Battery Management Circuit for Rest-State SOH Estimation
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Solution Overview
Problem
Current methods fail to accurately determine the State Of Health (SOH) of a battery at rest due to hysteresis and offset errors in voltage and current sensors, making it difficult to assess State Of Charge (SOC) changes during the transition from cycle to rest states within a predetermined time frame.
Innovation Solution
A battery management system that calculates a weighted State Of Health (SOH) by correcting Open Circuit Voltage (OCV) values for offset errors and using error curves to account for rest time, incorporating a control circuit to determine SOC changes and apply weights based on cycle history and sensor errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the OCV-SOC curve is used to determine SOC in the rest state, then the hysteresis effect is eliminated, but the determination cannot be performed within a predetermined time after the battery shifts from cycle state to rest state
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values in a correction map that compensates for hysteresis effects. Instead of waiting for the battery to fully stabilize in rest state, the system uses the correction map to adjust OCV readings immediately, enabling SOC determination within a predetermined time frame while maintaining accuracy.
2Productivity
If voltage sensor and current sensor measurements are used to determine SOC, then real-time monitoring is enabled, but offset errors accumulate over time reducing SOC accuracy
Solution Approach 1:
The patent implements feedback by continuously monitoring the battery state and using the correction map to adjust SOC calculations in real-time. The system compares measured OCV values with expected values from the OCV-SOC curve, applies appropriate corrections from the map, and updates the SOC determination dynamically, thereby maintaining both real-time monitoring capability and measurement accuracy.
Solution Approach 2:
The patent applies parameter changes by introducing correction values that modify the raw sensor measurements. The correction map contains pre-determined adjustment parameters based on battery history and state, which are applied to transform the measured OCV and calculated SOC into more accurate values, compensating for sensor offset errors and hysteresis effects.
3Adaptability or versatility
If ampere counting or Kalman filter methods are used in cycle state, then SOC can be determined during charge/discharge, but the methods are not suitable for determining SOC in rest state
Solution Approach 1:
The patent applies dynamics by implementing a dynamic SOC determination system that automatically switches between different methods based on battery state. During cycle state, ampere counting or Kalman filter is used; when the battery enters rest state, the system transitions to using the OCV-SOC curve with correction map. This dynamic adaptation ensures reliable SOC determination across all operating conditions.
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
Enables accurate determination of SOH at rest by accounting for SOC changes and error components, improving the reliability of battery state assessment during rest periods.
Implementation Method 1
a battery voltage and a battery current corresponding to information necessary to determine the SOC of the battery are measured by a voltage sensor and a current sensor, respectively
Implementation Method 2
each of the voltage sensor and the current sensor may have low SOC accuracy due to an offset error
Implementation Method 3
the voltage across the battery is not maintained constantly due to hysteresis generated by a cycle history in the cycle state
Data Source
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AI summary
A battery management system according to the present disclosure includes a current sensor to measure a battery current which is an electric current flowing through a battery, a voltage sensor to measure a battery voltage which is a voltage across the battery, and a control circuit. When the control circuit receives a key-on signal during a first rest period of the battery, the control circuit determines a fixed rest time, a fixed Open Circuit Voltage (OCV) and a fixed State Of Charge (SOC), and determines an integrated current value of the battery current during a cycle period of the battery. When the control circuit receives a key-off signal during the cycle period, the control circuit starts a second rest period of the battery. The control circuit determines an interest SOC corresponding to an interest OCV which is the battery voltage during the second rest period. The control circuit determines a State Of Heath (SOH) of the battery based on the fixed SOC, the integrated current value and the interest SOC.