Maybe it's just me, but I think have noticed something about using other usb and car/wall chargers besides the one specific to the brand of the phone you have.. It seems as though it takes longer to charge and doesnt hold a charge well or as long.. I have had several phones starting from bb tour - palm pre - samsung moment - htc evo and have used chargers from those previous phones or 3rd party chargers and they seem to make my battery not last as long/drain faster and again they take longer to charge.. I think this may be affecting the charge that some of the batteries can hold.. just an observation, but see how it holds up for yourself.. It also seems that swapping out batteries makes the battery drain faster or not hold a charge as well..