OTA updates keep failing because of low 12V battery State of Charge.

[dbsb3233]

if there is insuficent charge in the LVB to perform the update it should initiate a LVB top up automatically followed by rescheduling the update so it doesn't fail.

This. But I wouldn't limit it to just OTAs, it should be the case ALL the time. There's zero excuse for the car not constantly monitoring itself (hourly?) to automatically kick on an LVB charge any time it detects it's needed. As long as the HVB is over, say, 20%.

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[RickMachE]

This. But I wouldn't limit it to just OTAs, it should be the case ALL the time. There's zero excuse for the car not constantly monitoring itself (hourly?) to automatically kick on an LVB charge any time it detects it's needed. As long as the HVB is over, say, 20%.

Agreed. Both my vehicles are sitting at 43% today.

 

[dbsb3233]

Agreed. Both my vehicles are sitting at 43% today.

I don't know if this actually works, but yesterday I set an every-other-day departure time (w/o cabin heating). I'm hoping that kicks in the DCDC system too to give the LVB a top-up. I assume departure times only kick in for maybe 15 minute or so, but that should help the LVB some. I remember doing that last winter too as the temps got colder which zaps LVB performance a bit.

Being retired, it's not uncommon for our MME to sit for a week without use.

 

[RickMachE]

I don't know if this actually works, but yesterday I set an every-other-day departure time (w/o cabin heating). I'm hoping that kicks in the DCDC system too to give the LVB a top-up. I assume departure times only kick in for maybe 15 minute or so, but that should help the LVB some. I remember doing that last winter too as the temps got colder which zaps LVB performance a bit.

Being retired, it's not uncommon for our MME to sit for a week without use.

Departure times, depending on temperature, will run for well over an hour. They will use a lot of energy in comparison to running the vehicle with the HVAC and lights off.

 

[alexgorod]

This. But I wouldn't limit it to just OTAs, it should be the case ALL the time. There's zero excuse for the car not constantly monitoring itself (hourly?) to automatically kick on an LVB charge any time it detects it's needed. As long as the HVB is over, say, 20%.

I think it does - I left the car for 2 weeks at about 60% HVB and was a little nervous about the state of LVB when I come back from vacation. To my surprise, it was almost 90%. Normally, after a night in the garage (not plugged in) or in the parking lot at the end of the work day, it is 70 or lower. I don't know at what point the LVB gets charged from the HVB, but it does.

 

[HuntingPudel]

If the battery needs constant attention then the frunk should have already had easy access to the LVB from the start. From a consumers perspective having it all hidden away and a vehicle with a giant battery gives the impression they should not need to do anything to keep it topped up, which under normal circumstances is what you get as the system will top it up when needed from the HVB.

As long as there is ample charge in the HVB no update should have repated failures (I have had a few in the past due to low 12v when not using the vehicle much) if there is insuficent charge in the LVB to perform the update it should initiate a LVB top up automatically followed by rescheduling the update so it doesn't fail. Multiple messages stating it failed just sums up Fords piss poor approach to software.

Oh, I agree with this but in 2021 there was a rash of discharged LV batteries. Our software back then wasn’t sufficient to maintain the LV battery if the car sat a while. Since I was planning on doing FDRS updates, i just added a race car jump point to make access easier. Ford definitely needed to do this.

 

[dbsb3233]

Departure times, depending on temperature, will run for well over an hour. They will use a lot of energy in comparison to running the vehicle with the HVAC and lights off.

My car us usually in the garage so it doesn't get super cold. I set it for no cabin heat, but I assume it still runs the heater some for battery conditioning. I'll have to check the battery% before and after again, but I'm thinking last year it only drained maybe 1% each time. That's fine by me.

 

[dbsb3233]

I think it does - I left the car for 2 weeks at about 60% HVB and was a little nervous about the state of LVB when I come back from vacation. To my surprise, it was almost 90%. Normally, after a night in the garage (not plugged it) or in the parking lot at the end of the work day, it is 70 or lower. I don't know at what point the LVB gets charged from the HVB, but it does.

Hope so. If it does, we just need to get them to change that to multiple times a day rather than once a week (or whatever it is now).

 

[RobbertPatrison]

Nope, some vehicles just have trouble maintaining the 12V based on how they are used, or because they are woken up frequently while parked. Please see this topic for details on solving your problem:

How To Get Failed OTAs To Install

EDIT: Are you sure you're looking at the charge current correctly? Low voltage side not high voltage? At 60% it should be pulling probably 20+ amps. The correct parameter is LvbA "LVB current".

Thank you for the detailed information. That is very useful. I double checked, but I am looking at the proper signals.

I do see the LVB current of a paltry 1 Amp at 64% SoC of the 12V battery with a voltage of 14.6V. Yesterday I drove for 2+ hours and the SoC never reached above 67%. This seems out-of-spec. The initial current during the first few minutes after start is 20A when voltage is 14.4V, but then quickly drops off as the voltage rises. Obviously it should throttle charging with this high voltage.

The 12V battery SoC is calculated by the car, so I do wonder what that is based on. Could that be wrong and is the battery actually full?
Or is this my second bad 12V battery? This one is 4 months old. If it failed twice then one would think that there is another root cause.

If the battery is bad indeed, why doesn’t the car throw a MIL warning when it detects the odd combination of low SOC with high voltage? That would be better than debugging failed updates.

 

[dbsb3233]

The initial current during the first few minutes after start is 20A when voltage is 14.4V

If you're reading voltages of 14+, you're likely reading the DCDC feed rather than the battery voltage. Start the car then turn it off. That will turn off the DCDC feed and then you can read actual battery voltage until the time-out or door opening shuts the power off.

 

[RobbertPatrison]

If you're reading voltages of 14+, you're likely reading the DCDC feed rather than the battery voltage. Start the car then turn it off. That will turn off the DCDC feed and then you can read actual battery voltage until the time-out or door opening shuts the power off.

You are right. The off voltage is 12.3V. The bottom line is that it doesn’t accept a charge at 14.6V. Looks like a bad battery… It would be nice if the car tells this straight, rather than failing updates while listing a plethora of reasons.

 

[Mike G]

When the car is on, the DCDC power is on too providing power from the HVB. We see either full charge (~14.8v) or trickle/maintenance (~13.5v).

To give the 12v a good long charge in my garage, I turned the car on, left the fob in the car, turned off the 30 minute shutoff, and turned off climate, headlights, and radio. Let it run all night for a deep charge last night. Reading a normal 12.5v now.

Thank you for the detailed information. That is very useful. I double checked, but I am looking at the proper signals.

I do see the LVB current of a paltry 1 Amp at 64% SoC of the 12V battery with a voltage of 14.6V. Yesterday I drove for 2+ hours and the SoC never reached above 67%. This seems out-of-spec. The initial current during the first few minutes after start is 20A when voltage is 14.4V, but then quickly drops off as the voltage rises. Obviously it should throttle charging with this high voltage.

The 12V battery SoC is calculated by the car, so I do wonder what that is based on. Could that be wrong and is the battery actually full?
Or is this my second bad 12V battery? This one is 4 months old. If it failed twice then one would think that there is another root cause.

If the battery is bad indeed, why doesn’t the car throw a MIL warning when it detects the odd combination of low SOC with high voltage? That would be better than debugging failed updates.

Do a BMS reset and then drive around to see if it charges back up.

 

[dbsb3233]

You are right. The off voltage is 12.3V. The bottom line is that it doesn’t accept a charge at 14.6V. Looks like a bad battery… It would be nice if the car tells this straight, rather than failing updates while listing a plethora of reasons.

12.3 may not necessarily be that bad. Readings can fluctuate. Sometimes a deeper (long) charge can bring it back, or so others have said. If you're in position to do so, let it charge continuously for 12-24 hours and see if that shows improvement. Also take multiple readings. The voltage reading can move a few tenths just from a light on or the radio on or other things we forget about.

I showed 12.5 yesterday after leaving the car on in my garage for 20 hours. But I need to check it again today and see if that was just a temp boost or whether it's holding it longer. That's where one of the cheap little cigarette lighter voltmeters comes in handy. I just keep it plugged in the center console storage plug. Don't have to mess with the whole OBD2 thing every time that way.

https://www.amazon.com/Electric-Cigarette-Lighter-Voltmeter-Indicator/dp/B0CN38MQRN/ref=sr_1_26?crid=3QK30FGN52116&keywords=car+voltmeter+cigarette&qid=1701014512&s=industrial&sprefix=car+voltmeter+cigarette,industrial,113&sr=1-26

 

[Mach-Lee]

Thank you for the detailed information. That is very useful. I double checked, but I am looking at the proper signals.

I do see the LVB current of a paltry 1 Amp at 64% SoC of the 12V battery with a voltage of 14.6V. Yesterday I drove for 2+ hours and the SoC never reached above 67%. This seems out-of-spec. The initial current during the first few minutes after start is 20A when voltage is 14.4V, but then quickly drops off as the voltage rises. Obviously it should throttle charging with this high voltage.

The 12V battery SoC is calculated by the car, so I do wonder what that is based on. Could that be wrong and is the battery actually full?
Or is this my second bad 12V battery? This one is 4 months old. If it failed twice then one would think that there is another root cause.

If the battery is bad indeed, why doesn’t the car throw a MIL warning when it detects the odd combination of low SOC with high voltage? That would be better than debugging failed updates.

This is one of those rare cases where I recommend doing the BMS reset. Procedure is near the bottom on that page.

Wondering if maybe it wasn’t reset when the battery was replaced a few months ago? It has to be reset after battery replacement.

 

[dbsb3233]

It would be nice if the car tells this straight, rather than failing updates while listing a plethora of reasons.

Mine did send me FordPass alerts twice last week telling me the 12v was low. So there's apparently some monitoring taking place. Although I don't know if it does that all the time, or just when an OTA is being attempted.

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