Low 12V battery voltage causing issues? (Update: Yes)

[PaulGrun]

I often see threads with folks musing about using Forescan to change the target SOC level, and/or doing a BMS reset.

My question is: Does anybody have actual knowledge of what the SOC setting actually does? I’m not looking for an empirical answer (“I changed mine and all my problems went away”), but rather actual insights into what is impacted by that parameter? I am under the impression from reading a couple of Ford patents that it doesn’t do what one might think based on its name.

Likewise with a BMS reset - can anybody say with authority what it does and when it should be used? I ask because I see threads where some guys reset the BMS almost routinely, whereas my impression was it should only be reset when the battery is replaced, since it gives the BMS a new baseline against which to measure the age of a newly replaced battery.

Any thoughts? I’m an engineer by vocation and avocation, with an aversion to changing things without an understanding of the original underlying engineering and design. And I’m curious by nature.

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[Gros Ventre]

I often see threads with folks musing about using Forescan to change the target SOC level, and/or doing a BMS reset.

My question is: Does anybody have actual knowledge of what the SOC setting actually does? I’m not looking for an empirical answer (“I changed mine and all my problems went away”), but rather actual insights into what is impacted by that parameter? I am under the impression from reading a couple of Ford patents that it doesn’t do what one might think based on its name.

Likewise with a BMS reset - can anybody say with authority what it does and when it should be used? I ask because I see threads where some guys reset the BMS almost routinely, whereas my impression was it should only be reset when the battery is replaced, since it gives the BMS a new baseline against which to measure the age of a newly replaced battery.

Any thoughts? I’m an engineer by vocation and avocation, with an aversion to changing things without an understanding of the original underlying engineering and design. And I’m curious by nature.

Here's a link to some fundamental lead acid battery characteristics. https://www.engineeringtoolbox.com/lead-acid-battery-d_1544.html As it turns out 12.69VDC appears to be the theoretical resting 100% charge voltage. If you look around you'll find that AGM batteries are more susceptible to overcharging damage. I think because of their thinner plates. So, my inference is that Ford set the 80% program level at what is really the fully charged condition in order to ensure the battery is not over charged. That said... they have then set the voltage as a variable depending on what is selected (for example put your fan in 4-7 and voltage goes up to 15.1VDC). My conclusion is that Ford either got a batch of bad batteries or those trucks set out in a field awaiting chips meant that their batteries were inactive for several months. Not good. Impurities plate out on cells reducing capacity but not terminal voltage. Hence many of us have had some funny readings, I did, took the battery in and the dealer, whom I trust, said it tested fine. Nevertheless I had replaced it since those funny readings happened on the road for Thanksgiving and the new battery has not even peeped, not even once (2 years and 2 Wyoming winters). Also, if you do get a new battery, it is common practice in the submarine world to gave a new battery a "wetting down" charge. This is an 8-12 hour, low rate, maybe 2 amps, charge to bring all active material into play. There's a lot of heresy running around on these batteries. At one point one guy said that the different ratios of active materials in the AGMbattery meant its voltage was different then a flooded cell lead acid battery. Note that the construction of an AGM battery gives it lower internal resistance, but the basic electro-chemistry remains the same, hence voltages remain the same. These AGM batteries are capable of higher burst currents, but then have somewhat lower overall capacity. Keep in mind that if you open the door or walk nearby with the key fob in your pocket, several modules kick in and put a drain on the battery changing terminal voltage. If you're going to measure battery voltage, pop the hood so you don't have to open the door and leave the key fob in the house.

 

[Rinn69]

Ya know.......with all the sensors in the BMS, regulating how and when it charges, how much it's allowed to charge (SOC)....how it senses when it's being charged with a charger since you hook the ground to a ground vs on the battery post, and yet, you have to do a BMS reset if you install a new battery......the BMS is pretty damn dumb if ya ask me. Or should I say, the programming that regulates the way it runs was done poorly at best.

 

[Snakebitten]

I'm guessing the reason for the BMS reset is because no chip or onboard tech could determine that the battery was brand new. Yet the battery management code does take into consideration the length of time a battery has been in service.
So it's simply a day 1 reset for the code.

My battery is still the original. I don't plan on doing a reset until I put a fresh AGM in

 

[Antimatter22]

My battery appears to be given up the ghost as well. Looks like I'll be buying a replacement in the next couple days

 

[Highway 11]

My battery appears to be given up the ghost as well. Looks like I'll be buying a replacement in the next couple days

Did your truck spend any time sitting or in production hell? I'm trying to figure out why so many owners are reporting battery issues this early on in their truck's life. My truck was built in late November 2022 and I took possession January 2023. It's frustrating that the battery had to be replaced within a year.

I understand putting an H6 battery in - but with so many electrical systems you'd think they'd prioritize a better quality battery to avoid dealer visits and warranty claims. I was going in for a GSM replacement... I'm pretty sure that dwarfs the cost of a quality H6 battery.

On an updated note: It has been one week with the new battery and not a single peep out of the electrical system. I'm looking at installing a battery monitor to track (I've learned Engineering Mode isn't the most reliable) but other than that I'm going to keep enjoying my truck.

 

[Antimatter22]

Did your truck spend any time sitting or in production hell? I'm trying to figure out why so many owners are reporting battery issues this early on in their truck's life. My truck was built in late November 2022 and I took possession January 2023. It's frustrating that the battery had to be replaced within a year.

I understand putting an H6 battery in - but with so many electrical systems you'd think they'd prioritize a better quality battery to avoid dealer visits and warranty claims. I was going in for a GSM replacement... I'm pretty sure that dwarfs the cost of a quality H6 battery.

On an updated note: It has been one week with the new battery and not a single peep out of the electrical system. I'm looking at installing a battery monitor to track (I've learned Engineering Mode isn't the most reliable) but other than that I'm going to keep enjoying my truck.

I'm not 100% sure about the production of my truck since I bought it off a lot instead of waiting for my original order.

I replaced my battery today and it looks like the OEM battery vented a little at some point recently. I didn't really start having noticable battery issues (deep sleep, etc) until about 3-4 weeks ago.

 

[PaulGrun]

I'm guessing the reason for the BMS reset is because no chip or onboard tech could determine that the battery was brand new. Yet the battery management code does take into consideration the length of time a battery has been in service.
So it's simply a day 1 reset for the code.

My battery is still the original. I don't plan on doing a reset until I put a fresh AGM in

I think, but do not know, that the SOC is a 'derived' value created by looking at a family of curves relating voltage to SOC.
Since any battery's ability to hold a charge is related to the battery's age, it is reasonable to notify the BMS when a battery is brand new, so it can select the correct curve relating observed voltage to SOC from the family of curves based on (among other things) the age of the battery.
So if true, it seems to me that doing routine BMS resets would screw up the BMS' ability to accurately calculate (estimate) the correct SOC.
BTW, we also know that the battery's so-called resting voltage changes over time as the battery sits quietly and its resting heart rate settles down, a process that can take a few hours. So I assume that every so often, like late at night, when the BMS decides that the battery has been quiet long enough that it's 'resting voltage' has stabilized, that the BMS recalibrates, thumbs through its tables (based on, among other things the battery's age), and pulls out the right one(s). it then uses those tables while the vehicle is working to dynamically look up the SOC based on instantaneous voltage (and other factors), which is the SOC figure reported in some PID somewhere.
But that's all supposition on my part, which is why I wondered if anybody had any actual engineering insights into the design of the electrical system, or are we mostly shooting in the dark. That's also why I wondered if anybody had any actual insight into the SOC threshold value you can change with Forescan.

 

[Snakebitten]

I personally believe that's some educated supposition.
There's a pretty hefty load of data gathering to support it.

I too leave room to be wrong about some aspects that make up the whole, but your way of describing the BMS lines up with everything I have observed myself.

 

[JThomas]

Hello I have been following this Battery issue because my truck was going into power save mode daily. I purchased my truck in Nov 2023, BLEND date is April 2023. It is a 2023 Powerboost, quad cab XLT with ProPower 7.2 4WD. Got it with 2000 miles, it was a courtesy vehicle and now has 4000 miles. Battery issues got worse after I had the level kit installed, (not sure if the battery was disconnected or if the short trips and in and out of the truck drained the battery more or what) the truck would disable features when driving to save power until it supposedly charged the battery. I tested the battery and it was always between 12.3 and 12.8 volts. I was charging my battery using and AMG battery maintainer connecting on the correct side of the BMS module to prevent power save mode every other day. Battery never showed below 12.3 volts. I was still getting low battery alarms. Finally I topped off the battery Battery Maintainer 100% then I performed the Battery Reset, (Light Flash and Brake). After that no issues, all fixed, never saw power save mode again except the on the day I installed my skid plates, I was in and out of the tuck all day, on and of the ramps. Other than the skid plate day, I never saw power save again even after sitting for 3 days. Anyway this may be a simple fix for allot of people, I think what may have happened is the truck sat at the dealer for and extended period of time and the battery died or got really low, so the dealer put it on a battery charger, but hooked it up on the wrong side of the BMS module now the BMS system is not calibrated and requires a reset. Anyway maybe this can help someone in a similar situation. Manuel says after charging it could take 8 hours resting for the vehicle to learn the new state of charge, however it did not really work for me, the battery sensor reset was the silver bullet that fixed my issue. Saved me a trip to the dealer.

 

[Spiffy]

I find it ironic. I remember a day where I stuck a battery in and that was that. The generator along with a charging regulator kept the battery up. My batteries lasted 5 years. I knew when it needed replaced.
Now there is tons of computing trying to maintain the battery. Is that supposed to extend the life?
I started reading here because after 12k miles it's acting up.

 

[Highway 11]

Now there is tons of computing trying to maintain the battery. Is that supposed to extend the life?
I started reading here because after 12k miles it's acting up.

Fuel economy, believe it or not. I think in the BMS thread it was brought up the alternator is engaged and disengaged to reduce load on the engine and thus fuel consumption.

Update: It's been 10 days since I last checked in. No issues, runs like a champ. We're into a cold snap here and there still hasn't been any issues with sluggish start or deep sleep. My shifter was still working well and not an issue at all. However...

My dealership finally got in the gear shift module in. After a bit of discussion we decided to swap GSMs as a precaution. My service advisor was concerned the issue went away temporarily because of the power to the car being cut when I swapped batteries, as well as concerned about any damage caused by the shifter repeatedly hitting its hard stops when it was jamming in drive.

Went in for an hour, shifter was swapped over, and I'm not sure if there's a new revision, but this thing is an improvement. It's lighter and smoother, yet the detents are more pronounced. The tech described the last shifter as smooth but sloppy.

I think that'll be the last update short of the shifter imploding or my car completely melting down.

 

[jenjeneer]

I went out today after letting the truck sit for six hours. Engineering mode showed the battery voltage at 11.9V.

11.9V!

So I did a thing.

Did your new battery resolve your issues? I, too, am having deep sleep, Fordpass issues due to voltage but I drive daily. Ford service says my battery health is fine and charging system is fine. Will a new, better brand battery solve the issues or do I need to upsize? Thanks.

 

[Highway 11]

So my battery replacement resolved all my issues, in addition to turning off parking mode on my dashcam as it was adding to the battery drain. I drive daily however I have a very short commute. There recently was an update for the battery management system which has made charging more aggressive for the F150.

I'm sure someone else on this forum can chime in as more of a subject matter expert, but I got an H8 because it was the largest battery that fits in a non-hybrid F150 and because I figured the extra capacity would give me a buffer to work with. There are a couple of people here that have done a like for like replacement without issue.

 

[Spiffy]

I forgot about this thread. On my truck things are getting really strange.
*Drivers window won't close automatically
*Trailer brake warning
*12v state of charge warning
*Charging system error
*Can't remote start
*OTA updates won't install.

So reading about others issues is it suggested that it's all related to the battery?

If someone can condense what I should do please?

If I go buy a battery what should I get?
Do I need to reset the BMS? Exactly how?

Should I reset the BMS first before I buy a battery?

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