Difference Between Battery's Actual Capacity Versus Rated Capacity

Battery capacity, is one of the important performance indicators to measure battery performance. It represents the amount of electricity released by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.).

The battery capacity is divided into actual capacity, theoretical capacity and rated capacity according to different conditions.

In battery storage, Actual capacity is the amount of energy that a battery can actually deliver under specific conditions, and it is typically measured in ampere-hours (Ah).

Theoretical capacity is the maximum amount of energy that a battery could theoretically deliver under ideal conditions. It is calculated based on the chemical composition of the battery and the amount of active material in the cells. It is typically measured in the same units as actual capacity, but it is often much higher.

Rated capacity is the amount of energy that a battery is designed to deliver under specified conditions. It is typically lower than the theoretical capacity, but it is more realistic than the actual capacity. It is typically measured in the same units as actual capacity, and it is usually specified by the battery manufacturer.

Actual Capacity refers to the capacity of the battery or the power bank, whereas Rated Capacity refers to the output capacity of the power when fully charged. 

What That Means Is This:

A battery manufacturer may use theoretical capacity to design a new battery.

A battery retailer may use rated capacity to label batteries for sale.

A battery user may use actual capacity to estimate how long a battery will last in a specific application.

Here are some examples of how these 3 types of capacity can be used in battery storage:

• A battery used to power a laptop computer may have an actual capacity of 5 Ah. This means that the battery can deliver 5 amperes of current for one hour, or 50 watt-hours of energy.
• The theoretical capacity of the same battery may be 10 Ah. This means that the battery could theoretically deliver 10 amperes of current for one hour, or 100 watt-hours of energy.
• The rated capacity of the battery may be 8 Ah. This means that the battery is designed to deliver 8 amperes of current for one hour, or 80 watt-hours of energy.

This is because the manufacturing process of battery cells is not perfect, and there will be some variation in the cells even from the same batch, due to factors such as changes in the manufacturing process or the availability of raw materials 

As batteries age, their rated capacity may decrease due to a number of factors, i.e.: 

Self-discharge: Batteries lose a small amount of energy even when they are not in use.

Cycle life: Batteries have a limited number of times that they can be charged and discharged before their capacity begins to decline.

Temperature: Batteries perform best at room temperature. Extreme temperatures can cause the battery to lose capacity or even damage it.

For this reason, it is important to check the battery's rated capacity when you purchase it, and also monitor the battery's performance over time. If you notice that the battery is not lasting as long as it should or used to, it may be time to have it either assessed or entirely replaced.

If you are concerned about the rated capacity of a battery, you should check the manufacturer's warranty. Most warranties will cover the rated capacity of the battery for a certain period of time. The manufacturer will typically replace the battery; if the battery's capacity falls below the rated capacity during the warranty period.