HYBRID 12V Battery Mystery SOLVED

[Mavster Mechanic]

I forgot about the parking brake iteration.

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[El Kabong]

I forgot about the parking brake iteration.

The what?

 

[Mavster Mechanic]

The what?

There was a proposed link to the electric parking brake draining 12v batteries.

 

[HeyBales]

The 2025 update is NOT the same as the one just released. And if YOUR battery is being drained as it's being driven, that's a different problem unique to your vehicle. There has not been one battery that is being drained that I've seen. If that was the case, the problem would be MUCH MORE widespread because there are a lot of people who drive various ways. In every vehicle we've seen, the vehicle will go to deep sleep first and will continue draining until dead if left alone. That's a drain issue primarily. Try the most recent update. Then tell me what happens. If the dealership connects the scan tool and says that there's no update available. And your Maverick is losing charge as it is driven, you are NOT having the same problem as everyone else. Ford did buy back one of the vehicles we had because they couldn't find the drain (it was BEFORE the most recent software release. ) But Every other vehicle WE had was cured by the previous update. They even still used the flooded battery. One has the original battery. The vehicles have been here for their oil changes. So I know the problem was solved.

Ok - drained, as in what the SSM's are talking about intermittently happening - dead battery some morning - is not what is happening during driving.

But you can see the evidence in this thread from more than his truck.
You may have the tools to see exactly the same thing.
Doesn't take much of a setup.

There is a DRAW that does happen.
The 12V battery goes from being a receiver of amps from the DCDC just like all the other 12V systems running then - to receiving nothing and amps is allowed to come from it.
Simple Battery Sensor reading of volts and amps. It's accurate any other time the 12V system is disconnected from the HVB system - there is a draw, reverse current in sensor figure.

I'll bet you Ford will not be interested.

Again - Ford is stuck on a parasitic draw. Tried to point this out many times.
There is a totally different reason for batteries SLOWLY going bad - not overnight or two nights - over months and months.

 

[johnDeere]

Ok - drained, as in what the SSM's are talking about intermittently happening - dead battery some morning - is not what is happening during driving.

But you can see the evidence in this thread from more than his truck.
You may have the tools to see exactly the same thing.
Doesn't take much of a setup.

There is a DRAW that does happen.
The 12V battery goes from being a receiver of amps from the DCDC just like all the other 12V systems running then - to receiving nothing and amps is allowed to come from it.
Simple Battery Sensor reading of volts and amps. It's accurate any other time the 12V system is disconnected from the HVB system - there is a draw, reverse current in sensor figure.

I'll bet you Ford will not be interested.

Again - Ford is stuck on a parasitic draw. Tried to point this out many times.
There is a totally different reason for batteries SLOWLY going bad - not overnight or two nights - over months and months.

Correct,
Ford knows of the draws from the controllers, and came up with a fix for them, weather they work is another story.
But we have not heard Ford talking about when the SOC goes over 91% (like on my mav hybrid) and changes to 12.8 volts.
That is way to low for a floating charge for AMG or EFB.
That is what is under charging the batteries.

We have not heard Ford mention that its not a good idea to trick the charging system to charge the battery when the SOC is over 91%.

If the battery is truly SOC of 91%, than the charging system is correct to change, but the voltage is way too low.
If the SOC from the system is not correct, it could over charge a fully charged AGM battery, and that is bad.

 

[Darryl]

Ford gets information from the field (us) . They test vehicles they had to buy back. They come to the shops to work with us. They had OTHER vehicles where they had to tweak the change strategy. So it not as if they're too stupid to know a parasitic drain vs an undercharge. Part of our tests include making sure the charging system is working properly. That's the basics. Give us some credit.

 

[Glen Baker LLC]

🤏 When I can take my Maverick into a service center. And they can tell me, sir this is why there's parasitic drain that's killing your battery. This is what we're going to do to fix it. Plus we're going to change your charge settings to allow at least 95% charge.
Then you get this much 🫸---🫷credit.

 

[rslilly76]

Ford gets information from the field (us) . They test vehicles they had to buy back. They come to the shops to work with us. They had OTHER vehicles where they had to tweak the change strategy. So it not as if they're too stupid to know a parasitic drain vs an undercharge. Part of our tests include making sure the charging system is working properly. That's the basics. Give us some credit.

An SLA and AGM should always be charged to 100% (not 101% but 100%)
Failure to do so shortens the battery life. So tell me again they aren't too stupid! Cause they have the system draining the battery prior to reaching 100%

 

[Darryl]

Om

An SLA and AGM should always be charged to 100% (not 101% but 100%)
Failure to do so shortens the battery life. So tell me again they aren't too stupid! Cause they have the system draining the battery prior to reaching 100%

Ok

 

[rslilly76]

Ford gets information from the field (us) . They test vehicles they had to buy back. They come to the shops to work with us. They had OTHER vehicles where they had to tweak the change strategy. So it not as if they're too stupid to know a parasitic drain vs an undercharge. Part of our tests include making sure the charging system is working properly. That's the basics. Give us some credit.

Maybe when they get information from US, I mean you! You can show them their retarded charging program. They will possibly give you a raise, and you'll look like a hero for figuring it out. It's a programming issue for that, so surely someone isn't too stupid to rewrite that!

 

[Darryl]

Darryl:

My 2022 Hybrid never had a resting voltage higher than 12.3 volts from factory new.

As you know; it takes very little juice to start a hybrid, so this "got by" or was "barely sufficient" for 3 years. But there was no reserve. I got by because I drove 6 days a week.

My 12 v quickly "setttled in" at 60% SOC and stayed there. For 3 years.

The truck did not attempt to charge it higher. When I bench charged it to 100% within a few days the truck intentionally drained it down to 60% again.

Can you tell me the reason for this?

I pulled fuse 11. Never used any connected services or remote starts, etc.
I put a data logger in mine after.
No parasitic draw.

Now, with a brand new battery, the truck is intentionally draining it down in to 80% range. While driving.

Why is it doing this?
I had all recalls done that were available as of Summer 2025. Has not been to a dealer since.

Darryl:

My 2022 Hybrid never had a resting voltage higher than 12.3 volts from factory new.

As you know; it takes very little juice to start a hybrid, so this "got by" or was "barely sufficient" for 3 years. But there was no reserve. I got by because I drove 6 days a week.

My 12 v quickly "setttled in" at 60% SOC and stayed there. For 3 years.

The truck did not attempt to charge it higher. When I bench charged it to 100% within a few days the truck intentionally drained it down to 60% again.

Can you tell me the reason for this?

I pulled fuse 11. Never used any connected services or remote starts, etc.
I put a data logger in mine after.
No parasitic draw.

Now, with a brand new battery, the truck is intentionally draining it down in to 80% range. While driving.

Why is it doing this?
I had all recalls done that were available as of Summer 2025. Has not been to a dealer since.

Well, it does not matter if you had every recall done or not, unless you had the ACCM updated, then nothing that they did would have affected the battery issue. The most recent update involves the ACCM and the Abs. Modules being done simultaneously. Unfortunately, most dealerships probably don't even do that because Ford issued it as a special service message rather than a technical support bulletin. Unfortunately, many texts don't even read those. So unless you specifically mention the air condition control module are they specifically mentioned they had updated it, then nothing was done for that issue

 

[Darryl]

There was a proposed link to the electric parking brake draining 12v batteries.
[/QUOTE well, the electric parking brake is operated by the ABS module. So even if that is part of the issue, it will be taken care of with the latest updates

 

[Glen Baker LLC]

Well, it does not matter if you had every recall done or not, unless you had the ACCM updated, then nothing that they did would have affected the battery issue. The most recent update involves the ACCM and the Abs. Modules being done simultaneously. Unfortunately, most dealerships probably don't even do that because Ford issued it as a special service message rather than a technical support bulletin. Unfortunately, many texts don't even read those. So unless you specifically mention the air condition control module are they specifically mentioned they had updated it, then nothing was done for that issue

So that I know what I'm asking for when I go into my dealership.
Are you able to post that special service message?

 

[HeyBales]

Ford gets information from the field (us) . They test vehicles they had to buy back. They come to the shops to work with us. They had OTHER vehicles where they had to tweak the change strategy. So it not as if they're too stupid to know a parasitic drain vs an undercharge. Part of our tests include making sure the charging system is working properly. That's the basics. Give us some credit.

Except I'm very doubtful that you as a tech at your level - are seeing ANY of the "bad battery" replacements that happen.
These are people that came in because of getting battery saver effects and DSM alerts - their battery is tested on the quick tester, unless service manager requests an overnight one.
And initial few visits their battery is not bad enough for warranty replacement.
It works - they drove there - no battery drain - they drove home, told to drive more.

When battery finally tests bad enough - they still drove there - are you the tech being given a bad battery warranty replacement that takes 15 minutes?

I doubt it - therefore Ford is never called in on 15 min warranty jobs for a bad battery.
There are no buy backs on that.

You are called in after other techs have done the software updates on a truck that was towed in because the battery drained overnight.
And it happened again - now your skilled troubleshooting is brought into play - truck systems are investigated - Ford engaged - buy back potential because of 3rd time in for this drain situation.
Your engagement is likely limited scope for what you get to see.

You'll never see this other issue if you don't recognize that limitation.
But cashier dollars to donuts in the break room - you got it on your truck.

 

[Mavster Mechanic]

Well, it does not matter if you had every recall done or not, unless you had the ACCM updated, then nothing that they did would have affected the battery issue. The most recent update involves the ACCM and the Abs. Modules being done simultaneously. Unfortunately, most dealerships probably don't even do that because Ford issued it as a special service message rather than a technical support bulletin. Unfortunately, many texts don't even read those. So unless you specifically mention the air condition control module are they specifically mentioned they had updated it, then nothing was done for that issue

You replied, but did not answer the main questions.

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