Ive done something daft ive managed to get the polarity wrong on a batribike granite live and earth wrong way round i heard the controller pop any ideas what it need to check /change in the controller
Pop, Oh dear . Most certainly a can (capacitor) has blown, usually identified at the time by a cordite type smell. It may be possible to solder a new can if you know the spec of it if its the only damage other wise a new controller.
There will be fibre everywhere when you open the controller and the remains of the overheated can, possibly with 2 legs still soldered.
The main capacitor across the battery input will be blown, and you might find that the shunt is blown too. You can try changing the cap and/or repairing the shunt, but the probability is that there'll be other damage, so you might be forced to take the opportunity to get a better controller.