Elevator Battery Health Monitoring via Load Testing
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Solution Overview
Problem
Existing battery-based emergency power supplies in elevators face challenges in accurately monitoring battery health, leading to potential failures during power outages due to the unreliable methods of determining the state of charge and health of batteries like VRLA or Li-ion batteries, which often results in premature replacement and safety risks.
Innovation Solution
The integration of a battery test module within the elevator control system that applies a defined load to the emergency power supply battery connected to the intermediate DC circuit, measuring voltage and current over a specified time period, and comparing these measurements with stored threshold values to determine the battery's health state and issue a replacement signal when necessary, utilizing existing motor and brake drive components to avoid the need for separate test resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If battery health monitoring is performed using open circuit voltage measurement, then the measurement is simple, but the accuracy of determining battery health state is insufficient
Solution Approach 1:
The patent introduces an intermediary resistive element (test resistor or existing brake resistor) as a mediator to apply a controlled load to the battery during testing. This intermediary component enables accurate measurement of battery voltage drop and current under load conditions, providing reliable health state determination while maintaining operational simplicity through automated control sequences.
Solution Approach 2:
The system performs preliminary charging of the battery to a known state before conducting the load test. This preliminary action ensures the battery starts from a standardized condition (fully charged or known state of charge), which is essential for accurate and repeatable health assessments. The control system manages this preliminary charging phase automatically before the actual measurement begins.
2Measurement precision
If a power resistor is used for battery testing, then the battery terminal voltage drop can be monitored, but the test resistor is big and takes space in the device
Solution Approach 1:
The patent applies the universality principle by making the brake resistor serve dual functions: it acts as both a safety component for the elevator system and as the test load for battery health monitoring. This multi-functionality eliminates the need for a separate dedicated test resistor, significantly reducing the space required while maintaining measurement accuracy. The brake resistor's inherent high power rating makes it suitable for the demanding battery test requirements.
Solution Approach 2:
The patent merges the battery testing function with the existing brake resistor component. Instead of adding a separate test resistor, the system combines the battery health monitoring function with the already-present brake resistor, which is necessary for the elevator's safety system. This merging approach consolidates components and reduces overall device volume while achieving accurate battery assessment.
3Device complexity
If a single test resistor is used for different battery types (12V, 24V, 48V), then the device structure is simplified, but the battery test current differs between each battery type requiring adjustment
Solution Approach 1:
The patent applies dynamics by implementing adjustable and controllable test parameters through the elevator control system. The control system can dynamically adjust the test current, test duration, and load application based on the detected battery type (12V, 24V, or 48V). This dynamic adaptability allows a single physical test resistor to effectively serve multiple battery types with different voltage and current requirements, maintaining device simplicity while achieving versatility.
Solution Approach 2:
The system changes operational parameters (test current magnitude, test duration, voltage thresholds) based on the battery type being tested. The control system detects or is configured for the specific battery voltage type and automatically adjusts the test parameters accordingly. This parameter adaptation enables accurate battery health monitoring across different battery types using a single unified hardware platform.
4Reliability
If battery replacement is performed every two or three years, then preventive maintenance is ensured, but the full capacity and lifetime of the batteries is not used and premature replacement occurs
Solution Approach 1:
The patent implements feedback by continuously monitoring battery health parameters (voltage drop under load, current characteristics, state of charge) and using this information to assess actual battery condition. The control system provides feedback on battery health status and can trigger replacement alerts based on actual performance degradation rather than arbitrary time intervals. This feedback mechanism enables condition-based maintenance, extending battery usage until actual failure signs appear while ensuring safety.
Solution Approach 2:
The system performs preliminary and periodic battery health assessments to detect degradation trends before critical failure occurs. By conducting regular but intelligent health checks (using the load test method) and analyzing the results, the system can predict remaining battery life and plan replacement timing optimally. This preliminary detection capability prevents both premature replacement and unexpected failures.
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 provides a reliable and efficient means to assess the functional status of emergency power supply batteries, enabling condition-based maintenance, reducing unnecessary replacements, and ensuring the battery is replaced before its usable lifetime is exceeded, thus ensuring the safety and functionality of elevator operations during power outages.
Implementation Method 1
Some techniques which estimate the health state (or the state of charge) of the battery according to the measurement of an AC or DC resistance of the battery
Implementation Method 2
In some basic techniques battery testing is done by connecting a power resistor to the battery terminals for a short period of time and monitoring how much the battery terminal voltage drops
Data Source
AI summary
The invention relates to an elevator comprising an elevator control having a motor drive of an elevator motor driving an elevator car on an movement path, which motor drive comprising a frequency converter with a rectifier bridge designed to be connected to mains, a converter bridge for feeding the elevator motor and an intermediate DC circuit located in-between, the elevator further comprising a brake drive for supplying energy to at least two motor brakes with the brake drive being connected to the intermediate DC circuit as well as an emergency power supply battery designed to allow safe release of passengers in case of a power outage. According to the invention the battery is connected to the intermediate DC circuit, and the elevator control has a measuring circuit connected to the intermediate DC circuit and the elevator control has a battery testing module which is configured to apply a defined load to the battery and to measure the voltage of the DC circuit for a defined time period. The battery testing module comprises a comparator for comparing the measured voltage with at least one stored first threshold value, whereby the elevator control is configured to issue a replacement signal for the battery dependent on the signal of the comparator.