12V Battery #2 is down for the count

[Deleted member 5597]

I had the original 12V battery replaced in November, 2024 on my ‘22 hybrid Lariat as I was down to 36%. The original battery was replaced under the bumper to bumper warranty. Fast forward to last week when I began getting the battery saver mode on my Ford App daily, even after I drove it. Took it in to the dealer today, and it’s down to 50%. Everything in the charging system checked out OK. It will be going back to the service dept tomorrow for a new battery under the original bumper to bumper warranty.

My wife’s hybrid Escape had the same fate. The battery was replaced at the same time as my Maverick and under the 36/36 warranty. Her battery was down to 40% today, but she’s out of bumper to bumper warranty, which ended this past February. Ford says the battery that was replaced in her car in November doesn’t have a warranty. Ford Customer Service says the battery that was replaced in her car goes back to the original date the warranty on the car began over three years ago.

Funny, because I can go buy that same battery at WM and will have a warranty on it.

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[HeyBales]

While it's not the fast drain effect and dead the next morning, and you've probably been in AC season longer than many - you might ask them to check into the ACCM software update from SSM.

All it would take is a few times of the AC module doing something it shouldn't to drain the battery each time you turn off, taking it too low.

Or you had a really good battery on the 1st one, and this one is really bad. Luck of the draw.
But I'm guessing different looking, and higher AhR and CA.

Heat is bad on batteries, and a problem one already...

 

[Master Blaster]

I've had 3 in my 23. This one seems to be lasting longer than the others. The misprogrammed BMS only allows the battery to get to about 70% charge, promoting maximized sulphation and early death. I had the a/c SSM done a month ago, so I'm watching. Unfortunately Ford seems to be really tardy with a simple BMS software fix that has been present since the vehicle was introduced, so I expect it to keep on killing batteries...

 

[ZABSMAV]

Given that they (Ford) admits (by the SSM on paracytic current drain) that the Maverick is killing the batteries, demand to speak with the general manager of the dealership and demand that they warranty replace the battery that was replaced for the original.

By the way, in one day, just sitting, our 2023 Lariat hybrid's battery drops from a 70% SOC down to a 50% with not a thing running on the vehicle, and yes, we had the SSM update on the AC Module.

 

[Escapologist]

Hmm, I would be tempted to dig out where the BMS is sensing voltage from and stick a diode inline, 0.6-0.7V drop, so it keeps trying until it's 0.6-0.7 higher.

 

[canuckford]

Hmm, I would be tempted to dig out where the BMS is sensing voltage from and stick a diode inline, 0.6-0.7V drop, so it keeps trying until it's 0.6-0.7 higher.

I'm not sure that's a good idea, but if you're going to do this, you need to know how many Amps inline and get a diode that can handle the current.

But, just curious, do the Hybrids not have an alternator? They charge from the high voltage battery?

 

[ZABSMAV]

I'm not sure that's a good idea, but if you're going to do this, you need to know how many Amps inline and get a diode that can handle the current.

But, just curious, do the Hybrids not have an alternator? They charge from the high voltage battery?

The Maverick hybrid does not have an alternator. It "attempts" (poorly) to recharge the 12v battery through a DC-DC converter that reduces the HV down for that purpose.

 

[canuckford]

Thanks Gary, I wonder why the engineers left out the alternator, no room ? I understand that while the car is running on the HV battery, the ICE is not running so even if it did have an alternator, it wouldn't help, but for the time the car is under ICE power it could have charged the 12volt batt if it had the alternator. Maybe there's no room since you would have to put the mechanism for the belts, etc, but if anyone knows the real answer I'd appreciate it.

 

[Master Blaster]

Thanks Gary, I wonder why the engineers left out the alternator, no room ? I understand that while the car is running on the HV battery, the ICE is not running so even if it did have an alternator, it wouldn't help, but for the time the car is under ICE power it could have charged the 12volt batt if it had the alternator. Maybe there's no room since you would have to put the mechanism for the belts, etc, but if anyone knows the real answer I'd appreciate it.

I don't understand why you think an alternator is a good thing. Not having an alternator to fail and the belts to break is a big plus. You already have 240V power at all times, that can be stepped down pretty easily to push 12V to the electronics battery. Ford screwed up the common BMS algorithm on the Maverick, Escape, Corsair, Mustang and F150, but that's easily fixed if they ever get around to admitting the software error.

 

[canuckford]

Why suck precious power from the HV battery when running the ICE and alternator, power is essentially free.

 

[canuckford]

I don't understand why you think an alternator is a good thing. Not having an alternator to fail and the belts to break is a big plus. You already have 240V power at all times, that can be stepped down pretty easily to push 12V to the electronics battery. Ford screwed up the common BMS algorithm on the Maverick, Escape, Corsair, Mustang and F150, but that's easily fixed if they ever get around to admitting the software error.

BTW, I don't think it's easily fixed, otherwise the software engineers would have done it long ago. I imagine getting the algorithm tuned is a balancing act, a compromise , a hole which they have dug for themselves by not including an alternator. I have read many posts here that suggest getting a better battery has helped alot and for many solved their issue, which to me suggests the software modifications are basically a work around.

 

[ZABSMAV]

BTW, I don't think it's easily fixed, otherwise the software engineers would have done it long ago. I imagine getting the algorithm tuned is a balancing act, a compromise , a hole which they have dug for themselves by not including an alternator. I have read many posts here that suggest getting a better battery has helped alot and for many solved their issue, which to me suggests the software modifications are basically a work around.

Those who say that an AGM is a "better" battery, and the "solution" are giving out disingenuous information. There is nothing inherently "better" about an AGM versus a flooded lead acid battery. Each has its own advantages and disavantages. The 2025 models are having the same deep sleep problem as the 2022 through 2024 hybrids and the 2025s came with an AGM 12v battery. The problem is likely a combination of not quickly and completely recharging the 12v battery and additional circuits causing paracytic current drainage from the battery.

 

[HeyBales]

Why suck precious power from the HV battery when running the ICE and alternator, power is essentially free.

Because you are sucking power from the ICE, and can only charge when ICE is running.
So you are ruining the gas mileage when that happens.

And adding complexity.

Besides - vehicles for couple decades load cycle the alternator anyway to vary the output to the 12V system. Just like they are doing with current system.

The load on the 1.1 kW battery or while moving basically no load is much easier to do, and really isn't much of a load anyway.

Especially the way Ford does it!

Ahh! crack myself up.

 

[canuckford]

Maybe this is how it works, if someone who knows could verify. Perhaps the 12 volt batt is indeed being charged when the ICE is running, I think it's possible. The ICE is already producing DC to charge the HV battery, it's easy to tap off that line, step down the HV DC through a DC-DC converter and charge the 12 volt batt. If this is how it's working, then this answers why they don't have an alternator.

 

[ZABSMAV]

Maybe this is how it works, if someone who knows could verify. Perhaps the 12 volt batt is indeed being charged when the ICE is running, I think it's possible. The ICE is already producing DC to charge the HV battery, it's easy to tap off that line, step down the HV DC through a DC-DC converter and charge the 12 volt batt. If this is how it's working, then this answers why they don't have an alternator.

Nope. The ICE does not send current to the DC-DC converter to charge the battery as your sketch shows. The HV battery does.

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