maybe it's just me, but 5100 mAh seems small for the relative size of this thing...
There are plenty of battery chargers out there that are smaller, have bigger batteries in them, and cost much less. Also, Unless I'm missing something, this thing will ONLY charge phone/small battery devices well. anything with a battery larger than 3500mAh will charge extremely slowly, and you might get one full recharge out of it.