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I too am now on my third T4 battery, in a Mav built in 08/23. So far its showing 80% charge, but that's a new battery every 7 months on average. My original and smaller factory battery lasted 11 months, while the beefier warranty replacements are not lasting as long. These batteries should be lasting 5-8 years. This fix coming in 2Q25 had better work really well...

 

Update! Well, It had deep sleep this morning, after driving & charging 14 hours prior. It woke up and lights came on, but at turn of key to 2nd position showed on 11.5 volts!!! Drivable, but battery absolutely BAD.

Will go to dealer ASAP for 4th battery.

 

Software

 

Hardware. Simply poor quality. Batteries do NOT contain software. They are extremely simple. They either continue working, or have cells that go bad.

If it was vehicle software, it wouldn't be perfectly fine for months or a year, and then suddenly be defective; a brand new battery would consistently die right away.

Strain on a hybrid battery is inherently low; you could use a 12V flashlight battery for electronics initially to get a hybrid to READY mode. You would just fairly soon lose flashers if broke down on side of road unless you have key position all the way ON for gas engine to cycle on and off to keep battery charged.

 

That's not how you measure the battery voltage. You're measuring the charging voltage, which should always be in the 13-15V area. Measure after 8hrs or more with the vehicle off, to prevent measuring the temporary surface-effect voltage. A fully charged brand new battery will measure 12.6-12.8V. A degraded battery will measure about 11.5-12.5V, as will a partially-charged one after the BMS does its thing incorrectly. Deep sleep appears to kick in when it hits around 12.1V (about 52%) or lower. RV Tech Library - Battery Charge Voltage

 

That's not how you measure the battery voltage. You're measuring the charging voltage, which should always be in the 13-15V area. Measure after 8hrs or more with the vehicle off, to prevent measuring the temporary surface-effect voltage. A fully charged brand new battery will measure 12.6-12.8V. A degraded battery will measure about 11.5-12.5V, as will a partially-charged one after the BMS does its thing incorrectly. Deep sleep appears to kick in when it hits around 12.1V (about 52%) or lower. RV Tech Library - Battery Charge Voltage

I'm not reading it wrong. The morning after the day of putting on charger, after the day it appeared completely DEAD (full turn of key did nothing), the voltage read 11.5V.

 

Software. Period.

 

.

 

Update! When to Ford today, and they checked battery and said it was OK, But I seriously still believe it is on its last legs. Just a couple hours after getting home, FordPass says it is in deep sleep mode. ONLY a failing battery would do that.

The S.A. said they are aware of a battery draining problem, and a fix is in the works but not completed yet. My battery issue are more than that. After a new battery, it performs flawless for many months. If battery is draining, then I would have problems right off the bat with a new one. Simple logic.

 

My smaller original factory battery lasted 11 months before dying. It could only get up to 11.3V in the morning and was causing all the deep sleep symptoms. My second battery only lasted about 5 months and was down to 11.8V every morning. I have a sneaking suspicion that the technician did not install it correctly, since they checked the charge and did it in only two hours. You're supposed to fully charge the battery, do the physical install, reset the BMS and then wait eight hours to allow the BMS to learn how to charge it. That's an all-night job at a minimum. Otherwise the BMS cuts off charging really early, thinking that it already has enough charge. I'm now on my third battery (same type as the second one) for the last 4 months, and so far its holding at 12.2V. Its not 12.6V like it should be to prevent sulphation, but that's what the faulty BMS code is doing. So far the much-delayed BMS fix for just my truck has cost Ford about $1k including labour, and will probably have another 30% adding for the next replacement under warranty. You would think that much would incentivise them to get it together and actually release the fix...

 

My smaller original factory battery lasted 11 months before dying.

By smaller, you mean not the 400V hybrid battery, right? Nothing small about the 12V one, as there are NEVER high current draws, like if you have an actual old fashioned starter. All the vehicle needs is the proper voltage and LOW current. Heck, you could replace with a small motorycle battery, to power computer enough to get rolling and charging, regenerative and otherwise.

 

Question.....are these bad batteries all of the same manufacturer?

 

Question.....are these bad batteries all of the same manufacturer?

My original and replacements appear to be. Ford label.

 

I've had to have my 22 jumped 3 times. My dealer sent me a notification from Ford that they are working on a software fix, hopefully this quarter. AAA has to pay for the company to keep coming to the house.

 

I've had to have my 22 jumped 3 times. My dealer sent me a notification from Ford that they are working on a software fix, hopefully this quarter. AAA has to pay for the company to keep coming to the house.

WHY NOT buy a little jumper box from Temu for $15???

Whilst my battery is not brand new and is questionable, I keep rear seat up with + cable of jumper box attached to battery, with negative just hanging. If I open door to go somewhere and it does not wake up from deep sleep, I simply attach jumper box ground, turn key to start, and whilst still in P, I disconnect ground, and then get in and drive away. Easy peasy!

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