NiMH is Nickel Metal Hydride, the chemical composition of the battery itself. Others are NiCd (Nickel Cadmium), LiPo (Lithium Polymer), LifePo (Lithium Ferrite Polymer) among others. The mAh (milliamp per hour) rating is whats used to estimate the shots per battery upon full and stable charge. You are correct in the voltage is what affects rate of fire.
Running an 8.4V is perfectly fine for gaming. There are a large number of options for batteries in the 8.4V flavour, as well as the 9.6V. The lower the voltage the lower your rate of fire, but this also reduces the wear on your gearbox thus elongating the potential life of the gearbox. The higher the voltage the lower the potential lifespan. Anything higher than a 9.6V for NiMh/NiCd or 7.4V for Lithium batteries is not needed in terms of rate of fire. Those are perfectly usable. When players decide to go higher they are usually experienced in working their way around a mechbox and are able to replace and maintain as needed. Don't think rate of fire (or FPS for that matter as most new players think is the be all end all) makes you a better player or your gun better. Start with the standard batteries and options, then if you decide to make the switch do it after seeing a need as opposed to a want or by a misconception. Im not saying you show these traits, this is more of a general message to most new people who have similar thoughts.
My trust is in whiskey, in weed and in Slayer, its GODDAMN ELECTRIC
Originally Posted by Pliskin
This is the equivalent to knocking on deaths door and blowing his head off with a shotgun.