SailorSam20500

I just read a post on a different forum. Guy claimed that the GM trucks increase the electric power going to a trailer when the truck is put in tow/haul mode. Supposedly helps charge the trailer batteries. Two questions - is this true? Does Ford do the same with the F series?

PerryB

Absolute hogwash.

Gene K

Actually on the 2015+ it won't even charge the battery until you name the trailer (in the Productivity Screen) and step on the brakes the first time. I assume that circuit isn't hot on a trailer without a battery.

Trailbreak74

Isn't the amount of current limited by the wire between the battery and the trailer? Not sure how you would just increase this by pushing a button? Sounds like a dealer invented feature to me.

SKBORDERS

They set the voltage higher with the lights on. There is a service bulletin that describes people having issues with the trailer batter not getting charged. The System voltage is controlled by the computer except under certain conditions. The system voltage is set anywhere from 11.8V to 15.5V depending on battery state of charge and operating conditions. It is done mostly to save gas but also improves battery life. Turning the lights on causes the system to keep the voltage high, I think 14.5V.

Before you say hogwash, google GM Regulated Voltage Control.

I don't know what the all the Ford parameters are, but it has a similar system on it. I would not be surprise if tow mode sets the voltage higher but running the headlights will. Ford calls theirs smart charge

PerryB

OK, I was thinking he meant they were regulating trailer charge line voltage separately from the vehicle system voltage.

old_programmer

The factory charge line on my 2015 F-150 is 18 gauge wire. I was told by Ford that its intent was to only maintain the trailer battery charge while driving. Its been a while since I did all of the the measuring but recall it can only handle an amp or two of current before the voltage starts dropping off pretty quickly.

SKBORDERS

Yeah, 18 gauge wire is not going to carry much current. Charging systems are only meant to run accessories and maintain a battery. Not to charge them.

msgtord

I've watched the voltage on my Scanguage go from 13.4 to 14.3.

SKBORDERS

Yes, the computer commands the alternator to adjust the voltage to different levels depending on the state of charge of the battery (Target is between 80-90%) and electrical needs. The battery charges best at 13.5 volts and 15.5 if it has a AGM battery in it as mine does. 13.5 and 14.5 on a regular flooded battery. Below 13.5 the battery won't charge much if it is above 80% charged.
If electrical needs are low, the battery is charged, the truck is on level ground and at a moderate speed, you may see it fall to near 12V to save gas. The voltage settings are 11.8 to 15.5 depending on conditions.