Bests & Worsts Reviews from Amazon

. - - - Overview - - - Many brands to choose from. Prices are bouncy and coming down. This 8400 mAh model is enough to charge your iPhone 3-4 times, your iPad-2 80%, or your iPad-3 40%. Tablet users may want larger. (Note 1 explains mAh) They're not forever. Usually rated for 500 charge cycles, but they can die much sooner. Warranty and customer service matter. - - - Price Alerts - - - You can save money by waiting for price dips. There's an "Online Price Alert" that will email you whenever this or any amazon product dips below your target price. Google it. Or try camelcamelcamel. - - - Disclosure - - - The manufacturer gave me this product for review. I believe my review is impartial. - - - About the PowerGen 8400mAh - - - After checking it out for a month, I'd say this is a solid product, probably comparable to the alternatives listed below. PROs: - 1 year warranty (see comparison below) - Charges iPhone 3-4 times at full speed (see Note 2) - Fit and finish are very good - Power-in is a standard Micro-USB connector. (Use substitute cords of any length, and any AC adapter. Some other brands have a round power-in jack with dedicated AC adapter.) OKs: - Capacity 8400 mAh: Great for smartphones. Tablet users may want more. - Reliability: New model, but the identical Anker 8400 has been out for 1+ year with few Amazon review gripes. Mine had a bad cable (which i didn't plan to use anyway -- see Note 3). - 2 outputs: 0.6 Amps and 2 Amps (markings are hard to read) - Comes with a 7-piece interconnect system for most devices. I'd leave it in the box and use regular cables instead (see Note 3). - Comes with 1 Amp AC adapter (10 hours stated charge time). Faster recharge possible with 2 Amp AC adapter. - Battery status is 4-light method, no percentage readout. (see Note 4) CONs: - Glossy finish: Fingerprint magnet. Can slide around. Bad idea. - - - Size & Weight - - - 2.45" x 3.9" x .87" (Deck of cards) 6.6 oz. - - - Embedded Cable Alternatives - - - An embedded Micro-USB cable is a big plus. Save space. No tangle, mess, or leaving behind. - Anker 6000mAh - PowerGen 6000mAh - PowerGen 9000mAh - - - Notes - - - Note 1: mAH stands for milli-Amp hours. It's how much juice the battery pack holds. 8400 mAh is 8.4 Amp-hours. Note 2: Charging Specs: I tested an iPhone 4S with the PowerGen's 2A port. Did not test tablets or other phones. Capacity was 3.43 iPhone charges. (9%->90% + 49%->90% + 29%->90% + 5%->90% + 50%->90% + 28%->63%). Manual says the slower 0.6 amp port can achieve 4 iPhone charges. Charging speed averaged 1.0% per minute from the 2A port -- same as an Apple wall charger. Charging speed does not diminish as the PowerGen runs down. (At times it achieved 1.11% per minute, even with bits of screen use during the test. My testing stopped at 90%. iPhone charges slower from 80% to 100% with all chargers). PowerGen did not seem to heat up, ever. Note 3: 7-piece interconnect system includes Apple, USB-mini, USB-micro, 2mm round (Nokia), and 4mm round (PlayStation Portable). Plus special 6" and 25" cables. I find it cheesy, awkward, and losing pieces is way too easy. Use regular device cables. Note 4: Battery status indicator - 4 lights indicate 0-25%, 25-50%, etc. They show a lower reading while charging than when at rest. ~~~ Comments & questions welcome ~~~