BMS reset question

[americanv8]

My oem battery went out and decided to upgrade to the xs d4700. I'm fully charging it now as recommended and will swap it in tomorrow. I understand there is a bms reset procedure that needs to be done, but I also saw that if you leave the car alone for 8 hours it will do it on it's own. Is this correct? After I hook up the battery and see if it starts up fine, do I just turn off and leave it alone for 8 hours and it will automatically reset the bms?

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[Elp_jc]

I honestly don't think that resets the BMS. It just records the current battery charge, or SOC. I did the reset; it's quick and easy. Up to you.

 

[Grimmer]

If the car sits with less than x amount of draw on the system for y number of hours, then it will try to assess and "reset" its idea of what the current state of charge is on the battery.

I don't recall exactly the numbers without looking them up, but if you haven't added any devices that draw power continuously then leaving the car alone (no lock/unlock, no fob buttons, don't open the doors, etc.) you should be under the draw limit. And I think you are correct that it is 8 hours undisturbed.

If you use FORScan to reset it, it is quick and easy (if you already have the hardware and software) but I think it expects the battery to be fully charged when you do it... Not sure about that though. I don't recall if it assesses the charge state or assumes fully charged when reset through FORScan.

 

[Grimmer]

There is reported to be section in the AS-BUILT data that tells the BMS what type and size the battery is. Although you have to pick from the available choices and can't just define what it is directly. I haven't seen any confirmation for this AS-BUILT data on the Mustangs, but the F-150 guys list it in their spreadsheet.

I replaced my battery with an AGM H6. I think there is an option for AGM H6, but until I find some confirmation that this AS-BUILT option is the same for both the Mustangs and F-150's (some are, some aren't), I'm choosing to leave it alone. AGM and the flooded lead acid batteries are different, but not wildly so.

 

[GT Pony]

My oem battery went out and decided to upgrade to the xs d4700. I'm fully charging it now as recommended and will swap it in tomorrow. I understand there is a bms reset procedure that needs to be done, but I also saw that if you leave the car alone for 8 hours it will do it on it's own. Is this correct? After I hook up the battery and see if it starts up fine, do I just turn off and leave it alone for 8 hours and it will automatically reset the bms?

Correct per the service manual but sounds like only when charging the battery. But there's also a statement about battery replacement - see snip-its below.

I replaced the battery in my 2015 and never did a BMS Reset. Saw zero issues, so not sure what a BMS Reset would have changed. Sounds like the BMS module keeps track of how long it thinks the battery has been in use ("time in service counter" in memory), and a BMS Reset is apparently the only way to clear that info when a new battery is installed. Of course, only the dealership has the correct scan tool to do the reset and charge you about the same as what the new battery cost you.

Battery Charging BMS Reset Info

Battery Replacement BMS Reset Info

 

[GT Pony]

I honestly don't think that resets the BMS. It just records the current battery charge, or SOC. I did the reset; it's quick and easy. Up to you.

Can it be done without FORScan/scanner? If so, how?

 

[Elp_jc]

The BMS reset is so the system knows it's a new battery, and charges it at 100% levels. The '8-hr' crap is not going to do that; it only triggers a SOC. And no, you need FORScan or a dealer computer to do it. I did that after fully charging the new battery first (outside the car), and installing it fully charged. It might not matter, but I almost always fully charge batteries before installation, for maximum longevity.

 

[Grimmer]

I did that after fully charging the new battery first (outside the car), and installing it fully charged. It might not matter, but I almost always fully charge batteries before installation, for maximum longevity.

+1. All automotive battery manufacturers recommend the battery be fully charged before being put into service. Best to use a good charger that has multiple charge modes (bulk, topping, and float).

Edit: Duh, my other post didn't mysteriously disappear, it was in a different thread for a different question. You didn't ask about a tuner and AS-BUILT has nothing to do with BMS reset. In FORScan, you'll find the BMS reset on the perform tests tab.

 

[americanv8]

The BMS reset is so the system knows it's a new battery, and charges it at 100% levels. The '8-hr' crap is not going to do that; it only triggers a SOC. And no, you need FORScan or a dealer computer to do it. I did that after fully charging the new battery first (outside the car), and installing it fully charged. It might not matter, but I almost always fully charge batteries before installation, for maximum longevity.

Yeah, fully charging it before install. Guess I need to look into Forscan, was hoping to not have to go that route as I'm not familiar with it. Is there an adapter you recommend?

 

[Grimmer]

I use the OBDLink MX+ Bluetooth. It is a little more expensive than others but I chose it because it looked to be more capable as an OBD scanner for all my other cars too. Back in the day the reviews said that the Bluetooth version was more stable/reliable than their WiFi version.

In the FORScan threads they discuss the minimum capabilities required and several other options.

 

[Elp_jc]

Is there an adapter you recommend?

I don't remember where I got it, but it was less than $15 delivered, so super cheap. Mine has the MS/HS switch, but I don't mind. It's just a cable, but that's all you need for FORScan. Sorry I couldn't be of more help.

 

[Farkel]

Can I skip the BMS reset if I put a new (AGM) battery in a two-month old car? I don't have FORScan. (I don't even have or want a computer, after 30-plus years of programming and systems analysis!)

 

[GT Pony]

Can I skip the BMS reset if I put a new (AGM) battery in a two-month old car? I don't have FORScan. (I don't even have or want a computer, after 30-plus years of programming and systems analysis!)

I would say you would be fine in that case. I put a new battery in my 2015 when it was ~2 years old and didn't do a BMS reset. Don't see anything odd going on.

 

[Farkel]

I would say you would be fine in that case. I put a new battery in my 2015 when it was ~2 years old and didn't do a BMS reset. Don't see anything odd going on.

Thanks. That's what I was hoping to hear.

 

[Elp_jc]

Can I skip the BMS reset if I put a new (AGM) battery in a two-month old car?

Well, the important age is from the BUILD DATE . I changed the battery on my new Bullitt when it was days old to me... but it was already 9 months old. I did reset it, but it's not a big deal, so don't worry about it. But wanted to mention the real age, since you should also consider that when changing the brake fluid (2 years from THAT date, not when you bought it), engine oil, etc. My car is just past 1 year old, and will change the oil next week at 1,1xx miles. It coincides with the mileage I wanted to do, and it's already over a year old, so it needs to get replaced.

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