Hybrid battery drain issue / ACCM update (as of 11/8/25) -- Latest info from a tech's perspective

[johnDeere]

I have the "car scanner" app on my iphone and connected to the big screen on my 23 mav hybrid XLT, and monitor things like temperature of the HVB, engine temperature, transmission temperature, and shutter position, and others.

I have been using this app on this truck for almost a year now.
There is some crazy programming going on with the shutter.
In the summer time, without the AC on, I can watch the engine coolant temperature go up to 210 degrees before the shutter opens.
And then it will close, then the temperature goes back up and then it will open, and then close.
Don't know if ford can proportion the shutter angle degree to temperature correctly or is there something wrong.
Noticed something strange last week, its cold here in Michigan, and noticed my shutter was 46 percent open all the time, it has been working correctly for months.
I Logged into forscan and checked for error code, and guess where there was a error code, ACCM.
I didn't note down the error number, but reset the ACCM, checked for codes again, and it was clear.
Now my shutter goes through it learning thing when i start the truck, and stays closed.
I have not got the ACCM update yet.

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[Mavster Mechanic]

If you don't have an issue m there's no need to do anything. . The reason the battery drains is because something is not allowing a module to completely go to sleep. But even in sleep mode , which can take over a half hour for all modules to go to sleep, Ford allows up to a 0.05A parasitic current draw.

I just bought an entry-level travel trailer.

The manual states "0.500A to 0.700A parasitic draw from the coach battery is normal and expected."

For contrast. Not a fair comparison.
The RV has wired carbon monoxide and wired propane detectors that can not be shut off. And at least a few status LED's that are on continuously.

 

[Mavster Mechanic]

I treat my 2023 hybrid XLT like a plug in hybrid. I bought a battery tender 800 ma mounted it under the hood with zip ties and plug in every couple of days, seems to work.

Mine just turned 40.... months old.

I wonder if doing a manual charge from household power just once a month would work wonders.

So many stories indicate a slow decline over many months.

 

[Mavster Mechanic]

I don't really have an explanation. But if you connect the battery to A charger that reads the state of charge, it will likely agree with the battery percentage the vehicle sensor is showing. That's what happens when we do it. Sadly it's still not figured out by people who are a lot smarter and I am. Even more frustrating is the fact that the vast majority do not have this issue. But those that do. Do

Right.

Let's assume MTC is a random sample, it probably, almost certainly, isn't. But lets's assume it is.

Are 5% of MTC participants having this issue? Or more like 1%?

 

[Mavster Mechanic]

Has anyone tried pulling fuse 11 and seeing if that helps? I doubt it does but I cant help but be curious lol

I pulled mine 2 years ago.
Still on stock battery. Just turned 40 months old.
I drive 5 days a week.
Truck often sits Friday night til Monday morning.

Starts every time. Dome lights welcome me every time.

Battery seems weak. But gets the job done. 11.6v with headlamps on. 12.2 or 12.3v with headlamps off.

 

[Mavster Mechanic]

I find that my hybrid which sleeps for the winter, connected to a battery maintainer, will not turn the dome lights on after a few days of inactivity. No battery saver mode indicated on the Ford app. Green light indicating full charge on the maintainer but no dome or dash lights. I didn't check other functions. It just seems to me to be a very complex issue that is somehow baked in and it really lets an otherwise fine product get a black eye. It did the same thing last year.

I think in YOUR case this is exactly the design intent. It's doing what it should do.

After sitting week or more, it is designed to shut everything off. No need to monitor things while in storage.

This IS a designed feature.

 

[HeyBales]

I find that my hybrid which sleeps for the winter, connected to a battery maintainer, will not turn the dome lights on after a few days of inactivity. No battery saver mode indicated on the Ford app. Green light indicating full charge on the maintainer but no dome or dash lights. I didn't check other functions. It just seems to me to be a very complex issue that is somehow baked in and it really lets an otherwise fine product get a black eye. It did the same thing last year.

The system should be smart enough to know if there is incoming or outgoing current - it can't get a good reading on the voltage - not accurate figure.

Therefore failsafe would be battery saver, just in case it's actually low.

It's why the BMS Relearn info says some electronics will be disabled during the process.
So you can't get a good SOC value either in the system, so the one in place is not seeing the charging and likely a tad low.

 

[2seater]

The system should be smart enough to know if there is incoming or outgoing current - it can't get a good reading on the voltage - not accurate figure.

Therefore failsafe would be battery saver, just in case it's actually low.

It's why the BMS Relearn info says some electronics will be disabled during the process.
So you can't get a good SOC value either in the system, so the one in place is not seeing the charging and likely a tad low.

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In my case, the battery was just replaced after a three hour service at my Ford dealer and then parked and battery maintainer connected. The only driving in between the battery replacement and the parking for the winter was 13 miles, primarily highway. The maintainer connection is the studs under the hood so there are undoubtedly other factors before the actual battery. it is true that voltage readings at those studs wanders all over the place. Simply opening and closing the drivers door causes a major voltage change at the studs, most of the time. Whatever the reasons, the complaints are real and continue to vex this otherwise enjoyable vehicle after several model years.

Just to be clear, the most recent battery replacement was precipitated by what I stated earlier. During the summer, the Maverick is my daily driver. The last trip of the season is fifty miles to my cottage where it is stored indoors. When I arrived I unloaded the things I needed for the weekend and after less than five minutes, there were no dome or dash lights. I checked the app which said it was in battery saver mode. The Ford dealer is relatively close to my cottage and the oil change and battery test was scheduled for the following morning. This is the second battery replacement in three summers of use so it would appear that the design as a battery saver is not effective.

 

[CD_SM]

Is this type of digital 12V DC monitor (cigarette lighter) of any value in monitoring the Hybrid's 12V battery condition?
https://www.amazon.com/Suvnie-Car-Cigarette-Lighter-Voltmeter/dp/B0CPXZVP24/ref=sr_1_5?crid=3OUSJGS7E9ZCF&dib=eyJ2IjoiMSJ9.3sW-SgMCq9YyTF-_nKtkK7wUBoidFK01MZJe6_WDu4hZc8BryC8rnnIzmdcOUVcE05yIWS8sDVTz06VMM-QYf8r31MXG1iUa0FxH2MnDzgD0AnmENR1WNuhBdT72Btt9ljeafXxGG5ece6z_nGth7OICGSP-81JJBd0wOEIpYdEEXEXg3KEFdTblatoKwNgt3ZK0T8tbzOZl0nEFz1rtJD_971bDffXinZkm26UWOsw.CZhyNX-utbX061GBa7Fh1zxY_1QWKfrQ7dLhUg8WeNs&dib_tag=se&keywords=cigarette+lighter+12V+gauge&qid=1762986322&sprefix=cigarette+lighter+12v+gauge,aps,155&sr=8-5&th=1

Yes, since you can see it go off when you open the door once your battery gets weak - that's the first symptom, even before loss of dome lights or sleep mode.. You can get a USB charger that also displays the voltage, which is what I did. I spent a little extra to get what seems to be a nicer one - metal body, fast charges phone, green LEDs.

 

[SpaceCowboy]

I just got my maverick back from service for the second time within 2 weeks.

The first time my dome lights and FordPass would not work.

After the immediate return to the dealer apparently more update were made and they put a new AGM battery in it.

No problems after the last updates and battery was changed. The cold winter is coming so hopefully no more issues.

 

[wax87]

I always manually shut off the AC. The difference that I have observed is that driving stop and go with no AC means no "sleep messages." Driving for 9 hours with the AC on, guarantees a "sleep" message the next morning. I hope this answers your question?

I have never had the sleep mode, live in Texas, AC runs 95% of the time. The only thing consistent about the sleep mode seams to be is the inconsistency of it all.

 

[HeyBales]

Yes, since you can see it go off when you open the door once your battery gets weak - that's the first symptom, even before loss of dome lights or sleep mode.. You can get a USB charger that also displays the voltage, which is what I did. I spent a little extra to get what seems to be a nicer one - metal body, fast charges phone, green LEDs.

I was just reminded this morning to another aspect of this.
I keep saying measure voltage at the port to see how far off the adapter is showing.

Actually - it would be better to measure voltage at the battery, and just look at the adapter reading - to see how far off it is.

I checked battery this morning to see if amp clamp had enough space to be used on just negative cable - 12.16 while I was there.
Adapter - 12.0 - which always read .02 higher than port - which I didn't measure this morning - so perhaps it's getting more accurate - ha!

But I found my paper with noted figures when I first tested.
Battery 12.2, port 12.15, adaptor 12.4 (some rounding of course).

 

[Darryl]

I have never had the sleep mode, live in Texas, AC runs 95% of the time. The only thing consistent about the sleep mode seams to be is the inconsistency of it all.

Exactly! And that's the frustration of it all. That is likely why Ford is having such a problem solving it. It doesn't even happen all the time to the same vehicle. The vehicle May sit for a week with no battery drain. Or it may drain overnight. Even though the driver did the exact same thing both times. It doesn't happen to most of the Mavericks. And the new Air conditioning module update seems to solve it for a good portion. But there's some stubborn cases out there still

 

[Doburden]

Hi, I Start having battery saver mode since 2-3 months. Recently I bought a 12v battery charger and it shows always above 12v and even if it Start charging the time is very small untill it shows full charger.
But my Truck is keep going in batt saver mode. It is very frustrating because now with the winter coming I can not use my remote Start (application).
I think this is totaly a software issue.

 

[How15]

How long does it have to sit unused for the excessive drain to happen?

Ive never gone more than 3 days between uses, how do we know it happens does the Mav just refuse to start?

My 23 xlt Hybrid did the drain a few times over the last year but the weather was colder when it happened., wasn't using AC but defrost does use it. I didn't thinking much of it until earlier this fall, now it is everyday. I can drive it 20 miles and an hour later it is trying to save my battery. Going in next Friday to the dealer to see what they say.

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