The one downside of the higher resolution camera was that it eats batteries. If you are using an android phone to control it, it is running its own WiFi hotspot all the time, which means it has a battery life of about an hour.
I decided to get a second battery, but then came across this – for 18 quid, 3 batteries plus a triple USB charger, allowing me to charge the batteries away from the camera.
What is more, when it arrived, I saw the batteries were no just compatible – they were Yi branded batteries, the same as the one that came with my camera. And they all came in plastic protective cases.
The whole thing is very neat, and can fit in a pocket, or (more likely) the pocket of my camera bag.