Sometimes the batteries will swell a little if they are attempted to be recharged after the scooter has been in storage for a long time.
If the batteries are stuck in the scooter's frame then it will take brute force to remove them. Using a pry bar, large screwdriver, or other similar tool that can force them out of the frame is usually the most effective way to remove them.
Please let us know how it goes.
Jennyb