Battery String Sequencing for Self-Priming Pre-Charge
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Solution Overview
Problem
Existing lithium-ion battery systems face challenges in managing the pre-charge process to prevent inrush currents, which can cause damage and require complex auxiliary power sources, increasing costs and potential failure points.
Innovation Solution
A method is introduced where only a first subset of batteries is initially brought online by pre-charging one battery string, with an electronic control module drawing power from this subset to progressively bring additional subsets online, reducing the initial current draw and enhancing operational flexibility and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If all battery strings are connected simultaneously during power-up, then the system can provide full power immediately, but inrush currents cause excessive heat generation, component stress, and potential contactor welding
Solution Approach 1:
The battery pack is divided into multiple strings that are connected sequentially rather than simultaneously. The system selectively connects individual battery strings or groups of strings in a staged manner, allowing each string to contribute to power output separately. This segmentation prevents the simultaneous inrush current that would occur if all strings were connected at once, while still achieving full power output through progressive connection.
Solution Approach 2:
The system performs preliminary assessment of battery string states (charge levels, health status) before connection and establishes a predetermined connection sequence. Control logic pre-determines which strings should be connected first based on their readiness and operational requirements, enabling a controlled power-up sequence that avoids inrush currents while ensuring appropriate strings are activated at the right time.
2Object-affected harmful factors
If auxiliary power sources are added to manage pre-charging, then inrush currents can be controlled, but system complexity and cost increase
Solution Approach 1:
The battery strings themselves provide the pre-charging function by being connected in a controlled sequence without requiring external auxiliary power sources. The system uses its own battery strings to gradually build up power availability, with each string serving dual purposes: both as power sources and as the mechanism for controlled power delivery. This self-service approach eliminates the need for separate pre-charge batteries or complex auxiliary power management circuitry.
Solution Approach 2:
Each battery string is designed to serve multiple functions: providing power output, enabling controlled power-up sequences, and acting as both the load and the power source during connection. The same battery strings that deliver operational power also perform the pre-charging function through their sequential connection, eliminating the need for dedicated auxiliary power components and reducing overall system complexity.
3Object-affected harmful factors
If selective battery string connection is implemented, then initial current draw is reduced, but control logic complexity increases
Solution Approach 1:
The control system monitors and responds to changes in battery string parameters (voltage, current, state of charge) during the power-up sequence. Based on these parameter changes, the control logic dynamically adjusts the connection sequence and timing. This parameter-based control approach provides a systematic method for managing selective string connection that scales with system size and reduces the need for complex hard-coded control sequences.
Data Source
AI summary
Various techniques are described for initially bringing only a first subset of available batteries online, such as by initially pre-charging the system using only one battery string of a battery pack. Once the first subset of batteries is online, an electronic control module draws power from the first subset of batteries to pre-charge and then proceeds to bring one or more additional subsets of batteries online. These techniques improve the efficiency and functionality of battery systems by introducing a self-priming capability that reduces an initial current draw, thereby enhancing the operational flexibility and reducing the cost and complexity of the system.