Exactly, the easy access is certainly usefull when you have to keep opening it (which you will lol). Sounds like a lose connection perhaps, these electronics can be a bit tempremental tbh. If you dont mind me asking what version (metal tracks, gbox etc?) did you get if it cost £100 and where from? Sending it back for replacement may be a good idea.
I have two of the batteries Glen recommended, great value for money for certain!
Cheers, Dave