Yes, the voltage must be exactly (probably +/- 10%) what the device expects, but apparently, the battery can provide higher Ah and the device will simply consume whatever amps it needs to run.
Originally Posted by Tuc
Anyway OP, if you have the space needed to put a short USB cable to an external battery pack, and make it stay attached, (big hassle with my Nexus on my car charger), go for it!
Indeed, it's something I worry about, which is why I'll buy an
angled cable if not provided by the big external battery.