Tech

# Actual Capacity vs Rated Capacity of a Power Bank Have you ever used a Power bank? If you have, you would have noticed that the actual charging capacity of the Power bank is different than the rated one.

### The question is, how different is it?

Today, we will shed some light on the difference between the actual and rated capacity of a Power Bank. We will explain what these terms are and let you know how you can calculate the actual capacity of the Power bank.

## What is the Actual Capacity of a Power Bank?

The actual capacity of the Power bank is dependent on the output voltage available at the USB port. You can get your choice of high voltage and low voltage Anker power banks in Sri Lanka at 3000store.lk.

To understand why this is different, you have to first look at the type of cells used in the Power bank. Usually, these are lithium-ion cells or lithium polymer cells.

The standard voltage of such sales can range from 3.7 V to 3.85 walls. Usually, the cells have a voltage of 3.7 V.

Most Power banks use multiple such cells. However, the voltage is still not equal to the theoretical USB voltage of 5 V.

All the mobiles designed for connection through a USB port are designed to accept a voltage of 5 V.

On the other hand, the power bank can provide a voltage of usually 3.7 W due to the lower voltage of the cells. That is why; the actual charging capacity of the Power bank is usually much lower than advertised.

The advertised numbers are at a voltage of 3.7 V, or the voltage of the inner cells. However, when the mobile needs to be charged at 5 V, the capacity of the Power bank when converted to 5 V is much lesser.

If a power bank is rated for 10,000 MH at 3.7 V, it will only provide 7400 MH at 5 V. That is why; the actual capacity of the Power bank is usually lower than the advertised capacity.

## What is the Rated Capacity of a Power Bank?

The rated capacity of the Power bank is the capacity of the internal cells of the Power bank. For example, if it consists of a 3.7 V cell, it is the capacity that the cell can provide at that particular voltage.

Since the actual amount of power that needs to be delivered to the gadgets is certainly higher, the USB ports are designed for 5V capacity, which significantly reduces the Power bank’s actual capacity.

There are a few other reasons for the lower capacity of the Power bank that we will highlight below.

## Why are Actual Capacity and Rated Capacity different?

We already spoke that most cells in the Power bank are 3.7 V, and the USB is designed for 5 hours of power. Besides this, there are a few reasons that the rated and the actual capacity of the Power bank are different.

We will cover these reasons below so that it is easy to understand how a Power bank functions in actual situations.

### 1. Power loss:

There is a simple equation to calculate the actual capacity of the Power bank, taking into account that USB requires 5V. The equation is as follows:

Actual capacity = (3.7 volts x (Rated capacity) ) / 5V

If you use this equation for a Power bank of 10,000 mAh, you’re likely to get an actual capacity of 7400 mAh.

However, even this does not consider the power loss that happens in the Power bank.

No Power bank is 100% efficient. For that matter, no circuit is 100% efficient either. That is why losses due to the circuit’s inefficiency further reduce the power bank’s capacity.

### 2. Drain current:

Whenever a power source is connected to the circuit, some of the other components might pass on the drain current. Due to the same, there is a constant loss of power as long as the power source is connected to the circuit.

Since the power source in the Power bank is the charge of the battery cell, it is constantly connected to the circuit, and therefore the current drains slowly but constantly.

The effect of this current is that the battery’s capacity reduces further. Sure enough, if you charge the cells again, they will get charged and provide a higher capacity, but it consistently loses power when it is idle or in the standstill mode.

### 3. Battery age:

As the battery cells age, their power loss increases. Their efficiency decreases. The drain current can be higher as well.

Moreover, they might not be able to store the same amount of charge. The voltage they provide can be even lower.

If the voltage they provide is even lower, keeping it in mind, the capacity of the Power bank will reduce even further. That is another reason why the actual capacity of the Power bank is low.

### 4. Storage:

We refer to the battery’s storage and the conditions of the cells inside the battery.

Firstly, whenever power is stored inside the battery’s cells, there is constant heat dissipation. Due to this, the charge inside the battery will be lost, albeit at a slower rate.

Additionally, if the Power bank is stored in an environment that is hot and humid, this reduces the efficiency of the power cells in the battery further. After that, it will be difficult to get the same charge from the Power bank.

It is another reason for the difference between the actual capacity and the rated capacity of the Power bank.

These are the four reasons why there is a difference between the actual charging you get from the Power bank and the one for which it is rated.

The question now arises is, how to know about the actual capacity of the Power Bank?

## How to test the actual capacity of a power bank?

The first thing you need to do is calculate the actual capacity using the equation above. We are once again mentioning this equation for ease of calculation.

Actual capacity = (3.7 volts x (Rated capacity) ) / 5V

This capacity is, however, not the real capacity. That is because of the factors above impact the working of the Power bank. In reality, a Power bank can only work at 85% efficiency.

That is why the number you get from the question should be multiplied by 0.852 factors in this 85% efficiency.

A 10,000 mAh battery will provide you with a real capacity of 6882 mAh.

As the Power bank ages more, this 85% efficiency will move to 80% and reduce even further.

## Conclusion

Thus, the Actual and the Rated Capacity of a Power Bank are certainly different. Now that you are aware of the reasons for the same, you can gain an idea what exactly you can get out of your power bank.