Ford Battery Monitoring System (BMS) Explanation

[CurtisB]

The following is a screenshot of my BdyCM settings prior to me messing with anything. They have the battery type set to AGM from the factory, despite giving us flooded batteries. It has been speculated that this may be a cause for the short lifespan of the stock batteries. BMS doesn't manage them correctly and inadvertently ruins them.

Two-ish months in with an AGM battery in my truck, not on fire yet. The charging system still doesn't really replenish what I lose to idle drain during my short commute (1-2A output is nothing), but I've been using FORScan to monitor the charge level. Have to hook it to the wall every ~3 weeks or so to keep it above 50%.

Did you do the BMS reset when you installed the AGM battery?

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[acapaldi]

Did you do the BMS reset when you installed the AGM battery?

Yep, that was step 1 in troubleshooting this issue. I've been at this for a while now. I've used three methods, FORScan, Pedal-Pump and leaving it locked without touching it for 12 hours at various points. And yes, BMS was reset after upgrading the battery.

Resetting the BMS doesn't change any of the settings in this list. It isn't that smart, it won't change your battery type for you. It re-learns the battery SOC and that's it as far as I can tell.

Screenshot was actually taken before I'd upgraded, because I figured I'd need to change the settings for it and wanted to be sure I could before buying one. Lo and behold, Ford already did it.

 

[CurtisB]

I have a Diehard Gold T4 470 CCA 585 CA 70 minute reserve capacity battery in my Maverick now. Took 4 weeks to get my first "sleep" message. Did an overnight trickle charge and its been 2 weeks since. Now that I know I can buy an AGM battery, that will be my next step once this batter goes kaput.

 

[MakinDoForNow]

So will adding aftermarket AGM battery screw something up in the system since it thinks it's not AGM?

The new battery learn procedure should figure out the new battery type and update the installed battery type and with the bms on the negative could possibly read an RFID chip on the battery and set the charging parameters to the battery manufactures recommendations which could be verified by the online connections through Ford connection to truck. They don't have several thou chips in vehicles for nada.

 

[Deweyordeweynot]

Thank you!!! I take delivery of my '24 Mav Lariat EB tomorrow and will be anxious to see if FORScan has been updated for MY 24 (I had read last month that it didn't yet work on 24's).

My understanding from reading the Forscan forum is the update for the 24s is on the Forscan site.

 

[acapaldi]

The new battery learn procedure should figure out the new battery type and update the installed battery type and with the bms on the negative could possibly read an RFID chip on the battery and set the charging parameters to the battery manufactures recommendations which could be verified by the online connections through Ford connection to truck. They don't have several thou chips in vehicles for nada.

What's your source on this? Battery type is defined at address 726-02-01 in the BdyCM. By default on hybrid it's 0707. Type 07, corresponds to a 45AH battery. By changing these digits, I've been able to access battery types not listed in FORScan. I'll make a chart at some point.

I've changed it to type 04 before, reset BMS, and it'll stay at type 04, despite me not having a 60AH battery. The value doesn't change until I change it, It's not that smart, it can't guess what battery is installed.

I've never heard of using an RFID chip to communicate what battery is installed in a vehicle. Good idea, but coordinating that between OEMs and battery suppliers would be a nightmare.

 

[MakinDoForNow]

What's your source on this? Battery type is defined at address 726-02-01 in the BdyCM. By default on hybrid it's 0707. Type 07, corresponds to a 45AH battery. By changing these digits, I've been able to access battery types not listed in FORScan. I'll make a chart at some point.

I've changed it to type 04 before, reset BMS, and it'll stay at type 04, despite me not having a 60AH battery. The value doesn't change until I change it, It's not that smart, it can't guess what battery is installed.

I've never heard of using an RFID chip to communicate what battery is installed in a vehicle. Good idea, but coordinating that between OEMs and battery suppliers would be a nightmare.

Reset the BMS with the light flash brake press either zeros out the soc or orders the computer to schedule an soc update, not type, date installed, etc (will work fine if you charge existing or replace with fully charged same type battery and might change installed date if new battery is installed,). The 6-8 hour battery learn procedure with truck locked undisturbed (opening the door interrupts the procedure according to manual) I expect should change battery type. If not Ford would state in manual to have dealer change it or have battery type installed an option in Ford pass or in menu selections. There was a post sometime that showed a table as I remember it from a Ford site that showed battery types, manufactured by, plus other things. I don't have forscan so I cannot check. It would be nice if BMS ifo was disclosed. Is it possible that the field type you are changing is the "as built" and there is somewhere else a "current installed type". I would imagine not but ??? Does the 8 hour learn not update the field?

 

[Deweyordeweynot]

Thank you!!! I take delivery of my '24 Mav Lariat EB tomorrow and will be anxious to see if FORScan has been updated for MY 24 (I had read last month that it didn't yet work on 24's).

My understanding from reading the Forscan forum is the update for the 24s is on the Forscan site...I'll know when I hook up to mine on Tuesday.

 

[Packer Bill]

Does the 8 hour learn not update the field?

I would like a definitive answer to this question...

 

[CurtisB]

I would like a definitive answer to this question...

Me too!! I feel we are all so close to solving this thing on our own. I did the BMS brake reset procedure with my new battery two weeks ago after receiving a "sleep" message after 4 weeks with the new battery and not having done the BMS thing. I am sold if after doing the BMS thing I don't see the message for a long time. If I do, I carry a jumper and, in a pinch, I can do an overnight trickle charge till the battery goes out. Then its a top of the line AGM battery for me.

 

[acapaldi]

Reset the BMS with the light flash brake press either zeros out the soc or orders the computer to schedule an soc update, not type, date installed, etc (will work fine if you charge existing or replace with fully charged same type battery and might change installed date if new battery is installed,). The 6-8 hour battery learn procedure with truck locked undisturbed (opening the door interrupts the procedure according to manual) I expect should change battery type. If not Ford would state in manual to have dealer change it or have battery type installed an option in Ford pass or in menu selections. There was a post sometime that showed a table as I remember it from a Ford site that showed battery types, manufactured by, plus other things. I don't have forscan so I cannot check. It would be nice if BMS ifo was disclosed. Is it possible that the field type you are changing is the "as built" and there is somewhere else a "current installed type". I would imagine not but ??? Does the 8 hour learn not update the field?

A Ford dealer is going to put the same recommended Motorcraft battery in every time it's changed. It wouldn't need to have its type updated, it'd just need to relearn how much charge is in that newly installed battery. And so that's all it does. Probably puts a small load on it over the 8 hour period, sees how much the voltage drops.

This screenshot was taken on December 15th, 3 days had passed since the battery was fully charged, this was a BXT99RT4A supplied by my dealer after my initial battery failed. BMS had been reset 3 days prior. Capacity from the truck reads 45AH, type is flooded, battery size is H4.

This screenshot was taken January 2nd, 15 days after replacing my battery with an H4-XEV battery, BMS was reset 15 days prior during initial install. Capacity reads 45AH, type is flooded, battery size is H4. It all reads the same, because the truck does not adjust battery type on its own, it's still type 07.

For reference, changing the values at the address I indicated to 0404, (Which yes, updates both the installed and factory fields, first two digits are one field, second two are the other) yields this: The same battery is now reading as an H6, with a 70AH capacity etc.

To conclude. No, resetting BMS does not cause it to learn the new battery capacity or chemistry. This needs to be defined in the BdyCM settings and any changes to these settings will persist until that specific module is reflashed (I.E. the blinker recall)

I've considered trying to change these battery settings to see how they impact charging behavior, see if telling the truck it has a bigger battery in it than it actually does encourages it to keep the little battery charged more. I haven't done this because it also sounds like a great way to ruin a battery by overcharging it.

 

[MakinDoForNow]

A Ford dealer is going to put the same recommended Motorcraft battery in every time it's changed. It wouldn't need to have its type updated, it'd just need to relearn how much charge is in that newly installed battery. And so that's all it does. Probably puts a small load on it over the 8 hour period, sees how much the voltage drops.

This screenshot was taken on December 15th, 3 days had passed since the battery was fully charged, this was a BXT99RT4A supplied by my dealer after my initial battery failed. BMS had been reset 3 days prior. Capacity from the truck reads 45AH, type is flooded, battery size is H4.

This screenshot was taken January 2nd, 15 days after replacing my battery with an H4-XEV battery, BMS was reset 15 days prior during initial install. Capacity reads 45AH, type is flooded, battery size is H4. It all reads the same, because the truck does not adjust battery type on its own, it's still type 07.

For reference, changing the values at the address I indicated to 0404, (Which yes, updates both the installed and factory fields, first two digits are one field, second two are the other) yields this: The same battery is now reading as an H6, with a 70AH capacity etc.

To conclude. No, resetting BMS does not cause it to learn the new battery capacity or chemistry. This needs to be defined in the BdyCM settings and any changes to these settings will persist until that specific module is reflashed (I.E. the blinker recall)

I've considered trying to change these battery settings to see how they impact charging behavior, see if telling the truck it has a bigger battery in it than it actually does encourages it to keep the little battery charged more. I haven't done this because it also sounds like a great way to ruin a battery by overcharging it.

Thanks for your answer. My question is not about the "BMS RESET" (the light flash and brake pressing) is but is "when a fully charged new battery of a different type is installed and the 6-8 hour new battery installed LEARNING with truck locked procedure is done, does the battery type show to be updated to the proper type?". The naming of the procedure in manual strongly implies that the procedure sets the BMS to determine battery type which should then be used for proper charging. The BMS could be following the new charging procedure with the battery type In the BCM along with the battery installed date not being updated if you run the battery learn procedure please check to see if the type and date are updated. Bear in mind if the battery installed date is several months or years old the BMS could be modifying the charging procedure to prevent overcharging an aged battery. I personally expect the BMS to periodically test charge the battery (weekly? Monthly?) When some of the middle of night clicking happens?.
Thanks in advance for checking, I don't have the equipment.

 

[MavDan]

Is this why a lot of us have the deep sleep issue? I only drive 5 miles away for work.

 

[acapaldi]

Thanks for your answer. My question is not about the "BMS RESET" (the light flash and brake pressing) is but is "when a fully charged new battery of a different type is installed and the 6-8 hour new battery installed LEARNING with truck locked procedure is done, does the battery type show to be updated to the proper type?". The naming of the procedure in manual strongly implies that the procedure sets the BMS to determine battery type which should then be used for proper charging. The BMS could be following the new charging procedure with the battery type In the BCM along with the battery installed date not being updated if you run the battery learn procedure please check to see if the type and date are updated. Bear in mind if the battery installed date is several months or years old the BMS could be modifying the charging procedure to prevent overcharging an aged battery. I personally expect the BMS to periodically test charge the battery (weekly? Monthly?) When some of the middle of night clicking happens?.
Thanks in advance for checking, I don't have the equipment.

The truck kicks out an error if you don't let it sit for 6-8 hours post BMS reset. Bat_State_Det_Type has an "Out of Range" fault. It attempts to learn the SOC when you tell it to via FORscan, when you pump the brake pedal and flash the brights, and it'll do it just by allowing it to sit. I've done it all three ways, all of these accomplish the same thing, it learns the SOC and clears that fault. And none of them impact the battery type settings in the Bdycm. The battery age does update, you can see that in all the screenshots I posted.

Given that I always allow it to relearn SOC overnight whenever I reset the BMS and, as I stated in the post, both screenshots were taken 72 hours and 360 hours post-reset respectively, no it doesn't change any battery type settings during this relearn period. It does not work that way.

I bought the equipment so I could prove this out, so I could monitor what the truck is doing, so I could fix my own problem. And I've got a pretty good handle on things now. And I have 3 months of data to back up my statements. Regardless of what your interpretation of the manual is, or how you think it should function, that doesn't change what it's actually doing.

 

[mcc63303]

Being old and working on cars since 1970 I was taught to never connect both of the jumper or charger cables to the battery terminals. Reason back then the fumes from the battery were explosive and just the spark from connecting a clamp on the terminal could cause the battery to explode. Always connected the positive clamp first on the positive terminal then the negative somewhere on the engine. Remove the negative first then the positive. Another thing, in the winter a dead battery can actually freeze, before sealed batteries we would open the caps and if ice inside was noticed we had to have a charger on low for the first hour until ice was gone. Even with that I have had several batteries explode while charging. One thing more, if disconnecting cables or removing a battery, always take the negative off first and on last when connecting. Then if you ground a wrench while removing the positive no issue. Be Safe.

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