The output of a typical computer USB port is a half an amp at five volts DC. If you get a charger, wall or cigarette plug, that is meant for an iPad, it will output 2.1 amps at five volts. It's best, for the battery life and phone, if you don't use a modded kernel for fast charging. Batteries last longer, overall life before replacing them, if they are slow charged. Heat from rapid charging will reduce the overall lifespan of a battery. I'm talking tech like in one hour or less chargers for AA batteries but it still holds true for lithium ion. Heat and hitting a battery hard with an aggressive charging circuit will kill a battery faster. My suggestion is to use a charger that has a max output of 2.1amps, like used with the stock and iPad chargers, to recharge the battery if you're impatient. Better yet, get an official Samsung external charger with battery so you can rotate batteries and have one charging or charged without forcing yourself to have the phone tethered to a charger often. There have been high profile instances where extended capacity batteries have burned up a phone, when charging, because the electronics of the battery were crap or the cells were of crappy quality. Be safe, be smart. Samsung OEM batteries might be expensive and low run time, but they won't usually cause a phone to go into meltdown mode because of their subpar electronics or cells.