Low voltage DC-DC voltage changes when moving vs slowing/stopped

[Runaway Tractor]

Here's a Ford software engineering mystery. The DC-DC converter is changing the voltage when you slow down / stop vs moving. When speed drops below 5mph, the DC-DC converter voltage increases from 12.8v to 13.3v. When you accelerate above 7mph, the DC-DC converter drops the voltage back down to 12.8v. Been watching this for days. 100% consistent. This is definitely a programatic setpoint change for seemingly no reason.

I cannot think of any logical reason for this. The LV load doesn't suddenly change with speed. The only thing this seems to "accomplish" is randomly charging and discharging the LV battery.

Here's a screen recording from Car Scanner. You'll see the DC-DC amps and LVB volts changing instantly and consistently with the speed.

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[Maquis]

It’s programmed to emulate the alternator on an ICE?

 

[bmwhitetx]

I’ve seen it change from 13.x to 14.x depending on 12V load. Your battery is at 100% SOC so it doesn’t need to be charged. That’s why you’re likely only seeing 12.8.

For example when I have AC on high speed, the voltage will increase. I used this back when trying to charge a low SOC battery while in the driveway when OTAs were failing due to low 12V SOC.

It may also be prioritizing motors at speed over charging the LVB.

 

[Runaway Tractor]

It’s programmed to emulate the alternator on an ICE?

Lol that's the first thing I thought of but then I realized it's the other way around.

 

[Ricks Lightning]

i noticed my low voltage battery was at 14.9 when i started the truck this morning. seems very high for a 12 v agm battery to charge at.

Rick

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