Browse Topic: Battery cell chemistry
This study addresses safety concerns within the rapidly evolving Electric Vertical Takeoff and Landing (eVTOL) aircraft domain, focusing on efficient tools to quantify uncertainties in lithium-ion battery behavior - a critical aspect of eVTOL. One major issue with quantifying uncertainty is the prohibitive computational cost associated with many queries of an expensive-to-evaluate computational model. This work employs three physics-based battery models models of varying fidelity and cost to estimate the mean and the variance of the selected quantities of interest through a multifidelity method to reduce the computation cost. By combining information from multiple cheaper, lower-fidelity models through the Multifidelity Monte Carlo method, we significantly reduce the number of high-fidelity samples required for a prescribed mean-squared error, consequently reducing computational costs down to a tractable level. The proposed methodology is applied to estimate the mean and the variance of the battery temperature and voltage, accounting for uncertainties in flight conditions and materials. The first example focuses on a 580-second flight and is benchmarked against a standard Monte Carlo sampling technique. Results indicate a notable fourfold speed-up using the Multifidelity Monte Carlo method compared to the standard Monte Carlo method for the same mean-squared error for the voltage estimate. To showcase the method's generality, the multifidelity method is then applied to a longer flight of 3580 seconds for estimating the mean and the variance and utilizing these statistics to approximately estimate the probability of the flight completion. This demonstrates the adaptability of the methodology to various power profiles and considered uncertainties, with potential extensions to any battery chemistry. In conclusion, the presented multifidelity method offers a robust approach to enhance eVTOL safety by efficiently estimating uncertainties in battery behavior.
xEVs involved in incidents present unique hazards associated with the high voltage system (including the battery system). These hazards can be grouped into three categories: chemical, electrical, and thermal. The potential consequences can vary depending on the size, configuration, and specific battery chemistry. Other incidents may arise from secondary events such as garage fires and floods. These types of incidents are also considered in the recommended practice (RP). This RP aims to describe the potential consequences associated with hazards from xEVs and suggest common procedures to help protect emergency responders, tow and/or recovery, storage, repair, and salvage personnel after an incident has occurred with an electrified vehicle. Industry design standards and tools were studied and where appropriate, suggested for responsible organizations to implement. Lithium ion (Li-ion) batteries used for vehicle propulsion power are the assumed battery system of this RP. This chemistry is the prevailing technology associated with high voltage vehicle electrification today and the foreseeable future. The hazards associated with Li-ion battery chemistries are addressed in this RP. Other chemistries and alternative propulsion systems including hydrogen fuel cells are not considered in this version of SAE J2990. Recommendations for hazards associated with hydrogen vehicles can be found in SAE J2990/1.
Semiconductor chip technology has miniaturized by leaps and bounds over the past couple of decades, enabling the modern era we live in with smartphones, tablets, and small electronic gadgets everywhere. However, battery technology, which provides the lifeblood to power these devices, has been at a near standstill since the commercial availability of lithium-ion batteries in the early 1990s. In no other application is this discrepancy more profound than in medical implants.
There is a great need for energy sources that can power unattended sensors for more than a decade. Unattended sensors can be located in harsh and remote locations that are often dangerous for personnel maintenance and power source replacement. The power source must last the lifetime of the sensor. Unlike chemical batteries, the higher energy densities of radioisotopes allow the sensors to operate for infrastructure lifetimes (~150 years). Isotope batteries (iBATs) have the potential to become reliable, robust, and maintenance-free power sources for remote, long-term, low-power sensors. iBATs are different from chemical batteries because they are self-contained energy sources using radioisotope decay.
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