HYBRID 12V Battery Mystery SOLVED

[Mavster Mechanic]

what about the current draw from an amp for an upgraded stereo system?

It's not current draw related.
It is exact device you turn on related.

The computer needs to see one or more of Headlamps on, Parking Lamps on; or Trailer lamps on.

That simple. Weird. But simple.

Or fan speed 6 or 7.

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[rslilly76]

It's not current draw related.
It is exact device you turn on related.

The computer needs to see one or more of Headlamps on, Parking Lamps on; or Trailer lamps on.

That simple. Weird. But simple.

Or fan speed 6 or 7.

Yeah I read your post, was just curious.

What about auto fan at high?

 

[HeyBales]

Yeah I read your post, was just curious.

What about auto fan at high?

That will still ramp down to slower fan speeds when it's gotten to set point fast.
And since it usually can get there fast, not going to have that fan at 6 for potentially very long.
Maybe AZ or AK? (or equally hot or cold extreme)
Know what 6 sounds/feels like - and test it in Auto for your usage.

 

[rslilly76]

Ok another question, I have a phone charger with volt meter on it. I turned the ac off no headlights on only drl, no trailer attached. The volt meter reads 14.3 which would mean it's charging the 12v battery. when truck is off it reads 12.5 which means it's not being charged. 2025 here though so maybe it's been changed? Also my truck has had an the software upgrades that supposedly affect the sleep mode battery stuff.

 

[rslilly76]

That will still ramp down to slower fan speeds when it's gotten to set point fast.
And since it usually can get there fast, not going to have that fan at 6 for potentially very long.
Maybe AZ or AK? (or equally hot or cold extreme)
Know what 6 sounds/feels like - and test it in Auto for your usage.

South Texas ac always set to 60-69 degrees so it's blowing 6 or 7 a lot

 

[MakinDoForNow]

It's not current draw related.
It is exact device you turn on related.

The computer needs to see one or more of Headlamps on, Parking Lamps on; or Trailer lamps on.

That simple. Weird. But simple.

Or fan speed 6 or 7.

If all the above devices are controlled by the same modules programming PERHAPS a different device turned on in only that module sets the flag that triggers the charging. (Is the logic for the headlights in the same code packet as the bms logic????)

 

[MakinDoForNow]

Ok another question, I have a phone charger with volt meter on it. I turned the ac off no headlights on only drl, no trailer attached. The volt meter reads 14.3 which would mean it's charging the 12v battery. when truck is off it reads 12.5 which means it's not being charged. 2025 here though so maybe it's been changed? Also my truck has had an the software upgrades that supposedly affect the sleep mode battery stuff.

14.3 means that there is enough voltage to charge the 12v if the bms logic chooses to do so and at what current it wants to.

 

[rslilly76]

14.3 means that there is enough voltage to charge the 12v if the bms logic chooses to do so and at what current it wants to.

there would be no reason for the dc to dc converter to be on then if the battery isn't being charged

 

[HeyBales]

there would be no reason for the dc to dc converter to be on then if the battery isn't being charged

Sure - it's powering the whole 12V system.

 

[rslilly76]

Watch this video.

12.x volts and discharging to 14.x volts and charging. All I did was manually turn on my headlamps.

What program is this that you are using? I use Car Scanner Pro and can't find those settings, although I see the Hybrid battery charging voltage. I don't know if the BECM voltage charging is the 12v or the Hybrid

 

[rslilly76]

Sure - it's powering the whole 12V system.

If you have the headlights off, and you have the a/c off, and radio off what exactly is there left to power?

 

[MakinDoForNow]

If you have the headlights off, and you have the a/c off, and radio off what exactly is there left to power?

The computers, possibly the pump to cool the HVB, whatever you have plugged into the powerpoints, +++

 

[rslilly76]

The DC/DC converter is the only thing that can charge a 12v battery.

But it's variable. It can output any voltage it's programed to within design limits.

For whatever reason, it's being told to output only 12.3 or 12.4 volts much of the time.

Doing one of the "tricks" mentioned forces it to put out 14.4 to 14.8 volts ALL OF THE TIME.

OK well I am curious if Ford has done some sort of software upgrade to fix this on the 25+ and here are my reasons for that. I had all software updates done (12 total a month after getting the truck in April of 25, the truck was built in Jan of 25) including the ACCM for the a/c that is supposedly a fix lol. I also have an AGM cause it's a 25 so it came with one.

At rest I am 12.9 volts
With key in the on position (not running) I am at 13.0 volts
With the Truck on (no lights on, no radio on, no A/C on, nothing connected to trailer light plug) 14.2 volts

Voltmeter connected directly to the 12v battery shows 14.37 volts which would indicate it's being charged at the current time.

I don't have the same program that the mechanic has, so I can't seem to find a way to verify what state of charge my 12v is in at the moment. (Does anyone know if Car Scanner Pro will show the 12v state of charge?)

 

[rslilly76]

If you have the headlights off, and you have the a/c off, and radio off what exactly is there left to power?

Wonder if the voltmeter phone charger is enough to trigger the BMS to charge to 100% too? MMMM

 

[Hcopter]

Just posted below - don't have to be driving.
May or may not be easier to use this method, once a week in the driveway while washing the truck, or cleaning it out.
Start it with trailer light in - do your thing for an hour - knowing it's charging high for that time.

Then again - an actual charger may be more effect at those times.

I'm not sure that leaving the truck on while you're not in it will add any charge. This morning I got out and left it running with the headlights on, and locked the door. The voltage dropped to 12.8v and stayed there until I got back in and closed the door, and it went back up to 14.4v.

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