Modular Battery String Control for Scalable Pack Balancing
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Solution Overview
Problem
Large moving work machines require complex battery systems with multiple battery strings connected in parallel, which poses challenges in safety, reliability, and performance due to potential imbalances in state of charge across battery cells.
Innovation Solution
A control system comprising identical battery strings, contactors, sensors, and an electronic controller that allows individual control of each battery string to meet system requirements based on sensor measurements, enabling flexible scaling of the battery system by adding identical battery strings without reconfiguring the controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery strings are connected in parallel to provide sustained energy power, then the power output and energy capacity are improved, but the system complexity and control difficulty increase
Solution Approach 1:
The battery system is segmented into multiple identical battery string modules, each with its own contactor and sensor. This modular segmentation allows the system to scale power output by adding more identical units while maintaining manageable complexity through standardized interfaces and independent control of each segment.
Solution Approach 2:
A universal electronic controller is designed that can manage any number of identical battery string modules through standardized communication and control protocols. The controller performs multiple functions including monitoring, balancing, and power management across all strings, reducing overall system complexity despite increased power capacity.
2Power
If multiple battery strings are connected in parallel to increase power output, then the energy capacity is improved, but the reliability and safety decrease due to state of charge imbalances
Solution Approach 1:
Each battery string is equipped with sensors that continuously monitor voltage, current, and state of charge. This feedback is sent to the electronic controller, which uses the data to detect imbalances between strings and adjust operation accordingly, preventing unsafe conditions while maintaining high energy capacity.
Solution Approach 2:
The system performs preliminary balancing actions by selectively controlling individual battery strings before critical imbalances develop. The controller monitors state of charge levels and preemptively adjusts current distribution to prevent harmful equalization currents, ensuring safety and reliability are maintained throughout operation.
3Adaptability or versatility
If battery strings with different state of charge are connected in parallel, then the system flexibility is improved, but harmful factors increase due to high equalization currents
Solution Approach 1:
The system dynamically controls the connection and disconnection of individual battery strings through electronic contactors. Rather than statically connecting all strings in parallel, the controller dynamically adjusts which strings are active based on their state of charge and system requirements, preventing harmful equalization currents while maintaining operational flexibility.
Solution Approach 2:
Electronic contactors serve as intermediaries between the battery strings and the load. These contactors enable the controller to selectively connect or disconnect individual strings, acting as a mediator that prevents direct parallel connection of strings with significantly different state of charge, thereby eliminating harmful equalization currents while preserving system flexibility.
Data Source
AI summary
Various control systems and methods are discussed including a method of controlling a battery pack id disclosed, the method optionally including: providing a plurality of battery strings each having an identical construction, each battery string including a plurality of battery cells connected in series, wherein each of the plurality of battery strings is connected to a respective pair of contactors; providing a sensor configured to measure at least one of a voltage and a current of each of the plurality of battery strings, wherein respective sensor is electrically connected to an electronic controller; and selectively controlling individually ones of the plurality of battery strings to meet a requirement with the electronic controller based upon measurement from each sensor.