Battery Degradation Detection Using Root-Mean-Square Current
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Solution Overview
Problem
Existing methods for detecting battery degradation level, such as integrating charging and discharging current, are inaccurate as they do not account for varying current conditions, leading to inconsistent degradation level determination.
Innovation Solution
The method detects battery degradation level by using the root-mean-square (Irms) of charging and discharging current, accumulated over a set time period, and considers voltage limits, providing a more accurate assessment of battery health (SOH).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If battery degradation level is detected by integrating charging and discharging current, then degradation level can be detected, but the detection accuracy is insufficient because varying current conditions are not accounted for
Solution Approach 1:
The patent transforms the detection parameter from simple integrated current (Ah) to root-mean-square current (Irms). This parameter change accounts for varying current conditions by considering both magnitude and duration of current flow, thereby improving degradation detection accuracy without requiring complex additional hardware
Solution Approach 2:
The patent adds a temporal dimension to current measurement by using root-mean-square calculation over time periods. This transforms the one-dimensional integrated current measurement into a two-dimensional assessment that considers both current magnitude and its distribution over time, enabling more accurate degradation detection
2Measurement precision
If full charge capacity is determined by integrating discharge current from fully-charged to completely discharged state, then full charge capacity can be accurately determined, but the battery cannot operate in applications that limit charge-discharge ranges
Solution Approach 1:
The patent implements continuous degradation level monitoring using Irms-based detection, providing feedback on battery health status. This enables the system to adaptively manage battery operations within limited charge-discharge ranges by detecting degradation trends and adjusting charging/discharging strategies accordingly, rather than requiring complete charge-discharge cycles
Solution Approach 2:
The patent performs preliminary degradation assessment through Irms calculation during normal operation before the battery reaches critical states. This allows proactive management of battery health and capacity estimation without requiring the battery to be discharged to completely depleted states, enabling operation in applications with restricted charge-discharge ranges
3Duration of action of stationary object
If battery charging and discharging are controlled within a specified residual capacity range to reduce degradation, then battery lifetime is extended, but accurate detection of full charge capacity becomes difficult
Solution Approach 1:
The patent replaces the mechanical approach of complete charge-discharge cycling with an electrical calculation method based on Irms. This substitution allows full charge capacity to be determined through electrical measurements and calculations during normal operation within limited ranges, eliminating the need to physically discharge the battery to complete depletion while maintaining detection accuracy
Data Source
AI summary
A method of detecting battery degradation level detects charging and discharging current flow in the battery and determines battery degradation level (state of health, SOH) from the charging and discharging current. The method detects the battery degradation level (SOH) from the root-mean-square of the charging and discharging current flow (Irms) in the battery, which is designated effective current.