What Is Battery C Rating?

1C means 1 hour discharge time.

2C means 1/2 hour discharge time.

0.5C means 2 hour discharge time.

For most of lithium battery, here is the picture to show the discharge curve in different C rate.

A battery’s C rating is defined by the time of charge and discharge.

C-rate is an important information or data for any battery, if a rechargeable battery can be discharged at that C rating, a 100Ah battery will provide about 100A, then the battery has a discharge rate of 1C. If the battery can only provide a maximum discharge current of about 50A, then the discharge rate of the battery is 50A/100Ah=0.5C.

C-rate (C) = charge or discharge current in amperes (A) / rated capacity of the battery(Ah)

100Ah Lithium Battery C Rate Example

For same 100Ah lithium battery,

1C means 100Ah*1C=100A discharge current available.

1C means 100Ah/100A=1 hours discharge time Capable.

It means the battery can be use for 60minute (1h) with load current of 100A.

2C means 100Ah*2C=200A discharge current available.

2C means 200Ah/100A=0.5 hours discharge time Capable.

It means the battery can be use for 30minute (0.5h) with load current of 200A.

0.5C means 100Ah*0.5C=50A discharge current available.

0.5C means 100Ah/50A=2 hours discharge time Capable.

It means the battery can be use for 120minute (2h) with load current of 50A.

The C rate is very important to know as with the majority of batteries the available stored energy depends on the speed of the charge and discharge currents.