Shop you can the battery pack via a Micro-USB port either on the PC or via commercially available charger eg smartphone.
Not so great is solved as displaying the charge status is still just, you have to count that is at a flashing LED how often it flashes. This is a bit cumbersome.
My Xperia Z1 with 3.000mAh battery I can even fully charge the battery pack. After that is a little remaining capacity available, but this is hardly enough even for another load of 20-30%. So invite the promised 2malige is not possible with the Z1.
However, this is consistent with my experience that you have to deduct from the nominal output mostly good 20% in order to obtain the actual possible charging power. The Sony is here therefore no exception but takes its place in the performance of similar battery packs.
Conclusion: to load completely as Notladegerät with enough strength to even my Z1 I take the battery pack very much. The flat design I can load it in your pocket then even. If you want more power, I have to look at larger battery packs.
