Segmented Battery String Charging via Dynamic Reconfiguration
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Solution Overview
Problem
Conventional high voltage charging schemes for series-connected battery strings face challenges in controlling voltage variations, leading to potential component failure, overcharging, and imbalances, especially as the number of batteries increases, requiring complex and expensive monitoring systems.
Innovation Solution
The method involves subdividing the battery cells into smaller sub-strings and charging them using a lower voltage power source, allowing for separate charging and balancing of sub-groups before recombining them, which can be done automatically without interrupting the power bus, using a processor to manage and control the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional high voltage charging schemes are used for series-connected battery strings, then the charging voltage can meet the full charge voltage requirement, but voltage variation at nodes increases linearly with charging voltage, leading to component failure, overcharging, and imbalances
Solution Approach 1:
The battery string is divided into multiple parallel groups, each containing series-connected battery cells. A power supply charges each group separately at lower voltage, avoiding the linear voltage variation problem that occurs with high voltage charging of the entire string. This segmentation allows the charging voltage to be distributed across multiple lower-voltage paths.
Solution Approach 2:
The system dynamically reconfigures the battery groups during charging operations. Switches enable the power supply to connect to different combinations of battery groups in series or parallel, adjusting the charging configuration based on the state of charge and voltage requirements. This dynamic reconfiguration allows flexible voltage management without exceeding component ratings.
2Power
If the number of batteries in the series-connected string increases to provide higher voltage outputs, then the voltage output capability improves, but the complexity and cost of monitoring systems increases to control voltage variations
Solution Approach 1:
Instead of monitoring a single high-voltage string, the system segments the battery string into multiple parallel groups and monitors each group independently at lower voltage levels. This reduces the voltage range that each monitoring circuit must handle, simplifying the monitoring system design and reducing costs while maintaining accurate voltage control.
Solution Approach 2:
The power supply and switching network serve multiple functions: they enable charging of different battery group configurations, provide voltage regulation, and facilitate balancing operations. This multi-functionality reduces the need for separate dedicated monitoring and control systems for each function.
3Power
If high voltage charging is applied to series-connected battery strings, then full charge voltage is achieved, but voltage variation causes some battery cells to be overcharged while others are undercharged
Solution Approach 1:
The battery string is divided into parallel groups that can be charged independently. The power supply connects to specific groups based on their charge state, enabling selective charging of undercharged groups while already-charged groups are bypassed. This eliminates the voltage variation problem that causes uneven charging in series configurations.
Solution Approach 2:
Different battery groups receive different charging treatments based on their individual charge states. The switching network enables the power supply to apply charging current selectively to specific groups that need it, rather than forcing uniform charging across all groups. This localised charging approach ensures each group is charged to its appropriate level.
Data Source
AI summary
Systems and methods for performing low voltage charging of a high voltage, series-connected string of battery modules are disclosed. A battery pack system may include a plurality of battery cells, including one or more groups of battery cells coupled in parallel. A processor may be configured to select a sub-group of battery cells from a group of battery cells for charging separately from other battery cells of the selected group of battery cells. The group of battery cells may be reconfigured to allow charging of the sub-group of battery cells separate from the other battery cells. The sub-group of battery cells may be charged, and then the group of battery cells may be reconfigured to allow operation of the sub-group of battery cells with the other battery cells. During charging, the sub-group of battery cells may be unavailable but other battery cells may continue to discharge.