it will draw the power from the big battery -- and that's when you'll see the power drain (and that's normal).

I normally leave my car plugged in (and only charge it to 80%) when not using it so the 12v gets maintained from the house AC power. So I haven't got a good feel for how much daily drain is normal when it is not plugged in. I hear about 1%/day is probably normal.
 

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There's a module that monitors the charge state of the 12v battery and it will periodically decide the 12v needs a charge. If the car is plugged in then it will draw power from your charger (AC power). If the car is not plugged in it will draw the power from the big battery -- and that's when you'll see the power drain (and that's normal).
Wow, I had no idea that the big battery supplied charge to the 12v. I wonder if the 12v battery life gets extended as a result?
 

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I didn't drive my car for a day, but kept it plugged in. Yesterday I went for a drive. The app reported it was still at 90% charge. When I got in, it reported 89% charge, and had dropped to 86% by the time I just backed out of the driveway. After that drop it went back to dropping normally. Seems like if the car is just sitting there it doesn't update the app with current SoC often. And possible the car doesn't check either since the dash dropped almost immediately after starting the car.
 
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It wasn't connected at that time. Since its not cold here in SoCal, I just hit the current max (90%) and unplug it. Wait till I get to the ~50% before I plug it back in...a few days later.
 

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Wow, I had no idea that the big battery supplied charge to the 12v. I wonder if the 12v battery life gets extended as a result?
No. If anything, it's the opposite. Not for that reason per se but because the 12v battery gets used a lot more in a BEV, like for heating and cooling (cabin and battery pack).
 

mark360

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It wasn't connected at that time. Since its not cold here in SoCal, I just hit the current max (90%) and unplug it. Wait till I get to the ~50% before I plug it back in...a few days later.
Yeah I don't know then if it was parked in your garage. The normal rate is 2% per 24 hour period of phantom drain, unless it's really cold out. 4% isn't anything I'd get too worried about and it could just be a bug in their software. I'd just keep a close eye on it and if anything your service manager is only a call away.
 

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Do you leave your car plugged in?
I have not been leaving it plugged in, but I think it's a good idea to do so and may start tonight.
I've just been lazy up till now.
 

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No. If anything, it's the opposite. Not for that reason per se but because the 12v battery gets used a lot more in a BEV, like for heating and cooling (cabin and battery pack).
Forgive my ignorance: So there is no alternator in the MM-e?
 

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Forgive my ignorance: So there is no alternator in the MM-e?
There's a component that performs a similar function that charges the 12V from the 400v battery
 

dbsb3233

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Forgive my ignorance: So there is no alternator in the MM-e?
Correct, no alternator. In an ICE car, an alternator is needed to convert the fuel (gas) to electricity. In a BEV, electricity is already the fuel. Much more efficient to just transfer electricity to the 12V battery from the high voltage battery.
 

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