HYBRID 12V Battery Mystery SOLVED

[Mavster Mechanic]

Haven't been here in a while, my 2024 Maverick Hybrid has 50K on it and yesterday was my first issue. Went to unlock it, nothing, unlocked it with the key, put it in the ignition and nothing. Obviously no 12V. Called Ford service and within 30 min they were there. As soon as he connected the booster to the under seat battery it came alive. Started normally. He disconnected the booster, while he waited, I turned it off, waited about 2 min, inserted the key and started normally. To me that doesn't sound like the battery does it? It has been normal every start since, maybe 10-12 times. I have an appt at the dealer tomorrow morning. What can I expect? I checked and it is a flood battery.

Sounds like the 12v battery, yes.

It's all or nothing. No warning. No slow cranking in a hybrid.

Get a new battery ASAP.
THEN run headlamps or parking lamps via the manual switch 50% of your drives or more.

It's a hidden feature that the manual headlamp switch doubles as a manual 12v battery charge switch. A cheat code for you.

Of course only do this with truck running.

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[KenE]

Sounds like the 12v battery, yes.

It's all or nothing. No warning. No slow cranking in a hybrid.

Get a new battery ASAP.
THEN run headlamps or parking lamps via the manual switch 50% of your drives or more.

It's a hidden feature that the manual headlamp switch doubles as a manual 12v battery charge switch. A cheat code for you.

Of course only do this with truck running.

As I reported earlier my 25 Lariet Hybrid behaves just as you discovered. My truck was built Jan 2025, purchased late April 2025, roughly 15k miles to give perspective. The 1st year didn't know about tricks, and only once or twice did a manual charge battery when lights didn't come on when door opened, but always started regardless. I'm now using Parking lights and charges to 99% given enough time. But, after sitting for 12 hours, initial SOC drops to 88-89%, not terrible, but much further than yours. And my CarScanner indicates quietscent draw is typically ~9%, quite acceptable. Starting drive with battery at 89% SOC, I find Tricks not required, same charging lights or not, until ~92%, which seems to be the upper limit of 12V charge w/o lights trick. At that time voltage drops immediately from 14.1 to 12.8V and current discharges. Conclusion: my AGM still has a lot of life, but overnight SOC level of drop even with low parasitic draw indicates it's somewhat compromised by not knowing tricks it's 1st year of life. Does all this make sense? Also, fan speed '5' triggers the boosted charge. I recall that number being '6', but not sure, this thread is a learning course in and of itself. Lol! You & Haybales are to be commended for your contributions. Thanks.

 

[Master Blaster]

Given the fact it started again immediately after being boosted then turning off immediately, then restarted fine, my current theory is not the battery itself. I do recall an instance about a year ago where it would not unlock with the button on the fob but I opened with the key and it started normally. Nothing since then untill now. Maybe a bad connection somewhere? The dcs?

Maybe in the bottom of the fusebox under the hood. Corrosion there was an issue on the 22s, but it would be unusual on your year.

 

[HeyBales]

As I reported earlier my 25 Lariet Hybrid behaves just as you discovered. My truck was built Jan 2025, purchased late April 2025, roughly 15k miles to give perspective. The 1st year didn't know about tricks, and only once or twice did a manual charge battery when lights didn't come on when door opened, but always started regardless. I'm now using Parking lights and charges to 99% given enough time. But, after sitting for 12 hours, initial SOC drops to 88-89%, not terrible, but much further than yours. And my CarScanner indicates quietscent draw is typically ~9%, quite acceptable. Starting drive with battery at 89% SOC, I find Tricks not required, same charging lights or not, until ~92%, which seems to be the upper limit of 12V charge w/o lights trick. At that time voltage drops immediately from 14.1 to 12.8V and current discharges. Conclusion: my AGM still has a lot of life, but overnight SOC level of drop even with low parasitic draw indicates it's somewhat compromised by not knowing tricks it's 1st year of life. Does all this make sense? Also, fan speed '5' triggers the boosted charge. I recall that number being '6', but not sure, this thread is a learning course in and of itself. Lol! You & Haybales are to be commended for your contributions. Thanks.

Makes sense - battery was living around 12.4 V the first year probably, or a tad below depending on time of drives.
So it likely sulfated a bit, just can't hold a high charge now.
12.3 V starting voltage and temp could cause some SOC's to be higher or lower.

It's really too bad the tricks don't work at the 87% for a higher current, instead of only getting float current until at 92%, then the tricks work.

Be glad - that happened in like 2 weeks of new SLA warranty replacement last year.
But neither battery type like constant sitting below a full charge.
Mine just lost is faster.

 

[KenE]

Makes sense - battery was living around 12.4 V the first year probably, or a tad below depending on time of drives.
So it likely sulfated a bit, just can't hold a high charge now.
12.3 V starting voltage and temp could cause some SOC's to be higher or lower.

It's really too bad the tricks don't work at the 87% for a higher current, instead of only getting float current until at 92%, then the tricks work.

Be glad - that happened in like 2 weeks of new SLA warranty replacement last year.
But neither battery type like constant sitting below a full charge.
Mine just lost is faster.

Thanks Mike. Without a doubt by battery lived at the 12.3 - 12.4 level for the 1st year. Many of my 15k miles have been on 1 day longer trips, 600+ highway miles, then a lot of short duration trips. So roughly 15 days account for 10k miles, 530 days for 5k miles. And now we know that even the long trips w/o Tricks the battery isn't fully charged. As I replaced an LED light in the house this morning I'm again reminded the 20,000 "promised" LED lifespan is a stretch... So I use Parking Lights trick during daylight on my 25 Lariet, which consist of obvious rear tail lights, and the two little marker lights down low in the front; all are inexpensive replacable bulbs when they burn out, vice the $1,000 front headlight assemblies.

 

[Glen Baker LLC]

Posted today.
Flooded outperforming AGM ?
Jump to 19:30 for the wrap-up.


Truth be told, when the time comes I think I'll buy an AGM off the internet.

 

[MavStangVa]

Posted today.
Flooded outperforming AGM ?
Jump to 19:30 for the wrap-up.

Good information but flawed case study. Just like CR when they test 1 vehicle randomly purchased. If they happen to get that 1 destined to be bought back as a lemon they condemn the model. Same here. He could run the same tests on 1000 of each batteries and then it would be more conclusive.

 

[Glen Baker LLC]

Good information but flawed case study. Just like CR when they test 1 vehicle randomly purchased. If they happen to get that 1 destined to be bought back as a lemon they condemn the model. Same here. He could run the same tests on 1000 of each batteries and then it would be more conclusive.

Flawed as it may be.
Unless someone can do it better hint, hint.
I don't think we're going to see anybody stepping up to the plate anytime soon. Buying 1000's of anything just to satisfy a "what if scenario.
99.5% is good enough for me.

 

[Mavster Mechanic]

Posted today.
Flooded outperforming AGM ?
Jump to 19:30 for the wrap-up.


Truth be told, when the time comes I think I'll buy an AGM off the internet.

How do you and I get the same video recommendations at home?

 

[BK007]

 

[HeyBales]

Thanks Mike. Without a doubt by battery lived at the 12.3 - 12.4 level for the 1st year. Many of my 15k miles have been on 1 day longer trips, 600+ highway miles, then a lot of short duration trips. So roughly 15 days account for 10k miles, 530 days for 5k miles. And now we know that even the long trips w/o Tricks the battery isn't fully charged. As I replaced an LED light in the house this morning I'm again reminded the 20,000 "promised" LED lifespan is a stretch... So I use Parking Lights trick during daylight on my 25 Lariet, which consist of obvious rear tail lights, and the two little marker lights down low in the front; all are inexpensive replacable bulbs when they burn out, vice the $1,000 front headlight assemblies.

I'd never looked before because I never used Parking Lights, but just did Sat night - 24 XLT includes the front yellow turn signal lights.

Son and I had just seen so many drivers with lights off, or parking lights only - I was curious how bright they would be in the dark. Not enough to be confused.

Ditto on LED's - and if their estimate uses a very narrow temp operating band for those expected max hours - they ain't getting it here!
I'm expecting cracks in the logic board before the lights actually. Same end result though.

 

[KenE]

I'd never looked before because I never used Parking Lights, but just did Sat night - 24 XLT includes the front yellow turn signal lights.

Son and I had just seen so many drivers with lights off, or parking lights only - I was curious how bright they would be in the dark. Not enough to be confused.

Ditto on LED's - and if their estimate uses a very narrow temp operating band for those expected max hours - they ain't getting it here!
I'm expecting cracks in the logic board before the lights actually. end result though.

Amen. Logic board failure as likely or more so to fail before the actual LED, but the same $$$ value failure.

 

[KenE]

I'd never looked before because I never used Parking Lights, but just did Sat night - 24 XLT includes the front yellow turn signal lights.

Son and I had just seen so many drivers with lights off, or parking lights only - I was curious how bright they would be in the dark. Not enough to be confused.

Ditto on LED's - and if their estimate uses a very narrow temp operating band for those expected max hours - they ain't getting it here!
I'm expecting cracks in the logic board before the lights actually. Same end result though.

I'm not keen on parking lights usage, except it does trigger the tricks to allow full 12v charging. But I really dislike DRL usage by the majority of US drivers, and there's no tail lights illumination until dark enough to force the head lights On. There's quite a time interval when there is no rear end illumination. At least in Canada taillights are mandated with DRL usage. Should be here! That's why I changed that in Forscan. But, DRL usage is not for me because it won't trigger full charging.

 

[Mavster Mechanic]

Update:

I kept 12v battery 96% minimum while parked and 100% while driving for over 3 months.

This week Mon-Tue-Wed I kept parking lamps off (DRL on).

Wednesday night, parked at 90%.
Same 4% drop overnight.

Thursday AM left home with 86% showing. No tricks.
Truck started charging at about 20 amps. Quickly dropped to 14 amps. Then 10 Amps at 90%. 91% came around.

Then I got distracted by driving for 2 or 3 minutes. ()

Looked at gauge: says 90% and flat.
0 amps neither charging nor discharging. Holding steady at 90%.

After a few more minutes I flip parking lights on. Instantly 10 amps charging with a slow taper.

9A at 91%
8A at 92%
5A at 95% etc.

Hit 98% at same time I got to destination. Parked at 98% on 12v battery.

 

[KenE]

Update:

I kept 12v battery 96% minimum while parked and 100% while driving for over 3 months.

This week Mon-Tue-Wed I kept parking lamps off (DRL on).

Wednesday night, parked at 90%.
Same 4% drop overnight.

Thursday AM left home with 86% showing. No tricks.
Truck started charging at about 20 amps. Quickly dropped to 14 amps. Then 10 Amps at 90%. 91% came around.

Then I got distracted by driving for 2 or 3 minutes. ()

Looked at gauge: says 90% and flat.
0 amps neither charging nor discharging. Holding steady at 90%.

After a few more minutes I flip parking lights on. Instantly 10 amps charging with a slow taper.

9A at 91%
8A at 92%
5A at 95% etc.

Hit 98% at same time I got to destination. Parked at 98% on 12v battery.

Exactly as my Mav operates. Very happy with the tricks forcing Peak charge. Beyond thankful for for findings & helping us.

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