Tested a diverse set of EV battery chemistries, formats, and cooling systems. NCA has triple the energy losses of NMC but half the physical footprint. High-power cycling can be done 5x as frequently using forced-liquid cooling. New methods for ranking EV batteries by energy, volume, and thermal performance.
In addition to individual cells’ capacity utilization and individual cells’ energy utilization, individual cells’ terminal voltage is also an important indicator of the battery pack’s performance. The operating condition is set to discharge the single cell at a 1C rate and reaches the single cell’s discharge cutoff voltage.
The energy utilization of the series-connected battery pack by Cell 1 and Cell 2 can be expressed as 3.1.1.2. Different Capacity between Individual Cells Suppose C1 < C3 and other state parameters of single Cell 1 and single Cell 3 are the same. Single Cell 1 and single Cell 3 initial SOCs are 100%. Combining eqs 2 and 3 can give the battery’s OCV.
The voltage difference analysis approach is proposed to determine the faulty type with different criteria according to three fault characteristics. Diagnosis experiments are implemented to demonstrate the effectiveness of the proposed multi-fault diagnosis technique based on the aging data of the series-connected lithium-ion battery pack.
The influence of the battery capacity difference on the battery terminal voltage is gradually increasing, because the battery capacity, the SOC, and the OCV of the battery are also different in the actual situation, which leads to the difference in the battery terminal voltage.
Theoretical Analysis of Individual Cell Parameter Difference of Series-Connected Battery Pack The common parameter differences among individual cells in series-connected battery packs include Ohmic resistance difference, polarization difference, and capacity difference.