I modeled the battery case for bigger batteries than the original 18650 or 21700. This case is for 26650 batteries. You can fit the original PCB board inside. Video instructions on how to disassemble the original battery: https://youtu.be/7jVF2c7a8OM?si=4-iGGpvNNaOWmDEZ . After opening up the battery you need to desolder wires and push the batteries outside from the case, they are glued so you need to push them a bit, but do it gently to prevent battery damage. For assembling it you need 3x M2 screws. LAST THING, the lights from the battery PCB may not light through your filament and you will not see the battery indicator light, so be careful about what filament you use and do the test print and see if the lights will glow over those few layers(holes for indicator light arent cut through all so water doesn't get inside through that holes).