I have rebuilt a few packs before. Pop the open and measure the size, goto digikey or mouser and pick the one that matches. They can even weld them together for you. A couple years ago my makita 9.6v batteries were selling for $30-$35 and it would cost me $25 for new cells plug a bit to ship. Now my batteries are selling for $35-40 so its getting more economical for me to rebuild one. I'll probably order a set of cells next time I place an order from one of the above.