The iSpot will hold a charge if you plug it in to most USB power sources, but it will not actually charge the battery. The manufacturer-suplied charger puts +5v on the normall unused 'x' pin in the Mini-USB connector. With +5v applied from the USB power pin, the iSpot will then charge normally.
|1||+5||USB +5 power|
|2||D-||USB Data - (not connected)|
|3||D+||USB Data+ (not connected)|
|4||Charge||+5 (shorted to pin 1)|