HYBRID 12V Battery Mystery SOLVED

[HeyBales]

2023 xlt

I'm getting some massive drawdowns after parking in my garage randomly. Not all the time, but it does happen. When I park I always turn off HVAC controls before turning off the vehicle. F11 is in and ATT service is excellent here.

You can see it on June 10th, 12th, and 13th. Without these massive drawdowns the battery would be great. My warranty runs out in Sept and apparently Ford will charge shop time to apply a fix (terrible customer service) so hopefully they figure it out before then.

No way I can recall everyone that has done what.
Were they willing to do the SSM updates for ACCM and ABS?
I know - you haven't had a battery drain - but perhaps that graph would be enough to show you got something that COULD have drained it, if it kept going.

That's encouraging to see it has the ability to charge it up so well with so few/short trips at least to cause a recovery, still not great something is causing that hard of a hit on a regular basis.

Also - do you have any truck settings enabled to look for updates?
We ain't getting any.

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[inline_five]

Pull fuse 11 and repeat.
Post what happens or doesn't happen.

Was thinking the same thing, but in my previous tests with it, I got zero drawdown with the fuse in.

 

[inline_five]

No way I can recall everyone that has done what.
Were they willing to do the SSM updates for ACCM and ABS?
I know - you haven't had a battery drain - but perhaps that graph would be enough to show you got something that COULD have drained it, if it kept going.

That's encouraging to see it has the ability to charge it up so well with so few/short trips at least to cause a recovery, still not great something is causing that hard of a hit on a regular basis.

Also - do you have any truck settings enabled to look for updates?
We ain't getting any.

I haven't actually gotten the ABS and ACCM updates yet, was on my list of things to do. But at least we have a baseline now, I will try to get to it over the next week or two.

I'm still on my original FLA battery from Sept 2023, but I do keep in on a NOCO if not using the vehicle for a week or so. I think June 7th was the last day on the charger in that pic. If I didn't have those random drawdowns the battery would be at like 12.5-12.6v the entire time, which is still healthy, but those drawdowns are killing it.

 

[Tall Hobbit]

Further observations:
note: I don't have sophisticated monitoring gear, nor the time, focus and energy to order my life around problematic 12v charging programming, as Ford knows all too well. Basing what I see off a simple USB adapter readout in the powerpoint of the cab.

1) as noted before, my replacement AGM has gone quite a bit longer that the previous one that failed. I've been faithfully using The Tricks™ ever since I learned about them, usually parking lights. Always parked & locked 9-10 hours each night; cold starts in the morning are around 12.x on the powerpoint readout, and I thankfully see no sort of worrying trend.

2) my average trip is in town, gently on surface streets and under 15min a trip. It's a daily driver and I've never gone more than 2 consecutive days without a drive. That having said, the voltage readout doesn't do anything wiggy when toggling The Tricks™ on/off until I've recently driven at least about 200 highway miles. Then for several days afterward the voltage readout responds dramatically to toggling. Then it goes back to showing 14.x no matter what I do, until the next ~200mi highway trip.

3) perhaps most interesting for the forum, the voltage readout doesn't respond to The Tricks™ until the initial turn of the shifter dial. By that I mean any movement: shifting out of park, but also depressing the brake and turning the shifter in the direction past park, then the readout goes wiggy with any toggling. Simply shifting into park after driving does not prevent the readout from responding to The Tricks™ at that point. However, idling on startup and leaving the shifter alone, the readout doesn't go up or down with lights or hi fan.

 

[Mavster Mechanic]

Nice. I'll see if I can replicate that in my 2022.

I think I can explain no.2.
Number 3 I had not noticed.

Re: 2

If your battery is 88% or below, The Tricks™ may not be apparant because the truck is boosting voltage on it's own. Switching the lights on won't boost voltage that is already boosted.
The "problem" is, charging current may be zero and the voltage stays at 14.7 ish because that is coming from the DC/DC converter.

When you drove a long(er)'trip your battery went past 88% then the voltage dropped. Switching on lights gets you from 89% to 100% the truck won't do this on it's own. With lamps on current flow stays on all the way to 100%.

 

[KenE]

Nice. I'll see if I can replicate that in my 2022.

I think I can explain no.2.
Number 3 I had not noticed.

Re: 2

If your battery is 88% or below, The Tricks™ may not be apparant because the truck is boosting voltage on it's own. Switching the lights on won't boost voltage that is already boosted.
The "problem" is, charging current may be zero and the voltage stays at 14.7 ish because that is coming from the DC/DC converter.

When you drove a long(er)'trip your battery went past 88% then the voltage dropped. Switching on lights gets you from 89% to 100% the truck won't do this on it's own. With lamps on current flow stays on all the way to 100%.

Yes, yes & yes. My 2025 Mav hybrid - lights On hack never saw changes before. DC-DC Converter constantly showed 14.x. Volts engine On SOC never above low 80s%. So, Fully charged with NOCO Gen 5 for 36 hours (I've done this before to no avail). But THIS time, removed battery charger, shortly thereafter voltmeter showed 13.4V with truck still untouched. Proved battery charged. Closed hood, immediately performed 12v battery Reset with high beam flash 5 times & brake pedal 3 times. Then closed/locked doors for 10 hours to "Relearn". Then last evening drove 4 miles to filling station, Car Scanner showed 98% SOC, 12V driving voltage 12.8v, returning home from station still showed 12.8v, battery needed no further charge due to previous charging, Relearn and/or Reset. AGM is 14 months old, original. Have never seen 98% SOC since following this thread, so fully charging a relatively new battery, then Reset & Relearn seems to have done trick. Departing this morning on 600 mile trip to visit family in North Carolina. Will monitor 12v voltage, SOC behavior today, lights ON. Not positive battery "Reset" was necessary along with Relearn, but it certainly proved your findings. Such a great knowledge base here. Thanks.

 

[Mavster Mechanic]

Yes, yes & yes. My 2025 Mav hybrid - lights On hack never saw changes before. DC-DC Converter constantly showed 14.x. Volts engine On SOC never above low 80s%. So, Fully charged with NOCO Gen 5 for 36 hours (I've done this before to no avail). But THIS time, removed battery charger, shortly thereafter voltmeter showed 13.4V with truck still untouched. Proved battery charged. Closed hood, immediately performed 12v battery Reset with high beam flash 5 times & brake pedal 3 times. Then closed/locked doors for 10 hours to "Relearn". Then last evening drove 4 miles to filling station, Car Scanner showed 98% SOC, 12V driving voltage 12.8v, returning home from station still showed 12.8v, battery needed no further charge due to previous charging, Relearn and/or Reset. AGM is 14 months old, original. Have never seen 98% SOC since following this thread, so fully charging a relatively new battery, then Reset & Relearn seems to have done trick. Departing this morning on 600 mile trip to visit family in North Carolina. Will monitor 12v voltage, SOC behavior today, lights ON. Not positive battery "Reset" was necessary along with Relearn, but it certainly proved your findings. Such a great knowledge base here. Thanks.

If driving voltage means voltage while driving it should not be 12.8.

You should only see 12.x while at rest.

Anytime truck is turned on you should see high 13's to low 14's.

Lights on forces voltage up and forces a trickle charge. If you see 12's while driving you are in a battery discharge mode.

 

[HeyBales]

Yes, yes & yes. My 2025 Mav hybrid - lights On hack never saw changes before. DC-DC Converter constantly showed 14.x. Volts engine On SOC never above low 80s%. So, Fully charged with NOCO Gen 5 for 36 hours (I've done this before to no avail). But THIS time, removed battery charger, shortly thereafter voltmeter showed 13.4V with truck still untouched. Proved battery charged. Closed hood, immediately performed 12v battery Reset with high beam flash 5 times & brake pedal 3 times. Then closed/locked doors for 10 hours to "Relearn". Then last evening drove 4 miles to filling station, Car Scanner showed 98% SOC, 12V driving voltage 12.8v, returning home from station still showed 12.8v, battery needed no further charge due to previous charging, Relearn and/or Reset. AGM is 14 months old, original. Have never seen 98% SOC since following this thread, so fully charging a relatively new battery, then Reset & Relearn seems to have done trick. Departing this morning on 600 mile trip to visit family in North Carolina. Will monitor 12v voltage, SOC behavior today, lights ON. Not positive battery "Reset" was necessary along with Relearn, but it certainly proved your findings. Such a great knowledge base here. Thanks.

Well see - battery is good enough to test this on.
Great!

Well - as long as it can hold the charge overnight high enough.
So you got down to below 92% SOC during your drive since it was discharging - now curious what the next morning voltage was.

Ya with 25MY - relearn probably not as important, as battery specs are an entered value, not estimated from a test draw.

Since you have a Scanner, should be interesting during your trip, after you reach 92% SOC and it shows 12.8 V while doing discharge, how long does it take to reach 100% again after you turn lights on.

I'm curious if that part of the charging strategy remained the same from 22MY to 25MY.

And then if you turn lights off at 100%, and it's back to 12.8V showing discharge - how long that takes to reach 92% again.
Since a long trip - maybe you'll be brave enough to allow the drop to 88%!
Got a kid to assign this task of noting these numbers as you are driving?

 

[KenE]

Well see - battery is good enough to test this on.
Great!

Well - as long as it can hold the charge overnight high enough.
So you got down to below 92% SOC during your drive since it was discharging - now curious what the next morning voltage was.

Ya with 25MY - relearn probably not as important, as battery specs are an entered value, not estimated from a test draw.

Since you have a Scanner, should be interesting during your trip, after you reach 92% SOC and it shows 12.8 V while doing discharge, how long does it take to reach 100% again after you turn lights on.

I'm curious if that part of the charging strategy remained the same from 22MY to 25MY.

And then if you turn lights off at 100%, and it's back to 12.8V showing discharge - how long that takes to reach 92% again.
Since a long trip - maybe you'll be brave enough to allow the drop to 88%!
Got a kid to assign this task of noting these numbers as you are driving?

No on the kids with us, just me monitoring while wife sleeps or reads. 550 mile drive. So I'll try to summarize. While driving, Voltage from DC-DC Converter was 14.0 to 14.1, never a higher voltage. I'm thinking the SOC at 7am today when we started was 88%. 95%. Very slowly it increased to 99%, never 100%. Then throughout the day it would drop to as low as 95%, then slowly rise to 99%. During this hours long slow charge interval the 12v current was a meager 0 to 1A charge - thus the very slow increase from 95% to 99%. All day lights were on. A time or two the 12v dropped to 12.8v while driving, obviously discharging, then the slow recharge interval began again. One time I noticed 8 amp charge to battery. Stopped twice today for 45 minutes. I'll check battery voltage tomorrow but failed to bring meter, plus at a motel, so can't check until opening doors and bringing online. We'll be visiting our family this weekend, but I'll monitor on 550 mile return trip Monday with and w/o lights to check behavior. The most encouraging thing is battery is being charged to almost 100%. Never have I seen this since started monitoring. I'm guessing based on your guys findings that no lights on return portion of trip I will have different results?

 

[KenE]

No on the kids with us, just me monitoring while wife sleeps or reads. 550 mile drive. So I'll try to summarize. While driving, Voltage from DC-DC Converter was 14.0 to 14.1, never a higher voltage. I'm thinking the SOC at 7am today when we started was 88%. 95%. Very slowly it increased to 99%, never 100%. Then throughout the day it would drop to as low as 95%, then slowly rise to 99%. During this hours long slow charge interval the 12v current was a meager 0 to 1A charge - thus the very slow increase from 95% to 99%. All day lights were on. A time or two the 12v dropped to 12.8v while driving, obviously discharging, then the slow recharge interval began again. One time I noticed 8 amp charge to battery. Stopped twice today for 45 minutes. I'll check battery voltage tomorrow but failed to bring meter, plus at a motel, so can't check until opening doors and bringing online. We'll be visiting our family this weekend, but I'll monitor on 550 mile return trip Monday with and w/o lights to check behavior. The most encouraging thing is battery is being charged to almost 100%. Never have I seen this since started monitoring. I'm guessing based on your guys findings that no lights on return portion of trip I will have different results?

Screen capture of Mav sitting overnight, locked, 11 hours. As you can see 12.8v resting overnight (never been that high since monitoring), 92%SOC, LvbA (12v charging amps). Maintained a good SOC & resting voltage overnight. And DC-DC immediately applying 1A charging current to battery, same as all day yesterday, 0 - 1A. MavsterMechanic & you may have experienced somewhat different results? But I'm very pleased with my Mav's charging behavior now compared to a few months ago before MavsterMechanics amazing find. Thank you guys. As always, will stay posted. But today my 53 year old son needs dad's help. I'm 80 in a couple months, but my son still calls on Dad from time to time. Working alongside my son today, and tomorrow being Father's Day, doesn't get much better. Plus my Great grandson has started to crawl, making my wife a happy Great Grandma today. Happy Father's day guys, be safe & thankful!

 

[Tall Hobbit]

Nice. I'll see if I can replicate that in my 2022.

I think I can explain no.2.
Number 3 I had not noticed.

Re: 2

If your battery is 88% or below, The Tricks™ may not be apparant because the truck is boosting voltage on it's own. Switching the lights on won't boost voltage that is already boosted.
The "problem" is, charging current may be zero and the voltage stays at 14.7 ish because that is coming from the DC/DC converter.

When you drove a long(er)'trip your battery went past 88% then the voltage dropped. Switching on lights gets you from 89% to 100% the truck won't do this on it's own. With lamps on current flow stays on all the way to 100%.

Yes, yes & yes. My 2025 Mav hybrid - lights On hack never saw changes before. DC-DC Converter constantly showed 14.x. Volts engine On SOC never above low 80s%. So, Fully charged with NOCO Gen 5 for 36 hours (I've done this before to no avail). But THIS time, removed battery charger, shortly thereafter voltmeter showed 13.4V with truck still untouched. Proved battery charged. Closed hood, immediately performed 12v battery Reset with high beam flash 5 times & brake pedal 3 times. Then closed/locked doors for 10 hours to "Relearn". Then last evening drove 4 miles to filling station, Car Scanner showed 98% SOC, 12V driving voltage 12.8v, returning home from station still showed 12.8v, battery needed no further charge due to previous charging, Relearn and/or Reset. AGM is 14 months old, original. Have never seen 98% SOC since following this thread, so fully charging a relatively new battery, then Reset & Relearn seems to have done trick. Departing this morning on 600 mile trip to visit family in North Carolina. Will monitor 12v voltage, SOC behavior today, lights ON. Not positive battery "Reset" was necessary along with Relearn, but it certainly proved your findings. Such a great knowledge base here. Thanks.

Thanks you two. Mavster, this is more or less what I supposed without the education to say as much. KenE, thanks for your reply too and enjoyed your writeup on your trip. A generous helping of my relatives are in/from the Old North State and I need to get back over there some day too.

As regards 12v SOC and The Tricks: do they do me any benefit until SOC is higher from one of my longer trips? (perhaps things I dimly grasp like differences in amperage and trickle charges apply) Am I prematurely burning out parking bulbs for no reason?

If for the sake of 12v SOC (to say nothing of overnight voltages), drivers have to frequently put their engines under a sustained period of hard work instead of taking it easy, that's a ridiculous expectation for an economy vehicle, and doubly so for a hybrid.

What say everyone?

 

[KenE]

Thanks you two. Mavster, this is more or less what I supposed without the education to say as much. KenE, thanks for your reply too and enjoyed your writeup on your trip. A generous helping of my relatives are in/from the Old North State and I need to get back over there some day too.

As regards 12v SOC and The Tricks: do they do me any benefit until SOC is higher from one of my longer trips? (perhaps things I dimly grasp like differences in amperage and trickle charges apply) Am I prematurely burning out parking bulbs for no reason?

If for the sake of 12v SOC (to say nothing of overnight voltages), drivers have to frequently put their engines under a sustained period of hard work instead of taking it easy, that's a ridiculous expectation for an economy vehicle, and doubly so for a hybrid.

What say everyone?

Tall Hobbit, Mavster Mechanic I recall is the discover guru of this charging phenomenon, so anything I say is from my experience based on previous posters discoveries. Returning today from Creedmoor, NC to Kentucky. Parking lights or headlights definitely force an immediate charge to 12v battery, until literally full charge, last few percentage SOC increase is at 1 amp current, perfect recipe. While driving, if i turn headlights off, I see "Immediate" changes on scanner display, i.e. 12v battery current discharging because DC-DC Converter stops charging, allowing 12v drop immediately from 14.0 to 12.8V. SOC slowly decrements. If I turn headlights back on, battery immediately starts charging again with applied 14v from DC-DC Converter, & battery slowly returns to 99% charge with a small charging current. The lower the SOC allowed, the greater the charging current. IMHO, the perfect charging algorithm. Lastly, I dont think the headlight "trick" will work with a severly degraded 12v battery. And an otherwise good battery needs to be FULLY charged with a quality charger, then the Relearn procedure (truck closed/locked/undistrubed) immediately performed for at least 8-9 hours. All my experiences are leveraged from Mavester Mechanic's. Info sharing is A+ on this forum.

 

[SafetyGuy]

Good day

I have an early 2025 Mav hybrid with awd and 4k pkg and have the original agm battery in our truck.

So I have been monitoring my battery voltage when driving and doing shorter runs for appts etc to and from the city. 10 km hwy into the city, city speed driving and then 10 kms hwy back home.

I have been charging my battery at least once a month with a smart charger since November. Truck has had battery relearn carried out with the 9 hr rest after charging while all locked up.

So far, since implementing MM's lights on trick (in daytime I just put park lights on), I haven't seen too much variance in my charge amounts as seen on my power point voltage indicator...when starting I would see 14.9-ish volts and that would slowly decrease to appx 14.3 volts. Repeat...lights on, lights off, pretty much the same.

Every time I metered the truck battery the next day (I pop the bonnet when arriving home in garage, so I do not wake the truck by opening the truck door to pop the hood) and the battery is always reading over 12.82 volts in the am. All good in my books!

We went on a bit of a drive on Fathers Day, went fishing at a little dam where we used to fish (now my wife and I), caught a couple fish and released them.

Did a crop tour on way to cemetery to visit my dad's, mom's and one brother's graves...visited some friends after and headed home.

On the hwy at 335 kms (207 miles) since the am, Wednesday hadn't had our lights on yet, and suddenly my voltage indicator twitches and drops to 12.9 volts!

I click my running/park lights on and immediately voltage indicated a quick climb back to 14.3 volts. I turned off the park lights and down the voltage went, to 12.9 volts.

So I turned my park lights on again, voltage rose to 14.3 and stayed there till we got home.

This am, when I checked my battery voltage with my tester on the boost points under the hood, battery was sitting right at 12.82 volts.

Perfect! This just proves once again, if you have fully charged your battery, do the relearn so the truck figures your battery out as to its proper charge level and combine with keeping your park/running lights or headlights on, it can really help make sure your battery is kept in much better charge state.

That's my story, I just had to wait for a good long run to check it out a bit further.

Have a good one,

Andy

Edit to add...I do have a hitch light plugged into the 4 pin trailer plug. I have cut the wire to the signal/brake light, so it only illuminates when I turn on the park lights or headlights.

 

[Mavster Mechanic]

I pulled my trailer 6 hours today.
No parking lamps needed.
Trailer did the trick.

Eventually float / sustain voltage went to 13.5v and stayed there for hours.
Never dropped into the 12's.

Used a cheap-o volt meter in the RV trailer. It also read 13.5v when I checked at camp site at end of trip.

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