Bests & Worsts Reviews from Amazon

After having purchased over 20 different power banks, I received this unit free for review. It compares well with others in it's capacity class. The slim, brushed aluminum case looks very nice. It weighs 9 ounces, measures 2 & 7/8 by 5 & 1/2 inches and 9/16 inches thick. It has a small test button to determine the charge. During re-charge the lights stay on; during discharge they light only briefly to conserve power. It is capable of being re-charged at up to 2A. When charging other devices, it has dual USB outputs of 1A and 2.1A with single and dual lightning symbols. The charging cord supplied is heavy duty and carries the high currents better than most. Trying some other cords limited the current severely due to thin gauge wires. Unlike most power banks, which show 3-4 lights for a long time then die fast, this unit still has 47% of its available charge when it goes to a single light and about two-thirds available when it goes to 2 lights on. Upon receipt, it showed two lights on. It charged to 100% in about 2.5 hours starting at 1.4A with a current meter in the circuit, which can limit the current. The 4 charge indicators are not linear. Instead of each one representing 25% charge, when re-charging: all 4 on indicates 90-100%, so leave it on the charger a while longer after it lights that fourth light, 4th blinking is 60-90%, 3rd blinking is 30-60%, 2nd blinking is 10-30%, and one blinking is 0-10%. My rough checks indicate the re-charge lights work as specified. When discharging: all 4 on is 90-100%, 3 on is 70-90%, 2 on is 40-70%, 1 on is 10-40%, and none on, but still providing power, is less than 10%. My initial tests indicate that the fourth and third lights go out quicker. Then the final lights last much longer. I started my tests with both outputs supplying .86A while maintaining 4.90V for a combined power of 1.72A. After 2 hours, my Kindle keyboard was fully charged, having started at about half charge. During that time the power bank got noticeably warm. As expected the 4th light went out quickly and the third not quite as fast. I continued charging the second device for another 2.6 hours at .85A. Total power delivered was 1.72A x 2 hr + .85A x 2.6 hrs = 5.65 amp hours. It then had one light lit. I assumed it was probably near empty, so re-charged it in about 7 hours. For the second test, I took it all the way from 100% to empty as follows: Charged my Clip Zip from 66% to 100% at .15A in 40 minutes while the MP3 player continued to play. Not a heavy test, but rather shows that the stated 80ma cutoff current is low enough to fully charge small music players - something many power banks cannot do. About .1Amp-hr (Ah) supplied so far. Charged my simple Alcatel cell phone from zero to 100% with a starting current of .61A. It finished in 1.75 hrs, tapering off at the end for another .8Ah. Total so far of .9Ah or 9% of capacity - bank showed 3 lights - on the edge of the predicted state. Then I charged my ASUS HD 7 tablet from 56% to 100% in 2.25 hr, starting at 1.2A from the high power outlet. 44% x 3.8 = 1.67 Ah, 2.57 Ah so far or 26% of capacity - 2 lights still lit. Amp-hr supplied was calculated from the charge state of the tablet, which may be on the low side, since the tablet was in sleep mode and drawing a small current. Predicted state would have been still 3 lights. At this point I had charged all my devices except some of the other power banks. I picked a depleted ECTech 12K bank as the final test load, charging at a steady rate of .95A again through the current meter. After 1 hour, the Poweradd bank was down to 1 light. Total power supplied was 2.57 + .95 = 3.52 Ah or 35% supplied thus far. Predicted state would have been 2 lights. Not looking good at this point. But I continued. After another 1.85 hr the last light went off for another .95 x 1.87 = 1.78 + 3.52 = 5.3 Ah so far. I figured it was near the end. But it kept supplying .95A for another 1.4 hr, maintaining a steady 4.90V, with the current actually rising to just over 1.0 A in the final minutes. So another 1.4 x .95 = 1.33 + 5.30 = 6.63 Ah delivered. Total delivery of 6630 mAh x 4.90 V or 32.5Watt-hr. Figuring the average Li-polymer cell voltage was 3.7V, the bank holds 3.7 x 10 = 37 Watt-hr for a decent converter loss of 12%. After the last light went off, it continued to supply about 20% of the total delivered power, not 10%. When it went to a single light on, it still had 47% of the total delivered power left, not 40%. Li-polymer cells sometimes take a few charge cycles to reach maximum capacity, so I will report again after a few more cycles. In summary, don't give up hope when those lights start going out, those last lights indicate more power left than you think. It should keep delivering full current and voltage right up to shut down - much better than most power banks. It is packaged in a slim, elegant case with good versatility. Use the better than average provided USB cord, if possible, when transferring high currents. Light duty cords will not deliver full power. While you can use both outputs at once, do so with caution - that heat build up indicates extra power loss. If you trip the (unstated) maximum current draw or hit the high temperature limit it will go into safety shut down. That requires disconnecting it, cooling down, and putting it back under re-charge for a while to reset the limit circuits. Update 4/14/2014: Ran one more test today. Discharged the bank from 100% to off at .83A to .89A, current meter in circuit always. Obtained a total of 6950 mAh or 34.2 Wh at 4.92V output. A little higher than the previous test showing only 8% loss in the converter. During this test the lights changed by: 4 lit - 97-100% 3 lit - 68-97% 2 lit - 47-68% 1 lit - 4-47% none lit 0-4% This time the bank was near empty when the last light went off. It still went to one light at about 47% remaining.