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

[KTM753]

Every time I think I understand something on this truck, the rabbit hole gets deeper. Thanks!

Always!

Windows built in calculator has a programming option that converts integers (whole numbers) into hex if you want to see different values for SOC options.

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[HammaMan]

I have changed mine to the hex for 94%. My 12v SOC is always 100%(or hits it within a few minutes of starting, the underhood batt is 100%, the aux batt is not, throwing off the 12v's SOC as it's a combination of both batts in the PB).
My voltage with the fan 5 trick (hybrid/EV only) is 14.3v (+/- .3/1.1, measured at 10ms intervals, no smoothing)

 

[KW58]

I have changed mine to the hex for 94%. My 12v SOC is always 100%(or hits it within a few minutes of starting, the underhood batt is 100%, the aux batt is not, throwing off the 12v's SOC as it's a combination of both batts in the PB).
My voltage with the fan 5 trick (hybrid/EV only) is 14.3v (+/- .3/1.1, measured at 10ms intervals, no smoothing)

I’ve seen where you were experimenting with a lithium aux battery, you still running that setup or back to AGM? I’ve wondered about the parallel setup throwing off SOC values, I may have to isolate the two LV batteries from eachother to get resting voltages and see if it’s my under hood or under seat battery that’s actually the weak one.
The other day when I got to 85% for the first time I’ve noticed and the DC/DC voltage dropped down in the 13s I tried your fan trick…what an oddity but pretty cool.

 

[HammaMan]

I’ve seen where you were experimenting with a lithium aux battery, you still running that setup or back to AGM? I’ve wondered about the parallel setup throwing off SOC values, I may have to isolate the two LV batteries from eachother to get resting voltages and see if it’s my under hood or under seat battery that’s actually the weak one.
The other day when I got to 85% for the first time I’ve noticed and the DC/DC voltage dropped down in the 13s I tried your fan trick…what an oddity but pretty cool.

Yes, I still have the LFP in the truck. The SOC value is a combination of all batteries in the truck if wired to where the CT/shunt can see them. With the LFP in place the SOC value is moot as the truck gets back to 100% very quickly as the LFP eats current as it's being monitored from the current transformer the aux batt's negative cable. The AGM batteries are always at 100%. The SOC value only sees the missing energy from the LFP, which replenishes quite quickly. Truck has been sitting for about 37 hours now and the batt voltage is pretty much 13.3

 

[KW58]

@KW58 Take a look at this post. The hex value for 22' & 23' might be different than 21'.

https://www.f150gen14.com/forum/threads/new-battery-h7-or-h8.21266/post-424022

Text I was referring to:

"Changes made. While updating the SOC at 726-08-02 I had a thought. Stock value was 05 00, which in hex is 1280. The spreadsheet shows that this value is divided by 16 to give you 80. 05 A0 is 1440, divided by 16 is 90. Are we sure this is a percentage, rather than target voltage to the hundredths place? ie 1280 = 12.80V, 1440 = 14.40V. Not that this change has seemed to do anything, but where is the division by 16 coming from?"

I went back and looked at some asbuilt data that I saved a couple months ago and I had the same 0500 in those bits. Will take a look to make sure it hasn't changed with some update the truck has received since then next time I have the truck hooked up to forscan.

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