Is there a reason why it doesn't keep the 12v topped off when charging?

[mach-ebert]

I'm just curious, is there an actual reason why it doesn't keep the 12v battery topped off when you're plugged in?

This seems like a no-brainer to me. If you're charging the main battery, why not charge the 12v battery at the same time? I feel like if this would occur, it would be really easy to mitigate failed updates due to a low 12v.

Of course this is an issue I'm running into now with the weather being cold. We "remote start" the car in the morning and the heated steering wheel and seats are on. Drop off our son at pre-school and come home. It's just over a mile. And now I have PU 6.6 waiting and it keep failing because I assume the 12v is low.

Super annoying.

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[Mirak]

There's a reason for everything. It probably is not a good one.

 

[azerik]

Just leave the car running, turn off the 30 minute auto-off and lock the car with it running using 7-8 9-0 on the door buttons. It'd 'cost' about 3 cents to charge the battery that way to get the PU.

 

[mach-ebert]

Just leave the car running, turn off the 30 minute auto-off and lock the car with it running using 7-8 9-0 on the door buttons. It'd 'cost' about 3 cents to charge the battery that way to get the PU.

Any guess as to the rate of charge?

 

[azerik]

I've watched it, sadly 30 min will bump the battery about 15% soc.

 

[RickMachE]

I'm just curious, is there an actual reason why it doesn't keep the 12v battery topped off when you're plugged in?

This seems like a no-brainer to me. If you're charging the main battery, why not charge the 12v battery at the same time? I feel like if this would occur, it would be really easy to mitigate failed updates due to a low 12v.

Of course this is an issue I'm running into now with the weather being cold. We "remote start" the car in the morning and the heated steering wheel and seats are on. Drop off our son at pre-school and come home. It's just over a mile. And now I have PU 6.6 waiting and it keep failing because I assume the 12v is low.

Super annoying.

Your title is wrong. It charges the 12v WHILE CHARGING. It does not charge the 12v once charging is complete, which is what your question seems to be.

 

[Trick.Mach-E]

I'm just curious, is there an actual reason why it doesn't keep the 12v battery topped off when you're plugged in?

This seems like a no-brainer to me. If you're charging the main battery, why not charge the 12v battery at the same time? I feel like if this would occur, it would be really easy to mitigate failed updates due to a low 12v.

Of course this is an issue I'm running into now with the weather being cold. We "remote start" the car in the morning and the heated steering wheel and seats are on. Drop off our son at pre-school and come home. It's just over a mile. And now I have PU 6.6 waiting and it keep failing because I assume the 12v is low.

Super annoying.

What's odd is that we get notifications to plug in our FE to maintain the 12V battery. But from what I am reading here is that even when you do plug in your 12V is not charged.

I just got notice that 6.4 has failed to install and it's probably because the 12V battery is low. We just got 6.2.1 on Friday and I am not sure what happened to 6.3 as we have not gotten any notices that was installed.

<edit I was writing my reply when @RickMachE posted his own with a good explanation... thanks>

 

[garapatisri]

I got the message today to my MME, what is the resolution? i did charge my car to 95% last night.

 

[HuntingPudel]

I got the message today to my MME, what is the resolution? i did charge my car to 95% last night.

You charged the high voltage battery, not the 12V battery. Pull the beauty covers and put your 12V on a 12V battery charger, leave the car running, or drive around for a few hours and your 12V will get charged up. ??

 

[Mach-Lee]

Charging the 12V all the time would waste energy because the car would have to stay awake. It’s only charged when the high voltage battery is charging.

 

[garapatisri]

Yes i did change my high voltage battery not the 12V battery. why would a 1yr old car 12V battery die so soon. and i do drive 150miles a day.

 

[Richard L.]

Charging the 12V all the time would waste energy because the car would have to stay awake. It’s only charged when the high voltage battery is charging.

The original designed charging strategy allowed for LVB charging when parked and off. Made sense for those parked for extended time periods. Ford could have changed this which would explain the recent low charge warnings. Charging strategy would transfer 300 watt-hours of energy 48 hours after LVB reached 40% charge state. If for some unknown reason reached 30% charge state, energy transfer would happen immediately. A lot could have changed since 2021.

 

[dj_stang]

Charging the 12V all the time would waste energy because the car would have to stay awake. It’s only charged when the high voltage battery is charging.

Seriously? It would just charge until both 90% LVB and charge limit of HVB are satisfied, and then it would shut off as usual. No energy wasted at all.

 

[2021-MMEx-RT1]

My KonaEV would charge the 12v whenever it dropped below a certain voltage, e.g. 11.5? who knows.

Then the traction battery would come on and charge the 12v

It used to have a setting that I could turn that feature off. Then on one OTA, they set it to ALWAYS ON.

What would happen is the DashCam was hard wired, it had a magic box that would turn the cam off when the 12v dropped below a set voltage, e.g. 11.5

But then the traction battery would sense that that 12v battery was low and charge the 12v. That would activate the DashCam again, and the magic box would allow it to run until 11.5 again.

endless loop

this kills the 12v battery.

A 12V battery has 6 cells, I ended up killing a cell in two different 12v batteries until we figured it out.


So maybe the Mach E only charges the 12V when you are charging so this kind of thing doesn't happen.

 

[mach-ebert]

If my car is plugged in and the HVB reaches my 85% target but my LVB is at 60%, why not top off the LVB? Especially, if updates rely on a certain LVB SoC.

The energy needed to maintain the LVB is negligible. If my car is plugged in, why not use it as a trickle charger?

Or, since it's ran by software, how about charging the LVB when an update fails due to low SoC and the f'ing thing is plugged in?

I've ran into this numerous times now since it's been cold and it's stupid.

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