Parallel Battery Pack Activation with Compensation Current Control
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Solution Overview
Problem
Unintended charge equalization currents flowing between battery packs in parallel connection, especially in cold temperatures and high state of charge scenarios, limit battery power capabilities and lead to lithium plating and degradation.
Innovation Solution
A computer-controlled system that determines and applies a compensation current to counteract charge equalization currents before activating additional battery packs, ensuring balanced energy management and preventing lithium plating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery packs are connected in parallel to increase power capabilities, then power output is improved, but unintended charge equalization currents flow between packs causing lithium plating and degradation
Solution Approach 1:
The system performs preliminary assessment of battery pack states (temperature, state of charge, internal resistance) before allowing parallel connection. Compensation currents are pre-calculated and applied to counteract expected charge equalization currents before they can cause harmful effects, preventing lithium plating and degradation while enabling multiple packs to operate in parallel
Solution Approach 2:
The system dynamically adjusts operational parameters including compensation currents, activation thresholds, and connection permissions based on real-time battery conditions. By changing parameters such as temperature thresholds, state of charge limits, and internal resistance criteria, the system enables safe parallel operation when conditions are favorable while preventing harmful charge equalization when conditions are adverse
2Device complexity
If a maximum current threshold is set to allow connection of multiple battery packs, then device complexity is reduced, but power capabilities are limited and battery utilization is reduced
Solution Approach 1:
Instead of using a fixed maximum current threshold, the system dynamically adjusts connection criteria based on multiple parameters including temperature, state of charge, internal resistance, and expected charge equalization currents. This allows the system to permit parallel connections and maximize power capabilities when conditions are favorable while maintaining safety, thereby increasing battery utilization without excessive complexity
3Reliability
If battery packs are activated sequentially to prevent charge equalization currents, then battery reliability is improved, but activation time is increased
Solution Approach 1:
The system performs preliminary assessments and pre-calculates compensation currents for all battery packs before activation. By preparing compensation strategies in advance and applying them simultaneously or in optimized sequences, the system prevents charge equalization currents without requiring slow sequential activation, thereby reducing activation time while maintaining safety
Solution Approach 2:
The system dynamically determines activation sequences and compensation current applications based on real-time battery conditions. Rather than following a fixed sequential protocol, the system can activate packs in optimized sequences or simultaneously when conditions permit, reducing activation time while maintaining reliability through real-time monitoring and adjustment
Data Source
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AI summary
A computer system (100; 600) for controlling activation of a plurality of battery packs (20) in parallel connection, the computer system (100; 600) comprising processing circuitry (102; 602) configured to: activate a first battery pack (20-1) from among the plurality of battery packs (20); determine a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack (20-n) from among the plurality of battery packs (20); apply the compensation current to currently activated battery pack(s) (20); and activate the additional battery pack (20-n).