Cycle time is a useful metric that can help estimate when a test will be completed.
Cycle time measures how long it takes to complete one cycle. This is commonly estimated by calculating the nominal time duration using each step's C rate. However, the cycle time decreases with each cycle because of decreasing capacity, variations in CV charging, and/or hitting voltage limits. These variations make it difficult to produce an accurate estimate of when a test will be completed.
One use case of cycle time is to estimate the remaining time in a test. For example, if we wanted to estimate how much time it will take for the green trace to go from 800 to 1000 cycles, we can plot Total Cycle Time vs Cycles. We can estimate the remaining test time as (3 hours)*(200 cycles) = 600 hours.
Another use case is estimate the cycle time at a certain % of the initial discharge capacity. In this example, we can plot Discharge Capacity vs. Cycles, and then annotate a line at 80% capacity retention. For these three cells, it is now clear how much time is spent charging and discharging during each cycle. This is useful for predicting the cycle time at lower capacities, like 60% or 40%.
Try it yourself:
1. Plot 'Total Cycle Time' on the x Axis, and 'Discharge Capacity' on the y Axis.
2. Alternatively, try plotting 'Cycle Number' on the x Axis, and 'Total Cycle Time' on the y Axis.
