I think it's more usual for the controller to be in the battery holder, in the box below where the battery slots in (see for example image in the Amazon reference above).
If it is all working well except the battery you can then just replace the battery. I understand there are two or three different styles of battery connection for the Hailong batteries so you need to be careful.
You must replace with the same voltage. You can use different capacity batteries depending on the range you are after.
Thanks for replying, by the wayAha, that makes sense. I'm after this kind of battery with this connector then?