UC San Diego

Lithium-ion batteries anchor transportation electrification and grid-scale energy storage. Usable capacity fades with age. Safe operation, second-life screening, and investment decisions therefore largely depend on the capacity-based state of health (SoH). A reference capacity test measures it directly but is costly and interrupts service. This dissertation connects health estimation to economic value in three parts.The first part estimates SoH for cells cycled under randomized loads mirroring real-world usage. Each cycling stretch is summarized by cell voltage and temperature probability density functions. The expectation–maximization algorithm identifies the assumed bimodal voltage and normal temperature distribution parameters. Identified parameters and statistical descriptors most correlated with SoH feed a support vector regression. On the NASA random walk benchmark it reaches 2.63 % mean absolute error and 3.31 % root mean square error. Its maximum error, 6.77 %, is the lowest of forty algorithm-input combinations. Moreover, the accuracy extends to three more predictable test groups. The second part carries SoH estimation to three retired electric-vehicle packs. These packs supply scarce labels and sense only voltage and current. A Transformer encoder is pretrained as a masked autoencoder on raw cycling data and fine-tuned on labeled stretches. A transfer study shows that corpus composition, not size, decides whether pretraining helps. A pool mixing a wide-SoH public NASA dataset and the second-life packs lowers error on the two lithium-manganese-oxide packs, which make up most of this pool, by up to 35.5 % versus no pretraining. On the chemistry-distinct nickel-cobalt-aluminum-oxide pack, however, the same pool raises error by 41.6 %. The NASA dataset alone is instead the most accurate and most stable source for that pack. The third part turns from battery health to economic worth. A dispatch model maximizes energy-trading revenue subject to a battery model’s constraints. Piecewise linear approximation and McCormick envelopes relax them into a mixed-integer linear program. Vanadium redox flow, sodium-ion, and lithium-ion systems, dispatched for energy time shifting against 2022 California real-time prices, earn aggregated daily revenues of $111.08, $67.63, and $31.17. Higher C-rate and stronger power capability let a system cycle more often and earn more per cycle.