Here is a review from John freml who likes keeps his mobiles in full power all day long. He has been used RavPower 10400mAh and likes its portability, 2 USB output. the LED status bar and an attractive price ($37.99 from Amazon). This model has a large power capacity that enables to charge your devices more than 4 times and it's a great option for hiking and a long-distance trip with it. You can get it from Amazon here: Amazon.com: RAVPower® PB07 10400mAh Power Bank Pack / Portable External Battery Charger, Fit for iPhone 5, S4, S3, Note2, Nexus 4, Apple iPad 4,The New iPad, iPad mini, iPhone 4S, iPod(Charging tip not Provided); HTC Sensation, EVO 4G, 8X, One X, Dro The RAVPower Dynamo-On-the-Go 10400mAh Power Bank is an external charger with an emphasis on reliability, affordability, and value. It allows you to charge two mobile devices at the same time, and supposedly can withstand up to 500 discharges with little degradation in capacity. The package includes the Power Bank itself, two USB to microUSB cables, a USB charger, and a bonus flannel bag that doubles as a dust and lint magnet. As a side note, the manufacturer cautions that due to Nokia’s unique design, some of its cell phones might not be compatible with the charge port on this Power Bank. So how well does this work in daily use? Recently I took this with me on a trip to Six Flags – the Sprint service at the park near St. Louis is generally overloaded and slow, causing my phone’s battery to drain quite quickly. I thought this would be the perfect test scenario. Right on cue, within just a couple hours after arrival, my HTC EVO 4G LTE only had about 50% of its battery left, so I went back to the car and picked up the Power Bank. I noticed that it didn’t really add too much weight to my bag – this is important for an accessory like this, which will often be used out and about for extended periods of time. I noticed no delay in charging my phone using the second output, so it seemed like the output listed above was accurate. And perhaps most importantly, I was able to keep my phone charged the rest of the day at Six Flags, in addition to in the car on the way back (the other car charger was being used by my partner). I realize that this is a highly unscientific test of the Power Bank itself, but it’s similar to how most people will end up using this thing. Most people who end up purchasing the RAVPoer Dynamo-On-the-Go Powerbank will simply want to keep their devices powered all day long while out hiking, on the train, or – like me – at the amusement park. And it gets this job done well. One nice feature is the intelligent LED status bar that indicates the current battery status, and the bag is a nice touch even though one of the drawstrings that keeps it closed ended up breaking on me during my trip. I appreciate that it comes with two USB to microUSB cables (although I seem to have misplaced one of them…), and the wall charger is great since so many accessories like these never seem to include this. Granted, this isn’t going to last you several days on an extended trip into the wilderness, but it’s not meant to. For the price, it’s perfect – and because of the price, I’d recommend this over many of the other solutions out there.