Battery pack aging channel

Though varieties of battery pack-level models can be developed, their reliability and accuracy can be a concern referring to the lack of a standard procedure or guidance . The pack-level aging models can be derived either from real-life on-road vehicles or lab-level investigations [7, 8].

Impedance growth of an aged battery pack with cells connected in series is simply the sum of the impedance growth of each cell, while capacity loss of an aged pack is more complex. Hence, we will only focus on capacity loss of battery packs and impedance growth of single cells will not be addressed in this paper when we refer the term “cell aging”.

Experimental results show that the lifetime prediction errors are less than 25 cycles for the battery pack, even with only 50 cycles for model fine-tuning, which can save about 90% time for the aging experiment. Thus, it largely reduces the time and labor for battery pack investigation.

The cells are connected in series at the beginning of the second stage, and the environment is kept unchanged. The battery pack is cycled 200 time at a 1C charge and discharge rate, during which it is also rested for 10 days after the 60th cycle so as to simulate a real pack aging process which should also consider calendar aging.

Among others, it is conceivable to use the battery aging dataset to derive degradation models based on semi-empirical or machine-learning approaches or to use the raw cycling data to test and validate SoC or cell impedance estimators. Graphical abstract of the battery degradation study and the generated datasets.

The aging experiments for battery cells and the battery pack are carried out. The aging process consists of constant current charging and constant discharging with a rest between them. The battery is made of LiFePO 4 (LFP) cathode and carbon anode; the nominal capacity is 100 Ah.