Battery Capacity

Overview

Battery capacity represents the energy storage capability of a battery, measured in watt-hours (Wh) or milliamp-hours (mAh). A battery with higher capacity can store and deliver more energy, allowing devices to run longer on a single charge. For example, a high-capacity battery in a smartphone means extended usage time without recharging.

The battery’s capacity also depends on the mass of active materials inside it, as these materials drive the electrochemical reactions that produce electricity. The more active material present, the higher the battery capacity and the longer it can sustain device operations.

How Does Battery Capacity Work?

Battery capacity is the total charge stored within the battery, determined by the energy produced through electrochemical reactions. The capacity is proportional to the amount of usable active material participating in these reactions. In simpler terms, the more active material available, the more charge a battery can hold and deliver.

The formula for battery capacity is derived from the relationship between electrical current and time:

Q = I × t

• Q: Charge in coulombs (C)
• I: Current in amperes (A)
• t: Time in seconds (s)

To convert charge (Q) into ampere-hours (Ah):

Battery Capacity (Ah) = (I × t) / 3600

This calculation helps determine how much energy a battery can provide over a given period.

Factors That Affect Battery Capacity

1. Battery Chemistry and Type

The materials and chemical composition of a battery significantly affect its capacity. Different chemistries, like lithium-ion (Li-ion), lithium polymer (Li-polymer), or sodium-ion (Na-ion), result in varying energy densities and efficiencies. These chemistries influence the flow of electrons, which generates the current powering devices.

2. Aging and Life Cycle

Over time, a battery’s capacity diminishes due to repeated charging and discharging cycles. This natural aging process reduces the amount of active material available for electrochemical reactions, limiting the battery’s performance and storage capability.

3. Temperature and Environmental Conditions

Temperature plays a critical role in battery capacity. High temperatures can improve capacity by enhancing chemical reactions, but excessive heat may degrade the battery. Conversely, cold temperatures slow down reactions, reducing capacity and efficiency.

4. Active Material Mass

The amount of active material within a battery directly impacts its capacity. More material allows for greater electrochemical activity, increasing the amount of energy the battery can store and release.

Conclusion

Battery capacity is a vital aspect of battery performance, determining how long a device can operate without recharging. In electric vehicles (EVs) and other applications, higher capacity ensures extended usage, enhances operational efficiency, and contributes to longer battery life.

By understanding and optimizing factors like battery chemistry, aging, and environmental conditions, manufacturers can improve battery performance for various applications.