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

[Russ B.]

We've performed the ACCM update on 4 Mavericks for battery drain. We've had success on 3 out of 4. Trust me. It's frustrating for US also.

On this one vehicle, it MIGHT drain overnight. And it MIGHT sit 2 weeks with no drain. I have performed a drain test. And it was clearly excessive. But it was quitting time. So when I fully charged the battery the next day and retested, the drain was 0.01A which is well within the acceptable 0.05A specified upper limit. Ford hotline escalated the report to the next level engineering team. Two days later they suggested disconnecting the Air conditioning control module (ACCM) and repeating the test during a high drain episode. Their conclusion was that in SOME cases the software update did not work. But they seem to think that the ACCM is still the source. Their advice was to release the vehicle to the customer. And they would be inform us when they had a permanent solution. And they are still working on a solution that will work for ALL cases.

That explains why the solution continues to be a SSM (special service message) because if a solution works in ALL cases, they usually upgrade it to a TSB (TECHNICAL SUPPORT BULLETIN).

What's the difference? From the technicians perspective , an SSM is a suggested repair. But we can try our own solution. But a TSB is something that REQUIRES us to attempt before doing something else. Otherwise they won't pay us.

So it seems that Ford was aware it would not fix every problem. But they were confident enough that it would fix a good number of them.

I had my first deep sleep experience this week. I returned form 7+ weeks working abroad to find my truck in the, "patient shows no signs of life" category. I put a volt meter on the batt and it showed 1.75 vdc. I put a 6amp charger on it and in a few minutes it started issuing a single tick every 10 seconds or so. I walked around the truck listening and guessed it was trying to sound the "open door / alarm still armed" honking. A single remote disarm click and that stopped.
In a few hours I had dash lights, more voltage coming from the battery, and signs of life.
I am not up for learning everything about this problem as I feel Ford will eventually issue a TSB and fix it. I intend to replace the puny battery with an AGM batt. Would it be asking for a problem to leave a battery trickle charger/maintainer connected to the battery and just plug it in when I have to go away again?

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[Darryl]

I had my first deep sleep experience this week. I returned form 7+ weeks working abroad to find my truck in the, "patient shows no signs of life" category. I put a volt meter on the batt and it showed 1.75 vdc. I put a 6amp charger on it and in a few minutes it started issuing a single tick every 10 seconds or so. I walked around the truck listening and guessed it was trying to sound the "open door / alarm still armed" honking. A single remote disarm click and that stopped.
In a few hours I had dash lights, more voltage coming from the battery, and signs of life.
I am not up for learning everything about this problem as I feel Ford will eventually issue a TSB and fix it. I intend to replace the puny battery with an AGM batt. Would it be asking for a problem to leave a battery trickle charger/maintainer connected to the battery and just plug it in when I have to go away again?

Yes. A trickle charger would be appropriate for extended periods of sitting. Seven Weeks may be explained by excess draw OR a tired battery or a combination of both. Ford tells the sales department to start the vehicles on the lot and let them run for a while to keep the battery charged at least once every 3 weeks.

 

[JohnCondren1933]

Yes. A trickle charger would be appropriate for extended periods of sitting. Seven Weeks may be explained by excess draw OR a tired battery or a combination of both. Ford tells the sales department to start the vehicles on the lot and let them run for a while to keep the battery charged at least once every 3 weeks.

Or a small $2 wrench to disconnect the positive cable if storing a car for a couple weeks?
Bonus points, a thief may not immediately figure out a hybrid 12vdc is under the back seat, vehicle fails to start & thief looks under the hood & gives up

 

[Russ B.]

Thanks, all. On another note having nothing to do with Ford. I went looking for a trickle charger and a larger one (mine finally died) and find they all have a "de-sulfation" mode. That seems superflous and could harm an AGM battery, or am I being paranoid.

 

[HeyBales]

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.

Is the truck going into Battery Saver mode where cabin lights are off instantly when door opens on exit or much faster than prior, or overhead lights turn off quickly when you get in?

I know you are getting Deep Sleep Mode with notice from Fordpass - but that's an extra step when battery is worse.

Which sounds like you don't actually have, if comments about charger are reliable.

And there has been at least 1 poster I've seen where a stored value regarding the battery state in the TCU was not being updated from actual readings, but a frozen figure when it was bad, or maybe it was totally off never bad.
So on turnoff, TCU saw what it thought was low battery figure, sent up final notice to Ford servers which the app got, and modem was disabled.
But the actual battery figure that should have been used was fine, so no actual Battery Saver functions kicked off, only that DSM with modem.
Took a TCU software rewrite to correct.

 

[HeyBales]

Thanks, all. On another note having nothing to do with Ford. I went looking for a trickle charger and a larger one (mine finally died) and find they all have a "de-sulfation" mode. That seems superflous and could harm an AGM battery, or am I being paranoid.

Why it's good to have one that has AGM mode specifically - they'll do that routine correctly.

 

[Darryl]

Thanks, all. On another note having nothing to do with Ford. I went looking for a trickle charger and a larger one (mine finally died) and find they all have a "de-sulfation" mode. That seems superflous and could harm an AGM battery, or am I being paranoid.

Many chargers now have a setting for AGM batteries, especially those that have a desulfation mode. Check to see . Also, the desulfation mode actually can extend the life of a battery that has become deeply discharged. Most chargers today are gentler on the battery than the older chargers. Again, look for one that has an AGM setting don't let the desulfation mode scare you. It doesn't do it unless it determines that it's needed.

 

[Darryl]

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.

It's likely that either your battery is bad or your battery monitor has gotten out of whack and needs to be reset. But at the very least mid mention the special service message involving updating the air conditioning control module to them. Sadly, some Techs don't automatically check for the messages if they're in a hurry. Even if you have a bad battery, I suggest getting the update done. Again, it doesn't fix all cases. But it fixes many of them

 

[How15]

It's likely that either your battery is bad or your battery monitor has gotten out of whack and needs to be reset. But at the very least mid mention the special service message involving updating the air conditioning control module to them. Sadly, some Techs don't automatically check for the messages if they're in a hurry. Even if you have a bad battery, I suggest getting the update done. Again, it doesn't fix all cases. But it fixes many of them

When I asked them to check it, they looked for anything ford might have sent out and said there wasn't anything mentioned. I'm going to mention the AC drain issue but this dealership is not the most trustworthy in my opinion. Probably end up buying an AGM battery then using forscan to update the software.

 

[Master Blaster]

When I asked them to check it, they looked for anything ford might have sent out and said there wasn't anything mentioned. I'm going to mention the AC drain issue but this dealership is not the most trustworthy in my opinion. Probably end up buying an AGM battery then using forscan to update the software.

The system is already programmed for an AGM from the factory, so its a mystery why they put an EFL battery in and didn't change the charging settings to match. Having said that, putting in an AGM battery only delays the sulfation problem caused by the broken BMS software never charging it past 70%. Several people have posted that they used Forscan to alter the setting from factory 70% to 99%, but nobody has posted about whether the battery now gets properly charged. Is that just an unused configuration setting?

 

[Darryl]

When I asked them to check it, they looked for anything ford might have sent out and said there wasn't anything mentioned. I'm going to mention the AC drain issue but this dealership is not the most trustworthy in my opinion. Probably end up buying an AGM battery then using forscan to update the software.

Mention SSM 53801 It applies to all habits made before February 17th 2025. Some techs don't check for SSMs (special service messages). They only check for technical support bulletins (TSBs). SSMs aren't as prominent. But they're usually worth looking into. And they often solve the problem

 

[HeyBales]

The system is already programmed for an AGM from the factory, so its a mystery why they put an EFL battery in and didn't change the charging settings to match. Having said that, putting in an AGM battery only delays the sulfation problem caused by the broken BMS software never charging it past 70%. Several people have posted that they used Forscan to alter the setting from factory 70% to 99%, but nobody has posted about whether the battery now gets properly charged. Is that just an unused configuration setting?

It drops to float charge after 80% - under 1A, which is using Ford's SOC scale of 85% is max fully charged.
If you drive long enough below 1A - it'll get back to 85%.
Just like a charger - hours of driving, or I guess sitting in drive doing something. At that point - real charger is cheaper!

Well, actually - 60 is the new 80!
After the battery degrades enough, just hit 3 months, so sad. Just like this morning, about to drop to 1A when it hits 60%, and then bounce between showing 0 & 1 - because it rounds.
Just like a charger - the system has the ability to do 8-10 Amps no problem, it just chooses not to.

ETA:
Here's what it does at almost full charge - bounces between showing 0, which is probably just a tad above but rounding, and going negative while driving.

Ahhh, 1 day old. I guess this would be the Cumulative Discharge while Running PID. Now that's a rare reading!

 

[Darryl]

The system is already programmed for an AGM from the factory, so its a mystery why they put an EFL battery in and didn't change the charging settings to match. Having said that, putting in an AGM battery only delays the sulfation problem caused by the broken BMS software never charging it past 70%. Several people have posted that they used Forscan to alter the setting from factory 70% to 99%, but nobody has posted about whether the battery now gets properly charged. Is that just an unused configuration setting?

Was the ACCM update performed? If not, do that. It actually works for most of the trucks. It may not work. But it may. I suggest doing that along with ensuring that the current battery is fully charged and in good shape along with doing a bms reset. We did that combination on 4 vehicles . And it has worked on 3 of them. Those are decent odds .

 

[BDennis]

We've performed the ACCM update on 4 Mavericks for battery drain. We've had success on 3 out of 4. Trust me. It's frustrating for US also.

So know at 70,000 miles replacing the 12 volt battery in my 2022 hybrid would not be covered under warrant, but with this being a known issue would the software update be free?.

 

[icegradner]

So know at 70,000 miles replacing the 12 volt battery in my 2022 hybrid would not be covered under warrant, but with this being a known issue would the software update be free?.

It's not a customer satisfaction program or recall, so it would be on your dime.

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