[Goldman]

If the mechbox is turning over, the battery shouln't be an issue. It is the spring that controls FPS, not the battery. It also is not likley to slip while trying to wind up unless his anti-reversal latch is MIA.

Have you checked your barrel? As well as your hop? have you tried firing the AEG without a hop up unit on it? Does the Nozzle move correctly? How does the AEG sound when it fires? What ammo are you using?

In the end, you'll want to find a local gun-tech and get him to take a look at it, as internet diagnoses are rather hard.

Good luck.