What Is Active And Passive Cell Balancing | Why Cell Balancing Is Required

Hello guys, welcome back to my blog. In this article, I will discuss what is active cell balancing, what is passive cell balancing, why cell balancing is required in lithium-ion batteries, etc. Each and everything I will try to explain in a simple way.

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Cell Balancing

What Is Active And Passive Cell Balancing | Why Cell Balancing Is Required


The cell balancing is a very important thing when it comes to lithium-ion batteries. Nowadays, lithium-ion batteries are used in electric vehicles. Celling balancing means making the terminal voltage of all the lithium-ion cells equal by charging or discharging each cell. The cell balancing is done by BMS(Battery Management System), it is a microcontroller used to maintain the lithium-ion batteries. The battery management system is required only for lithium-ion batteries. The purpose of the battery management system is celling balancing, protecting the battery from short circuits, measuring the state of charge, state of health, etc.



Proper cell balancing is required otherwise the life span of lithium-ion battery decreases. The cell balancing is classified into two types, such as active cell balancing and passive cell balancing. Well, let's see what is active cell balancing and what is passive cell balancing.

What causes cell unbalancing?

The cell becomes unbalance due to internal resistance and temperature. As the life-span of the cell increases the internal resistance will also vary this causes the cell to unbalance. The cell may also become unbalanced due to the surrounding temperature.

Active Cell Balancing


In an active cell balancing, the voltage across each cell is made equal without wasting any energy through a resistor. Suppose consider there are two cells of terminal voltage 4v and 6v. The 4v cell will be charged and 6v cell will be discharged through the same methods, later the voltage across each cell will become 5v.



Let's see one more example, Person 'A' has 20-liter water in the tank, Person 'B' has 10-liter, and Person 'C' has 30-liter, now to make equal water in all the three tanks, the person 'C' share water of 10 liters to Person 'B', now the water in the tanks becomes equal. This is what the active cell balancing does.

The active cell balancing makes the voltage of each cell equal without wasting any energy.

Passive Cell Balancing


What Is Active And Passive Cell Balancing | Why Cell Balancing Is Required


In a passive cell balancing, the voltage across each cell is made equal by wasting the energy through a resistor. Suppose, consider there are two cells having the terminal voltage of cell one 4 volts and the terminal voltage of the second cell 5v. The 1v of the 2nd cell is dropped through the resistor to make voltages of each cell equal.

Well, let's see one more example, Person 'A' has 40-liter water in a tank and Person 'B' has 50-liter water in a tank, to make water equal in both tank, the person 'B' waste 10-liter of water to make 40-liter. This is what passive cell balancing does.

Why Cell Balancing Is Required

What Is Active And Passive Cell Balancing | Why Cell Balancing Is Required




The cell balancing is required to increase the life-span of battery, to make the motor run efficiently, to increase the efficiency of lithium-ion batteries, etc. 

I hope this article may help you all a lot. Thank you for reading.
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