Battery Pack Voltage Sag Detection for Adaptive Power Tool Output
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Solution Overview
Problem
Existing power tools with battery packs face challenges in interoperability and efficiency due to differences in battery pack capabilities, which can lead to inconsistent performance and reduced flexibility in use.
Innovation Solution
Implementing a common interface format for battery packs allows for easy swapping between tools and charging on a single charger, while using voltage drop measurements to determine battery pack capacity and optimize control signals for the power tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a common interface format is implemented for battery packs, then ease of operation and adaptability are improved, but device complexity increases due to the need to handle different battery capabilities
Solution Approach 1:
The controller performs a voltage drop test before normal operation to pre-characterize the battery pack's internal resistance and capacity. This preliminary measurement allows the system to store battery capability data in advance, eliminating the need for complex real-time adjustments during operation and simplifying the control logic while maintaining ease of use.
Solution Approach 2:
The system continuously monitors battery voltage during operation and uses feedback from voltage drop measurements to dynamically adjust control parameters. This feedback mechanism enables the controller to adapt to different battery capabilities automatically, resolving the complexity issue while maintaining a simple common interface for users.
2Measurement precision
If voltage drop measurements are used to determine battery capacity, then measurement precision is improved, but device complexity increases due to additional sensing and control circuitry
Solution Approach 1:
The battery pack itself provides the measurement signal by exhibiting its natural voltage drop response when a known current is applied. The existing power tool circuitry serves dual purposes: it draws test current and measures the resulting voltage drop, eliminating the need for separate dedicated measurement hardware and reducing overall device complexity while maintaining high measurement precision.
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 approach enhances the flexibility and efficiency of power tool systems by allowing for seamless battery pack interchangeability and optimized performance based on real-time battery capacity assessments.
Implementation Method 1
a sensing circuit configured to detect a voltage of the battery pack
Implementation Method 2
the voltage drop V exhibited by a battery pack in response to a given load (such as current I) to determine a capacity of the battery pack... the voltage drop V may be expressed as a function of the current draw I and the internal resistance R of the battery pack according to Ohm's law
Data Source
AI summary
A battery-pack-powered device includes an interface configured to receive a battery pack, a sensing circuit configured to detect a voltage of the battery pack, and an electronic controller. The electronic controller is configured to receive a first signal from the sensing circuit indicative of a no-load voltage of the battery pack, determine a threshold voltage based on the no-load voltage, generate a control signal to drive an electric motor at a first operating parameter in response to an activation of a trigger switch, receive a second signal from the sensing circuit, and update the control signal to drive the electric motor at a second operating parameter less than the first operating parameter in response to the second signal indicating that the output voltage is below the threshold voltage. The second signal is indicative of an output voltage of the battery pack during operation of the electric motor.