Battery Pack Compensation Current for Parallel Equalization Control
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Solution Overview
Problem
Unintended charge equalization currents between battery packs in parallel connection, especially under cold temperatures and high state of charge scenarios, lead to limited power capabilities, lithium plating, and battery degradation, with existing solutions either limiting power or introducing imbalances and safety risks.
Innovation Solution
A computer system calculates a compensation current range by considering the voltages and impedances of both newly activated and currently activated battery packs, along with the maximum discharge ability of the electrical system, to counteract charge equalization currents, ensuring optimal current flow and preventing lithium plating and degradation.
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 control system performs preliminary calculations of compensation current before connecting additional battery packs to parallel operation. By pre-determining the appropriate compensation current value based on voltage differences and expected equalization currents, the system prepares the necessary counteracting current in advance, preventing charge equalization issues before they occur.
Solution Approach 2:
The system applies a compensation current that acts in opposition to the expected charge equalization current before and during the connection of additional battery packs. This preliminary anti-action counteracts the harmful equalization current flow, preventing lithium plating and battery degradation while allowing multiple packs to operate in parallel.
2Reliability
If a maximum current threshold is set to prevent charge equalization currents, then battery safety is improved, but power output and battery utilization are limited
Solution Approach 1:
Instead of using a static maximum current threshold, the system dynamically calculates the compensation current based on real-time voltage differences between battery packs and their internal resistances. This dynamic approach allows the system to safely utilize higher currents when voltage differences are small while providing appropriate compensation when differences exist, optimizing both safety and power output.
Solution Approach 2:
The system changes the control parameter from a fixed current threshold to a dynamically adjusted compensation current value. By continuously monitoring voltage differences and calculating appropriate compensation values, the system adapts the current limits based on actual battery pack conditions, allowing maximum power utilization while maintaining safety.
3Reliability
If compensation current is applied to counteract charge equalization currents, then battery health is improved, but system complexity increases due to calculations and control requirements
Solution Approach 1:
The control system automatically performs the necessary voltage measurements, calculations, and compensation current adjustments without requiring external intervention. The system self-regulates by continuously monitoring battery pack voltages and internally calculating the appropriate compensation current, reducing the need for complex external control mechanisms while maintaining battery health.
Data Source
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AI summary
A computer system (100; 600) for determining a compensation current adapted to counteract at least parts of a charge equalization current expected to be generated by an activation of an additional battery pack (20-n) in parallel connection with one or more currently activated battery packs (20). The compensation current is determined as a current range between a lower and upper compensation current limits. The lower limit is based on a voltage of the additional battery pack (20-n), and a voltage and impedance of the currently activated battery packs (20). The upper limit is based on a maximum discharge ability of a system powered by the currently activated battery packs (20), a maximum discharge ability of the currently activated battery packs (20), a voltage and impedance of the additional battery pack (20-n), and a voltage and impedance of the one or more currently activated battery packs (20).