External USB Battery Pack Suggestions?

I am looking to buy an external usb battery pack to use primarily with my HTC Thunderboldt. Ideally I would like one that uses my rechargeable AA batteries rather than one that has its own built in battery pack. I was looking at the Tekkeon TekCharge MP1550 (Tekkeon - TekCharge MP1550, emergency power, emergency battery), but it is rated for a maximum output of 800ma and I am concerned that this is insufficient for the power hungry Thunderboldt.

1) Does anybody out there use this charger with their Thunderboldt and have any comments?

2) Does anybody know what the maximum current consumption of the HTC Thunderboldt is? I can't find this listed anywhere.

3) Any other recommendations for external USB battery packs?

Thanks!