Backup Battery Capacity Detection Using Internal Resistance
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Solution Overview
Problem
Existing battery monitoring techniques for lithium-ion batteries in backup systems are inefficient, as they require lengthy discharge cycles, making the backup system unavailable during testing and increasing the risk of failure during power outages.
Innovation Solution
A battery monitor ASIC that continuously monitors battery temperature and internal resistance using a load resistor and thermistor, allowing for rapid capacity assessment without disrupting the backup system, and issues alerts for aged or faulty batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent battery capacity measurements are taken using traditional discharge cycle testing, then battery capacity monitoring accuracy is improved, but system availability deteriorates due to lengthy testing time
Solution Approach 1:
The patent changes the measurement parameter from discharge cycle capacity testing to internal resistance measurement. By measuring internal resistance at open-circuit voltage conditions rather than performing discharge cycles, the system achieves capacity monitoring without removing the battery from service, thus maintaining system availability while still detecting battery degradation through resistance changes.
Solution Approach 2:
The patent replaces the mechanical/electrical discharge cycle testing process with an electrical measurement process. Instead of physically discharging the battery through load cycles, the system uses electrical measurements of internal resistance at open-circuit conditions to infer capacity degradation, eliminating the need for lengthy discharge testing.
2Reliability
If traditional battery testing is performed to detect capacity degradation, then battery aging detection is improved, but testing time increases making the backup system unavailable
Solution Approach 1:
The patent performs preliminary measurement of open-circuit voltage before the brief load application. By having the voltage measurement already available before applying the test load, the system minimizes the total testing time while still obtaining the necessary data to calculate internal resistance and detect aging. The voltage measurement is taken in advance, so no additional time is lost during the actual test execution.
Solution Approach 2:
The patent rushes through the battery testing process by using a very brief load application (only 100 milliseconds) compared to traditional discharge cycle testing that takes hours. The system skips the lengthy discharge process and directly measures internal resistance through a rapid load pulse, dramatically reducing testing time while still detecting battery aging.
3Loss of information
If battery capacity is monitored using discharge cycle testing, then capacity degradation is detected, but the backup system becomes unavailable during testing
Solution Approach 1:
The patent enables the battery to serve itself during monitoring by measuring its own internal resistance through a brief self-test. The battery remains in the system and continues to provide backup capability while undergoing rapid assessment. The monitoring process uses the battery's own electrical characteristics without requiring external testing equipment or removal from the system, maintaining both detection capability and system availability.
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 continuous monitoring of battery health, reducing the risk of failure by detecting hazardous conditions in advance, ensuring the backup system remains available during power outages.
Implementation Method 1
A battery monitor ASIC that continuously monitors battery temperature and internal resistance using a load resistor circuit
Implementation Method 2
A battery monitor ASIC that continuously monitors battery temperature and internal resistance
Data Source
AI summary
A method, system, and integrated circuit are provided for monitoring a battery capacity within a battery backup system. A battery degradation profile is provided for a battery including first data associating operating temperature over accumulated time with second battery degradation data. The battery is kept charged in a failover battery backup circuit. The operating temperature of the battery is measured over time and third data is stored for the operating temperature over accumulated time. While the battery is operated in the backup system, the battery degradation profile is accessed based on the third data to obtain an associated battery degradation estimate. Responsive to the battery degradation estimate meeting a designated condition, the battery is electronically switched from operation to a test circuit, and the internal impedance of the battery is measured. Responsive to an unacceptable value of the internal impedance, an alert is issued.