Battery SOC Calculation Using Voltage-Based Discharge Correction
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Solution Overview
Problem
Existing battery management systems struggle to accurately estimate the state of charge (SOC) of batteries during discharging, leading to sharp decreases in SOC, which can cause electricity consumption abnormalities and affect planning.
Innovation Solution
An SOC calculation method that involves obtaining the battery core voltage and discharge parameters when the voltage is below a preset threshold, calculating a correction coefficient based on the voltage difference and discharge parameters, and using this coefficient to adjust the SOC calculation, ensuring a smoother and more controlled discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of bits for representing SOC is increased to improve precision, then measurement precision is improved, but use of energy increases due to more look-up tables and longer calculation time
Solution Approach 1:
The patent divides the SOC representation into two segments: an integer part (4 bits) and a fractional part (4 bits). This segmentation allows the system to achieve 8-bit precision without requiring a full 8-bit look-up table, thereby reducing memory usage and energy consumption while maintaining measurement precision.
Solution Approach 2:
The patent uses partial action by implementing only the necessary precision level (8 bits total) rather than using excessive precision. The fractional part uses a simplified denominator (16) instead of a larger power of 2, reducing the complexity of calculations and energy requirements while still providing sufficient precision for battery management.
2Measurement precision
If the number of bits for representing SOC is increased to improve precision, then measurement precision is improved, but device complexity increases due to larger look-up tables and longer calculation time
Solution Approach 1:
The patent segments the SOC value into integer and fractional parts, allowing independent handling of each part. The integer part uses standard 4-bit representation, while the fractional part uses a simplified 4-bit representation with denominator 16. This segmentation reduces the complexity of the overall system by avoiding the need for complex floating-point arithmetic or large look-up tables.
Solution Approach 2:
The patent changes the parameter of the fractional representation by using a fixed denominator of 16 instead of variable or larger denominators. This parameter change simplifies the mathematical operations required for SOC calculation, reducing device complexity while maintaining the desired precision level.
3Ease of operation
If conventional SOC calculation methods are used, then ease of operation is maintained, but reliability decreases due to extreme values affecting accuracy
Solution Approach 1:
The patent applies preliminary anti-action by pre-defining and restricting the range of extreme values for current, voltage, and power parameters. By establishing these bounds before calculations are performed, the system prevents extreme values from corrupting the SOC calculation, thereby improving reliability without complicating the operation. The restricted extreme values are used as safeguards in the calculation process.
Data Source
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AI summary
An SOC calculation method includes: obtaining a battery core voltage of a battery module in a discharging state; obtaining a discharge parameter of the battery module when the battery core voltage is less than or equal to a preset voltage, where the preset voltage is greater than an under-voltage protection voltage of a battery module; obtaining a first voltage difference between the preset voltage and the battery core voltage; calculating a correction coefficient of an SOC according to the first voltage difference and the discharge parameter, where the correction coefficient is positively correlated with the discharge parameter and inversely correlated with the battery core voltage; and calculating a value of the SOC according to a rated full-load capacity of the battery module, the discharge parameter, and the correction coefficient.