Auto stop/start disable?

[TJC]

Yes, I am sure. There are other threads here that discuss it in detail. Its function is to calculate the battery state of charge. One reason is to make sure the battery has enough charge to restart the engine if ASS has stopped it. If there is not enough battery charge, it disables Auto Start Stop. But it also is used to control the charging rate of the battery. When you unplug the BMS, the state of charge can no longer be known.

I don't think that statement is absolutely true.

My research showed me that when the sensor was unplugged, the BMS defaulted to a charging system very much like the one in 2005 Ranger.

I monitored both trucks under identical conditions watching charging behaviors and the only difference between the two was that the unplugged 2020 Ranger charged the battery at 0.2v higher than the 2005 Ranger. The charge patterns were identical. That extra 0.2v I attributed to the 2020 algos being tuned for AGM vs standard flooded batteries that came with my 2005 Ranger.

I drove both trucks the same route(a 40 mile circuit with a stop at the 20 mile mark for 30 minutes) during the day and at night, one right after the other so weather conditions would be close. I watched both voltage and amperage. Both batteries were extremely healthy with 100% SOC and 100% SOH, and had sub 3.5milliOhm internal resistance. Those are pretty impressive numbers for 6 and 7 year old batteries.

My goal was to validate what was happening when the sensor was unplugged. I have since plugged it back in and set SOH to 100%. I'm not sure I'm going to leave it as it is. I can see the advanced BMS doing it's thing, but the SOC target setting drifts lower over time... and I think it is not intentional. I think there is an error in the firmware.

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[THORNRIDER]

Interesting. In the real world, I have had my BMS unpluged for 5 years and 40K miles with no issues at all. An AGM battery life is 5 to 7 years so I plan to replace it next year.

 

[Texasota]

If only ford would have installed something like a switch or button you can push to turn it off

I'm old. Always forgetting to push the dang Dumb ASS off button.

 

[RangerBill]

It does more than disabling Auto Start/Stop. Disconnecting it will also disable the Battery Management System that controls battery charging and presumably extends battery life and helps fuel economy.

The BMS also monitors battery temperature and voltage, which info is lost to the BCM if the sensor is unplugged.

 

[TJC]

The BMS also monitors battery temperature and voltage, which info is lost to the BCM if the sensor is unplugged.

I believe both the voltage and at least ambient air temp can still be used to charge the battery (old school method), and I can quickly confirm it again.

You're correct that the backup charging system isn't as advanced... You are also correct that the BMS senses temps from the neg battery terminal, and does read the voltage through the sensor.

The BMS normally gets its voltage measurement through its B+ sense connection, but the truck's charging system/PCM still has access to voltage information elsewhere.

The same goes for battery temperature... The backup system can use ambient air temps instead of those from the BMS sensor. My advanced chargers use precisely that technique to great effect -an ambient air temp sensor on a 4"- 8" pigtail from the charger.

You also lose the SOC and SOH (without severe penalty), which are derived from feedback and historical battery decay rates, and the key word here is "derived", and for me that has negative connotations.

If I can keep sulfation under control better than the general public (or Ford's in house testing which I suspect tends to follow a battery manufacture's standard degradation chart), my battery will age at a much slower rate. Ford's decay rate will have a serious negative impact on my efforts to extend the battery's useful life.

I accomplish this by keeping the battery at a full 100% SOC, (not a SOC of 70% or 75%), and constantly run a desulfation program when the truck is charging the battery above 13.5v. It is surprisingly simple, with a history of my batteries lasting at least 2X as long as most.

Once I do this I can throw Ford's charging Algo's out the window. This means I can unplug the BMS sensor, and use the backup charging methodology to achieve my battery longevity goals.

Presently, I'm testing the BMS system to determine the system reliability. And I've witnessed the SOC target drift lower twice in a relatively short time, and this bothers me enough that I am considering going back to disabling the BMS by removing the sensor from the equation. I've tried setting the BMS parameters with Forscan, and they have helped, but I do not like the SOC target drift down.

Time will tell....

 

[RangerBill]

I believe both the voltage and at least ambient air temp can still be used to charge the battery (old school method), and I can quickly confirm it again.

You're correct that the backup charging system isn't as advanced... You are also correct that the BMS senses temps from the neg battery terminal, and does read the voltage through the sensor.

The BMS normally gets its voltage measurement through its B+ sense connection, but the truck's charging system/PCM still has access to voltage information elsewhere.

The same goes for battery temperature... The backup system can use ambient air temps instead of those from the BMS sensor. My advanced chargers use precisely that technique to great effect -an ambient air temp sensor on a 4"- 8" pigtail from the charger.

You also lose the SOC and SOH (without severe penalty), which are derived from feedback and historical battery decay rates, and the key word here is "derived", and for me that has negative connotations.

If I can keep sulfation under control better than the general public (or Ford's in house testing which I suspect tends to follow a battery manufacture's standard degradation chart), my battery will age at a much slower rate. Ford's decay rate will have a serious negative impact on my efforts to extend the battery's useful life.

I accomplish this by keeping the battery at a full 100% SOC, (not an SOC of 70% or 75%), and constantly run a desulfation program when the truck is charging the battery above 13.5v. It is surprisingly simple, with a history of my batteries lasting at least 2X as long as most.

Once I do this I can throw Ford's charging Algo's out the window. This means I can unplug the BMS sensor, and use the backup charging methodology to achieve my battery longevity goals.

Presently, I'm testing the BMS system to determine the system reliability. And I've witnessed the SOC target drift lower twice in a relatively short time, and this bothers me enough that I am considering going back to disabling the BMS by removing the sensor from the equation. I've tried setting the BMS parameters with Forscan, and they have helped, but I do not like the SOC target drift down.

Time will tell....

I made the statements to inform others that unplugging the BMS sensor is doing more than disabling ASS. It disables ASS because the truck programming disables it when the battery state of charge is too low to ensure reliable restarts of the engine. Unplugging the sensor cuts off several of the parameters that are used for battery charging rates and battery state of charge calculation.
Disabling ASS is a side effect of unplugging it, not its main purpose. Some seem to believe it is only for the Auto Start/Stop function.

 

[got3fords]

I believe both the voltage and at least ambient air temp can still be used to charge the battery (old school method), and I can quickly confirm it again.

You're correct that the backup charging system isn't as advanced... You are also correct that the BMS senses temps from the neg battery terminal, and does read the voltage through the sensor.

The BMS normally gets its voltage measurement through its B+ sense connection, but the truck's charging system/PCM still has access to voltage information elsewhere.

The same goes for battery temperature... The backup system can use ambient air temps instead of those from the BMS sensor. My advanced chargers use precisely that technique to great effect -an ambient air temp sensor on a 4"- 8" pigtail from the charger.

You also lose the SOC and SOH (without severe penalty), which are derived from feedback and historical battery decay rates, and the key word here is "derived", and for me that has negative connotations.

If I can keep sulfation under control better than the general public (or Ford's in house testing which I suspect tends to follow a battery manufacture's standard degradation chart), my battery will age at a much slower rate. Ford's decay rate will have a serious negative impact on my efforts to extend the battery's useful life.

I accomplish this by keeping the battery at a full 100% SOC, (not an SOC of 70% or 75%), and constantly run a desulfation program when the truck is charging the battery above 13.5v. It is surprisingly simple, with a history of my batteries lasting at least 2X as long as most.

Once I do this I can throw Ford's charging Algo's out the window. This means I can unplug the BMS sensor, and use the backup charging methodology to achieve my battery longevity goals.

Presently, I'm testing the BMS system to determine the system reliability. And I've witnessed the SOC target drift lower twice in a relatively short time, and this bothers me enough that I am considering going back to disabling the BMS by removing the sensor from the equation. I've tried setting the BMS parameters with Forscan, and they have helped, but I do not like the SOC target drift down.

Time will tell....

IIRC, that lower SOC is there so when you are coasting, the regenerative charging can kick the charge voltage up to 14V or above and it has someplace to go. (I had a hard time putting that into words for some reason.)
I think with the BMS sensor disconnected it acts more like a traditional charging system without regen charging, no?

 

[THORNRIDER]

This is all good information. I think we can all agree that ASS does harm to the engine and needs to be disabled. There are several ways to make that happen, and 5 years ago, I saw on YouTube disconnecting the BMS sensor will disable it. In those 5 years I have seen zero issues with my battery or charging system. I just purchased 2 USB LED lights to plug into the rear of my center console. I will try this on my 2020 Ranger and 2024 Bronco Sport. I learned about the USB LED lights from this forum so I will let you know if that works.

Are we not all glad that we don't own a GM 6.2L gas engine?????? Just read it could be as many as 1MM engines effected and they will blow up!!!!! Makes this BMS and ASS discussion seem very trivial.

 

[TJC]

IIRC, that lower SOC is there so when you are coasting, the regenerative charging can kick the charge voltage up to 14V or above and it has someplace to go. (I had a hard time putting that into words for some reason.)
I think with the BMS sensor disconnected it acts more like a traditional charging system without regen charging, no?

Essentially Yes.

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