Battery Self-Discharge Rate Estimation for Health Monitoring
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Solution Overview
Problem
Batteries stored for long periods self-discharge due to irreversible side reactions, leading to capacity loss, which can exceed compensation during balancing and charging, potentially causing battery failure if not addressed.
Innovation Solution
A system and method to estimate and monitor the self-discharge rate of battery cells by taking snapshots of cell state values over time, converting voltage to state of charge and capacity, and calculating a self-discharge rate, with thresholds to recommend remedies for cells exceeding acceptable rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If batteries are stored for long periods, then capacity is lost due to self-discharge, but replacing cells increases device complexity and cost
Solution Approach 1:
The system performs preliminary monitoring of cell voltage during idle periods to detect self-discharge trends before they cause battery failure. By estimating self-discharge rates in advance and comparing them to thresholds, the system can identify problematic cells early and recommend replacement before actual failure occurs, preventing the need for emergency replacements and reducing overall device complexity.
Solution Approach 2:
The system continuously monitors cell voltage, estimates self-discharge rates, and provides feedback by comparing estimated rates to predefined thresholds. This feedback mechanism enables proactive identification of cells with abnormally high self-discharge rates, allowing timely intervention through replacement recommendations before the cells cause battery failure, thus improving reliability without increasing operational complexity.
2Reliability
If self-discharge rate is monitored continuously, then battery health can be improved, but energy is consumed during monitoring
Solution Approach 1:
The system performs voltage snapshots at periodic intervals during idle periods rather than continuously monitoring. By estimating self-discharge rates based on voltage changes between periodic snapshots and comparing these estimates to thresholds, the system achieves effective battery health monitoring while consuming minimal energy, as monitoring only occurs when the battery is not in active use.
3Measurement precision
If cell voltage is monitored to detect self-discharge, then measurement precision is improved, but difficulty of detecting and measuring increases due to distinguishing self-discharge from other processes
Solution Approach 1:
The system focuses monitoring efforts specifically on individual cells rather than the entire battery pack, examining local voltage changes of each cell during idle periods. By calculating self-discharge rates for each cell independently and comparing them to thresholds, the system achieves precise detection of problematic cells while simplifying the measurement process, as each cell is analyzed in isolation rather than attempting to measure complex interactions across the entire battery system.
Data Source
AI summary
Various embodiments of a technique to estimate and monitor a self-discharge rate for use as a measure of battery health are described herein. In some embodiments, the technique includes a system including a processor and a memory coupled with the processor. The memory is configured to provide the processor with instructions that when executed cause the processor to receive a plurality of snapshots obtained by monitoring a battery system in a quiescent state at a plurality of times. Each snapshot includes a plurality of cell state values at one of the plurality of times. The memory is further configured to provide the processor with instructions that when executed cause the processor to estimate a self-discharge indicator using at least one snapshot in the plurality of snapshots, compare the self-discharge indicator to a threshold, and recommend a remedy for the battery system in response to the self-discharge indicator exceeding the threshold.