Ampere-hour (Ah) is a unit of measurement for electrical energy storage, expressing the amount of electrical charge an battery can store. It indicates how much current a battery can provide over a given period before discharging.
What does ampere-hour mean?
Ampere-hour indicates how much current (in amperes) the battery can deliver for one hour:
Formula: Capacity(Ah) = Current(A) × Time(h)
Example: A 10 Ah battery can deliver 10 amperes of current for 1 hour, or 1 ampere for 10 hours.
What is ampere-hour used for?
Ampere-hour is most commonly used to express the capacity of batteries, for example:
- In car batteries: The ampere-hour value shows how much energy the battery can provide to the vehicle when starting or operating.
- In solar energy systems: Battery capacity determines how much solar energy can be stored and used later.
- In portable devices: The ampere-hour value determines how long the device will operate on a single charge.
Relationship between ampere-hour and power (energy)
Ampere-hour does not directly represent energy content but rather the storable electrical charge. To calculate energy, the battery's voltage (volt, V) must be taken into account:
Energy (Wh) = Capacity (Ah) × Voltage (V)
Example: A 12 V, 100 Ah battery can store a total of 1200 Wh (1.2 kWh) of energy.
What influences ampere-hour?
Discharge rate (C-rate): Battery capacity can vary depending on the discharge rate. Under higher loads (fast discharge), the actual capacity may decrease.
Temperature: At low temperatures, battery capacity may decrease, while under ideal conditions, it provides maximum performance.
Lifespan: Over the battery's cycles, its capacity gradually decreases due to aging.
Summary
Ampere-hour (Ah) is one of the most important metrics for battery capacity, indicating how much electrical current it can deliver over a given period. Knowing the ampere-hour value is fundamental for selecting and sizing batteries, whether for vehicles, solar systems, or portable devices. A battery tailored to precise needs ensures long-term efficient operation.