Battery String Charging Control via Sequential Contactor Engagement
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Solution Overview
Problem
Existing battery power systems lack closed loop control mechanisms that account for individual battery string current limits, leading to potential damage from overcharging or undercharging, and result in prolonged connection and recharge times.
Innovation Solution
A battery system with a charger and control devices that monitor and regulate the charging voltage based on individual string currents, using contactors to sequentially connect battery strings when the charger voltage exceeds their voltage, ensuring safe and efficient charging within predetermined current limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open loop control is used to synchronously connect all battery strings to the charger, then the connection process is simple, but the response time is long and individual string current limits are not respected
Solution Approach 1:
The system performs preliminary actions by pre-charging each battery string individually through sequential connection before full charging begins. This preliminary connection phase prepares each string by bringing it to a standardized voltage level, ensuring all strings are ready for simultaneous full charging while respecting individual current limits during the preparation phase
2Power
If constant voltage or constant current charging is applied to all battery strings, then the overall battery system current can be controlled, but individual string current limits are overridden and batteries may be overcharged or undercharged
Solution Approach 1:
The charging system is segmented into two distinct phases: an initial connection phase where each battery string is charged individually with its own current limit protection, and a subsequent full charging phase where all strings are charged simultaneously. This segmentation allows individual string protection during connection while enabling efficient bulk charging afterward
Solution Approach 2:
Different charging control strategies are applied to different battery strings based on their individual states. During the connection phase, each string receives localized current control tailored to its specific voltage and current requirements, ensuring no string exceeds its individual limits while preparing for synchronized full charging
3Power
If step incremental voltage control or voltage ramping is used, then voltage can be increased within current limits, but the response time is long and closed loop control is not provided
Solution Approach 1:
The system performs preliminary individual string connection and pre-charging actions before initiating full charging. This preliminary phase quickly brings each string to readiness without requiring gradual voltage ramping, as each string is prepared separately with appropriate current limiting, then all strings are connected simultaneously for efficient bulk charging
Data Source
AI summary
Systems and methods for charging a plurality of battery strings are provided. The individual string current of each of the individual battery strings can be monitored and used to regulate a charging output provided by the charger. For instance, the output voltage of charger can be controlled as part of a closed loop control system based on the individual string current of the battery string under the constraint of an individual string current limit and/or a charging voltage limit. As the charging voltage of the charger increases as a result of the closed loop control based on the individual string current, other battery strings can be coupled to the charger when the charging voltage provided by the charger exceeds a battery string voltage associated with the battery string.