Yeah, it's possible. And not too hard. But if you have little to no soldering experience, you might have a tough time. It takes practice to get the solder to stick to the batteries. If you don't mind sacrificing one, go for it. Take the shrink wrap off first and then unsolder the leads. Remember to be careful about what you touch. It's easy to accidentally dead short a pack when you're tinkering with it. If it's a pre-fab pack, it probably has battery bars. Not sure if you'll be able to unsolder them but you can try. I have never done that so I don't know how strong the stick them on. If not, you'll have to cut them. Then use Goop or some silicone glue to glue the batteries together in the shape you want. Take time to arrange the polarities so you can wire + to - easily. Then just use new battery bars or wire to connect them. Solder on your main leads and connectors and it should be good.
