Battery Module Disconnection for SOC Imbalance Control
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Solution Overview
Problem
In power supply devices with multiple battery modules connected in series, the imbalance of State of Charge (SOC) between modules leads to premature depletion of smaller-capacity batteries, making them unusable, and the cost of balancing circuits increases to address this imbalance. Additionally, existing SOC estimation methods suffer from errors related to internal resistance estimation, especially in vehicles where stopping charging/discharging is difficult.
Innovation Solution
The power supply device includes a control unit that forcibly disconnects or connects battery modules from the series connection based on a gate signal, adjusting current flow to balance SOC and uses a phase difference in the gate signal with a delay to manage current accumulation, eliminating the need for a balancing circuit and improving SOC estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If balancing circuits are provided in each battery module to eliminate SOC imbalance, then SOC balance between modules is improved, but device cost and circuit complexity increase
Solution Approach 1:
The patent extracts the balancing function from separate balancing circuits and integrates it into the existing switching circuit control system. By using the switching circuits to forcibly disconnect or connect specific battery modules based on SOC status, the patent eliminates the need for dedicated balancing circuits while achieving the same SOC balancing effect.
Solution Approach 2:
The switching circuits, originally designed for voltage control during charging/discharging, are made multi-functional by adding SOC balancing capability. The same switching circuits now perform both voltage control and SOC balancing functions, reducing overall system complexity and component count.
2Stability of the object's composition
If balancing circuits are provided in each battery module to eliminate SOC imbalance, then SOC balance between modules is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the need for separate balancing circuits by extracting the balancing function and implementing it through the existing switching circuit control logic, thereby reducing component count and manufacturing cost.
Solution Approach 2:
The patent merges the SOC balancing function with the voltage control function, both performed by the switching circuits. This consolidation eliminates redundant components and reduces manufacturing complexity and cost.
3Adaptability or versatility
If battery modules with different capacities are connected in series, then system adaptability is improved, but smaller-capacity batteries become unusable earlier due to SOC depletion
Solution Approach 1:
The patent implements dynamic control of battery module connections based on real-time SOC status. The switching circuits dynamically adjust which modules are connected in series, allowing smaller-capacity modules to be temporarily disconnected when their SOC approaches the lower limit, thereby extending overall system usage duration while maintaining adaptability to different battery configurations.
4Ease of operation
If conventional SOC estimation methods using internal resistance estimation are used, then SOC can be estimated during traveling, but estimation accuracy deteriorates due to error influence
Solution Approach 1:
The patent employs feedback mechanisms where the control unit continuously monitors actual battery voltage and current, compares estimated SOC with actual battery status, and adjusts the estimation algorithm accordingly. This feedback loop reduces cumulative errors in internal resistance estimation and improves overall SOC estimation accuracy during traveling.
Solution Approach 2:
The patent implements periodic calibration of SOC estimation by temporarily disconnecting battery modules to measure open-circuit voltage, which provides a reference point for correcting estimation drift. This periodic action reduces accumulated errors while still allowing continuous SOC monitoring during traveling.
Data Source
AI summary
A power supply device is provided with a disconnection means (AND element) for forcibly disconnecting a battery module from a series connection regardless of a gate signal. The power supply device forcibly disconnects partial battery modules from the series connection by the disconnection means (AND element) during powering by a power supply output, thereby performing control so that the accumulated discharge current amounts thereof per unit time become smaller than those of the other battery modules.