Battery OCV Timing Control for More Stable SOC Estimation
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Solution Overview
Problem
The frequent resetting of elapsed time counters in energy storage devices due to temporary currents exceeding thresholds leads to increased frequency of obtaining open circuit voltage (OCV), which can result in unstable voltage readings and inaccurate state of charge (SOC) estimation.
Innovation Solution
A management apparatus for energy storage devices that adjusts the elapsed time counter based on predetermined conditions such as current integration amount and duration, allowing for reduced resetting frequency by determining whether the voltage is stable before resetting, thereby improving SOC estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the elapsed time counter is reset every time current exceeds the threshold, then the voltage stability is ensured, but the resetting frequency increases and SOC estimation accuracy deteriorates
Solution Approach 1:
The patent changes the parameter of counter resetting from a fixed rule-based approach (reset whenever current exceeds threshold) to a conditional approach based on voltage stability assessment. The management apparatus evaluates whether voltage has stabilized before deciding to reset the counter, thereby adapting the resetting behavior to actual battery conditions rather than following a rigid parameter threshold.
Solution Approach 2:
The patent introduces feedback by continuously monitoring voltage stability and using this information to control the counter resetting operation. The management apparatus determines whether to reset the elapsed time counter based on the assessed voltage stability state, creating a closed-loop control system that adjusts resetting frequency according to real-time battery conditions, thus preventing unnecessary resets that would degrade SOC estimation accuracy.
2Reliability
If the elapsed time counter is reset frequently, then unstable voltage is prevented from being used as OCV, but the frequency of obtaining stable OCV decreases
Solution Approach 1:
The patent applies preliminary action by assessing voltage stability before the counter reset operation is executed. The management apparatus evaluates whether voltage has reached a stable state in advance, and only resets the counter when necessary. This preliminary assessment prevents premature resetting that would unnecessarily extend the time required to obtain stable OCV values for SOC estimation.
3Device complexity
If the counter resetting operation is performed based on current threshold only, then the control logic is simple, but the voltage stability assessment becomes inaccurate
Solution Approach 1:
The patent transforms the static, fixed threshold-based control logic into a dynamic assessment system that adapts to changing battery conditions. Instead of using a predetermined current threshold alone, the management apparatus dynamically evaluates voltage stability characteristics and adjusts the counter resetting decision accordingly. This dynamic approach maintains relatively simple control logic while significantly improving voltage stability assessment accuracy.
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
This approach reduces the frequency of resetting the elapsed time counter, increases the frequency of obtaining stable OCV, and enhances SOC estimation accuracy by preventing unstable voltage from being determined as open circuit voltage.
Implementation Method 1
the voltage of the energy storage device fluctuates because a chemical reaction continues inside the energy storage device immediately after the current becomes equal to or smaller than the threshold
Data Source
AI summary
A management apparatus for an energy storage device, wherein after the start of counting an elapsed time since a current of the energy storage device became equal to or smaller than a first threshold, when a predetermined condition in which the voltage of the energy storage device is possibly not stable is satisfied at a time point where the count reaches a stabilization time (predetermined value), the count of the elapsed time is changed.