Ni-Cd Battery State of Charge Indicator with Continuous Monitoring
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Solution Overview
Problem
Existing Ni—Cd battery state of charge indicators are inaccurate due to failure to account for variations in voltage, current, and temperature between measurements, and do not recalibrate for self-discharge, making it difficult to determine the available capacity and safety of the battery, especially for standby or backup systems.
Innovation Solution
A battery with sensors for continuous voltage, current, and temperature measurements, a control unit to determine charge/discharge history, and data storage to calculate the theoretically available capacity, with a device to display the state of charge, including features for recalibration and self-discharge considerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage, current and temperature measurements are performed periodically (not continuously), then the device complexity and energy consumption are reduced, but the measurement precision and reliability of state of charge indication deteriorate due to unaccounted variations between measurements
Solution Approach 1:
The patent implements continuous measurement of voltage, current, and temperature parameters throughout battery operation. The control unit constantly monitors these parameters and updates the state of charge calculation in real-time, eliminating the inaccuracies caused by periodic sampling and ensuring the indicator always reflects the actual battery capacity available.
2Measurement precision
If recalibration is performed only at full charge and complete discharge, then the manufacturing and operational simplicity is maintained, but the measurement precision deteriorates due to unaccounted self-discharge and condition variations between measurements
Solution Approach 1:
The control unit continuously compares actual voltage, current, and temperature measurements with expected values based on the charge/discharge history. When deviations exceed predetermined thresholds indicating self-discharge or capacity changes, the system automatically triggers recalibration. This feedback mechanism ensures high measurement accuracy while minimizing unnecessary recalibrations that would reduce operational efficiency.
Solution Approach 2:
The system performs preliminary assessments of battery conditions by analyzing charge/discharge history and operational parameters. Recalibration is proactively scheduled based on predicted capacity changes from self-discharge patterns, rather than waiting for significant inaccuracies to develop. This maintains precision while optimizing the timing of recalibration events.
3Reliability
If the indicator does not account for self-discharge and charge/discharge conditions, then the device complexity is reduced, but the reliability of the state of charge indication deteriorates, especially for standby or backup batteries
Solution Approach 1:
The control algorithm dynamically adapts to different battery operating conditions including standby mode, charging, discharging, and temperature variations. It continuously adjusts the state of charge calculation based on real-time measurements and detected operational mode, ensuring reliable indication regardless of battery condition. The system automatically identifies self-discharge events and compensates for them, providing accurate reliability information for standby and backup applications.
4Measurement precision
If continuous monitoring and recalibration are implemented, then the measurement precision and reliability are improved, but the use of energy and device complexity increase
Solution Approach 1:
The system implements continuous monitoring of all parameters but performs full recalibration only when necessary based on detected conditions. During normal stable operation, the system uses simplified calculations with less frequent updates. When self-discharge, temperature extremes, or abnormal conditions are detected, the system intensifies monitoring and performs comprehensive recalibration. This partial action approach maintains high precision while minimizing energy consumption during stable periods.
Data Source
AI summary
A battery made up of nickel-cadmium cells includes an indicator for displaying a state of charge comprising sensors for performing continuous measurements of voltage and current and of temperature of the battery, a memory storing at least a history of charge/discharge, a predefined reference voltage, current and temperature, and the measurements and history determined, and a control unit for determining an operation mode of the battery and determining a correction to be applied to the voltage and current measured, calculating a theoretically available capacity of the battery depending on the operating mode and the correction, determining a need for recalibration of the theoretically available capacity of the battery enabling a capacity actually available of the battery to be calculated, and based on the capacity actually available, defining the state of charge of the battery.