18V

18V is a nominal voltage designation used for a family of battery packs and the cordless tools they power. It signals the intended voltage level, but it is not a universal electrical standard. The actual voltage varies during use and charging; for lithium-ion 18V packs, the nominal voltage is about 18V and the full-charge voltage is typically around 20–21V. Most 18V packs use five lithium-ion cells in series (5S), yielding roughly 18V nominal.

Capacity is measured in ampere-hours (Ah) or milliampere-hours (mAh). The energy content in watt-hours (Wh) is the product of voltage and capacity. For example, an 18V pack rated at 4.0 Ah stores about 72 Wh. Battery chemistry, certification, and built-in electronics influence runtime, charging speed, and safety features such as overcurrent protection, temperature monitoring, and cell balancing.

18V tools are common in drills, impact drivers, circular saws, grinders, flashlights, and small vacuums. Major brands include DeWalt, Makita, Milwaukee, Bosch, and Ryobi; many systems marketed as 18V have evolved to use the “18V/20V Max” branding, reflecting the typical peak voltage when fully charged. Some brands maintain distinct 18V and 20V lines, while others have standardized around the higher peak voltage for marketing and compatibility considerations.

Users should use the correct charger and battery for their tool system; never mix chemistries in a device; avoid exposing packs to extreme heat or moisture; recycle spent batteries properly. Proper maintenance can extend pack life, including adhering to manufacturer recommendations regarding charging, discharging, and storage.