Yes - overcharging is possible!!! And it can shorten the lifetime of the device to a few seconds. Believe it or not, I killed two Samsung Note 10.1 tablets in just 2 weeks! One was electrocuted by using a fast charger (Output 5V 3A) and it died within 3 seconds. I sent it for repair, but it would have costed as much as a new one. The other one was slowly fryed to dead by leaving it connected to a charger overnight (5V 2A). In the morning, both the charger and the tablet were hot like hell, and the tablet refused to boot. Yes, call me stupid... Whether using only original Samsung chargers and cables is safer I don't know, but I reommend to be more carefull than I was.