How to understand the cycle life of Lifepo4 cell?
A very important parameter of lifepo4 cell is cycle life. How should we understand the cycle life of lifepo4 cell?
The original specifications we obtain usually read as follows:
(Image source: MB31 Specification, for the full document, please click: MB31 Specification)
8000 cycles, 70% SOH, SOH definition: State of health, share a picture of the health of an iPhone battery:
First, let's define the battery cycle，
A cycle means the cell being charged and discharged once according to the charging and discharging standards. The cell shall be charged and discharged once according to the specified charging and discharging standards as a cycle. The cycle includes short-term normal charging or a combination of regenerative charging and discharging processes. In the charging process,sometimes there is only normal charging and no regenerative charging. The discharge can be formed by combining some partial discharges.--Described in the EVE specification.
To put it simply, 0.5P full charge and discharge is a battery cycle.
The cycle life of MB31 can be expressed in this way: at 25 degrees Celsius, the MB31 battery cell is charged and discharged at a power of 0.5P. After 8,000 cycles, the actual remaining capacity is greater than or equal to 70%.
(The capacity of the battery will decay during use, just like our mobile phones. The time it takes to fully charge becomes faster, and the usage time also becomes shorter. 70% = current actual capacity / nominal capacity.)
(Another interesting question: How to define the capacity of a battery?
This is test data obtained under harsh testing conditions. So, what factors affect the service life of battery cells?