Anker® Astro2 8400mAh Portable Dual-Port External Battery Pack Power Bank Backup Charger with Built-In Flashlight Vouchers

 S. carico :
Ive tried 5 external battery packs and this one is the best by far. sleek design, well constructed and truley puts out 8400mah like it says. The best bang for your buck.

 brad:
seems to charge which is what I want it for, but the flashlight never worked (which I don't really need anyway).

I came back to edit this review because very soon after I wrote it, the vendor read that my flashlight wasn't functioning and offered to replace my device. I am not going to take them up on the offer because I need to go away on a trip soon and need to use it, but that is my choice and truthfully I don't care about the flashlight functionality. I am bumping them up a star here because they quickly offered to make things right.

 Harrisre1 (USA):
Have been looking for ways to extend battery life for my beloved HTC Thunderbolt with its sadly shortlived battery. (Amazing that a device designed to do so many things, plus doing them over the further battery consuming Verizon 4LTE network - can't be depended on to last long enough - I can actually watch my battery meter draining down minute by minute!) Have tried all the recommendations over tech forums for extending battery life, have tried various apps - nothing works. Have an extra charged battery at all times, but highly inconvenient to have to change out - usually in the middle of something important. NOW, finally, I have the Anker8400 model. I reviewed all the portable battery chargers, including the various Anker models, and decided on this one because of its capabilities for repeated smartphone recharges and the fact I could continue to use my Thunderbolt while it was being charged. The Anker is very easy to figure out (even with written directions in Chinese which I don't read) simple to use, a whole aray of adapters, (Also bought 6ft long USB to Micro cable, so as not to be limited when charging the Anker8400 with its short connector.) Only drawbacks for me, even with its sleek relatively compact form factor, is its size & weight. When I have used the 8400 more, I'll update here - maybe will be able to give a full 5 stars.