The C-rate is a measurement of the **amount of power and discharge time** that a battery can deliver. When a battery has a C-rate of 1, it may discharge its whole capacity in one hour. A battery with a C-rate of 2 can drain its whole capacity in 30 minutes. A battery can discharge its whole capacity in two hours if its C-rate is 0.5. Therefore, if a battery has a C-rate of 1, a 4-kilowatt battery can produce an average of 4 kilowatts and will discharge in an hour. It can produce an average of 16 kilowatts and will discharge in 15 minutes if the C-rate is 4. Additionally, if the C-rate is 0.2, the device may produce 0.8 kilowatts and will discharge in 5 hours.

C-rates control how quickly a battery charges and discharges. A battery’s capacity is typically expressed as 1C, which means that a fully charged battery with a 1Ah rating should deliver 1A for an hour. The same battery should deliver 500mA for two hours on a 0.5C discharge, and 2C for 30 minutes on a 2C discharge. Fast discharge losses shorten the discharge time, and these losses also have an impact on charging times.

**How Can You Measure C-Rate?**

A battery analyzer can be used to measure a battery’s capacity or the amount of energy it can store. The **analyzer measures the amount of time** it takes for the end-of-discharge voltage to be reached when discharging the battery at a calibrated current. The end-of-discharge for lead-acid cells is typically 1.75V/cell, for NiCd/NiMH cells, 1.0V/cell, and for Li-ion cells, 3.0V/cell. An analyzer showing the findings as a percentage of the nominal rating will indicate 100% if a 1Ah battery delivers 1A for an hour. The battery has a 50% capacity if the discharge lasts 30 minutes before hitting the end-of-discharge cut-off voltage. Sometimes a brand-new battery is overrated and produces at or beyond its maximum capacity; other times, it is undervalued and never reaches 100 percent, even after priming.

A greater C rate will result in a **lower capacity measurement** when discharging a battery using a battery analyzer capable of applying varied C rates, and vice versa. The 1Ah battery should theoretically be capable of discharging at the quicker 2C rate, or 2A, in 30 minutes. Since the same amount of energy is dispersed across a shorter period of time, the total should be the same. Internal losses, on the other hand, convert some of the energy into heat and reduce the final capacity to roughly 95% or less. The capacity of the same battery will most likely expand to above 100% when discharged at 0.5C, or 500mA, for two hours.

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