Fundamentals and Applications of Lithium-ion Batteries in Electric Drive Vehicles
by Jiuchun Jiang, Caiping Zhang
4The Prediction of Battery Pack Peak Power
4.1 Definition of Peak Power
4.1.1 Peak Power Capability of Batteries
The battery instantaneous power refers to the product of the terminal voltage of the battery and the current flowing through the electrode in the specific state of the battery. Suppose that the open-circuit voltage (OCV) is UOCV, the internal resistance R, the current controlled by the exterior power supply I0 and the terminal voltage of the battery U1. As Figure 2.13 shows:
Here, UOCV can be obtained from the plot of the battery OCV versus its SOC (Figure 4.1).

Figure 4.1 Plot of OCV versus SOC for lithium manganese oxide batteries.
If the battery is discharged with power P for t s, assuming that the SOC of the battery at time t is SOC′, the open-circuit voltage OCV and internal resistance of the battery are, respectively, UOCV′ and R, and the current It at time t then Equation 4.2 is satisfied:
The terminal voltage of the battery keeps changing because of its charging and discharging with constant power, so the current keeps changing inversely with the voltage. If the ampere hour efficiency of battery charging and discharging is 1, the battery can satisfy the following ...