LFP Backup Battery Abnormality Detection by Voltage Drop Comparison
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Solution Overview
Problem
Existing methods for detecting abnormalities in sub batteries, particularly iron phosphate-based lithium-ion batteries, face challenges due to the flat area in their SOC-OCV property, making it difficult to effectively determine voltage changes with state of charge.
Innovation Solution
A method involving charging the sub battery to a fully charged state, pre-discharging it to a state with a gentle voltage gradient, waiting for depolarization, and then performing an abnormality detection process by calculating voltage drop amounts and differences between battery cells to determine if the sub battery is abnormal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cell voltage is used to detect abnormality in iron phosphate-based lithium-ion battery, then the detection method can be applied to LFP batteries, but the flat area in SOC-OCV property makes voltage change difficult to see, reducing detection accuracy
Solution Approach 1:
The patent applies preliminary action by pre-charging the battery to a fully charged state and pre-discharging to a predetermined SOC range (20-40%) before performing abnormality detection. This preparation ensures the battery operates in a voltage range with sufficient gradient for accurate detection, overcoming the flat SOC-OCV characteristic of LFP batteries.
Solution Approach 2:
The patent changes the operating parameters by controlling the battery's state of charge to specific ranges (fully charged state, then 20-40% SOC) and adjusting discharge current parameters. This parameter control ensures measurements are taken when voltage changes are most detectable, resolving the contradiction between LFP applicability and detection accuracy.
2Productivity
If detection current is discharged immediately after charging, then the detection process is faster, but the battery may not be in a stable state, affecting measurement accuracy
Solution Approach 1:
The patent performs preliminary charging to full charge and preliminary discharging to predetermined SOC before the actual abnormality detection. This preliminary action sequence ensures the battery reaches a stable, reproducible state, allowing accurate measurements while maintaining efficient detection timing.
Solution Approach 2:
The patent maintains continuous control over the battery's charge state throughout the detection process, keeping the battery within predetermined SOC ranges during measurement. This continuous state management ensures both stability for accurate measurement and efficiency for timely detection.
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 method enables effective abnormality detection in iron phosphate-based lithium-ion batteries by normalizing cell states and accurately calculating voltage drop differences, even in batteries with flat SOC-OCV properties.
Implementation Method 1
a sub battery 20 as an iron phosphate-based lithium-ion battery
Implementation Method 2
maintaining the sub battery in a state in which a current is a predetermined value or less until a predetermined time elapses after the predetermined amount of current is discharged
Data Source
AI summary
An abnormality detection method of a sub battery (LFP type battery) for backing up a main battery that includes the steps of charging the sub battery to a fully charged state, discharging a predetermined current amount from the fully charged sub battery, maintaining the sub battery in a state where the current becomes equal to or less than a predetermined value until a predetermined time elapses, discharging a detection current for detecting an abnormality of the sub battery from the sub battery after a predetermined time elapses, calculating a voltage drop amount, which is a difference between the cell voltage at the start of discharge of the detection current and the cell voltage at the end of discharge, for a plurality of battery cells constituting the sub battery, respectively, and determining that the sub battery is abnormal.