Battery Management System Reset

[Farkel]

My battery is getting drained an inordinate amount after just a few days. Don't remember that being the case before (at least not that fast), and it's not the battery, since it's new. It wasn't as fresh as I wanted it, since it had an AUG '20 sticker (rather than Sep), and I bought it Sep 26, but it shouldn't be bad (it had 12.52V). And it's an AGM (DieHard). And fully charged it before installing it. And everything is off. After 3 days installed, it had 12.48, so it discharged more in my car in 3 days, than almost 2 months by itself.

I'm no expert on batteries or the Mustang's high tech charging system, but have you tried the 8-hour reset procedure?
Here's my story: I've had AGM batteries for years in bikes and my Jeep, and I wanted to replace the stock battery with one ASAP. I wanted to buy locally, and that meant having to wait a while for Odyssey to build me a 96R (small town, long story). Since day 1 the stock battery was plugged in to a maintainer whenever it was parked in the garage. My maintainer shows percent of charge each time it gets plugged in. It was always fully charged before I drove, but while driving I noticed that the voltage gauge in my digi-dash only went up from 12+ to 14+ when I was off the gas, and when I'd plug it in after driving it was always down, sometimes as low as 70-something% on my maintainer's display. So I waited for it to fully re-charge, then I disconnected the maintainer and buttoned everything up for 8 hours. When I reconnected the maintainer the next morning, it had dropped to 70%! BUT (and it's a big butt ) when I drove it after that the voltage gauge immediately went to 14+ and stayed there. After an hour or so it came down to about 13.9. When I got home and plugged in the maintainer it showed 95%, which it had never done before.

I don't know if this pertains to your situation, but I wanted to throw it out there just in case.

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[Elp_jc]

Not sure if that will fix my issue, but it doesn't hurt to try, so I will try it tomorrow, after I use the car . Thank you.

BMS is supposed to only charge the battery if necessary, but maybe it's not enough, like you suggested. Who knows. Having said that, on the only trip I did after changing the battery, voltage showed a solid 14.0V all the time. Before, it was just like you described; basically between 12.5 and 13.5 (the latter mostly on deceleration). After that ride, I reset the BMS, so we'll see tomorrow. Maybe it needs to 're-learn' that behavior.

After that trip, I fully charged the battery, and 3 days later it was at 12.4x (yellow light). Unfortunately, my charger only shows lights, so can't correlate it to your percentage. At any rate, I connected the charger again (and it's been connected since). I'm thinking of running an aggressive desulfate cycle, since the battery sat for about 2 months before I bought it. Is it a good idea??? I'd use the Ctek Mus 4.3 for that. I normally use the Optimate6 to charge them.

But as far as the parasitic losses, I think it's a different issue, but we'll see. The battery is getting discharged rapidly. At that rate, it'd be completely dead in less than a week, which no way is normal at all. I left the doors partially closed (first click only), but everything is off, so it shouldn't discharge that much IMO. Maybe everything needs to be closed to be in 'deep sleep' or something.

 

[GT Pony]

But as far as the parasitic losses, I think it's a different issue, but we'll see. The battery is getting discharged rapidly. At that rate, it'd be completely dead in less than a week, which no way is normal at all. I left the doors partially closed (first click only), but everything is off, so it shouldn't discharge that much IMO. Maybe everything needs to be closed to be in 'deep sleep' or something.

You might have to measure the "full sleep" parasitic current draw to see if it's normal or not.

 

[Bit_the_Bullitt]

There has got to be something going on with the Bullitts I'd think. I've tried to mess with my dash cam, but I also tried a trickle charger and connected it to the car. It may be broken though as well, since it showed 0% battery right after I've driven it.

 

[Rod27]

How were you all able to take the 2 clips off that near the battery and fuse box?

 

[Bit_the_Bullitt]

How were you all able to take the 2 clips off that near the battery and fuse box?

There are 3 clips. If you look closely, there is a little narrow slit in them - put a thin flat blade screw driver in there and pop up slightly. The clip will loosen and then you can pull them out and take off the cover.
When putting back, make sure you rotate them in a way that you can always see the little slit.

If you still are not sure, I can take some pics when I get home tonight.

Edit - that ^ sounds REAL dirty.

 

[K4fxd]

ForScan has the ability to reset the BMS.

One thing I noticed is the BMS targets 80% charge. You can edit this. I set mine to 100%. You can also set battery capacity and type. IE AGM or Flooded.

I went Odessy AGM
I've read AGM's like to be charged to 105% but I'm afraid to go over 100. I think flooded like 110%

 

[Cobra Jet]

Just throwing this out there for future reference for those with BMS issues or questions...

One thing to mention, a M6G member thought it was the BMS acting up when he could not start his S550 - but it turned out to being a main fuse (125 amp) in the engine bay:

https://www.mustang6g.com/forums/threads/car-is-dead-need-help.137125/

 

[GT Pony]

Has anyone tried or verified what Rickloreto mentions about resetting the BMS without Forscan in this post?

https://www.mustang6g.com/forums/threads/vibration-between-50-70-mph.15990/post-3238841

" So far I’ve figured out quite a few things in general fords either truck/suv/mustangs (most cured with forscan) battery replaced needs a BMS reset done with ignition on/engine off pull high beam lever 5 times and press brake 3 times within a 6-10 second time and battery light will pulse a few times indicating its been reset, "

 

[Rod27]

There are 3 clips. If you look closely, there is a little narrow slit in them - put a thin flat blade screw driver in there and pop up slightly. The clip will loosen and then you can pull them out and take off the cover.
When putting back, make sure you rotate them in a way that you can always see the little slit.

If you still are not sure, I can take some pics when I get home tonight.

Edit - that ^ sounds REAL dirty.

That would help if you could share pictures of it. I find my car shutting down fast after stopping the engine or dome lights not wanting to come on until car engine is started

 

[Bit_the_Bullitt]

Has anyone tried or verified what Rickloreto mentions about resetting the BMS without Forscan in this post?

https://www.mustang6g.com/forums/threads/vibration-between-50-70-mph.15990/post-3238841

" So far I’ve figured out quite a few things in general fords either truck/suv/mustangs (most cured with forscan) battery replaced needs a BMS reset done with ignition on/engine off pull high beam lever 5 times and press brake 3 times within a 6-10 second time and battery light will pulse a few times indicating its been reset, "

Just tried that, def doesn't work. Altho I didn't replace a battery, was just curious.

That would help if you could share pictures of it. I find my car shutting down fast after stopping the engine or dome lights not wanting to come on until car engine is started

In my pics, the 3 tabs (at least on the Bullitt, but pretty sure same on all S550 Mustangs) hold the cover on.

Find the little slit/gap on each plug. Insert a flathead small screwdriver and slightly twist. Plugs will half pop off, pull off by hand.

When replacing, put them in a way that the slit faces out so you can get at it next time.

 

[melwff]

Just tried that, def doesn't work. Altho I didn't replace a battery, was just curious.



In my pics, the 3 tabs (at least on the Bullitt, but pretty sure same on all S550 Mustangs) hold the cover on.

Find the little slit/gap on each plug. Insert a flathead small screwdriver and slightly twist. Plugs will half pop off, pull off by hand.

When replacing, put them in a way that the slit faces out so you can get at it next time.

Both my 2017 and 2021 did not use that type of retainer. The type I have on both cars used a vertical tab that you just turn and then pull, no tool required.

 

[Rod27]

I was actually talking about the 2 sensor plugs for the BMS system like on pages 5 and 6.

 

[Bit_the_Bullitt]

Both my 2017 and 2021 did not use that type of retainer. The type I have on both cars used a vertical tab that you just turn and then pull, no tool required.

Interesting, I wouldn't have expected to see different ones. However! I did actually get a new battery now that I think of it, I got the car with 45 miles and the dealer had to throw in a new battery as the vehicle sat for a bit.
So I wonder if they busted the original retainers and used these generic ones...

I was actually talking about the 2 sensor plugs for the BMS system like on pages 5 and 6.

I kind of figured you weren't asking for pictures of removing a battery cover, but at the same time, I didn't mind trying to help. Sorry I couldn't deliver for you

 

[HoosierDaddy]

So I wonder if they busted the original retainers and used these generic ones...

Very unlikely. The factory ones are grab with thumb and finger, twist and lift. You can bet they dropped/lost them after they were out.

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