Battery Equalization Control for SOC-OCV Plateau Regions
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Solution Overview
Problem
Conventional voltage equalization processes in battery assemblies with storage batteries having SOC-OCV characteristics that include a plateau region are ineffective in accurately equalizing capacity, leading to reduced continuous operating time due to insufficient voltage changes relative to capacity changes.
Innovation Solution
A storage battery management device with a voltage measuring unit, current measuring unit, voltage equalization circuit, coulomb counting processing unit, internal resistance estimation unit, and target voltage calculation unit that performs constant current control based on capacity differences to accurately equalize remaining capacities of storage batteries, even when the average voltage is within the plateau region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If voltage equalization stops when individual battery reaches target voltage, then voltage equalization is completed, but capacity difference remains large in plateau region reducing continuous operating time
Solution Approach 1:
The invention introduces a feedback mechanism that continuously monitors both voltage and capacity during equalization. When the average voltage is detected to be within the plateau region and capacity difference is significant, the system uses capacity feedback (from coulomb counting) to determine the stopping condition, ensuring that equalization continues until capacity is actually equalized rather than stopping early based on voltage alone.
Solution Approach 2:
The invention adds a new dimension to the equalization control by introducing capacity as an additional control dimension alongside voltage. Instead of relying solely on the voltage dimension, the system incorporates capacity measurement and uses it as a complementary or alternative control parameter, particularly in the plateau region where voltage changes are insufficient.
2Device complexity
If average voltage is used as target voltage for all batteries, then simple control is achieved, but actual voltage attained deviates from target due to internal resistance variations
Solution Approach 1:
The invention applies local quality by recognizing that different batteries have different internal resistance characteristics and treating them differently. Instead of applying a uniform voltage target to all batteries, the system calculates individual target voltages based on each battery's internal resistance, or alternatively uses capacity-based control that inherently accounts for individual battery characteristics.
3Power
If constant current control is performed based on voltage target, then voltage equalization is achieved, but capacity equalization is insufficient when average voltage is in plateau region
Solution Approach 1:
The invention introduces dynamics by making the control strategy adaptive based on operating conditions. The system dynamically switches between voltage-based control and capacity-based control depending on whether the average voltage is within the plateau region. This dynamic adjustment allows the system to maintain effective control throughout the equalization process regardless of the SOC-OCV characteristic region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively extends the continuous operating time of the battery assembly by accurately equalizing the remaining capacity of each storage battery, ensuring that all batteries reach zero capacity simultaneously during discharge.
Implementation Method 1
a voltage equalization circuit configured to perform constant current control to reduce a voltage difference between the storage batteries by transferring electric charge between the storage batteries
Implementation Method 2
a coulomb counting processing unit configured to integrate the measured current with the current during the constant current control to calculate respective capacities of the storage batteries
Data Source
AI summary
A storage battery management device for managing an assembly of series connected storage batteries having SOC-OCV characteristics including a plateau region includes: a voltage equalization circuit that performs constant current control to reduce the voltage difference of each storage battery by transferring electric charge among the storage batteries; a coulomb counting processing unit that calculates the capacity of each storage battery; a target voltage calculation unit that sets a target voltage for each storage battery based on the average voltage and the internal resistance; and a voltage equalization control unit that controls the voltage equalization circuit to cause the voltage equalization circuit to perform the constant current control. If the average voltage is within the plateau region, the voltage equalization control unit continues constant current control when the capacity difference is ≥ a first capacity difference, and stops constant current control when the capacity difference reaches a second capacity difference.