open up the battery pack if it has screws to check if there is any leaking cells,if there is it wont work,,its bin!!! if all looks good,say the battery is 18volt,get 2 car batterys,and link them up,so you get 24volt use 2 bits of thick single core cable,and crocodile clip on the negitive to the drill battery,and touch the +positive 10 time with short bursts,it recycles the cells and brings them back upto hold a charge, and no it doesnt blow up,,,just touch it dont hold the + positive on, done it before and it works,its worth a try before you replace them,