i use a very thin knife. but it does not work well because my pack just cracked.

why cant they make them stronger like the force fx battery packs
Knife + battery removal = bad times, dude. Seriously.
You can damage your battery cells as well as yourself with a knife.
And Ultrasabers doesn't make the packs - they purchase the parts. I agree, it would be great to see a stronger, more resilient yet easier to interface with battery pack - especially something that could be adapted to snap soundboards into place rather than relying on adhesive.