How Big is a Battery? Understanding Battery Size, Capacity, and Power
Learn what determines battery size, including energy storage capacity (kWh), power rating (kW), charge rate (C-rate), storage duration, and energy density. Understand how
A battery energy storage system (BESS), battery storage power station, battery energy grid storage (BEGS) or battery grid storage is a type of energy storage technology that uses a group of batteries in the grid to store electrical energy.
Battery energy storage capacity is the total amount of energy the battery can store, measured in kilowatt-hours (kWh) or megawatt-hours (MWh). Think of this as like the size of a water tank where you measure the water capacity in litres.
Battery storage power stations are usually composed of batteries, power conversion systems (inverters), control systems and monitoring equipment. There are a variety of battery types used, including lithium-ion, lead-acid, flow cell batteries, and others, depending on factors such as energy density, cycle life, and cost.
Battery storage duration describes how long the battery can discharge at its rated power. It's calculated: Energy Capacity (MWh) ÷ Power Rating (MW). A 4 MWh battery with a 1 MW power rating has a 4-hour duration. A 1 MWh battery with a 2 MW power rating has a 0.5-hour duration. We've written about storage duration in more detail here.
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