Weird electrical problem - 2 phones won't charge

Longer USB cords tend to have problems charging modern devices. I stopped buying generic cords. I normally buy Samsung or Motorola cords/chargers from Amazon. There are specific charge cords available. They do not pass data.

I installed a power outlet in the towrig for daughters gadgets. Later I pulled the fuse and placed a multimeter inline to measure amperage. This allowed me to test different devices with different chargers and cords.