Ford BMS Battery Monitoring System: How it Works, How to Properly Charge, How to Power Accessories

[scott011422]

I've been trying to figure out these AGM batteries. The electro-chemical potential of a lead acid battery at no load is ~13.2 VDC.
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This its fully charged terminal voltage. I have charged up an AGM battery to 13.2 VDC. It then ran back down to 12.6 VDC.
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I've then taken a fully charged AGM battery out of the truck and observed its terminal voltage on zero float: 12.6 VDC... Not connected to the truck electrical system or anything. It stays stable at 12.6VDC... What gives? Anyone have an idea

Gros, I was re-reading this post of yours. This part i seperated, Was this in the truck?

If it is, Everything you are seeing is probably normal. There is alot of posts in this thread, But our trucks don't keep the battery fully charged. And if you are not driving more than 15m, Its probably lower than that. I've seen my battery as high as 12.83 with my SOC set at 95%. However once it hits that point the truck normally runs the battery down to 12.49 before it starts charging again.

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[Gros Ventre]

Gros, I was re-reading this post of yours. This part i seperated, Was this in the truck?

If it is, Everything you are seeing is probably normal. There is alot of posts in this thread, But our trucks don't keep the battery fully charged. And if you are not driving more than 15m, Its probably lower than that. I've seen my battery as high as 12.83 with my SOC set at 95%. However once it hits that point the truck normally runs the battery down to 12.49 before it starts charging again.

Well... I live in Wyoming. That state that's really a small town with very long streets... So I get trips of at least 30-45 minutes usually and frequently over a hundred and fifty miles. What I've seen is (& this is the OEM Battery) is that whether in the truck or not it's at 12.6VDC. And I'm aware that the trucks programming is set to about 12.6 VDC. (That kicked my butt the first time I got an electrical system warning and I was cross checking with a handheld voltmeter... leading to the getting the NAPA battery I've talked about.) I haven't been monitoring the NAPA battery for equivalency: It's in the truck and operating without a peep of trouble, so I'm leaving it aone.

 

[fordtruckman2003]

How are you all viewing battery days and BMS levels?
I don't have FDRS license anymore like he's using in video.

 

[scott011422]

How are you all viewing battery days and BMS levels?
I don't have FDRS license anymore like he's using in video.

Forscan

 

[Snakebitten]

This thread is chocked full of methods to monitor your battery with nothing to do with FDRS.

You can use PIDs as well as Bluetooth battery voltage monitors.
Pick your poison

 

[Joekr5]

Wow, I've never seen that documentation.

I didn't check for a DTC but I remember when I opened the driver's door I heard the electric parking brake engage. (it's an unmistakable sound)

A few other folks reported that the next morning they had the same parking brake experience.

I chalked it up to some kind of erroneous command sent from the cloud. I was reaching for some kind of logic.

I have on a couple of occasions shut the truck down and opened the door, only to be greeted with an unexpected alert tone. Both times being the headlights being in a mode other than "auto".
That too has been reported by others but I just figured I had bumped the switch with my knee when exiting.

Who knows though?
These datacenters on wheels are an adventure!

Older thread so my apologies, but did you ever find out what caused your parking brake to engage on its own? In about 18k miles since I bought the truck that's happened to me twice. Both times in my garage as I was walking up to it with the fob in my pocket. The running boards came out then the park brake engaged.

In unrelated news, I have twice seen both running boards extend when I open the door (normal behavior) and the driver's side board only will retract before I even step on it.

 

[Missmy3/4ton]

Out with the junk 21 battery, (built dec of 20)….thanks @Big Dog Daddy for the heads up. This was $200 out the door at Sam’s club, the regular one was ~$130. I think they’re both 3 year warranties

 

[gregs150xlt]

Out with the junk 21 battery, (built dec of 20)….thanks @Big Dog Daddy for the heads up. This was $200 out the door at Sam’s club, the regular one was ~$130. I think they’re both 3 year warranties

Is that gonna fit in the bay where the old one came out of?

 

[Big Dog Daddy]

Out with the junk 21 battery, (built dec of 20)….thanks @Big Dog Daddy for the heads up. This was $200 out the door at Sam’s club, the regular one was ~$130. I think they’re both 3 year warranties

You'll be very happy with that! Ford castrated our trucks with those little H6 batteries. After Installing the H8, I haven't given the battery or SOC another thought. Every OTA downloads and installs without problem, the truck nolonger goes into "deep sleep" mode, and auto start stop works consistently. It's probably the best upgrade I made to the truck since I bought it. I hope you find the same result.

 

[Missmy3/4ton]

Is that gonna fit in the bay where the old one came out of?

Oh yeah. Fits with plenty of room. I could probably fit 1-2 more inches of battery length in there.

You'll be very happy with that! Ford castrated our trucks with those little H6 batteries. After Installing the H8, I haven't given the battery or SOC another thought. Every OTA downloads and installs without problem, the truck nolonger goes into "deep sleep" mode, and auto start stop works consistently. It's probably the best upgrade I made to the truck since I bought it. I hope you find the same result.

I hope so too! That sounds exactly like my truck. So I’m hoping I have the same success as you!

 

[gregs150xlt]

Out with the junk 21 battery, (built dec of 20)….thanks @Big Dog Daddy for the heads up. This was $200 out the door at Sam’s club, the regular one was ~$130. I think they’re both 3 year warranties

Mixed bag of reviews on that battery on the net (including Sam's).

 

[Missmy3/4ton]

Mixed bag of reviews on that battery on the net (including Sam's).

Meh, who cares. The only people who write those (positive) reviews are overachievers (extreme minority), and people who have problems. Plus it’s a 3-year warranty. My truck will be 5 years old, itll have 150k miles on it and I’ll be on to my next work truck.

 

[scott011422]

While going through Forscan, I noticed there are different BMS Styles to choose from.

None
LIN
PWM

Has anyone played around with this? For instance, If you set it to "Off" Does it work like any other car??

BMSInCar_Cfg (BMSICC)
726-04-02 x*xx xxxx xx--
0 = BMSICC NONE 2 = BMSICC PWM 1 = BMSICC LIN

 

[Static]

While going through Forscan, I noticed there are different BMS Styles to choose from.

None
LIN
PWM

Has anyone played around with this? For instance, If you set it to "Off" Does it work like any other car??

BMSInCar_Cfg (BMSICC)
726-04-02 x*xx xxxx xx--
0 = BMSICC NONE 2 = BMSICC PWM 1 = BMSICC LIN

I was wondering the same thing. I have a shorter commute and even after getting a battery replacement under warranty earlier this year, it still appears to be failing OTA updates because of low battery SOC. Wondering if I just disable the bms so it doesn't limit the charging would maybe help. I suspect that to reach fleet MPG requirements the BMS is programmed to be less aggressive in charging and get better mileage by putting less load on the alternator while accelerating. I might just do the change in forscan and monitor charge rates while driving. Not sure what all this would disable in the truck, but I assume it would be similar to unplugging the BMS sensor? I feel like for a while maybe on the previous gen that was something people did for some reason.

 

[Snooker_ML]

@Bob_Mac
The battery BMS sensor appears to be identical and made in Mexico. The only exception is the date code. The same sensor p/n is called out for all 21 and 22 F-150's including the diesel which was factory equipped with the H8.
OEM number ML3T-10C652-BA replaced by ML3Z-10C679-A and superseded by ML3Z-10C679-B

2020-2021 Ford Fusible Link ML3Z-10C679-B | Varsity Ford (varsityfordparts.com)

Wow what a thread! I can't believe I ate the whole thing! (remember Alka Seltzer?)

I had Trouble Code B11DB-49 causing a daily Charging System Service Soon warning (but the truck started fine for months), and it was fixed by replacing this above noted "BMS sensor" ML3T-10C652-BA, aka "Fusible Link", acting as a current sensor. My 2023 was built in Nov. 2022 and I never had any actual battery charging issues (other than this warning screen). See more here:

https://www.f150gen14.com/forum/threads/2023-powerboost-“stop-safely-now”-no-start.15466/post-374933

Also, for the record I have a H7 battery, the original OEM one.

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