Improved Battery State Estimation Using Novel Sensing Techniques.

Lithium-ion batteries have been considered a great complement or substitute for gasoline engines due to their high energy and power density capabilities among other advantages. However, these types of energy storage devices are still yet not widespread, mainly because of their relatively high cost and safety issues, especially at elevated temperatures. This thesis extends existing methods of estimating critical battery states using model-based techniques augmented by real-time measurements from novel temperature and force sensors. Typically, temperature sensors are located near the edge of the battery, and away from the hottest core cell regions, which leads to slower response times and increased errors in the prediction of core temperatures. New sensor technology allows for flexible sensor placement at the cell surface between cells in a pack. This raises questions about the optimal locations of these sensors for best observability and temperature estimation. Using a validated model, which is developed and verified using experiments in laboratory fixtures that replicate vehicle pack conditions, it is shown that optimal sensor placement can lead to better and faster temperature estimation. Another equally important state is the state of health or the capacity fading of the cell. This thesis introduces a novel method of using force measurements for capacity fade estimation. Monitoring capacity is important for defining the range of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs). Current capacity estimation techniques require a full discharge to monitor capacity. The proposed method can complement or replace current methods because it only requires a shallow discharge, which is especially useful in EVs and PHEVs. Using the accurate state estimation accomplished earlier, a method for downsizing a battery pack is shown to effectively reduce the number of cells in a pack without compromising safety. The influence on the battery performance (e.g. temperature, utilization, capacity fade, and cost) while downsizing and shifting the nominal operating SOC is demonstrated via simulations. The contributions in this thesis aim to make EVs, HEVs and PHEVs less costly while maintaining safety and reliability as more people are transitioning towards more environmentally friendly means of transportation.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120815/1/nassimab_1.pd

An electro-thermal model for a Nickel-Manganese-Cobalt (NMC) Oxide Lithium-ion prismatic cell

This package includes an experimentally validated electro-thermal model of the Nickel-Manganese-Cobalt (NMC) Oxide Lithium-ion prismatic cell. The electrical dynamics of the cell are modeled as a three-state equivalent circuit model whose parameters are characterized as functions of SOC (state of charge) and temperature. The thermal dynamics of the cell are modeled as two states (one interior and one surface). The coupled electro-thermal model captures the state of charge, voltage, surface and core temperatures of the battery.Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000269https://deepblue.lib.umich.edu/bitstream/2027.42/117252/1/NMC_Battery_Model.zipDescription of NMC_Battery_Model.zip : experimentally validated electro-thermal model of the Nickel-Manganese-Cobalt (NMC) Oxide Lithium-ion prismatic cel