There are two versions of that specific m4 series battery. The new style battery is intended to be used with the new style USB charger that does not have a charge indication light on the actual charger. You tell by the battery LED.
However the old style m4 batteries LED do not light up no matter how long one charges it. For these the old style charger was used. The old style USB charger is corded, and had a charge indication LED on the charger.
What has apparently happened is they have supplied old batteries with new chargers in order to make up for lost time and back stock issues. It seems that a few Companies have done that over the Holidays. That does not make it acceptable however..
Pete: That does not sound good. You are very lucky your computers ports have an emergency surge cutoff.
Well that would make sense then. As I have the new usb charger with no light indicator, and neither of my batteries have shown a solid LED light indicating a full charge (even after a 12+ hour charge. never overheated though).
I have tried using the AC power plug as well with the light on it, and it has never gone green, would this be because of the battery as well? Or the usb adapter it uses in the charger? Either way my batteries always end up with plenty of power after a short charge, but I never get any indication that it has made it to a full charge.