I have been looking for a decent battery/ charger combo for my Nexus 5, which I recently purchased.

I'm looking for something not larger than approx 15cm x 12cm. I'd quite like it to be a wireless charger but these seem to be limited in their power.

The budget I'm looking at is 40, and would like it to be as high power as possible. I have read a lot about charge times, power discharge, and various other technical things, none of which I really understand so am looking for your help/ opinions.

Thanks very much for reading