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

[LSANC]

The small regular 12-volt battery is the one. Pop your hood and look for a small red plastic cover with a + sign on it. It is located in the center driver side area. Pop the cover off. Hook your + battery charger clamp to that lug. In the rear corner driver side area under the hood, you will see a negative lug sticking up that is screwed into the "chassis", it is aluminum in color. Hook your negative clamp on that lug. Yes, this is an inconvenience, about 5 minutes to hook up and then unhook. Nobody is enjoying this issue. However, if your battery is in a low state of charge your dome lights don't come on and your battery life will be shortened. That is a much bigger inconvenience. And more expensive. In my case I need to hook up the charger about every 10 days, when the dome lights fail to come on. Hope this helps.

I had this issue with my Prius C hybrid and installed a battery tender I could plug into a timer when I was out of town for more than a few days. Only had to charge it a couple of hours a day. Easier than wondering if it would start when I got home and having to repeatedly jump it.

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[mwolze]

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 don't know if they set your battery monitor when they replaced your battery. Sometimes a tech will forget to do it. If they didn't, it could be giving an inaccurate reading. But as long as it doesn't drop below 80% you won't have any problems.

I too wish to thank you for the write up of this. This sounds like what just happened to my Maverick! The vehicle was almost always in a deep sleep, the first time I brought it it they reset the BMS, That worked for about a week at best. The next time it was just about to be NPF'd again when the tech updated something on the ACCM and tested the battery again and the battery did fail and I did get a new battery, which I did suspect was coming through this. Your write up was more detailed than what I had received at the dealer but I did not push for more info since it was all covered within warranty.

I do love the Maverick and even if I wound up buying a battery every year would keep the truck, I view it like more gas at some point and the way it was going I did not believe that the vehicle was going to leave me stranded either. I do believe that there is a permanent fix in the pipeline, but for now all I can do is wait and see.
Thank you for the summary!
Matt

 

[Darryl]

I too wish to thank you for the write up of this. This sounds like what just happened to my Maverick! The vehicle was almost always in a deep sleep, the first time I brought it it they reset the BMS, That worked for about a week at best. The next time it was just about to be NPF'd again when the tech updated something on the ACCM and tested the battery again and the battery did fail and I did get a new battery, which I did suspect was coming through this. Your write up was more detailed than what I had received at the dealer but I did not push for more info since it was all covered within warranty.

I do love the Maverick and even if I wound up buying a battery every year would keep the truck, I view it like more gas at some point and the way it was going I did not believe that the vehicle was going to leave me stranded either. I do believe that there is a permanent fix in the pipeline, but for now all I can do is wait and see.
Thank you for the summary!
Matt

For what it's worth, I have not updated my ACCM at this time since I'm not having any symptoms. Before I took ownership of it, it was started once and sat on the lot untouched for a little over a month. And I had no issues with it. Even if my vehicle does now have an excessive draw, I suspect I will never know it because I drive it virtually every day. It may sit 24 hours about once every month. And I drive it 45 miles each way back and forth to work 5 days a week, so it would get a full charge anyway. I may update it a couple of days before the warranty expires for one reason. Since I work at the dealership, I can have the vehicle written up, and get paid roughly 1/2 hour or so to work on my own vehicle . Also, it will be to put it on record as having had the problem before the warranty expired just in case they offer another solution. But thus far I have had no issues. And because I drive so much, I put approximately 90 to 100 miles daily on my Maverick.

 

[Propane Burning Man]

I too wish to thank you for the write up of this. This sounds like what just happened to my Maverick! The vehicle was almost always in a deep sleep, the first time I brought it it they reset the BMS, That worked for about a week at best. The next time it was just about to be NPF'd again when the tech updated something on the ACCM and tested the battery again and the battery did fail and I did get a new battery, which I did suspect was coming through this. Your write up was more detailed than what I had received at the dealer but I did not push for more info since it was all covered within warranty.

I do love the Maverick and even if I wound up buying a battery every year would keep the truck, I view it like more gas at some point and the way it was going I did not believe that the vehicle was going to leave me stranded either. I do believe that there is a permanent fix in the pipeline, but for now all I can do is wait and see.
Thank you for the summary!
Matt

I sort of have the same thought. I spend less time hooking up the charger than the 3 times more time in the Costco gas line in my Ranger that the maverick replaced.

 

[Darryl]

Things have just become too damn complicated. Power everything. Why do we need, or who even requested a power parking brake. I never thought "it would be nice to not have to pull this stupid lever to engage the parking brake". Tire pressure monitoring sensors? Really? Isn't that the owners job? Yeah, back in Old School. I could go on. No going back. We are stuck with these headaches. Progress. And if you think only Ford has these issues just search for Toyotas latest recall of over 1 million Toyotas and Lexus backup camera issues, and their turbocharged V-6's blowing up.

I agree with you concerning the e brake. However, the hybrid itself would not be possible without a myriad of complex computers. It's more complicated than most of the other modules. PCM, SOBDM, DC-DC converter, ACCM, ABS,BECM, GWM,and BCM are all REQUIRED in order for the Hybrid/Gasoline engine/ regenerative braking/ and charging the 12 v battery to work together smoothly. But in the grand scheme of things, the electric parking brake is small potatoes. We complain against excessive technology. But the truth of the matter is that the Hybrid would be virtually impossible without a BUNCH of interconnected complex electronic modules.

 

[Darryl]

At the dealership I work @ we have had a Maverick in our bays for 5 weeks. It has been here 7 times in 2 years with this same problem. I have seen Fords engineers here twice and they have not yet come up with a solution.

I guess the most frustrating thing for us AND the engineers at Ford is that the problem is so random, It doesn't even occur in most of the Maverick hybrids. And in those it does occur, it may happen every day, then go away for weeks , then randomly return. We'll let it sit for a week with no problems, give it to the customer thinking it's fixed. They'll tell us they drove it for a month with no problems. Then it will happen daily. On this past Thursday our field service engineer called us and told us to give it back to the customer, and let him know that Ford is diligently working on a permanent fix. And they will inform us when it's available. It's easy to get upset with Ford. But in all honesty, the lack of a fix for this persistent problem has to be an embarrassment for them as well

 

[Darryl]

No one should have to keep a modern vehicle (especially a newer vehicle that is under warranty), hooked up to a charger!

Agreed. I'm sure Ford agrees too. I honestly believe they are truly trying to find a fix. Im wondering why this is a problem unique to the Maverick and not present on the Escape hybrid that uses essentially the same system.

 

[johnDeere]

Agreed. I'm sure Ford agrees too. I honestly believe they are truly trying to find a fix. Im wondering why this is a problem unique to the Maverick and not present on the Escape hybrid that uses essentially the same system.

Ok Darryl, that’s an interesting statement, sounds like you have not seen this happen to the escape?
There must be something different in some programming between the maverick and the escape. ?

 

[HeyBales]

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 don't know if they set your battery monitor when they replaced your battery. Sometimes a tech will forget to do it. If they didn't, it could be giving an inaccurate reading. But as long as it doesn't drop below 80% you won't have any problems.

They reset the BMS correctly.
It's why the PID for days in use is only 6 in that pic.

Ya - it kept heading downhill after that pic - now at 65% on regular basis, and 11.6 V this morning.
Only 3.5 months after install - of the bigger FLA battery.
It's a good long 30 min drive now to maybe get up to 70% calculated Ford SOC.

And yet the PID's for cumulative battery charge & discharge it tracks - shows there is more charge than discharge since battery installed and BMS reset.

That's what I mean by likely a sensor is wrong.

But the programming logic also must not do any adjustments - because if it really thought more charging than discharging per the logs - but it saw daily Voltage reading lower, and calculated SOC% lower - logic should declare there is obviously not more charging than discharging.
Change something.

ETA:
I'm getting the sense from the comments that there is thought to be only 1 issue.
Some sort of parasitic battery drain that is a problem in a day or 2, or 3.
ACCM was figured to be the main one, but there may be others. (just FYI - 3 posts I've seen on this forum prior to the SSM regarding parasitic drains, and the work orders showing what was done - none were the ACCM, 2 were the TCU)

But there is plenty of proof of undercharging on a constant basis by vehicles that should drive enough (90-100 daily should NOT be required frankly) - that is ultimately creating a bad battery that will soon die - not from a parasitic drain.

If you can find a Ford engineer that wants some data files on prior dead battery, and current one dying - I've got tons of drives showing exactly what is happening in log files.
Not a parasitic drain - undercharging issue.

Have you heard if it sounds like Ford knows about that issue?
If not - they are missing another issue, if everything is lumped under something like a parasitic drain.

 

[Matso]

To Bob, buyback vehicles are retitled as lemon which drastically reduces the value. They are then sent to auction to be sold as is. In this particular case, if someone knew exactly what the issue is, they could almost steal a really nice Lariat under 8K miles for probably less than $20K. It doesn't even need a trickle charger as it started every time. You just can't use the FordPass app. I wasn't willing to deal with it long term. But someone is going to land a gem of a deal even if they don't have knowledge of the details.

 

[Darryl]

They reset the BMS correctly.
It's why the PID for days in use is only 6 in that pic.

Ya - it kept heading downhill after that pic - now at 65% on regular basis, and 11.6 V this morning.
Only 3.5 months after install - of the bigger FLA battery.
It's a good long 30 min drive now to maybe get up to 70% calculated Ford SOC.

And yet the PID's for cumulative battery charge & discharge it tracks - shows there is more charge than discharge since battery installed and BMS reset.

That's what I mean by likely a sensor is wrong.

But the programming logic also must not do any adjustments - because if it really thought more charging than discharging per the logs - but it saw daily Voltage reading lower, and calculated SOC% lower - logic should declare there is obviously not more charging than discharging.
Change something.

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

 

[HeyBales]

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

They never agree.
Ford's SOC from many posters putting in new batteries - never goes above 85%.
External readers show the 100%.
Many that have recharged their battery have shown that.

If you read the forums regularly and I know you do.

There is a vast majority that have the undercharging issue, instead of a battery drain issue. (I agree vast majority don't have that)

And even those that refuse to use Fordpass app that may not get a notice about Deep Sleep mode when voltage or SOC is really low - they still have the other battery saver items turning off sooner and sooner.

The group that does actually use Fordpass app - I'd be curious what amount have no issue outside of expected 14 days non-started - that don't drive more than 45-60 min daily?

Even I had no issue with app declaring sleep mode, even when down at 11.2 V before battery replacement. I only got the notice when truck was in the shop, with battery being load tested, before it was replaced under warranty.
And work-order declared bad battery.

You mentioned 4 cases of the ACCM being done, due to battery drain and dead battery.
How many cases of bad batteries replaced under warranty - especially where there had been prior visits but battery not bad enough?

 

[pigsareus]

I think the real problem lies with the mix of stuff from different suppliers. This was a real issue in the 21’-23‘ time frame, where suppliers might change multiple times due to supply shortages or work stoppages. This means testing a bunch of different configurations for the same issue, but possibly from different causes. Only Ford knows how many configurations there are, and gathering enough data from customers vehicles in a given configuration to find a solution.

Combine that with Fords unwillingness to change the charging behaviour of the 12v batteries, and you have the current problems.

For example of changing configurations, we know that Ford changed simple things like how to release the electrical parking brake in the event the truck loses power. Early production units had a pull cord under the centre console, later ones don’t and it has to be done by a different mechanism.

I guess the most frustrating thing for us AND the engineers at Ford is that the problem is so random, It doesn't even occur in most of the Maverick hybrids. And in those it does occur, it may happen every day, then go away for weeks , then randomly return. We'll let it sit for a week with no problems, give it to the customer thinking it's fixed. They'll tell us they drove it for a month with no problems. Then it will happen daily. On this past Thursday our field service engineer called us and told us to give it back to the customer, and let him know that Ford is diligently working on a permanent fix. And they will inform us when it's available. It's easy to get upset with Ford. But in all honesty, the lack of a fix for this persistent problem has to be an embarrassment for them as well

on trucks that have this chronic problem with multiple attempts to diagnose and fix it with all resulting in failures Ford should have the decency and intelligence to say well we have a perfect test case to work with so let's give the customer a brand new truck and we'll keep this one along with the others in the so called 'small universe of failures' and then we'll concentrate on that stable of problem trucks to see what the similarites are among them and maybe, just maybe, they'd find the solution.

 

[billpitman]

I guess the most frustrating thing for us AND the engineers at Ford is that the problem is so random, It doesn't even occur in most of the Maverick hybrids. And in those it does occur, it may happen every day, then go away for weeks , then randomly return. We'll let it sit for a week with no problems, give it to the customer thinking it's fixed. They'll tell us they drove it for a month with no problems. Then it will happen daily. On this past Thursday our field service engineer called us and told us to give it back to the customer, and let him know that Ford is diligently working on a permanent fix. And they will inform us when it's available. It's easy to get upset with Ford. But in all honesty, the lack of a fix for this persistent problem has to be an embarrassment for them as well

It seems to me, there are 2 issues going on……
In the year & 3/4s I’ve my 2024 hybrid, I’ve had maybe 8-10 deep sleeps.
My issue is-
I can hook up a NOCO Genius 10 charger, let it fully charge,6-8 hours,
then, do a BMS/BCM reset, get proper indication of battery light,
lock the truck, double honk, & leave for 10 hours……,
then, look at the battery SOC and it’s rarely above 50% !
the battery is not being charged to 80%……. Bill P

 

[BLUEOVALRACER]

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.

Good idea but something You shouldn't have to do on a 2-3 year old Vehicle.

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