12v battery problem can have serious consequences

middleview

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here in Quebec we have been experiencing a wave of polar cold for a few days. We reached temperatures of less than 30 Celsius. Several Mustang Mach-E owners have had issues with the 12v battery. One of the people who had this problem was put in a situation that would have serious consequences as she described in her post on the FB site « propriétaires Mustang Mach-E Quebec ».
''A really worrying situation happened to me with my MME premium AWD this morning: I had 115km of autonomy and after a few stops during my shopping my car did not start and I heard a noise in the speakers . I called roadside assistance and there was a 1:30-2:30 wait so someone came to pick me up because I was with my 10 month old baby in the car. After 20 minutes when I got out of the car the door closed behind me and the doors wouldn't open anymore and my baby was stuck in the car for another 30 minutes while the police and the the tug arrives. The tug wasn't able to open the door as it's all electric and there is no emergency way to open the doors if the battery is dead...had to have my dealer move on place and he opens the hood with an intrumejt and dismantles plastic parts to access the battery so that the doors open and I can get my baby out. Words fail me to tell you how my mom's heart suffered during this episode and that I really don't want it to happen again…. After reflection I want to know if this happened to another of you? And here are my solutions and I especially want to hear yours. My car is at the dealership for diagnostics. I would like to be able to have confidence in my vehicle and I will need them to be very convincing for me to agree to take it back…
- change of battery for a more powerful one?
- added smart charger?
- display the level of the 12 volt battery and an alert if it drops below a critical threshold
- Make a reminder for doors that do not have an emergency opening system

Thanks for helping me think through all this….’’
I hope Ford will fix this problem once and for all….
Ps Sorry for m’y english

38334423-B147-44FD-ADC1-171E0526139D.jpeg
Glad the baby is ok, but I fully sympathize. Worst, I think the issue may not be with the battery(12V or otherwise) as much as software/sensors.

I have a 2-week old Mach-E in Montreal and last night and today. AFter removing car from charger in the driveway fully charged:

Sitting in driveway i pressed the accessory start button in the driveway. I did this to start the climate controls to warm cabin - but while accessory mode said it was on neither heat, nor steering heat or seat heat would activate. the car has also shown me the dreaded "Pull over now" and low battery icons! I did not believe it since the car was freshly off charger.

At that point I powered off and pressed brake pedal and start together. Same error state. I powered off.

I opened the door, closed the door, and pressed brake and start button again. Normal state, batteries, heat and operations restored. This has happened this way two times now at -20C.

My takeaway is the car is reacting to reading differences in an unpredicted way somewhere in the software. And i think there are other situations in cold weather that are doing the same way, and may have impacted the original post writer's experience.

For what it is worth. Other insights are appreciated.
 

dtbaker61

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I don't think this will work. I connected a bluetooth OBDII reader and it drained my battery down to 10% before I plugged it in and it recovered.

I was monitoring the LVB to see what would happen, and it seems that when the car is plugged in, it charges the LVB when it gets down to 40%. When it is not plugged in, it looks like it did a small charge at 10% but it really didn't do much of anything until I plugged it in.

So if you leave your car unplugged outside in the cold for a long time, I can see how the 12V could be damaged over time. However, I did notice that when the car is unplugged, it goes into a deep sleep (as most everyone knows) and unless you have something draining the battery (like my OBDII scanner), it should last for a long time unplugged.

It seems to me that people experiencing low LVB must have a problem with the car, assuming there isn't anything draining the battery like I did in my test (such as a heating blanket. ;-)).

20220127_151806.jpg
can you show actual LVB voltage instead of SOC ?

When working correctly, even a 'deep-sleep' MME should wake up HV dc-dc converter and re-charge LVB when it hits 11.9-12.1 volts

An alternative would be to leave the MME 'on', and auto-off setting=off. This would force the HV to maintain the LVB at 100% and keep HV batteries preconditioned even if you turn cabin heat off. It would use more HV, but may avoid the LVB problems by not allowing the MME to sleep.
 
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mkhuffman

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can you show actual LVB voltage instead of SOC ?

When working correctly, even a 'deep-sleep' MME should wake up HV dc-dc converter and re-charge LVB when it hits 11.9-12.1 volts

An alternative would be to leave the MME 'on', and auto-off setting=off. This would force the HV to maintain the LVB at 100% and keep HV batteries preconditioned even if you turn cabin heat off. It would use more HV, but may avoid the LVB problems by not allowing the MME to sleep.
My car did not maintain the battery as you expected when disconnected from the charger. It didn't start maintaining the battery until I connected it to a charger. It is possible it would have maintained it at 11.3V, but I am not ready to take one for the team and test that out. For sure my test demonstrated the battery is not maintained the same way when disconnected from a charger

I think in normal situations the battery would not drain hardly at all when sleeping, so my test really simulates a load which should be a lot less than a heating blanket.

I go back to my previous statement: if your battery is dying, there is something wrong. It should never happen when plugged in even with a load (like a heating blanket). Unplugged there should not be a sufficient load to kill it, unless you have something attached.

2022-01-27_09-33-14.jpg
 

mkhuffman

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Excellent test. What is your 12V standby drain average (quiescent) after obd2 dongle was connected so long? And normally without obd2 dongle connected overnight?
If you look at the time scale I only let it sit overnight with the charger attached, and a few hours in the morning with the charger not attached. I don't know how much current the OBDII scanner pulled, but it has to be pretty light. I am using the scanner to capture the readings so I cannot compare with and without. But when the charger was unplugged I got a "draining 12V battery error" when I started the car.
 

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I don't know how much current the OBDII scanner pulled, but it has to be pretty light. I am using the scanner to capture the readings so I cannot compare with and without.
You should compare with and without.

OBDII dongles when connected constantly drain the 12V battery, because they keep several electronic modules running, especially if dongle has no low-power mode. The drain is constant and may be significant, obd2 dongles without sleep mode repeatedly flatten ICE and EV 12V batteries overnight.

You can easily repeat this test with OBDII removed - connect it only briefly and get readings periodically, or at the start and end of test.

LVB current shows momentary flow from/to 12v battery, very useful sensor.

Another sensor seems to show average parasitic drain from periods when car was asleep: Aux 12V battery standby drain mA (quiescent average). It is probably average over several days, but I don't know exactly what period it measures. For our tests it should suffice to quickly note Quiescent average mA and 12V SOC then disconnect obd2 dongle. Connect it again in the morning and compare both readings.

If car is not turning into sleep properly or is disturbed periodically (PAAC proximity, FordPass requests, HV battery monitoring, other factors we all want to trace...) then 12VSOC will drop rapidly overnight while Quiescent will rise or remain stable, not sure yet.

I found elsewhere that in ICE Ford vehicles the limit is 30-50mA. Even 70mA or 100mA may seem very low, but is probably indicative that car was woken up way too often. What is your Quiescent average after this test?
 


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I don't think this will work. I connected a bluetooth OBDII reader and it drained my battery down to 10% before I plugged it in and it recovered.

I was monitoring the LVB to see what would happen, and it seems that when the car is plugged in, it charges the LVB when it gets down to 40%. When it is not plugged in, it looks like it did a small charge at 10% but it really didn't do much of anything until I plugged it in.

So if you leave your car unplugged outside in the cold for a long time, I can see how the 12V could be damaged over time. However, I did notice that when the car is unplugged, it goes into a deep sleep (as most everyone knows) and unless you have something draining the battery (like my OBDII scanner), it should last for a long time unplugged.

It seems to me that people experiencing low LVB must have a problem with the car, assuming there isn't anything draining the battery like I did in my test (such as a heating blanket. ;-)).
12V will freeze/die plugged in also and you also think that is at around 40% SOC? My experience is it will drain a new battery at -28C plugged in. Plugged in will not help here. Why is it dropping from 90% to 40% so fast is a question? There has to be a large phantom drain here somewhere, something is sticking and quickly depleting the 12V now it is cold. It happens in hours (quick) not days. You could be shopping come out and it is dead. It could be so dead that you can not even get the doors open again to remove your child.

My car just has not worked well so far this winter starting early December. Have had similar weird behave as others note above with errors and driving it with no regen no awd no mode selection no cruise etc. and then sometimes it just plain won't go into gear. 12V died twice so far "this" winter while plugged in. My car is certainly not something you can depend on during this season. Ran well all summer then the temperature started going down and now after cold for a bit it's a bit of a mess. Definitely temperature related and therefore can not be explained by the behavior of this vehicle above 32F. Need to try at -16F.

Cars.com
“A 100 percent fully charged battery will not freeze until approximately minus 76 degrees Fahrenheit. A fully discharged battery can freeze at or around 32 degrees,” Kimbrough said in a telephone interview. The difference between a fully charged and discharged 12-volt battery is not that big."

Will a 12V freezes at -16F (-27C) at 40% soc? Above freezing temperature behavior of this car is not the problem here. What it should do and is not doing when it gets cold is.

Based on my service guy I may have been leapfrogged by someone in Quebec with "similar" problems. Thinking they post on FB and is not totally related. At least we may be getting the problem acknowledged that has been ongoing here since the beginning of December. I expect to see a fix as you can not live with a vehicle that acts like this. Time frame is the question and maybe another software fix again early April like last year? Which will be time bombed and only work until next fall; early December. ;)

I have not left anything plugged in that could draw on the 12V such someone can point a finger at but if it was working I would think of leaving the dongle in also to see what happens.
 
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middleview

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My car just has not worked well so far this winter starting early December. Have had similar weird behave as others note above with errors and driving it with no regen no awd no mode selection no cruise etc. and then sometimes it just plain won't go into gear. 12V died twice so far "this" winter while plugged in. My car is certainly not something you can depend on during this season. Ran well all summer then the temperature started going down and now after cold for a bit it's a bit of a mess. Definitely temperature related and therefore can not be explained by the behavior of this vehicle above 32F. Need to try at -16F.
I think you're on to it Mike. I have my car parked outdoor at home (cold soaking, but plugged in) but I have a warm garage at work, where so far no odd behavior. I think something is staying awake as you surmise, but the cold is the variable hitting the battery too hard much more frequently. I've ordered an OBD2 to join the hunt.
 

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a very unfortunate and I am sure scary set of circumstances. A lot of the stress could have been avoided if the OP knew there was the emergency charge port on the front bumper, which would have powered up the car enough to use the door pillar unlock code.

The baby-in-the car stress could have been avoided by disabling the 'lock on walk away' setting. I would suggest that its a big mistake to ever lock a baby in a car... whether its hot or cold, or just for a minute.

....and for all those living in frigid places, I would highly recommend buying a 12v electric blanket, pull the Frunk panels and stuff the blanket around the 12v battery, connect it to the 12v connection points next to the battery with some D-rings that won't shake loose, and leave that sucker on all winter. It will pull energy from the HV battery, but avoid all the temperature related problems.
Has something new been changed with the front bumper access door regarding what you stated about an emergency charge port? I thought that was just for opening the Frunk hatch to access the battery to then charge or jump your battery to open the door
 

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I think you're on to it Mike. I have my car parked outdoor at home (cold soaking, but plugged in) but I have a warm garage at work, where so far no odd behavior. I think something is staying awake as you surmise, but the cold is the variable hitting the battery too hard much more frequently. I've ordered an OBD2 to join the hunt.
Two here have agreed that when it is plugged in it charges the battery when it gets to a 40% SOC. @mkhuffman above and @louibluey Here? Joe is not as detailed ;). When not plugged in it goes to even a lower soc from what I understand. Both a large drain and poor logic?

Ford Mustang Mach-E 12v battery problem can have serious consequences lead-acid-battery-freezing-temperature


Edit: -32C this morning 91% soc on the 12V and all good at 7am here?
 

dtbaker61

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Has something new been changed with the front bumper access door regarding what you stated about an emergency charge port? I thought that was just for opening the Frunk hatch to access the battery to then charge or jump your battery to open the door
the bumper port leads are only for popping the Frunk hood if and when the 12v battery is completely dead.

THEN you have to remove the drivers side 'beauty cover' to actually charge the 12v... or cut access holes to the connection points so you don't have to remove the covers in the Frunk.
 

dtbaker61

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My car did not maintain the battery as you expected when disconnected from the charger. It didn't start maintaining the battery until I connected it to a charger. It is possible it would have maintained it at 11.3V, but I am not ready to take one for the team and test that out. For sure my test demonstrated the battery is not maintained the same way when disconnected from a charger

I think in normal situations the battery would not drain hardly at all when sleeping, so my test really simulates a load which should be a lot less than a heating blanket.

I go back to my previous statement: if your battery is dying, there is something wrong. It should never happen when plugged in even with a load (like a heating blanket). Unplugged there should not be a sufficient load to kill it, unless you have something attached.

Ford Mustang Mach-E 12v battery problem can have serious consequences lead-acid-battery-freezing-temperature
this chart shows expected wake-n-charge behavior while plugged in.....

....and 'bad' behavior when not plugged in; MME should not have allowed the LVB voltage to drop below 11.9. So, I'd say this chart is exactly what is needed to show your Dealer and @Ford Motor Company to request a check on any related modules updates that may be required.
 

dtbaker61

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You should compare with and without.

OBDII dongles when connected constantly drain the 12V battery, because they keep several electronic modules running, especially if dongle has no low-power mode. The drain is constant and may be significant, obd2 dongles without sleep mode repeatedly flatten ICE and EV 12V batteries overnight.

You can easily repeat this test with OBDII removed - connect it only briefly and get readings periodically, or at the start and end of test.

LVB current shows momentary flow from/to 12v battery, very useful sensor.

Another sensor seems to show average parasitic drain from periods when car was asleep: Aux 12V battery standby drain mA (quiescent average). It is probably average over several days, but I don't know exactly what period it measures. For our tests it should suffice to quickly note Quiescent average mA and 12V SOC then disconnect obd2 dongle. Connect it again in the morning and compare both readings.

If car is not turning into sleep properly or is disturbed periodically (PAAC proximity, FordPass requests, HV battery monitoring, other factors we all want to trace...) then 12VSOC will drop rapidly overnight while Quiescent will rise or remain stable, not sure yet.

I found elsewhere that in ICE Ford vehicles the limit is 30-50mA. Even 70mA or 100mA may seem very low, but is probably indicative that car was woken up way too often. What is your Quiescent average after this test?

it shouldn't matter what parasitic drains are.... the MME is supposed to 'wake up' the HV dc-dc and charge LVB when it hits 12.1-11.9 whether it is plugged in to charger or not. If it's not, then something is WRONG and MME needs service/update.
 

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it shouldn't matter what parasitic drains are.... the MME is supposed to 'wake up' the HV dc-dc and charge LVB when it hits 12.1-11.9 whether it is plugged in to charger or not. If it's not, then something is WRONG and MME needs service/update.
Mine sits better when unplugged and I have never got a charging fault, Hybrid battery positive contactor - circuit stuck open or a dead 12V when parked and not plugged in. Of course it is a lot warmer when it is not plugged in and always plugged in when below freezing.

You also vote that it goes to 40% state of charge before it maintains the 12V.

Ford Mustang Mach-E 12v battery problem can have serious consequences battery-state-of-charge-chart_v2


What temperature would the 12V freeze at when at 40% soc around 9F (-15C)? Thinking we may not have the full picture yet and it may have a minimum 40% soc value when warm but monitor the temperature senor and adjust based on temperature also? Have not seen a lot of brilliant software in there yet but possible. When my 12V is at 90% soc I never have problems. From what I have seen it is a problem with something being triggered on my MME that sucks the 12V down fast.

Parasitic drains may not matter for some conditions but are always unwanted. If you are green they count. I would say it depends on its extent and state the car is currently in but then mine is definitely not working right. Been at my service for near 2 months now and they still have nothing from Ford. But then it toke 4 1/2 months starting day 1 of purchase to have a functional charging schedule. Starting to understand the speed that Ford works at. Once my dealer is allowed to fix it it will go pretty fast.
 
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MTNestr

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Has anyone ever investigated hiding one of these on the exterior of your car? Like in the wheel well or near the (what would be) hitch area? I think this could pop the hood and then provide some charge to the 12v battery to get the car started again?

https://www.amazon.com/NOCO-GB40-Ul...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=
I’m working on an idea where I would put a small battery in the Frunk wired to the LVB with a remote controlled switch to make the connection between the 2 batteries.
 

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A failure when plugged in. Now there are 2 of us. 3 times here so far. Did you get a charge fault in fordpass? 2 different chargers and 2 different voltages (120 and 240). I think it is the MME and not the charger. It was not in hibernation is my guess and it was wide awake draining your 12V. Happens in a time frame of a few hours. 3 times now and not once where I could not open the door. It would not start throwing melt down errors but so far the door has always opened.

The basics kind of need to work which includes not just dying in yours or someone else's parking lot.
Good morning! Could you please privately message us with your VIN and the name and location of your Ford dealer. I’d like to look into this battery concern for you. Thanks!
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