I've had this happen several times after the car sat for some time, but it's never "stuck" on that screen. You mean yours is stuck in that mode even after starting the car and driving?
Interesting. So just disconnecting the sensors disabled it without a CEL or anything?
Nearly a year has passed, and I am wondering if thehunteroo solved his "low power" problem.If the BMS is messed up like mine is it will always think that the battery is bad no matter the charge because it will never reset on its own regardless of whatever charge the battery has. But otherwise it should reset after sitting for 8 hours if the system is working properly or if you go to the dealer and get a battery from them they can reset the BMS on the spot and skip the 8 hour phase if they know what they are doing.
For example when I just got another new battery put in the it was not in low power mode when I turned the car on. But as soon as I got home and turned the car off and ignition back on it was back in low power mode. Not really a big deal now though since the BMS charging silliness is bypassed and it will only go back into low power mode when my battery is kicking the bucket in the next few years
Best way is to disconnect both battery current sensor relays. It disables the smart charging BS and the battery charges like it normally would. The BMS system is still there but it doesn’t have control over the charging without the sensors. It doesn’t throw a check engine light but it will have a code though it is nothing to worry about. If I bought another Mustang I would just disable it from the get go.Nearly a year has passed, and I am wondering if thehunteroo solved his "low power" problem.
I had the car-shuts-off accessories-to-protect-the-battery effect that would stop everything after about five minutes. About a month ago I.replaced the battery with a stronger one, and the shut-off came after half an hour. It still seems as if the interval is longer after a lengthy road session. I believe the problem is in the Battery Monitor System, which apparently requires a "reset" when a new battery is installed. If no reset, the System thinks the old battery is still in place, and regards it as "aged", so it is treated differently as far as charging rate, etc.
I offer this as evidence that the BMS sees the new battery as "aged": I have a modern Schumacher battery charger which fully charged the new battery, but when left on overnight claimed the battery needed desulfating. After ten hours in desulfate mode, it declared the battery BAD and showed a few codes to support its contention. The BMS had told it there was an old, aged, failing battery in place.
I think the new battery is faultless—it behaves normally except for the half-hour shut-off—and the BMS is just doing its job as if there were an old, decrepit battery installed.
After perusing several forums' threads about BMS reset, I've begun the process necessary to using FORScan to do the deed. Got a laptop, downloaded the software, acquired the connecting bits. But just in case, tonight I put the car to bed with everything turned off and all locked up, which some have said should let the BMS reset itself.
We'll see. It would be a shame to have to go the the dealer and ask them to apply their tool, which I presume they have and know how to use.
Thank you for your response. Seems like a pretty straightforward solution, but I hesitate to disarm any of Ford's armory they must have valued in some way. As long as there are other approches to be considered, I reckon I will save that one for last.
The BMS can apparently tell the alternator and battery how to cooperate with one another, so I'm convinced it can evaluate the status of those components and report the results, even though erroneous. The battery charger manual makes it clear that users can expect certain status reports under certain conditions. It gets its information somewhere; I nominate BMS.