BMS not working…

[james cole]

Hello guys…

I did some forscan mods non related to BMS and after that the voltage reading is at a steady 14.5V even after charging the battery and a long trip, car is a 2022 Mach 1 with about 1,000 miles.

The voltage is supposed to drop for efficiency but I can seem to get it to work even after a BMS reset,

Anything else I should look out for?

Thanks!
JC


********UPDATE MADE IT WORK*********

OK, so in order to make the variable voltage from the alternator work, you need to do the following after swapping the battery, changing battery type in forscan or making a bms reset.

1. Leave it for at least 10 hours fully locked and charged
2. Reset PCM, resetting PCM without making the car go to sleep for 10 hours wont work... after this it should immediately work .

Reason is when monitoring BMS via forscan the Battery State Detection algorithm it requires around 10 hours to calculate the real state of charge of the battery, if it doesnt know it, the variable voltage will not work, it will default to 14.5 volts constant.

Why you need to reset PCM for it to start working is beyond me...

So I installed a AGM battery, modified the as built data from flooded battery to AGM, waited 10 hours, made a PCM reset and it works.

It was a bit of a pain to experiment and find this out, so I hope it really let's the engine make more power by freeing the alternator.

Sponsored

 

[MiamiGT350]

And what were those mods?

Did you do the BMS service in Forscan?

 

[Farkel]

Try this - with the battery fully charged, lock the car and let it sit for at least 8 hours. This will let the BMS recognize the battery's state of charge. If that doesn't change the charging back to normal, you might try disconnecting the negative cable for about 30 minutes.

 

[ice445]

Do a keep alive memory reset with a scan tool. I was having the same problem and that cured it.

 

[Farkel]

Do a keep alive memory reset with a scan tool. I was having the same problem and that cured it.

Please correct me if I'm wrong, but doesn't disconnecting the battery for a short time automagically reset the KAM?

 

[ice445]

Please correct me if I'm wrong, but doesn't disconnecting the battery for a short time automagically reset the KAM?

You'd think, but apparently some of the adaptations don't get reset and the car can get confused.

 

[james cole]

Hello Guys,

Thanks for all your replies!

Well I did:

-Body Control Module reprogramming to original values from Forscan
-Reset Module
-Reset BMS
-Fully Charged the battery with external charger

No dice... have driven about 20 miles and still reads at 14.5 Volts... wonder if this will damage the battery, I did replace the OEM battery with a Odyssey AGM96R because I like them and sold the OEM lead acid battery. OEM battery was new since car har around 1,800 miles.

 

[Farkel]

Not sure what the BCM has to do with it, but the BMS reset tells the system that the battery is new, which is not the same as the state-of-charge. Have you tried the suggestions in posts #3 and 4 above?

 

[ice445]

Hello Guys,

Thanks for all your replies!

Well I did:

-Body Control Module reprogramming to original values from Forscan
-Reset Module
-Reset BMS
-Fully Charged the battery with external charger

No dice... have driven about 20 miles and still reads at 14.5 Volts... wonder if this will damage the battery, I did replace the OEM battery with a Odyssey AGM96R because I like them and sold the OEM lead acid battery. OEM battery was new since car har around 1,800 miles.

You have to reset the PCM specifically, as it's the one that controls the charging strategy. There are several modes. If you have an advanced scan tool you can see which one it's stuck in. The BCM is responsible for learning the state of charge, but in my case the state of charge was never the problem, it was the PCM not switching over to the normal mode once SoC reaches over 90%.

I have the same battery as you, so maybe the issue is somewhat related to using an AGM. But once I reset the PCM adaptations and started the car, with SoC at 91%, the car started up at 14.5 and then quickly reduced to 13.4 or so after about 30 seconds to 1 minute, and then further followed the electrical demands of the car as it's supposed to.

 

[james cole]

Thanks Ice!

what mode should I check in advanced diagnostics in the PCM? What is it called… I can see in BCM the mode is in “fast regen allowed”

 

[WItoTX]

Borrow a battery and see if it works. I suspect your battery is the issue...

 

[Postal Bob]

I'll relate my experience when I replaced my battery, with a oem lead acid battery.
I replaced it a few days before I took a 3+ hr trip. Obviously a new battery may not have a full charge, depending how long it sat at the dealer before being sold. So after I installed it, and did a successful BMS reset, I hooked up my battery charger/tender. It took almost a full day before it indicated battery was fully charge. But my voltage wa still reading about 14.5V for a few days.
Then I took my 3+ hr road trip. I monitored the voltage the whole time. It wasn't until I almost completed the trip, that the voltage reading started coming down, and finally settled about 12.6V.
Point is a new battery may still require a lot of charging before it's completely charged. And now after a 3 month Winter storage, continuously attached to a battery tender, mine started out reading 14.5V again. And over the course of driving a few hours, has started coming down to normal. It's just the way it is I think.

 

[james cole]

Thanks so much for your comments:

I did charge the battery several times…

Battery state of max charge is set to 80%

What I find strange is the value squared off in black:

 

[ice445]

That is very unusual. Can you see what type of battery the car thinks is installed anywhere?

 

[james cole]

That is very unusual. Can you see what type of battery the car thinks is installed anywhere?

Yes… Flooded as it was the OEM one.

My factory OEM data shows “15” but not sure it applies to the mustang, mine is a 2022 Mach 1.

Sponsored