To cut a long story short I charged the Mini X 5 or 6 times with this yesterday. I think it would have gone on longer but I can only fly the Mini X so many times in one day
If I can find my other one I'll be able to charge two heli's away from a power source without resorting to the controller chargers, which seem a bit naff to me. This also has the advantage of running on rechargable AAs which the controllers sometimes whinge about.
This little battery pack unit is small but charges the Mini X almost as quickly as my laptop or wall socket USB charger. The difference is maybe a minute or two longer but no more than that.
The only requirement is a USB cable compatible with the Heli you want to charge.