Study of C rate

C Rate of battery -

A C-rate is a measure of the rate at which a battery is discharged relative to its maximum capacity. A 1C rate means that the discharge current will discharge the entire battery in 1 hour.

The above table shows us the C-Rate by giving the rated capacity and Amps with Discharge/charge time.

C rate importance -

This is a very important parameter to select a specific battery technology for transportation applications, where space availability is critical. Charge and Discharge Current: For practical purposes, the term C-rate is used to express the charge or discharge current relative to the rated capacity.

Formula to calculate C-Rate:

The C rating is misleading concept where C stands for the capacity of a battery usually measured in ampere hours (Ah) indicating the amount of active material within the battery available for discharge. Ampere is the measure of a current and gives the number of coulombs per unit time, so current times time give essentially the amount of charge in coulombs stored within the battery.

Eg: If there is a battery of 200Ah capacity & connected to circuit that draws 200 Amps of current for 30 sec, will this scenario result in loss of battery life?

Solution: Lets say ciruit draws 200 A for 1 hr then according to battery capacity of 200Ah there won't be loss of battery life.

• As, we know Battery life (hr) = `(Capacity (Ah)) / [load(A)]` = 1 hr
• If for the same capacity when ciruit draws 200 A for 30 sec there won't be loss of battery life. But, for 30 sec it will be 0.0083 hr time for ciruit to draw 200 A current.