Wtf is going on with my BMS

[sms2022]

Have the battery load tested. I’m willing to bet the battery is bad.

I think so too but it’s a brand new battery replaced by the dealer in January after the car had sat for a year. Unbelievable. So I’ll get the interstate today so I can drive the car to the dealer and then I guess it can sit at the dealer for a week getting diagnosed again.

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[17gt07]

I think so too but it’s a brand new battery replaced by the dealer in January after the car had sat for a year. Unbelievable. So I’ll get the interstate today so I can drive the car to the dealer and then I guess it can sit at the dealer for a week getting diagnosed again.

Car batteries are trash nowadays. Now a lot of times when a battery is completely drained, it’ll drop a cell. That’s probably what happened. It can show ok voltage while sitting but doesn’t put out the required amperage while cranking.

 

[fast306stang]

And ford wants the car towed in instead of just giving me a new battery

I had this issue on my 2018. I really didn't want them to tow my car since it was lowered. The next day (because it was already getting late) I took the battery out and took it to them so they could check it. They replaced my battery under warranty.

Now...when I had called them, they told me they wouldn't do it this way. So I took a chance and just drove up there and talked to them in person and was nice about it and explained everything. It worked out in my case, but ymmv. Good Luck!

Ummm...also on my wife's Explorer on a Sunday at my brother's house across town, came out and it wouldn't start. The battery was so corroded that the terminal came off the battery. So I had no choice other than to buy a new battery on the spot.

Took the old battery and the receipt for the new one to the dealer the next day, they refunded me for the new battery. The refund did take a few weeks for approval, not bad, but it wasn't done on the spot.

 

[sms2022]

Yeah I think I’ll swap to the interstate battery, drive my battery up to ford, see if they’ll swap it, and if not I’ll drive the car up there with both batteries. I’ll throw the interstate in my 68 when I get a new motor craft (that 68 is running a 20 year old Sears battery that is finally giving up the ghost)

 

[sms2022]

Problem solved.
Two issues: 1, the positive lead in the fuse box was loose!
2, the dealership that “replaced the battery” in January put in a 2022 date code battery, likely from another vehicle as it was dirty as hell on the bottom.

Swapped battery, tightened lead, reset bms, all is good. Plus I swapped my charging leads to the fuse box and shock tower ground as recommended.

 

[fast306stang]

Problem solved.
Two issues: 1, the positive lead in the fuse box was loose!
2, the dealership that “replaced the battery” in January put in a 2022 date code battery, likely from another vehicle as it was dirty as hell on the bottom.

Swapped battery, tightened lead, reset bms, all is good. Plus I swapped my charging leads to the fuse box and shock tower ground as recommended.

Good info for someone to troubleshoot with later on!

 

[Balr14]

My experience with my 2018 Mustang is that it has the best BMS system I've ever seen. Parasitic power loss was extremely low and sleep mode very effective. I'm glad to hear you got it sorted out. (Worst is Porsche 997.... leave the car unlocked overnight and you have dead battery in the morning.)

 

[Doug V]

Accidentally left the ignition on overnight and the BMS went into protect mode. It would not let the battery charge from my tender so I unhooked the battery and charged it outside the car. Since then, the car started once but would not restart even though the battery is 12 volts. What gives?

Should I reset the BMS? Can I just disable the BMS through Forscan so this can’t happen again?

Sound like an issue I had. I had to disconnect the battery from the car, and put a charger/tender on it for a while. Once it had enough charge, I hooked the it back up and had to charge it over night.

Its about three years old. I noticed the negative terminal had corrosion. I cleaned it and have not had an issue since. I bought a new battery but have not installed it.

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