Wouldn't life be wonderful if the Ampy worked? You could just stick this little flask-shaped gadget on your hip, or throw it in your bag, and let it automatically generate power from your motions. As soon as your phone needed a little juice, you could plug it into the Ampy's USB port and turn the kinetic energy from your exercise into additional emails, games and phone calls. You'd never run out of power, because your physical effort could always generate more.
That's what the $100 Ampy, a Kickstarter project, promised back in October 2014 and it raised $309,000 towards that goal. This December, I decided to put it to the test. But no matter what I did, I couldn't get the Ampy to generate any reasonable amount of juice. My first thought was just to see what happened if I drained the Ampy's battery, threw it in my pocket, and went about my daily routine. Weeks went by without a single one of the Ampy's LED charge indicators lighting up. So I tried shaking the Ampy, vigorously, non-stop, for a full hour while watching TV shows. When I plugged my phone in, the charging indicator lit up -- and immediately disappeared again.
So this January, I took an Ampy to the 2016 CES in Las Vegas to see if a full week of vigorous walking could do the trick. Using the optional belt clip, I mounted it on my hip the exact same way you see in Ampy's marketing materials, only removing it when I went to sleep. I logged 77,853 steps -- a respectable 11K steps per day. But though Ampy claimed that the device would be able to generate 3 hours of phone use for every 10K steps, my entire week of exercise only added a measly 2 percent of battery life to my iPhone 6S. Just to be sure I didn't have a broken Ampy, I asked for a second unit and handed it to a colleague who runs every day. She ran 3 miles with the Ampy without lighting a single LED. (She also thought it was way too heavy.)
When I spoke to Ampy's PR rep, he told me that it would realistically take 60+ hours of running to completely fill the Ampy's 1,800mAh battery. (This teardown suggests that the Ampy doesn't have any secret sauce to make it more efficient than weak kinetic gadgets we've seen before.) Plus, it's worth noting that at 1,800mAh Ampy has a smaller capacity than many smartphones have today, and batteries lose some of their energy when they transfer electricity or even just while sitting around. So assuming you did run 60+ hours before trying to use the Ampy, you probably still wouldn't get a single full charge.
Don't buy the Ampy. You're better off packing a standard external battery pack, or a hand crank for emergencies.