Ford BMS issues, research, testing, and solution results

[Mosey]

No problem. Ford service procedure recommends disconnecting both the main and aux batteries before unplugging the BMS from the harness to reduce the risk of voltage spikes, shorts, or failure for the main BCM to properly register the new BMS.

Why let the truck sit 6-8 hours if you are going to reset the BMS anyhow?

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[SilverPigeon]

...The build date is the only way of identifying the revision and yours is 2022-12-18 which would almost certainly be the NL3T-10C652-AD revision. Not all of the early revisions have issues but enough of them did that Ford revised it again in October of 2023. If yours is behaving itself then you got a good one but I'd still get the revised version to have on hand just in case...

Thanks for that Bret, it cleared it up for me that the build date of the BMS is what matters and indeed may be explaining the nonsensical behaviour of the BMS. I'll investigate getting one.

On a side note, the BCM software update, as one of its features, was meant to improve charging strategy if my memory is correct? Makes me wonder if that's an attempt to address the older BMS behaviours.

 

[Porpoise Hork]

You're welcome sir. That was my thought to but seemed to resolve it for some but others like myself it didn't make any difference until I replaced the BMS itself.

Why let the truck sit 6-8 hours if you are going to reset the BMS anyhow?

Ford designed the BMS to "accurately" detect the SOC when the 12v battery is in a resting state over a 6-8 hour time period. Now it may complete this in less time but this was what I found to be an adequate period to allow it to complete the SOC detection. Any key cycle during this initial resting period will reset the internal timer and will start over with each key-off state.

After resetting the new BMS it will default the SOC reading and report somewhere between 80-90% and remain there until the BMS can complete the new baseline SOC reading. I replaced mine late afternoon then had to drive it and noticed that mine used the flywheel starter each time despite the HV charge level being between 50-60% until the BMS had the time to properly update the SOC.

 

[FirstFord]

FORScan:
TargetSOC_Cfg: 0780=120%BCM0726-08-02RegenFunctionActive_Cfg 0=disabledBCM726-07-02RefreshFunctionActive_Cfg
1=enabledBCM726-07-01 And keeping it on my Noco10 AGM charging whenever it's in the garage. I've disconnected the battery a few times for testing with my Ancel and always comes up healthy and 100%SOC

A data point, perhaps?

Some time ago, I too made changes in FORScan to try to increase the charge level. However, I wasn't sure quite where to go (using Livingitup's spreadsheet), so I used the so-called "Easy Method". Now that you have identified the address, I decided to revisit the values and compare them to the original OEM values that I had as a backup. Only one value changed:

726-08-02:
Factory OEM:
0007-0805-00
Changed to:
0007-0805-A0

Armed with this revelation, I also revisited the spreadsheet to see what the "A" meant, but realized the values are determined using Hex2Dec, which is well outside of my wheelhouse, so I stopped there.

 

[Mosey]

A data point, perhaps?

Some time ago, I too made changes in FORScan to try to increase the charge level. However, I wasn't sure quite where to go (using Livingitup's spreadsheet), so I used the so-called "Easy Method". Now that you have identified the address, I decided to revisit the values and compare them to the original OEM values that I had as a backup. Only one value changed:

726-08-02:
Factory OEM:
0007-0805-00
Changed to:
0007-0805-A0

Armed with this revelation, I also revisited the spreadsheet to see what the "A" meant, but realized the values are determined using Hex2Dec, which is well outside of my wheelhouse, so I stopped there.

A0 hex equals 160 decimal. I doubt that is a % for an SOC.

 

[2Lazy2P]

Ford Parts product photo is stamped 01-11-2022. FordParts.com. I should assume this is an outdated image but one never knows.

 

[FirstFord]

A0 hex equals 160 decimal. I doubt that is a % for an SOC.

Thank you. Using the "Easy Method", I entered 96% (supposed to have been 95%, but fat fingers...). So, I don't know where 96% got turned into "160 Decimal". (Again, I am completely ignorant on Hex2Dec.)

 

[SilverPigeon]

@FirstFord , @Mosey, target SOC% is using four characters to describe it:

726-08-02

xxxx

xx**

**--

In the above example from Jeff, the actual hexadecimal value we are seeing is 05A0. Target SOC% is defined with a range up to 200%

If we look more closely at the definition:
TargetSOC_Cfg (TSOCC) • % = Hex2Dec(****) /16 • Range: 0 - 200
we see it's not just a matter of converting hexadecimal (hex) to decimal (dec). What it says is:
"take the four-digit hex number, convert it to decimal and divide by 16"
'Therefore, 05A0 -> 1,440/16 =90.

The factory SOC is 80%. That's why the value is 80*16 =1,280 -> 0500 hex.
My setting of 120% is 120*16=1,920 -> 0780 hex.

 

[FirstFord]

Geeezz, you guys kill me! Every day I get blown away at the knowledge and expertise of people who have such knowledge and insights into how these things work! Kudos to the nerds!

So, @SilverPigeon , your saying that using the "Easy Method" and putting in 96%, that translated to being actually 90%? (Still an increase over the OEM 80%.)

I have received shipping confirmation on my new BCM, and am very eager to install it, and start observing....

 

[SilverPigeon]

...So, @SilverPigeon , your saying that using the "Easy Method" and putting in 96%, that translated to being actually 90%? (Still an increase over the OEM 80%.)...

No, if you go back into the easy mode setting, it should say 90. If it does, you effectively did a typo . If it says 96, the asbuilt value should be 0600. If either of those are out of whack, then easy mode has a bug in calculating the correct value

 

[FirstFord]

No, if you go back into the easy mode setting, it should say 90. If it does, you effectively did a typo . If it says 96, the asbuilt value should be 0600. If either of those are out of whack, then easy mode has a bug in calculating the correct value

Okay, I'll double check - but because of other things going on, it may need a day or two (or three) before I can review that value. And I'm guessing that by then, I may have the new BCM

 

[gwb82]

This is the ongoing trials and tribulations I have dealt with on the Ford BMS system for my F150. My testing is ongoing but I wanted to go ahead and post how things have been going so far. There's a lot to sort through so I tried to break it up based on my experience, findings and results so far.

Early versions of Ford BMS sensors installed on 14th gen F150's reported to have issues with incorrect 12v and HV battery (PB versions) SOC, random SOC drops overnight of 10-20%, blocking of OTA updates, modules being put into deep sleep/failing to power up correctly due to inaccurate SOC readings leading to errors or warnings in both the FordPass app and cluster on startup.

Since I began monitoring the 12v SOC levels 6 months ago I have noticed some odd voltage related behaviors. I have had the 12v SOC set to 100% for the majority of time I have owned the truck and have a 20AH lithium battery piggy backed to the 7AH AUX battery for 3ish months now. The main battery is 14 months old and has tested good. The aux battery was original but also tested good.

Behaviors observed: I have seem random overnight drops in 12v SOC from 100 to 90-80% along with a drop in the HV battery SOC from 55-60% to under 35%. No OTA updates received or other indications leading to the drain issues. No alerts sent from the truck, no modules put into deep sleep but the low HV charge level would cause the truck to use the flywheel starter on system startup. This would happen at least 1-2 times a week but has progressively gotten worse over time. The random flywheel startup has been present since day one of truck ownership. Since I only recently started monitoring the SOC, I can only assume the voltage drop problem has been present since I bought the truck.

Testing:

Battery voltages taken: When BMS reports 80% SOC (overnight drop from 100%), voltages reported with handheld meter show resting primary 12v at 12.86v, aux battery 12.84v, and 20ah battery 12.62v. All showing 99-100% SOC when comparing to industry standards for their battery types.

Steps to attempt to correct the behavior when SOC drop appeared: Leaving the truck off for 8+ hours to see if it would update the SOC but still reports as low despite resting voltages showing otherwise. Charging all three batteries separately and allowing 6+ hours for AGM desulfation cycle to complete and Lithium cell balancing to complete at 14.8v.

Observation after charging: BMS may correctly update SOC levels but most of the time a 6-8 hour key off cycle required for correct SOC to report back. Incorrect SOC and random HV charge level drop occurrences still happens and increased to every 3-4 days despite having driven for 60+ miles the previous day.

Next Step to solve: Replaced Aux battery with 14AH AGM battery. Replacement charged for 6 hours before swap and tested 100% to make sure battery is healthy. BMS reset completed when aux battery replaced.

Observation: 12v SOC remained at 100% for 48 hours once BMS relearn completed then 12v dropped to 75% and HV dropped to 37% after being parked for 12 hours, 12v battery voltages again reported all at 100% SOC despite BMS reporting low. No OTA received.


Research / Findings:
This is when I started looking into replacing the BMS and here is what I discovered about the piece of crap.
Ford has had numerous issues with BMS modules produced from late 2020 to late 2023. Issued include the state of charge on affected vehicles to randomly drop by 10-20% overnight. Anecdotal reports also found that Powerboost HV battery levels also fell to below 40% despite being at 60% at key off when 12v SOC dain incidents happened. Ford has issued a Customer Satisfaction Program 23B70 replace BMS modules with part numbers NL3T-10C652-AC and NL3T-10C652-AD but when I contacted the dealer they said mine was not included despite it having a build date of 1/27/21.

I found that Ford released their latest version of the BMS "ML3Z-10C679-B" in mid October of 2023 which is reported to have addressed all the known issues of the earlier versions, but may not have begun installing them until early December to use up existing inventory.


Issues reported - Early BMS revisions dates of manufacture.
NL3T-10C652-AC - October 2021 to October 2022
NL3T-10C652-AD - October 2022 to October 2023

Current BMS revision - ML3T-10C652-B - Manufacture dates of November 2023 to current.
Replacement cost is roughly $20 + shipping from most online OEM parts vendors.

The BMS will have the Ford engineering part number "ML3T-10C652-BA" stamped on it just under the FoMoCo marking regardless of the actual part number on the packaging when received. How to identify what version or associated part number your BMS is will be the production date that is directly under the engineering number. So when you get the part be sure to verify the build date of the part. It should be early 2024 but still want to verify it.



Testing possible solution: BMS replaced with current revision

It has been 12 days (as of this post) since I replaced the original BMS with a build date of 11-12-2021 for ML3T-10C652-B with a build date of 02-17-2024. So far zero issues with random 12v or HV SOC drops. No flywheel starts, no random park assist not available errors, no APIM delayed boot (sending welcome chimes to cluster) issues. Both 12v SOC has remained at 100% and HV charge levels remaining the same as at key off with no overnight drops.

I am still watching things but so far replacing the BMS appears to have resolved all the issues I have been having. For anyone with a 21-23 both PB and non-PB versions and having odd issues as those stated you may want to consider checking the build date on the BMS installed and replace it if it shows anything before 10/23.




Replacement: Time -5 minutes.

Steps to replace: Non PB models - Disconnect ground lead at BMS and remove BMS from negative terminal. Carefully unclip harness lead to old BMS (it's a very thin plastic clip) and replace with new one then reconnect. Perform BMS reset procedure. Allow 6-8 hours of key off for new BMS to "learn" current battery SOC level.

For PB models disconnect the negative terminal on Aux battery and then the main 12v battery to replace the BMS sensor and reconnect all terminals then perform the BMS reset.
Allow 6-8 hours of key off for new BMS to "learn" current battery SOC level.


Ford F-150 BMS Reset Steps

1. Turn the ignition on (engine off), or press the start button without pressing the brake so the vehicle is in accessory mode.
2. Flash the high beam headlights five times quickly.
3. Now press the brake pedal three times quickly.
4. If done correctly, the battery (BATT) icon on the dash will flash three times, confirming the reset.

I'll continue to monitor how the SOC and truck behaves and will post back if the SOC drop or other related issues happen to return.

I know this has been discussed in other threads but since this is recent can you send me what aux batteries you purchased, both AGM and lithium? Thanks in advance.

 

[03PSDX]

That was an extremely well written and easy to understand write up!! Also, whoever was doing the HEX conversions, I’d guess you are a computer forensic examiner or a programmer? Ha ha.

I’d also like to know the aux batt you installed. Do you have pictures of the aux 20AH lithium battery piggy backed to the 7AH AUX battery as well? I’ve had some weak starts as of late and will probably be getting a new battery soon. I have the original Ford batt still (My PB is a 2022). I’m surprised my batteries have lasted this long!

 

[Porpoise Hork]

I know this has been discussed in other threads but since this is recent can you send me what aux batteries you purchased, both AGM and lithium? Thanks in advance.

I'm running the O'reilly Super Start Power Sport AGM Top Post Battery Group Size BTX14AH 220 CCA - ETX15 and the ECO-WORTHY 12V 20Ah Lithium piggyback with Cartman 4AWG 18-Inch cables.

The O'reilly battery is a fair bit taller and thicker than the OEM 7.5AH agm battery so some trimming needs to be done on the lower tray to fit it and on the battery itself so the terminals will bolt down. You'll need a longer bolt for the tie down strap to secure it and the lid won't completely close because of the increased thickness. I used black Gorilla duct tape to keep it down. Yeah.. I'm a redneck... I might end up swapping the bigger AGM out for a OEM sized one later on.

If you don't want to mess with all that then any parts house should have a direct replacement for the Ford BHAGM-AUX1-B auxiliary battery. You can then just get the 20AH or if you want more reserve capacity get a 30AH lithium cell instead. Definitely worth looking at Hammaman's testing an aux battery solution thread if you have not done so already.

 

[Mosey]

Hey guys. I just installed the new revision and while doing so I see there is a second BMS sensor on the aux battery as well. Any thoughts replacing it too?
Part number BT4Z-14B357-C.

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