Keep the discharge power unchanged, because the voltage of the battery continues to drop during the discharge process, so the current in the constant power discharge continues to rise. Due to the constant power discharge, the time coordinate axis is easily converted into the energy (the product of power and time) coordinate axis.
To ensure the safe and stable operation of lithium-ion batteries in battery energy storage systems (BESS), the power/current is de-rated to prevent the battery from going outside the safe operating range.
Constant current discharge is the discharge of the same discharge current, but the battery voltage continues to drop, so the power continues to drop. Figure 5 is the voltage and current curve of the constant current discharge of lithium-ion batteries.
When removing the load after discharge, the voltage of a healthy battery gradually recovers and rises towards the nominal voltage. Differences in the affinity of metals in the electrodes produce this voltage potential even when the battery is empty. A parasitic load or high self-discharge prevents voltage recovery.
In the literature, only a few papers have considered battery aging as a function of the charge/discharge current rate, but they agree that a higher current rate leads to faster battery aging. In any case, all of the tests have been conducted in a climactic chamber with a constant room temperature.
According to the battery specification reported in Table 1 this kind of cells can be discharged up to 10C. The choice to limit the current rate to 5C is due to the fact that for higher current rates the voltage drop over the internal resistance becomes comparable with the voltage range usable for the battery.