Common terminology of Lithium-ion battery (4)

Discharge platform

After the lithium-ion battery is fully charged, discharge to 3.6V and the capacity is recorded as C1. And then discharge to 3.0V and the capacity is marked as C0. C1/C0 is called the discharge platform of the battery.
Industry standard of 1C discharge platform is more than 70%.


Discharge rate

The discharge current of the battery is usually expressed by "discharge rate", that is, the discharge rate of the battery is expressed by the discharge time or the number of hours required for fully discharge at a certain discharge current. Therefore, the shorter the discharge time, the higher the discharge rate, and the greater the discharge current. (Discharge rate = rated capacity / discharge current)
According to the discharge rate, it can be divided into low rate (< 0.5C), medium rate (0.5-3.5C), high rate (3.5-7.0C), ultra-high rate (> 7.0C)
For example, if the rated capacity of a battery is 20Ah, and 4A current is used to discharge, it will take 5h to fully discharge, that is to say, discharge at the rate of 5 times, which is indicated by the symbol C/5 or 0.2C, which is low rate.


Memory effect
Memory effect is related to Ni Cd battery. Because the negative electrode in traditional process is sintered and the cadmium grain is big, if the nickel cadmium battery is recharged before they are completely discharged, the cadmium grains are easy to gather into blocks and form a secondary discharge platform when the battery is discharged.

The battery will store this discharge platform and use it as the end point of discharge in the next cycle, although the capacity of the battery itself can make the battery discharge to a lower platform. The battery will only remember this low capacity in the subsequent discharge process. Similarly, in each use, any incomplete discharge will deepen this effect and make the battery capacity lower.        
There are two ways to eliminate this effect, one is to use low current deep discharge (such as 0.1C to 0V) and the other is to charge and discharge with high current (such as 1C) several times.

Ni MH battery and Li ion battery have no memory effect.

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