Increase Battery Capacity for Xperia Z

Do you want to increase the battery capacity of your Xperia Z?
External battery case is the solution to increase the capacity, however it will increase your phone weight thickness.
If you are travelling a lot and don't have time to charge your xperia z, External battery case is the best solution

Update:
There are two currently External battery case for Xperia Z
Power Jacket 2800 mAh For Sony Xperia Z http://bit.ly/14OHf8o

Mugen Power 3000 mAh http://bit.ly/19o02pf

Some users didn't want the case because it will hide the beauty of Xperia Z
Both cases are made in China, in case you want to know the quality.
Don't charge the external battery case while charging your phone.