Is 12V battery covered until warranty? What's a healthy voltage?

[Mach-Lee]

I am wondering if something either happened to my 12V battery or if the car's 12V calibration got messed up when I had my car in for the HVBJB replacement in late Oct. I previously regularly saw it over 80% and up to 90%, but now it seems to quickly charge from the 50s% or 60s% to 75% while driving, but then is just barely goes up from there to 76% or 77% but no more, even after a 30-45 minutes drive.

I think I'll disconnect the 12V battery and put it on a charger then reinstall it and see what the Mach-E says, unless I get better advice here (love the advice on these forums!).

I'm not sure why it's so different now than before the service. Did they mis-calibrate the 12V SoC algorithm during the service?

I've only had the car for 19 months and ~33,500 miles.

I've seen this exact thing multiple times, and my theory is the dealers mess up the BMS by connecting a battery charger incorrectly during programming. This offsets the BMS SoC curve, which apparently isn't periodically corrected.

I've very curious the results of your experiment if you do this. Don't reset anything, just disconnect, charge, and reconnect and I want to know if that alone fixes it or not. It needs a 8 hour rest period after you reconnect to relearn. Thanks.

I don't think this thread ever answered the original question, or I missed it.

What is the warranty replacement voltage for the LVB and what is the term? 36k miles, 3 years?

Yes, 3YR/36k warranty applies to 12V battery.

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[hack-e]

I've seen this exact thing multiple times, and my theory is the dealers mess up the BMS by connecting a battery charger incorrectly during programming. This offsets the BMS SoC curve, which apparently isn't periodically corrected.

Really seems like what happened to mine, as you will see below.

I've very curious the results of your experiment if you do this. Don't reset anything, just disconnect, charge, and reconnect and I want to know if that alone fixes it or not. It needs a 8 hour rest period after you reconnect to relearn. Thanks.

I completely charged my battery, disconnected. I wasn't sure there was a way to do it without removing the frunk, so that was some work!
I was going to do it exactly as you stated, just charge and plug back in without calibration, but by the time it finished charging, I just wanted to calibrate and be done with it. So I immediately hooked the battery back up and quickly did the calibration procedure. Then I put the car back together and took it for a spin (actually still out right now... stopped to charge a bit at an EA station). SoC started at 96‰ but I had accidentally left my OBDII reader in the port, so I suspect it drained the battery a touch while I reassembled the car. After about 5 minutes or so of driving it hit 99%, then maybe 10 minutes later hit 100%.

I'll keep an eye on it. Wish I had checked SoC after charging but before calibration, but it was late.

 

[hack-e]

I'll keep an eye on it. Wish I had checked SoC after charging but before calibration, but it was late.

Thought I'd post an update. After the full 12V battery charge (disconnected from the vehicle), then reconnecting, and calibrating, I now regularly see the 12V SoC top out > 80%. For example, Monday I drove over 450 miles and near the end I checked and it was at 86%. It seems like it ought to top out over 90%, but I'm good with > 80% just so it doesn't mess with software updates.

I would say the 12V SoC calibration added ~10% to my top end SoC. I hope Ford adds a 12V SoC calibration to the HVBJB replacement procedure. If they don't, it could affect future OTA software updates being applied.

 

[Triggerhappy007]

I'm wondering about the OP's question, too. Is the 12V battery covered under the factory 36/36 warranty?

The evening news here in Vegas during the summer routinely states not to expect more than a 24-month lifespan for a battery due to the sizzling temps. That scares me about my EV battery, too. It's still 100 degrees at midnight some days. I'm only going to charge after dark and before daylight.

Yes, it's covered. Mach-Lee answered that 3 posts above you.

 

[GreaseMonkey]

Thought I'd post an update. After the full 12V battery charge (disconnected from the vehicle), then reconnecting, and calibrating, I now regularly see the 12V SoC top out > 80%. For example, Monday I drove over 450 miles and near the end I checked and it was at 86%. It seems like it ought to top out over 90%, but I'm good with > 80% just so it doesn't mess with software updates.

I would say the 12V SoC calibration added ~10% to my top end SoC. I hope Ford adds a 12V SoC calibration to the HVBJB replacement procedure. If they don't, it could affect future OTA software updates being applied.

This is extremely helpful. Thanks for posting. I’ll have to do the same on mine soon.

 

[RickMachE]

I've seen this exact thing multiple times, and my theory is the dealers mess up the BMS by connecting a battery charger incorrectly during programming. This offsets the BMS SoC curve, which apparently isn't periodically corrected.

My Lightning was updated by the dealer before delivery, as a condition of sale. Because my salesperson sent a picture of it being updated, and because I sent that picture to Lee, he observed that with mine also and we told the salesperson to tell the dealer to do it right, and the update might work.

Mike also helped out during the process, so if it was him who spotted the error, oops.

Point is - dealers often do it wrong.

 

[averyintucson]

I would like a review of my conclusion that the 12V battery in my 2022 MachE Premium AWD is failing. I have been getting a message that OTA updates are failing for several weeks now, with one of the possible causes being low 12V battery. I have also been getting warning of low 12V. I hooked up a BT battery monitor which showed about 12.0V, and using my regular voltmeter verified this reads about 0.1 to 0.2 V high. I connected a 12V battery charger which has about 1A capability, and it gradually boosted the voltage to nearly 14V, but the log shows that at the time scheduled for the update the voltage dropped to about 12V, and I got another update failure message. That was last night. For tonight, I hooked up a 20A 12V power supply set to about 13.6 VDC so I hope this will supply enough current for the LVB system to complete the update. I am planning on making a service appointment with my dealer in the near future. My understanding is that the OEM battery is an AGM with 35AH reserve capacity, so this should do pretty well under deep-cycle conditions. I am considering upgrading to an LFP 12V with 70AH that is supposed to have in internal BMS and be compatible with the MachE, but it is not cheap.

 

[Mach-Lee]

I would like a review of my conclusion that the 12V battery in my 2022 MachE Premium AWD is failing. I have been getting a message that OTA updates are failing for several weeks now, with one of the possible causes being low 12V battery. I have also been getting warning of low 12V. I hooked up a BT battery monitor which showed about 12.0V, and using my regular voltmeter verified this reads about 0.1 to 0.2 V high. I connected a 12V battery charger which has about 1A capability, and it gradually boosted the voltage to nearly 14V, but the log shows that at the time scheduled for the update the voltage dropped to about 12V, and I got another update failure message. That was last night. For tonight, I hooked up a 20A 12V power supply set to about 13.6 VDC so I hope this will supply enough current for the LVB system to complete the update. I am planning on making a service appointment with my dealer in the near future. My understanding is that the OEM battery is an AGM with 35AH reserve capacity, so this should do pretty well under deep-cycle conditions. I am considering upgrading to an LFP 12V with 70AH that is supposed to have in internal BMS and be compatible with the MachE, but it is not cheap.

Your 12V battery is not failing just because your updates are failing. If you're concerned, send me your VIN and I'll let you know if it's in good or bad shape. Many people just have low batteries from not driving enough, and a long-duration recharge will solve most issues.

Do not switch to LFP chemistry or you'll make things worse due to voltage setpoint differences. The battery must be AGM Lead Acid and 35 Ah capacity, which is what the BMS is programmed for. Anything else will cause issues.

BMS is very slow to adjust to increased SoC. You need to leave the power supply connected for 12+ hours set to 13.6V to fully charge it. Also I hope you hooked up the charger correctly with a body ground (very important). If you incorrectly connect the charger to the negative battery terminal, you'll make the SoC go down and the car could enter load shed mode (and your OTA won't ever install).

 

[hack-e]

Thought I'd post an update. After the full 12V battery charge (disconnected from the vehicle), then reconnecting, and calibrating, I now regularly see the 12V SoC top out > 80%. For example, Monday I drove over 450 miles and near the end I checked and it was at 86%. It seems like it ought to top out over 90%, but I'm good with > 80% just so it doesn't mess with software updates.

I would say the 12V SoC calibration added ~10% to my top end SoC. I hope Ford adds a 12V SoC calibration to the HVBJB replacement procedure. If they don't, it could affect future OTA software updates being applied.

A few hours into the 450 mile drive back today I checked the 12V SoC and it said 91%. So it's seemingly much better after the recalibration.

 

[Rt1AWD]

It shouldn’t because……..

Apparently it doesn't work


Hey Ford! You have a bug!

 

[averyintucson]

Your 12V battery is not failing just because your updates are failing. If you're concerned, send me your VIN and I'll let you know if it's in good or bad shape. Many people just have low batteries from not driving enough, and a long-duration recharge will solve most issues.

Do not switch to LFP chemistry or you'll make things worse due to voltage setpoint differences. The battery must be AGM Lead Acid and 35 Ah capacity, which is what the BMS is programmed for. Anything else will cause issues.

BMS is very slow to adjust to increased SoC. You need to leave the power supply connected for 12+ hours set to 13.6V to fully charge it. Also I hope you hooked up the charger correctly with a body ground (very important). If you incorrectly connect the charger to the negative battery terminal, you'll make the SoC go down and the car could enter load shed mode (and your OTA won't ever install).

I have made a service appointment with my dealer. I had a couple of service bulletins due anyway, so I will let the service department figure out if there is a defect in the 12V battery or the 12V BMS.

I connected a 20A power supply set at 13.8V to the designated jumper points, not directly on the battery. While this was connected, the OTA software update did succeed several hours later.

The company at this link claims that the built-in BMS in their LFP battery makes it compatible with the MachE. What are they missing?
https://www.ohmmu.com/product-page/12v-lithium-battery-for-ford-mustang-mach-e

 

[Mach-Lee]

I have made a service appointment with my dealer. I had a couple of service bulletins due anyway, so I will let the service department figure out if there is a defect in the 12V battery or the 12V BMS.

I connected a 20A power supply set at 13.8V to the designated jumper points, not directly on the battery. While this was connected, the OTA software update did succeed several hours later.

The company at this link claims that the built-in BMS in their LFP battery makes it compatible with the MachE. What are they missing?
https://www.ohmmu.com/product-page/12v-lithium-battery-for-ford-mustang-mach-e

They are just saying it fits, not that it will work right. They are missing that the voltage setpoint while driving is only about 12.8V at times, which will keep an AGM at 100% but will cause an LFP battery to drain down to 30% SoC. The voltage is too low to keep the LFP charged, and as a result you have your SYNC screen shut down while driving when it goes into load shed mode (since the BMS sees the battery draining).

LFP batteries only work with dumb charging systems that keep the voltage at 13.6+ volts all the time.

 

[averyintucson]

They are just saying it fits, not that it will work right. They are missing that the voltage setpoint while driving is only about 12.8V at times, which will keep an AGM at 100% but will cause an LFP battery to drain down to 30% SoC. The voltage is too low to keep the LFP charged, and as a result you have your SYNC screen shut down while driving when it goes into load shed mode (since the BMS sees the battery draining).

LFP batteries only work with dumb charging systems that keep the voltage at 13.6+ volts all the time.

The article in Battery University, BU-409b, seems to indicate that an LFP would be a reasonable Lead-acid replacement for automotive use, but not UPS use, because the float charge in automotive use is not continuous. It cautions that constant float charge may shorten LFP battery life in a UPS. It also has this note:
"LFP will not be fully charged but has more capacity than lead acid"
This is because the max charger voltage from a L-A systems is a bit less than from a specifically LFP charger system. I think that a little undercharging should not degrade LFP battery life, and may extend it. Also, the OEM AGM is rated at 35AH, while the LFP I linked before is rated at 70AH, so even not fully charged will have over half again the charge.
The BU-409b lists the L-A float charge as 13.5V, and then notes:
"Commonly used for UPS; float charge voltages for automotive may be higher"
My experience is that automotive electrical systems float the battery at about 13.6V. I don't have the battery monitor log data for driving the Mach-E, but I do have some for my other EV and it is entirely consistent with the table in BU-409b.
I have installed an LFP in my other (not Ford) EV, so I will see how long it lasts. So far, so good.
https://batteryuniversity.com/article/bu-409b-charging-lithium-iron-phosphate

 

[Mach-Lee]

The article in Battery University, BU-409b, seems to indicate that an LFP would be a reasonable Lead-acid replacement for automotive use, but not UPS use, because the float charge in automotive use is not continuous. It cautions that constant float charge may shorten LFP battery life in a UPS. It also has this note:
"LFP will not be fully charged but has more capacity than lead acid"
This is because the max charger voltage from a L-A systems is a bit less than from a specifically LFP charger system. I think that a little undercharging should not degrade LFP battery life, and may extend it. Also, the OEM AGM is rated at 35AH, while the LFP I linked before is rated at 70AH, so even not fully charged will have over half again the charge.
The BU-409b lists the L-A float charge as 13.5V, and then notes:
"Commonly used for UPS; float charge voltages for automotive may be higher"
My experience is that automotive electrical systems float the battery at about 13.6V. I don't have the battery monitor log data for driving the Mach-E, but I do have some for my other EV and it is entirely consistent with the table in BU-409b.
I have installed an LFP in my other (not Ford) EV, so I will see how long it lasts. So far, so good.
https://batteryuniversity.com/article/bu-409b-charging-lithium-iron-phosphate

I’m telling you people have put a LFP in their Mach-E, and their screen shuts down while driving. You’ve been warned. I monitor voltage while driving and it’s frequently down to 12.9V or so. Look up 12.9V (3.225V/cell) on a LFP SoC chart and it will make sense.

 

[UsernameChecksOut]

Plot thickens (for me at least)...

I just posted that I got my vehicle back from service.
https://www.macheforum.com/site/thr...battery-and-lift-gate-woes-are-related.32621/

They discovered a code that indicates my lift gate release actuator might have a short circuit. Methinks that a short circuit is continuously draining my 12V when the vehicle is off. <Ominous> dum dum dum ?

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