Semi-Modular Battery BMS With MOSFET Line Current Limiting
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Solution Overview
Problem
Existing battery management systems for lithium accumulator batteries face challenges in balancing currents across multiple cells, ensuring safety and reliability, particularly in high-current applications, due to the need for oversized components and complex architectures that include external monitoring systems, which can lead to inefficiencies and increased risk of overheating or fire.
Innovation Solution
A semi-modular battery management system (BMS) with a detection circuit that includes MOSFETs for each line, capable of independent control of charging and discharging, and featuring a unique disconnection mechanism using MOSFETs and optocouplers to manage voltage and temperature, allowing for precise current limitation and balancing without the need for shunts or magnetic sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If several lower-current components are connected in parallel to withstand high current, then the current handling capacity is improved, but the current balance becomes very difficult to achieve and components must be oversized
Solution Approach 1:
The battery management system is divided into independent line-level protection units, each with its own switching device and detection circuit. This segmentation allows each unit to handle current independently without requiring complex balance control across parallel components, as each line operates autonomously with its own protection mechanisms.
Solution Approach 2:
The system implements protection at the line level rather than requiring the entire battery system to handle excessive current through parallel components. By detecting and isolating faults at the individual line level, the system prevents excessive current propagation without needing oversized parallel components, achieving partial action protection where only affected lines are isolated.
2Measurement precision
If a shunt is used for current measurement, then current detection is achieved, but power consumption increases and requires standby and active modes
Solution Approach 1:
The system replaces traditional shunt-based current measurement (which requires continuous power) with voltage-based detection methods. By measuring voltage drops across known resistances or using voltage dividers, the system achieves current detection without the continuous power consumption of shunt resistors, eliminating the need for standby/active modes.
Solution Approach 2:
The detection circuit utilizes existing voltage signals in the battery system rather than requiring separate current measurement infrastructure. By leveraging the natural voltage drops that occur during normal operation and using these for detection purposes, the system achieves self-service current monitoring without additional power-consuming components.
3Reliability
If the tripping current is set high to handle short-circuit current, then protection against short circuits is improved, but protection is lost when internal resistance increases with aging or low temperature
Solution Approach 1:
The system continuously monitors battery parameters including voltage, temperature, and current, and uses this feedback to dynamically adjust protection thresholds. By comparing real-time measurements against stored reference values and historical data, the system adapts tripping currents to account for aging effects and temperature variations, maintaining reliable protection across different operating conditions.
Solution Approach 2:
The system changes protection parameters dynamically based on operating conditions. Tripping currents and voltage thresholds are adjusted according to temperature measurements and battery state of charge, allowing the system to maintain appropriate protection levels whether the battery is new or aged, hot or cold, charged or discharged.
4Measurement precision
If a complex BMS architecture with external monitoring systems is used, then monitoring capability is improved, but component size and system complexity increase
Solution Approach 1:
The system merges monitoring and protection functions into integrated line-level units that are directly embedded in the battery architecture. Rather than using separate external monitoring systems, each battery line has its own combined detection and switching device, eliminating the need for complex external infrastructure while maintaining comprehensive monitoring capability.
Solution Approach 2:
The detection circuits and switching devices are designed to perform multiple functions simultaneously: voltage monitoring, current detection, temperature sensing, and fault isolation. This multi-functionality allows a single integrated component to replace what would otherwise require multiple separate external monitoring devices, reducing overall system complexity while enhancing monitoring capabilities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively protects against short circuits, overcurrents, and deep discharge by activating disconnection when thresholds are reached, maintaining battery functionality even with faulty cells, while reducing component size and power consumption, thus enhancing safety and efficiency.
Implementation Method 1
electronic components limiting the current at the load
Implementation Method 2
a device for monitoring the voltage and temperature of a cell element
Data Source
AI summary
The present invention relates to a system for managing accumulator batteries (BMS) of a semi-modular element comprising a plurality of lithium cell elements connected in series to form a line, and comprising at least two parallel lines constituting the semi-modular element, and at least one detection circuit characterized in that the detection circuit comprises at least one discharge or short-circuit detection device and at least one device for monitoring the voltage and temperature of at least one, and preferably all, of the cell elements, the detection circuit controlling a circuit breaker device comprising one switching device per line.