8.4v 2500mah Inertia Generator Large Battery (NiCd) This battery is constructed of seven I.G. cells in a large pack configuration, made of Nickel Cadmium. This means several things in electrical and airsoft terms. The first is that the power output is only 8.4 volts, this makes it perfect for non-upgraded guns such as Tokyo Maruis, but a little under powered for some like Classic Army. The capacity on the battery is 2500 mah, which translates into about 2500 shots (maybe as much as 2800) before the battery loses charge and needs to be put on another cycle. The battery may not be able to turn over the motor to pull the spring in Classic Army's case. The second affects charging cycles. NiCd batteries have to be discharged before they can be charged during a typical charging cycle. If you don't discharge and instead just try and "top it off", the battery will eventually develop a memory like the older cell phone batteries. But this seeming deficiency is also a big positive in other areas. NiCd batteries are able to hold their charges longer during periods of time when they are not being used. They can also go through more charging cycles before loosing efficiency, on average about 450 versus the 300 that most NiMH batteries get. Note: This battery must either be drained completely or discharged before being put on a charging cycle. Failure to do so may result in recrystallization and the eventual development of "memory". (Memory is bad!)