I have a jvc 100u which i bought second hand it worked fine but then it developed a problem, it shut down and now i can not power it from the battery, it works fine when the dc adapter is plugged in but when i put on a battery nothing, can you tell me what the problem could be.

Clean the battery contacts and the contacts on the camera. You can use an eraser.

Also, verify the battery is holding a charge by using volt meter, or try the battery in another camera.

Battery contacts cleaned and polished batteries are good i even checked them on another camera to make sure. question is there like a seperate fuse for the battery and the dc supply?

If you use IDX batteries with the IDX bracket, the bracket have a separate fuse. Check out that.

Laszlo