What happens if the discharge rate of a lithium battery exceeds the original specified discharge rate?
The so-called charge (discharge) rate refers to the time required to fully discharge (charge) the entire capacity of the charge, as the standard speed for charging (discharge). It is generally used to indicate the rate of charging (discharging), for example, a two hour rate discharge refers to using a current of 0.5C to discharge the full capacity of the battery in two hours. The 20 minute rate indicates that the rated battery capacity is fully discharged within 20 minutes using a current of 3C. In the manufacturer's battery specifications, the hourly rate is often used to represent the standard discharge time. As long as it is converted based on the rated capacity, the standard discharge current can be determined. Usually, the rated capacity provided by the manufacturer is measured at a temperature of 20 ℃, while the discharge is measured at a 5-hour rate of 0.2C.
We all know that there are corresponding charging and discharging current requirements for lithium batteries when they leave the factory. It is recommended to use the batteries under the specified requirements. If the requirements are not followed, the discharge rate of lithium batteries will be higher than the original specified discharge rate, which may pose certain risks. Experiments have shown that the discharge systems of 15C pulse discharge and 15C continuous discharge have completely different effects on lithium batteries. The capacity decline of lithium batteries with 15C pulse discharge is very fast, and after 40 charges and discharges, 15C discharge cannot be carried out again, but 1C discharge can still be carried out. The capacity degradation of 15C continuous discharge batteries is relatively slow, and they can still discharge at 15C after 60 cycles, but the degradation rate of 1C rate is faster than that of 15C pulse discharge.
From the above analysis, we can see that both the charging current and the charging cutoff voltage have a value. When the charging current or voltage exceeds this value, the battery degradation will accelerate. For the above battery, the values are 1C and 4.2V. When the charging current and cutoff voltage exceed this value, the battery degradation will accelerate; When it is less than this value, increasing the charging current and cutoff voltage will not significantly increase the decay rate of the battery.
Overall, the discharge rate of lithium batteries exceeding the original specified discharge rate will affect the battery life, and in extreme cases, it can still cause danger of battery damage. Usually, discharge at different rates such as 0.2C, 0.5C, 1C, 5C, and 10C is performed based on different battery types or battery usage requirements.