Eu não penso assim, mas é definitivamente uma carga lenta.
Isso também pode ajudar você a decidir:
Actually, USB ports are 5 volts DC versus 110-120 volts AC for wall outlets in the US. But the issue here isn't voltage; it's current. USB ports are 500-900 mA versus about 1.5A in most wall chargers. That's up to three times more current than USB charging. More current, faster charging, although I don't know that I'd go much higher than 1.5A and risk damaging the battery.
Veja também algumas respostas aqui .