A Deep Look Into General Motors' Battery Management System (BMS)

Battery management system for electric vehicles that improves reliability of battery strings by selectively isolating faulty modules. Each battery module has a series switch and a bypass switch. The management module monitors the modules and keeps the series switches closed and bypass switches open for normal operation. If a fault is detected in a module, the management module closes the bypass switch to isolate the faulty module while keeping the series switch open to maintain charge balance in the other modules. This allows continued use of the remaining healthy modules while isolating the faulty one.

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A reference electrode assembly for secondary lithium ion batteries that can be integrated into commercial battery cells for real-time monitoring and optimization of charging and discharging. The assembly has a porous membrane with a carbon layer and a reference electrode layer deposited on one side. The carbon layer provides conductivity to an external connector tab, allowing the reference electrode potential to be measured. This enables individual electrode potentials and state of charge monitoring during cycling. The carbon layer facilitates manufacturing using printing techniques.

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Determining the state of charge (SOC) and state of health (SOH) of a mixed chemistry battery having modules with different chemistries connected in series. The SOC of the battery module is calculated based on the SOC of a reference module with a chemistry that has a distinct voltage variation. If the estimated battery SOC is within a tolerance of the reference SOC, it is set equal to the reference SOC. This provides accurate SOC determination for chemistries like LFP that have flat voltage curves. The battery SOH is also calculated using the reference SOC.

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Managing thermal propagation in battery electric vehicles with modular battery packs to prevent runaway thermal events from spreading and disabling the entire pack. The vehicle has multiple distinct battery cell module groups, each separately providing power. A controller monitors the groups, detects abnormal events, and responds like controlling cooling, limiting operation, or pulling over. This isolates failures to prevent propagation instead of full pack shutdown.

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Battery temperature regulation using anisotropic materials like graphite to create controllable temperature regions inside batteries and packs. The anisotropic materials like graphite foils are sandwiched between structural layers in the battery. When current flows, the graphite heats up due to anisotropic thermal conductivity. When current stops, the graphite cools passively. This provides localized heating and cooling to prevent issues like lithium plating and uneven wear. The anisotropic materials can be grouped and independently controlled for customized temperature profiles.

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A battery system and control method to detect and handle thermal runaway in a multi-cell battery pack with integrated cell sense circuits. The method involves a two-level logic executed by the battery controller. During low power/off mode, a first level runs continuously in the battery control module to monitor cell data from embedded cell measurement units. It uses variable sampling rates based on battery state. If a cell shows anomalous data, the second level is triggered to diagnose and mitigate a possible thermal runaway. This second level runs in the cell measurement units during normal battery operation. It uses faster sampling rates and more detailed analysis to quickly detect and respond to thermal runaway.

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Detecting and mitigating thermal runaway in vehicle battery packs to prevent cell short circuits from causing fires. The method involves monitoring cell voltage and temperature at regular intervals. If voltage decreases with modulation coinciding with temperature rise, it indicates a cell short. Further analysis using wavelet transforms and power spectra is done to confirm thermal runaway. Alarms are triggered when spectra exceed thresholds. Mitigation actions like stopping charge, releasing pressure, cooling, and notifications are initiated.

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Distributed feedback control system for monitoring battery modules and attendant hardware of wireless battery management systems. The system allows remote monitoring of battery modules and packs without manual connection. It uses a manager device that selects modules to collect data from. The manager connects wirelessly to the modules using their unique IDs. It downloads device data and switches operating modes. This enables simultaneous wireless monitoring of multiple modules without manual plugging.

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A dynamic control system for battery cells that accurately and efficiently maintains cell temperature, voltage, and current during charging and discharging to mitigate aging and capacity loss. It uses reduced order models of electrochemistry and heat generation, feedback control, model predictive control, and feed-forward control to dynamically set target parameters and control a heat exchanger like a heat pump. The system monitors cell parameters, generates internal variables, estimates heat generation, calculates work needed, and sets heat pump parameters to meet the target. This allows precise and real-time control of cell temperature, voltage, and current during charging/discharging without external cooling.

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A cooling system for electric vehicles that selectively cools components like batteries without wasting energy. The system uses multiple low temperature radiators, valves, and separate coolant circuits for the battery and the rest of the vehicle. A controller routes coolant flow through the radiators based on ambient temperature, comparing it to target ranges. This allows selectively cooling the battery when needed without always cooling the whole vehicle. This improves efficiency compared to constantly cooling the entire vehicle.

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Intelligent battery charging system for electric vehicles that predicts and mitigates charging behavior to extend battery life. The system monitors battery state of charge (SOC) and temperature during charging. It tracks low and high SOC excursions, charging at low temperatures, and time at high temperatures. If these exceed thresholds, it instructs the driver to limit charging outside those ranges. This prevents excessive cycling and temperature extremes that degrade battery life. The system also calculates risk based on charge history and provides feedback to the driver.

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Determining the association between a battery module and a battery sub-pack in a multi-cell electrical energy storage system. The method involves using voltage sensors mounted on each cell monitoring unit (CMU) that is electrically connected to a battery module. These voltage sensors detect the voltage across the cell groups in the module. By comparing the detected voltages from multiple modules in a sub-pack, the association between the modules and sub-pack can be determined. This allows identifying which modules belong to which sub-packs if the physical connections become disordered or mixed up.

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A method for accurately estimating battery capacity over time without needing a single consistent anchor point. It involves tracking battery data like voltage, current, and state of charge over time. If the integrated current error exceeds a threshold, it resets the current values using anchor points from the earlier time period. This prevents accumulating error when using a single anchor point. By combining and resetting data sets recursively, it estimates battery capacity using a slope of integrated current versus voltage.

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A temperature sensor for rechargeable batteries that accurately measures cell temperature in a non-invasive way. The sensor is integrated into the battery cell itself by attaching a resistive sensing element, electrodes, and separator layers directly to the cell separator. This allows the sensor to be immersed in the electrolyte and experience the same temperature as the electrodes. The sensor elements are made porous to match the separator permeability. This prevents electrolyte flow restrictions or gas trapping. A reference electrode is also integrated into the sensor. This enables accurate temperature measurement by compensating for resistance changes due to electrode plating. The sensor can be used to monitor battery cell temperature for charging, discharging, and cycle life analysis.

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Rechargeable energy storage system with improved wireless communication between the battery cells and the battery management system. The system uses a signal directing component like an antenna, reflector, or lens integrated into the battery module cover, interconnect board, or battery management unit. This component is oriented to direct the radio frequency signals through the low loss region of the battery pack instead of the high loss region. This reduces signal losses and improves reliability compared to transmitting through the entire pack. The integrated directing component reduces packaging space and assembly steps compared to adding it to the cell monitoring board.

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Improving battery parameter and state estimation accuracy in electric vehicles by injecting current oscillations into the battery pack's constant charging/discharging current when conditions indicate insufficient frequency content. The method involves estimating battery parameters like resistance and open-circuit voltage using a battery state estimator. If the parameter estimation accuracy degrades due to low frequency content, the controller selectively adds oscillations to the constant current. This increases frequency content and prevents parameter drift.

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Modular vehicle battery system with removable segments that allows easy scaling of battery capacity and voltage. The battery consists of multiple individually housed batteries connected by switches. A battery management module controls the switches to connect cells to the output terminals and provide the desired capacity and voltage. The removable segments enable expanding or reducing the battery size by adding or removing battery modules. This allows customization of battery capacity and voltage for different vehicle needs. The removable segments also allow easy battery replacement or service without removing the entire battery.

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Monitoring and preventing damage to weaker or faulty cells in a distributed battery pack to extend battery life. The system uses a battery controller to periodically request cell voltage data from the pack's voltage monitoring module. It analyzes the cell voltages to detect weaker cells with lower charge capacity or drooping cells with voltage droop. If weaker cells are found, the controller takes actions like isolating the cells or derating the pack to prevent overloading and further degradation. This allows using the remaining good cells in the pack while mitigating risks to the problem cells.

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Controlling internal circulating current between batteries in a battery system to prevent lithium plating and other issues. It involves monitoring battery states, identifying the weakest pack, limiting internal current to that pack, and disconnecting it when current exceeds limits. Techniques like feedforward control, feedback control, and resistive loads are used to manage current flow during light loads and high loads. The goal is to prevent uncontrolled current flow between packs that can charge weak ones and cause plating.

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Proactive thermal conditioning of rechargeable energy storage systems (RESS) in vehicles to improve cooling efficiency, reduce energy consumption, and extend battery life. The method involves accurately computing the heat generated by the RESS and proactively cooling the coolant to remove that heat before it builds up. A controller calculates the heat generation based on factors like current, voltages, and resistances. It then operates the cooling system to cool the coolant to a target temperature that will extract the computed heat amount. This feedforward control allows incremental cooling instead of waiting for temperature spikes, improving cooling efficiency compared to passive or over-cooling approaches.

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