8: Discharge characteristics Part 2

Lithium-ion batteries will deteriorate due to charge and discharge.

When taking a look at the transition of 1C charge and discharge at room temperature with its degree as the cycle characteristics, the internal resistance also increases due to charge and discharge cycles, so it is be estimated that not only the capacity simply will decrease but also the discharge rate characteristic and the discharge temperature characteristic will change.
According to the data published by manufacturers of lithium-ion batteries, 1C charge and discharge at room temperature is common.

Manufacturers usually specify the capacity on the specification with the capacity at 0.2C discharge, but it means that the capacity value of 1C discharge estimates the capacity value less for 0.2C discharge.
When performing a cycle test with 0.2C discharge, it will take 5 times longer to discharge and it will also take a long time to acquire data.
For this reason, a cycle is performed with 1C discharge and a method of periodically performing 0.2C discharge is taken, and in fact the lithium-ion cell deteriorates more rapidly with 1C discharge rather than 0.2C discharge.

About the performance the batteries should have
Regarding batteries, the battery manufactures generally disclose only limited data.
However, when comparing the manufacturers’ data sheet, specification of lithium-ion batteries will be seen.
In terms of the performance of lithium-ion batteries,if it is possible to spend for it, it is possible to make a lot of demands.

Using a very large battery at low current in order to discharge a large current at low temperature is not practical in terms of cost and size and so on.

By reviewing the specifications and performance required for lithium-ion batteries, it is possible to ease requirements.
For example, if the minimum required performance is guaranteed, there is no problem with actual operation.
As long as it is not used outside in a cold area, there should be many cases where there is no problem if the low temperature side moves at 0℃.

The maximum current also requires a large current when starting the motor, but it is not necessary except for the rising of the rotation.
Although the maximum current value is necessary for designing the protection circuit, it is not necessary to consider the capacity value.
Together with our customers, our company will consider and design a practical battery pack at low cost.



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