In theory, using an iPad charger should be fine. You can "over-volt" electronics, so you want to make sure that voltage output of the power supply matches the voltage requirements of the thing being powered so that you don't fry the phone (and when it comes to USB, everything is 5V, so no risk of a mismatch there), but you can't really "over-amp" them, so there is no harm in trying an iPad charger. When it comes to power supplies, think of amps as a measurement of potential capacity. The 0.5 - 1.5 amp range that Moto specifies would be the range that the G is capable of drawing from the power supply during a charge: it will draw as little as half an amp during charge (if connected to something that can only output 500mA, like, say, a computer USB port), but can draw as much as 1.5 amps if the source supports it. The phone will never draw more than 1.5 amps, even if the charger has a higher amperage rating.