Connected the single battery charge unit to the cig lighter using USB cable. Could not get it to charge (no green lights in battery). Using the gig lighter to charge DJI SPARK battery works well. Read that the charger needs 13.8v to work. They fitted a step up unit (12v to 13.8v) to get it to work.Has anyone else heard this, had success charging single battery from the car's cig lighter. THANKS.