BMS bad?

[duneslider]

I will start by saying I don't know exactly what the BMS is doing in the Ford but I don't think it is doing what a lot of people think it is doing. Based on what I have been able to dig up all it is doing is watching the voltage to make sure things (accessories like lights, chargers, radio, etc.) aren't draining the battery below the point the vehicle won't start. It is not managing how it is being charged, or some magic device that prevents self-discharge. I see online where people state the BMS is set to only charge the battery to 80%, I do not believe this is true, even if Forscan is showing some sort of setting like that. The 80% rule only applies to lithium family batteries like those used in hybrids or all electric vehicles, it would not be used on an AGM battery. I think when people see the 80% setting in forscan it must be a setting that is in the code for hybrids/electric vehicles.

AGM's need to be fully charged at all times to get the greatest life out of them. If you do a lot of short trips, and have auto S/S active the battery probably is not getting fully charged and will lot last as long. It would be good for people to put their batteries on a true battery charger on a regular basis to make sure their batteries are properly maintained and fully charged as much as possible.

If anyone has any official Ford documentation on the BMS I would be interested. Reseting the BMS (like mentioned) really isn't needed and should take care of itself in a short amount of time but I could see that maybe your remote start or auto S/S wouldn't immediately return after replacing a bad battery but likely by the next day it would all be active again.

 

[LokiWolf]

I will start by saying I don't know exactly what the BMS is doing in the Ford but I don't think it is doing what a lot of people think it is doing. Based on what I have been able to dig up all it is doing is watching the voltage to make sure things (accessories like lights, chargers, radio, etc.) aren't draining the battery below the point the vehicle won't start. It is not managing how it is being charged, or some magic device that prevents self-discharge. I see online where people state the BMS is set to only charge the battery to 80%, I do not believe this is true, even if Forscan is showing some sort of setting like that. The 80% rule only applies to lithium family batteries like those used in hybrids or all electric vehicles, it would not be used on an AGM battery. I think when people see the 80% setting in forscan it must be a setting that is in the code for hybrids/electric vehicles.

AGM's need to be fully charged at all times to get the greatest life out of them. If you do a lot of short trips, and have auto S/S active the battery probably is not getting fully charged and will lot last as long. It would be good for people to put their batteries on a true battery charger on a regular basis to make sure their batteries are properly maintained and fully charged as much as possible.

If anyone has any official Ford documentation on the BMS I would be interested. Reseting the BMS (like mentioned) really isn't needed and should take care of itself in a short amount of time but I could see that maybe your remote start or auto S/S wouldn't immediately return after replacing a bad battery but likely by the next day it would all be active again.

The BMS is the Battery Management System. It does many of the things you mentioned.

Yes, you are correct on an AGM battery, and sadly in a modern vehicle they NEVER get to 100, Never. Unless like you said they are charging them manually. That is a one main disadvantage of an AGM, but the rest of its advantages outweigh that.

The 80% is most definitely the desired Minimum SOC of the 12V system. I say system, because if there is an Aux battery, it is factored in to that also, like in the case of the under seat battery in a 150. Also, that setting has ZERO to do with the Hybrid system. How would I know that, well, my daily is a PowerBoost(Hybrid) 150. Its SOC and settings are managed in a completely different place. In any coding the Hybrid battery SOC is listed as High Voltage, or Hybrid.

Many of us in the PowerBoost Community have upped that SOC to 85% or 90% and seen a reduction in 12V low related messages, and it helps with getting OTA updates. What you have to be careful with is this is minimum and is also related to the rate of charge. AGM batteries perform better when they are charged to 100% regularly, BUT, after 80 the charge curve is supposed to change. This why many chargers have a specific AGM setting, Higher voltage, and a change beyond 80% on rate.

The BMS Sensor on the battery, senses load, current charge %, and Voltage, it also monitors discharge and charge rate in Amps. All of this can be monitored with the right adapter and app on your phone if you want to see it. When you disconnect it, it disables Auto Start/Stop because the system can't sense accurate battery voltage, so it doesn't know it can restart the ICE when needed. Don't get me started on how bad an idea it is to disconnect that sensor.

Yes, the BMS will attempt to prevent a non-start situation, but like you mentioned, it can only do but so much. If the battery is old or has a dead cell all of a sudden, done. It will turn off OTA updates and prevent them, it will eventually shut down the APIM, and the TCU that run in a low power state, all trying to prevent an issue.

 

[LokiWolf]

I would just spend the $200 or whatever and get a new battery, and move on with life. I think in almost all modern car forums, when they have had electrical issues on a car a few years old, a battery solves the problem. Treat it as a consumable.

(I've had batteries which test fine, good voltage, good delivery on load, then 24 hours later - unconnected - is almost down to single digit volts).

Yes, I 100% agree. The minute I saw 11.X resting, and it was cold and the battery was a few years old, new battery it is. Can't have the vehicle not starting when we need it to, for something that can be taken care of so easily.

 

[DieselMonk]

You can get replacement battery insulation blankets that will fit multiple battery sizes. Looking at https://parts.ford.com/shop/en/us/vehicle-battery-80-ah-800-amp-p-bagm94rh7800?pdp=y (the 94R size for my 2020 before the downsize) it looks like the part number for the heat shield is 10a687 and is about $30. That said, I'd probably not use the OEM one and get some of the better stuff online that will fit just about any modern car battery and has the aluminum foil backing.

I need a couple of blankets. One for the GT500 and the other for the H8 upgrade in the Expedition.

 

[BigOleFordFan]

Well, a somewhat funny side note:

When I bought my 011 EL back in '21, it STILL had the OEM Motorcraft battery in it, and started & ran just fine....

Well, until the winter of '22, which was a uber-chilled combo of sub-zero temps, high winds, ton's of snow & ice etc.....that & the fact that it sat in the driveway for about 2 weeks while I was sick....after which I went out to start it & no joy....I got it jumped & drove straight to the NAPA store a few miles away, and it tested as bad....

I replaced it with a top of the line + 1 size bigger AGM model, a new thermal wrap, new cables & clamps just to be safe, and wallah.....nottaproblemo since then

So apparently, those older batteries fell under the "they don't make 'em like they used to" category.....

 

[LokiWolf]

Well, a somewhat funny side note:

When I bought my 011 EL back in '21, it STILL had the OEM Motorcraft battery in it, and started & ran just fine....

Well, until the winter of '22, which was a uber-chilled combo of sub-zero temps, high winds, ton's of snow & ice etc.....that & the fact that it sat in the driveway for about 2 weeks while I was sick....after which I went out to start it & no joy....I got it jumped & drove straight to the NAPA store a few miles away, and it tested as bad....

I replaced it with a top of the line + 1 size bigger AGM model, a new thermal wrap, new cables & clamps just to be safe, and wallah.....nottaproblemo since then

So apparently, those older batteries fell under the "they don't make 'em like they used to" category.....

And the fact that your 11 just doesn't have the parasitic draw that eats batteries alive nowadays!

 

[Ugh_J]

I will start by saying I don't know exactly what the BMS is doing in the Ford but I don't think it is doing what a lot of people think it is doing. Based on what I have been able to dig up all it is doing is watching the voltage to make sure things (accessories like lights, chargers, radio, etc.) aren't draining the battery below the point the vehicle won't start. It is not managing how it is being charged, or some magic device that prevents self-discharge. I see online where people state the BMS is set to only charge the battery to 80%, I do not believe this is true, even if Forscan is showing some sort of setting like that. The 80% rule only applies to lithium family batteries like those used in hybrids or all electric vehicles, it would not be used on an AGM battery. I think when people see the 80% setting in forscan it must be a setting that is in the code for hybrids/electric vehicles.

AGM's need to be fully charged at all times to get the greatest life out of them. If you do a lot of short trips, and have auto S/S active the battery probably is not getting fully charged and will lot last as long. It would be good for people to put their batteries on a true battery charger on a regular basis to make sure their batteries are properly maintained and fully charged as much as possible.

If anyone has any official Ford documentation on the BMS I would be interested. Reseting the BMS (like mentioned) really isn't needed and should take care of itself in a short amount of time but I could see that maybe your remote start or auto S/S wouldn't immediately return after replacing a bad battery but likely by the next day it would all be active again.

My dude, some of us have actually changed the target state of charge from the default to something else like 95%, and we can objectively see the difference in what the truck does. This ain't rocket surgery.

I think you should probably do what some of us have already done and hook up an OBDII device with a good dashboard app and watch what your charge voltage/amps do based on things like estimated battery temp, current SoC vs target SoC, whether the headlights are on/off, etc. It definitely does not (on 4th gen Expeditions at least) factor in battery size as an environment variable in the software but it does have a setting for type (lead acid, AGM, etc.). It's a simple device, sure, but there's a lot more going on in the computer modules than just voltage and for batteries OTHER THAN lithium.

 

[duneslider]

My dude, some of us have actually changed the target state of charge from the default to something else like 95%, and we can objectively see the difference in what the truck does. This ain't rocket surgery.

I think you should probably do what some of us have already done and hook up an OBDII device with a good dashboard app and watch what your charge voltage/amps do based on things like estimated battery temp, current SoC vs target SoC, whether the headlights are on/off, etc. It definitely does not (on 4th gen Expeditions at least) factor in battery size as an environment variable in the software but it does have a setting for type (lead acid, AGM, etc.). It's a simple device, sure, but there's a lot more going on in the computer modules than just voltage and for batteries OTHER THAN lithium.

If this is true, it is a huge failure on Ford's part. Lead acid batteries (all varieties) should be maintained at 100%. So, if they really have programming set to 80% on an AGM that is just killing the battery, that is very disappointing to hear. I also agree, battery charging isn't rocket science and properly maintaining a Lead Acid battery isn't new science either and they should be able to do better given the computer power these things have nowadays. I'm a little curious what Ford is considering 80% when it comes to these batteries. 80% of 13.8 is 11v which can't be right. Capacity is mostly meaningless on a starting battery. AGM bulk charges at 14.7v, 80% of that is 11.8v which also seems low. Sort of curious what that 80% is referring to? Are they talking about charging current? That might make sense and a lower charging current would take longer to "fully" charge?

 

[DieselMonk]

If this is true, it is a huge failure on Ford's part. Lead acid batteries (all varieties) should be maintained at 100%. So, if they really have programming set to 80% on an AGM that is just killing the battery, that is very disappointing to hear. I also agree, battery charging isn't rocket science and properly maintaining a Lead Acid battery isn't new science either and they should be able to do better given the computer power these things have nowadays. I'm a little curious what Ford is considering 80% when it comes to these batteries. 80% of 13.8 is 11v which can't be right. Capacity is mostly meaningless on a starting battery. AGM bulk charges at 14.7v, 80% of that is 11.8v which also seems low. Sort of curious what that 80% is referring to? Are they talking about charging current? That might make sense and a lower charging current would take longer to "fully" charge?

All I can tell you is that the 24 Expedition is charging the hell out of the H6 compared to the 18 F150 with an H8 battery with a 160A alternator. I do a lot of short trips for work and combine errands. Even in the winter with seat heat and steering wheel heat and radio etc on, this Expedition always manages to charge that battery and give me start stop. My old truck would have to be charged after x many months.

 

[Ugh_J]

If this is true, it is a huge failure on Ford's part. Lead acid batteries (all varieties) should be maintained at 100%. So, if they really have programming set to 80% on an AGM that is just killing the battery, that is very disappointing to hear. I also agree, battery charging isn't rocket science and properly maintaining a Lead Acid battery isn't new science either and they should be able to do better given the computer power these things have nowadays. I'm a little curious what Ford is considering 80% when it comes to these batteries. 80% of 13.8 is 11v which can't be right. Capacity is mostly meaningless on a starting battery. AGM bulk charges at 14.7v, 80% of that is 11.8v which also seems low. Sort of curious what that 80% is referring to? Are they talking about charging current? That might make sense and a lower charging current would take longer to "fully" charge?

My understanding of State of Charge is wildly different from this. https://image.slideserve.com/666777/state-of-charge-l.jpg Looking at the things I've read, 80% should be around 12.4-12.5V OCV/resting (sources differ). What's even more odd is that when my battery was down around 12.6V resting, the truck would say it was about 60-65% SoC and things behaved oddly. Frankly, I'd agree that there is probably something screwy going on. Interstate Batteries mentions 12.64 being 75% SoC, but they don't specify whether that's AGM or something else.