Ampere-hour

Duracell rechargeable batteries

Ampere-hour (Ah) is a unit of electric charge commonly used to measure the capacity of batteries. It is defined as the charge transferred by a steady current of one ampere flowing for one hour. The ampere-hour is a unit that is part of the International System of Units (SI), albeit not a primary SI unit.

Overview

The concept of ampere-hour is crucial in understanding how batteries work and their capacity. A battery's capacity is a measure of the amount of electric charge it can deliver at the specified voltage. The higher the ampere-hour rating of a battery, the more electric power it can store and deliver to an electronic device. This makes the ampere-hour a vital metric for consumers when choosing batteries for various applications, from small electronics to large electric vehicles.

Calculation

The ampere-hour is calculated by multiplying the current (in amperes) by the time (in hours) over which the current is discharged. For example, if a battery discharges at a rate of 2 amperes for 5 hours, the total charge transferred is 10 Ah. This calculation helps in determining the energy capacity of batteries, allowing for comparisons and understanding of their longevity in practical applications.

Applications

Ampere-hour is widely used in the specification of battery capacities. It is applicable in various fields, including:

• Consumer electronics, where it determines the usage duration of devices like smartphones and laptops on a single charge.
• Electric vehicles, where it indicates the potential range or distance the vehicle can travel on a full charge.
• Renewable energy systems, such as solar power storage, where it helps in sizing the storage system to ensure adequate power supply during periods without sunlight.

Limitations

While ampere-hour is a useful measure of battery capacity, it does not account for the discharge rate's effect on the actual usable capacity, known as the Peukert's Law. Additionally, the voltage is not considered in the ampere-hour rating, which can lead to misunderstandings about the total energy a battery can store and deliver. For a more comprehensive understanding of a battery's capacity, the watt-hour (Wh), which takes into account both the voltage and the ampere-hour rating, is often used.

See Also

• Electric charge
• Battery
• Watt-hour
• Peukert's Law

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