What Is C Rate In Battery, Why It Is Important, C Rate Calculation

Hello guys, welcome back to my blog. In this article, I will discuss what is C rate in battery is, why it is important, the C rate calculation in a battery, and what is E rate in the battery is. battery specification.

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What Is C Rate In Battery

Hybrid and electric vehicles include a high-voltage battery pack that consists of separate modules and cells arranged in series and parallel. A cell is the smallest packaged form, a battery can handle, and is typically on the order of one to six volts. A module consists of several cells commonly connected in either series or parallel. A battery pack is then created by connecting modules together, also either in series or parallel.

In explaining batteries, the discharge current is often described as a C-rate in order to standardize battery capacity, which is usually very diverse between batteries. A C-rate is a measurement of the rate at which a battery is discharged comparable to its full capacity. A 1C rate indicates that the discharge current will discharge the whole battery in 1 hour.

For a battery with a capacity of 100 Ah, this correlates to a discharge of 100 Amps of current. A 5C rate for this battery will be 500 Amps, and a C/2 rate will be 50 Amps. Likewise, an E-rate represents the discharge power. A 1E rate is the discharge power to discharge the whole battery in 1 hour.

Applications that need a C rate of battery

There are an increasing number of applications and gadgets on the market that need a greater C Rate discharged battery. These contain industrial and customer applications like robotics, RC models, drones, and vehicle jump starters. All these applications need a powerful energy blast in a short period of time.

A battery’s charge and discharge rates are managed by battery C Rates. The battery C rating is the measurement of the current at which a battery is charged and discharged. The capacity of a battery is generally rated and labeled at the 1C Rate (1C current), this means a fully charged battery with a capacity of 10Ah should be able to provide 10 Amps for one hour. That same 10Ah battery being discharged at a C Rating of 0.5C will provide 5 Amps over two hours, and if discharged at a 2C Rate it will provide 20Amps for 30 minutes. The C rating of a battery is important to know as with the majority of batteries the available stored energy relies on the speed of the charge and discharge currents.

C rate for different hours

C Ratings	Time
30 C rate	2 minutes
20 C rate	3 minutes
10 C rate	6 minutes
5 C rate	12 minutes
2 C rate	30 minutes
1 C rate	1 hour
0.5 C rate or C/2	2 hours
0.2 C rate or C/5	5 hours
0.1 C rate or C/10	10 hours
0.05 C rate or C/20	20 hours

The above chart illustrates the various battery C Rates along with their assistance times. It is necessary to know that actually though discharging a battery at various C Rates should utilize the same calculations as a similar amount of energy, in fact, there are probably to be some inner energy losses. At higher C Rates some of the power (energy) can be lost and turned into heat which can result in reducing the capacity by 5% or more.

To obtain a politely good capacity reading, manufactories generally rate alkaline and lead-acid batteries at an extremely low 0.05C or a 20-hour discharge. Actually at this slow discharge rate, lead-acid rarely achieve a 100 percent capacity as the batteries are overrated. Manufactories deliver capacity offsets to adjust for the differences if discharged at a higher C rate than specified.

How to find the C rating of the battery?

Smaller batteries are typically rated at the 1C rating, which is also understood as the one-hour rate. For instance, if your battery is marked 3000mAh at the one-hour rate, then the 1C rating means 3000mAh. You will normally find the C rate of your battery on its title and on the datasheet of the battery. Various battery chemistries will occasionally display various C rates, for example, lead-acid batteries are typically rated at a very lower discharge rate usually 0.05C, or a 20-hour rate.

The chemistry and structure of your battery will decide the highest C rate of your battery, lithium batteries for example can tolerate vastly higher discharging C Rates than different chemistries such as alkaline. If you cannot see the battery C rating on the title or datasheet we recommend reaching the battery manufacturer instantly.

How to estimate the C rate of the battery or cell

A battery’s C Rating is specified by the rate of the period in which it carries to charge or discharge. You can raise or decrease the C Rate and as a result, this will impact the period it takes the battery to discharge or charge. The C Rate discharge or charge time shifts in respect to the rating. 1C is equivalent to 60 minutes, 0.5C to 120 minutes, a 2C rating is equivalent to 30 minutes, and just things you can read from the above table.

The formula is easy,

t = Time
Cr = C Rate
t = 1 / Cr (to view in hours)
t = 60 minutes / Cr (to view in minutes)

30C Rate Example

2300mAh Battery
2300mAh / 1000 = 2.3A
30C x 2.3A = 69A available
60 / 30C = 2 minutes

2C Rate Example

2300mAh Battery
2300mAh / 1000 = 2.3A
2C x 2.3A = 4.6A available
1 / 2C = 0.5 hours
60 / 2C = 30 minutes

0.5C Rate Example

2300mAh Battery
2300mAh / 1000 = 2.3A
0.5C x 2.3A = 1.15A available
1 / 0.5C = 2 hours
60 / 0.5C = 120 minutes

How to calculate the output current, power, and energy of a battery based on its C rating

Er = Rated energy (Ah)
Cr = C Rate
I = Current of charge or discharge (Amps)
I = Cr * Er
Cr = I / Er

This was about “What Is C Rate In Battery“. I hope this article may help you all a lot. Thank you for reading.

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Chetan Shidling

Automotive | Technical Blogger | Engineer | Content Creator

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