I bought this pack of 15 sub c nickel metal hydride batteries to revitalize my old but still perfectly functional Black & Decker 18 volt cordless drill. The original batteries were nickel cadmium and they would not hold a charge anymore. They would go dead almost immediately and even when fully charged it didn't have much power. I got such long life out of the original battery because as many are aware, with nickel cadmium batteries you have to completely discharge them before recharging so that they do not develop memory. I built a discharger out of the set of old car tail light bulbs that I would connect to the battery to completely drain it before recharging. However even then, nickel cadmium batteries have a limited cycle life. Despite being 6 years old and being the primary tool that I completely rebuilt my entire kitchen with, the drill is in very good shape. The battery was the only thing keeping it from continuing to be a useful tool. A new replacement battery would have been expensive and just another low capacity nickel cadmium like the original. So instead I ordered a set of 15 sub c 3000 milliamp nickel metal hydride battery cells from Tenergy. I assembled them in the original battery case and I cycled them with my battery discharger. After discharging the batteries I completely recharged them with the original charger that came with the cordless drill. At 3,000 ma hours capacity this battery has over three times the capacity that the original battery did when it was new. The only downside to using these batteries is the fact that the original battery charger takes 16 hours to completely charge this battery from dead. However unlike a nickel cadmium battery, I don't have to fully discharge the nickel metal hydride battery cells to prevent them from developing a memory like I had to with the nickel cadmium batteries so I won't always need 16 hours to recharge the drill. However just for anyone else who is considering doing this, it is good to fully discharge a nickel metal hydride battery once in a while as a maintenance procedure to prevent them from developing memory. Nickel metal hydride batteries don't do that as severely as nickel cadmium batteries do, but they will ultimately develop a memory if you don't occasionally completely kill them and recharge them. This drill was very useful when it had the original crappy battery, and now that it has three times the capacity, it is even more outstanding. The best part is in addition to getting to brush off my old soldering skills which I haven't used in a while, I also was able to rebuild this battery and Gain three times the capacity and do it with a fraction of the cost that it would have taken me to buy another original battery that might have lasted another 6 years but would not have been able to hold a candle to the performance of this now much improved rechargeable battery for my cordless drill.