Originally Posted by BFlinn181
I agree with luvlabs, 12.5-13v won't charge a 12v battery. At least 13.8v is considered a charging voltage, anything less will prolong the period before it goes dead, but it won't overcome internal resistance of the battery and charge it.
This is exactly what's happening with me.
I have a 2012 F150,essentially the same truck as you have.
I installed the same 15 amp "toad charging module" as you.
I have been happily towing my F150 for 2 years now without a mishap.
Last month I pulled the truck out of the garage to connect it up to the rv for a trip to the Smokey mountains.
Although I hadn't driven the truck in several months it started right up and I hooked everything up and we left.
Normal procedure for flat towing the F150 is to set it up for "Neutral Tow" and turn the ignition key off but leave it in the steering unlocked position.
Been doing it that way for two years ,no problems.
This trip however we overnighted at a campground in Virginia and did not unhook.
I noticed the next day while driving in the rv that my remote brake light indicator on the rv dash was not
Illuminating when braking like it always had before.
It's wired directly off the brake pedal stop light switch in the truck so it gives absolute confirmation of the Air Force One braking system applying the toad brakes .
Come to find out the truck battery was dead.
I checked the fancy toad charging system and it was powered up and working.
Problem was the voltage was never high enough to actually "charge" the truck's battery.
All this time during previous trips it had been fully charged before I hooked it up it and the small load on it while towing in "tow mode" never discharged it that much.
Except for this last time where the truck had sat for some time with,unbeknownst to me ,a half discharged battery.
I now make sure that the truck battery is fully charged before connecting it for flat towing.
Otherwise it's been a terrific lifestyle!!