When you see a notation like "50S" on lithium-ion battery packs, it typically refers to the number of cells connected in series. In this case, "50S" means that there are 50 individual cells connected in series within the battery pack. Connecting cells in series increases the total voltage of the battery pack while keeping the capacity (in terms of ampere-hours or milliampere-hours) the same as that of a single cell. Each cell contributes its voltage to the total, so if each cell has a voltage of, for example, 3.7 volts, then a "50S" configuration would result in a total voltage of 50 cells x 3.7 volts/cell, which is 185 volts.