HYBRID 12V Battery Mystery SOLVED

[SafetyGuy]

Since 25/26 have battery spec's that are entered - that relearn is probably a resistance test to decide how much it can charge safely as battery ages. Maybe an amp test to see how close it is to the logged values of new battery.
Or maybe Ford realized that for a user-replaceable item - very few are going to correctly take truck into dealer just to have battery specs entered, and it relearns the same as pre-25's.

It would be interesting if possible to compare the battery PID's for Ah and CCA and CA on new battery, to a year down the road, to see if the BMS adjusts them there, or another location.
I'm betting another location, due to the fact it already has that on pre-25's.

Yes, some very good thoughts and musings as to what Ford has changed over the years as to their battery management.

I personally feel that when/if I need to change my battery before I move on, it will be an exact replacement battery for what I already have.

And I WILL carry out the full-meal-deal as per the manual to reset the truck so it knows there is a new battery installed..after fully charging the new battery of course!

I don't have the meters some here have, to record my battery charge information during usage, so I keep it simple with what I do have.

I do know that since the end of last November I became more aware of and began monitoring my battery state. It was always in a low charge state and it was always charging at over 15.1 volts when I got my cigar lighter volt meter in March.

When I began keeping my lights, park lights or now led trailer tail light plugged in (full disclosure I also did a battery charge and relearn simultaneously as turning lights on when driving), which was at the start of May (which also coincided with the temperatures here in Manitoba to warm up a bit, at long last!) I have not seen a single voltage charge level over 14.9 volts.

There were a lot of moving parts when the change happened...was it temperatures here finally warming a bit, was it the battery relearn I did, or was it the turning the truck lights on everytime when driving or a combination of them?

I don't know, but I will continue keeping a weather eye on my battery charge levels and charging voltage, to see if/when I see a change.

Have a good day,

Andy

Sponsored

 

[Mavster Mechanic]

My 12v battery drops 4% parked overnight. Like clockwork.

Starting at 96% if lights are on, the next run cycle it will charge at 14.3v until it hits 100% then will drop to 13.7 to 13.9 volts to maintain. Less than 0.5 amp charging at this point so I see zero on my meter.

I used to see 15.3 or 15.4 volts all the time with my low charged old battery (stock). Not anymore.

 

[Master Blaster]

My 12v battery drops 4% parked overnight. Like clockwork.

Starting at 96% if lights are on, the next run cycle it will charge at 14.3v until it hits 100% then will drop to 13.7 to 13.9 volts to maintain. Less than 0.5 amp charging at this point so I see zero on my meter.

I used to see 15.3 or 15.4 volts all the time with my low charged old battery (stock). Not anymore.

More than about 14.5V will damage an AGM battery, so maybe it has understood that its AGM now.

 

[Finnster]

He started this testing/solution with a new battery.

As Finnster tested with a just charged battery.

Battery has to be in good enough shape the BMS is even willing to attempt 92% SOC and reach it.

I wouldn't be shocked if Finnster's battery can't hold that charge level.
Sounds like it was NOT above 92% SOC despite just having been on charger - or he would not have had to wait 5 min for the effect of the BMS dropping voltage thinking it reached 92% SOC.
So that calculated SOC% not being based on voltage during charging - I'm betting his resting is 12.4/.5.

Yours is probably below 12.1 V - do you have no battery saver things being seen?
But I think the BMS system looks at voltage some hours after turnoff to get decently accurate figure.
So even off a charger, yours may not get up to the level of 92% SOC for the effect to be possible.

Agreed! My 11 month old oem AGM 12V battery is definitely wounded! I think that I may be able to get a couple of more years out of it, but the coming winter may make a liar out of me, again .

 

[Red Eyes - Wide Shut]

And the discussions continue on. My third battery, in a little over 2 years is slowly being discharged. I think I'll get another one at this rate before the warranty runs out.

 

[Mavster Mechanic]

And the discussions continue on. My third battery, in a little over 2 years is slowly being discharged. I think I'll get another one at this rate before the warranty runs out.

Then, just run headlamps or parking lamps full time to = a full time charged battery.

 

[SafetyGuy]

And the discussions continue on. My third battery, in a little over 2 years is slowly being discharged. I think I'll get another one at this rate before the warranty runs out.

Good day

I completely agree to try the methods suggested here (and repeated many times to others), to see if one or all suggested steps are effective at raising your charge level.

If your battery is dying, it won't hurt to runs a few days of testing lights on to check and see if your truck responds as been noted...or not.

And if your battery is failing, run the test for a short time as results are immediate, if effective. Then go back to your normal driving routine (which you say is killing another battery)...then, when you get your new, fully charged, warranty battery installed etc, you can restart the lights on procedure (or an alternate light method) and from the very start keep your new battery charged with an anticipated longer life.

Have a good day,

Andy

 

[Finnster]

If your battery is dying, it won't hurt to runs a few days of testing lights on to check and see if your truck responds as been noted...or not.

I would add this caveat:
You may need to charge the hell-o out of your dying 12V battery before immediately hitting the highway at 70ish mph With headlights/parking lights on to see if the hack is working on your truck, and that it normalizes your charging voltage.
That was the only way I was able to verify that the hacks work on my 2025.
Good luck,

 

[Red Eyes - Wide Shut]

I would add this caveat:
You may need to charge the hell-o out of your dying 12V battery before immediately hitting the highway at 70ish mph With headlights/parking lights on to see if the hack is working on your truck, and that it normalizes your charging voltage.
That was the only way I was able to verify that the hacks work on my 2025.
Good luck,

Well if daytime running lights don't count, ain't doing it until I have to pay for a battery at the very least. I wasn't told this was a PHEV.

 

[KenE]

I would add this caveat:
You may need to charge the hell-o out of your dying 12V battery before immediately hitting the highway at 70ish mph With headlights/parking lights on to see if the hack is working on your truck, and that it normalizes your charging voltage.
That was the only way I was able to verify that the hacks work on my 2025.
Good luck,

Great knowledge base on this forum, this topic no exception. Most posters have 22-24MY Mavericks with FLA OEM installed batteries. I have a 25MY hybrid purchased April 2025, OEM equipped AGM. Currently have 13k miles, never a 12V problem. My car scanner shows consistant 14.3V charging voltage while driving, never dropping below. Driving with headlights on makes no appreciable difference in 12V charging current, only an uptick in DC converter current to make up the headlight current draw. So, I'm not experiencing12v battery failure, headlight on/off state seeming immaterial, and car scanner showing a very minor 8ma quiescent 12v battery current (very low) - what does all this mean? Was there a 25MY charging algorithm update, am I just lucky, waiting on my eventual 12V battery to fail prematurely?

 

[SafetyGuy]

Great knowledge base on this forum, this topic no exception. Most posters have 22-24MY Mavericks with FLA OEM installed batteries. I have a 25MY hybrid purchased April 2025, OEM equipped AGM. Currently have 13k miles, never a 12V problem. My car scanner shows consistant 14.3V charging voltage while driving, never dropping below. Driving with headlights on makes no appreciable difference in 12V charging current, only an uptick in DC converter current to make up the headlight current draw. So, I'm not experiencing12v battery failure, headlight on/off state seeming immaterial, and car scanner showing a very minor 8ma quiescent 12v battery current (very low) - what does all this mean? Was there a 25MY charging algorithm update, am I just lucky, waiting on my eventual 12V battery to fail prematurely?

Good day @KenE

It is hard to say when Ford may have made changes...possibly in my 2025 sometime?

My 2025 was assembled in December 2024, so an early model 2025.

As soon as I got my 12 volt plug-in indicator (in March of 2026), I was always seeing over 15.1 volts when driving.

Then, driving in to my Ford appt for updates etc on 14 May it was above 15 volts...on the way home it was 14.59 volts, and I have not seen over 15 volts since.

All I know is I already had a rear light that plugs into my trailer plug, and it is on my truck now, and I usually have my park lights turned on in daylight.

My battery, when I meter it, is always over 12.8 volts now the day after using our truck. (Yes, I pop the bonnet to have it ready the next day, so I don't wake the truck and spoil my voltage reading).

As in all things like this, try Mavster Mechanics remedy and see if it helps you, if you think your battery is not up to snuff.

Everybody's experiences may vary...and it doesn't cost anything to turn your park or headlight on and off.

Have a great day,

Andy

 

[Hootbro]

I would not recommend the trailer hitch light trick for a truck that sits. Last Friday afternoon I rented a Uhaul trailer that I left hooked up on the 4 pin overnight and the discharge curve was steep. Truck did start right up the next morning with no warning and charged fine.

 

[KenE]

Good day @KenE

It is hard to say when Ford may have made changes...possibly in my 2025 sometime?

My 2025 was assembled in December 2024, so an early model 2025.

As soon as I got my 12 volt plug-in indicator (in March of 2026), I was always seeing over 15.1 volts when driving.

Then, driving in to my Ford appt for updates etc on 14 May it was above 15 volts...on the way home it was 14.59 volts, and I have not seen over 15 volts since.

All I know is I already had a rear light that plugs into my trailer plug, and it is on my truck now, and I usually have my park lights turned on in daylight.

My battery, when I meter it, is always over 12.8 volts now the day after using our truck. (Yes, I pop the bonnet to have it ready the next day, so I don't wake the truck and spoil my voltage reading).

As in all things like this, try Mavster Mechanics remedy and see if it helps you, if you think your battery is not up to snuff.

Everybody's experiences may vary...and it doesn't cost anything to turn your park or headlight on and off.

Have a great day,

Andy

Indeed Andy there were some mid year changes in 2025. My resting voltage (hood opened for a day or so), is not as high as yours, more like 12.4. And I've never seen more than 14.5V charge, usually 14.3. I will begin using lights while driving to see if there's any change. Cheers!
Ken

 

[Mavster Mechanic]

Great knowledge base on this forum, this topic no exception. Most posters have 22-24MY Mavericks with FLA OEM installed batteries. I have a 25MY hybrid purchased April 2025, OEM equipped AGM. Currently have 13k miles, never a 12V problem. My car scanner shows consistant 14.3V charging voltage while driving, never dropping below. Driving with headlights on makes no appreciable difference in 12V charging current, only an uptick in DC converter current to make up the headlight current draw. So, I'm not experiencing12v battery failure, headlight on/off state seeming immaterial, and car scanner showing a very minor 8ma quiescent 12v battery current (very low) - what does all this mean? Was there a 25MY charging algorithm update, am I just lucky, waiting on my eventual 12V battery to fail prematurely?

14.3 "probably" means your battery is in the middle.

Not fully charged. Not significantly discharged.

Lower than 50% and the voltage normally goes up.

Higher than ~90% and the voltage goes down IF lamps are off. Or stays 14.3 to 14.8 all the way to 100% if lamps are on.

The lamps on trick is for fully charging that last 10% or so when the truck won't do it on it's own.

 

[Mavster Mechanic]

I would not recommend the trailer hitch light trick for a truck that sits. Last Friday afternoon I rented a Uhaul trailer that I left hooked up on the 4 pin overnight and the discharge curve was steep. Truck did start right up the next morning with no warning and charged fine.

Your exact trailer was defective (or your exact truck.)

This isn't normal. I leave a trailer and or hitch light pugged in for weeks at a time. Keeps my battery 100% 100% of the time.

Sponsored