Is it possible the battery was was warm when you went to charge? Need to let them cool a bit before charging.I had a funny issue with mine this past weekend. I flew the battery down pretty low, plugged it into my battery bank and an outlet. When I would come back to check on it, it would only have 1 blinking light (not the first light either what would be #4 or the fully charged light was blinking). This went on for well over an hour on both charging devices. I un-plugged the battery from the Spark and plugged it back in, after that it seemed to charge like it normally would.. No big deal, just thought I would share my issue.
Yes it was warm but not hot, I think it got even warmer sitting there on the charger without it doing anything (which makes sense).
I'm using all top of the line 2.1 - 5 amp QC chargers. An in-line meter shows that the actual draw is just shy of 2 amps.It all depends on the Wattage of the charger behind the usb port, not the usb port itself.