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

[Snakebitten]

^^^ Exactly

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[Snakebitten]

Interesting means you're interested in learning something new everyday. That's a good thing! Thanks for sharing your journey/progress. Others of us are reading and learning along with you.

It only takes one good fella to say one encouragement.
Now you have gone and done it.

But as you very well know, I GET way more here than I deposit. This place is amazing for such.

 

[scott011422]

Took the time to go do some learning on parallel charging differing AH sized batteries. While it is NOT recommended to do so for a number of reasons, The way Ford is doing it shouldn't be any issue. Simply put, Whatever battery has the least amount of resistance from the battery to the charge source is going to get the most power. In a situation where the batteries are a different size this is "usually" the larger battery since larger batteries usually have less resistance than smaller batteries. The cables also come into play here since they impart their own resistance. Like water, The path of least resistance and all that.................

This might be what you guys were describing and I just wasn't understanding. If so, My bad.

So long story short, The small battery isn't effecting charging in any meaningful way.

Back to the truck not putting out enough.

 

[scott011422]

If you're seeing the ~12.8v, the truck is trying to consume the under hood batt's SOC.

Why would that be? Battery was under 12.5v at the time!

 

[Gros Ventre]

There's a lot of half truths floating around. Two lead acid batteries in parallel will equalize their states of charge quickly. After that they will recharge proportional to their Amp-Hour capacity. Neither will reach full charge before the other. Batteries recharge based on the difference between applied voltage, which will be the same for batteries in parallel, and their state of charge. The two batteries, if they are at different states of charge when paralleled, will equalize their states of charge quickly. Once the states of charges are equal, they'll recharge at the same proportional rate. They will each arrive at a full charge at the same time, because the applied voltage is the same.

 

[HammaMan]

Why would that be? Battery was under 12.5v at the time!

doesn't make sense, a proper float voltage is in the 13s. It makes absolutely zero sense for a running vehicle to have voltage down in the 12s. ZERO

 

[scott011422]

FYI. Fully FDRS updated the truck. The fan 5 truck is alive and well again with a vengeance. With the HVAC below 5 or even off I see a -2 to -8 draw on the battery. Fan 5 or higher is +3 to +8 amps.

 

[Snakebitten]

FYI. Fully FDRS updated the truck. The fan 5 truck is alive and well again with a vengeance. With the HVAC below 5 or even off I see a -2 to -8 draw on the battery. Fan 5 or higher is +3 to +8 amps.

Similar on my fully updated truck.
Because the BMS sees the battery at 100% SOC, it's REAL stingy about voltage, and like you mentioned, it will actually draw on the battery by lowering the current from the DC/DC converter just enough to suck. Lol

Problem is that I don't like to drive around at fanspeed 5+. It throws off my perfect (for me) climate settings. And it's a bit noisy to boot.

I don't mind the anemic charging strategy since @HammaMan pointed out to me that all I need is a few moments of fanspeed 5 before arriving home and that little LFP will suck down the 14.xV/xAmps and top right back off again.

Sure enough, when I turn onto my road front road, I'm 2.5 miles from home and 30mph. So about 6-7 minutes before getting into the barn.
For a ~46-50 mile round trip commute, that's all it takes.

 

[scott011422]

So are you saying that even with the LeF battery, The fan 5 trick is still needed?? Wasn't expecting that..............

 

[Snakebitten]

So are you saying that even with the LeF battery, The fan 5 trick is still needed?? Wasn't expecting that..............

Depends on what voltage you desire, I suppose?
I'm probably just a little drunk on the 13.25V

After spending the last 1000 days watching, learning, monitoring, nursing....... in an attempt to keep the resting voltage above 12.2V, and being happy with 12.5-12.8 as a result of all those efforts........

Well, 13.X is like low voltage heroine. I can just relax and leave the truck in the barn without checking on it.

Honestly, I don't know just what I would end up with if I don't use the fan5Hack at all. I suspect the BMS is going to be stingy and bring that 100% SOC down. I'll give it a try and let's see what happens and where it settles?

 

[Big Dog Daddy]

It's been 700 days since I installed a H8 battery in my 2021 5.0 truck and set my SOC to 80%. It hasn't given me single problem since then!

 

[PaulGrun]

It's been 700 days since I installed a H8 battery in my 2021 5.0 truck and set my SOC to 80%. It hasn't given me single problem since then!

It’s been 2 1/2 years since I didn’t do anything to my ‘22 302a Powerboost, and it hasn’t given me a lick of trouble since. (Except of course staying up to date on OTA updates.) No idea what the truck’s current SOC is, ignorance is bliss I guess.

Admit it - you guys are having wsssy too much fun with your PIDs. I have an old out of service iPhone that I keep hangin’ on to thinking that some day I’ll load ‘er up with an OBD system, but everytime I get the urge I go watch the news or mow the lawn or something until the urge goes away.

But I’ll admit it’s great fun seeing what you guys are learning. My engineer’s curiosity didn’t completely vanish after I retired.

 

[Snakebitten]

Busted!

 

[Spiffy]

Here is something to chew on. I went through all the battery issues and known problems. I fought with Ford to get a H7 battery installed. That worked for a few days and I still had voltage drop. I posted several images that had snapshots of the voltage drops even after I replaced with H7.
In the end I had both batteries out over night. Put them back in and my drain went away. Proving that in my case it wasn't the battery. It's had been days and my battery level was stable. Leading me to believe that removing both batteries and extended time somehow reset some module that was hanging.
I have been messing around and for shits and giggles I installed a old H6 from an another truck that was laying around. 4 days now my battery level sitting is a constant 12.6. This battery was considered as junk. I was going to use it as a core. I put it on my smart charger until it got to 85% (that's the highest it woukd charge)

Me thinks "in my personal case" that these battery issues were not from batteries. But from uncooperative modual. The act of removing both batteries for a lengthy time some how reset a module.
My old junk battery i had in my 2016 f150 is doing fine. I see that I can reboot moduals one at a time in forscan. I might try that next time or or use my topdon smart scanner and scope to see what module is hanging.
Go figure.

 

[raydulce]

That "Logic error" may be a noise immunity, or shielding ussue. Often sensitive circuit wiring cannot be run next to heavier current or electrically noisy wiring. Especially that these trucks have RF transmitters, 3-phase AC power sources, pulse-width modulation signals, etc.

This probably happens more than we realize, but very uncommon for us to be there to notice it. Hopefully it times out instead of running continuously.

I always have my NOCO jump pack in the back, pretty compact. Always have with last vehicle too. It gets used for others more than myself but is good peace of mind.

Man... I'm only on page 31 of 72. I'm here to learn more about the BMS system, especially the SOC setting. By chance I might have just learned why my headlights have been an issue on-and-off (pun intended). Came out of a restaruant to 1/2 my lights on. Drove to a hotel 30 min away, and later that night, my lights are on. Had to pull my battery negative termal for the rest of the trip. Dealer of course said "no problem found" a few days later when I could take it to them. Nice to know this might be a "common issue" instead of a ghost.

Thanks! Now back to Page 31.

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