Dynamic Shut-off Delay for Handheld Power Tool Battery Protection
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Solution Overview
Problem
Electric hand-held power tools with rechargeable batteries face excessive discharge when delayed shut-off is implemented for control electronics, leading to battery damage and user-unfriendly operation due to unexpected startup delays.
Innovation Solution
An exhaustive-discharge safeguard device adjusts the shut-off delay time based on the battery's state of charge, reducing energy discharge and preventing further battery damage by shortening the delay time as the battery level drops and shutting off devices without delay when critical thresholds are reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If delayed shut-off is implemented for control electronics, then user-friendliness is improved by preventing dead times during restart, but battery discharge increases leading to potential battery damage
Solution Approach 1:
The shut-off delay time is made dynamic rather than fixed. The control unit continuously monitors battery charge level and adjusts the delay time accordingly - longer delays when battery is well-charged, shorter or no delays when battery charge is low. This dynamic adaptation resolves the contradiction by allowing delayed shut-off benefits when energy is abundant while preventing excessive discharge when energy is scarce.
Solution Approach 2:
The delay time parameter is changed based on battery charge state. The system transitions from a static delay parameter to a variable one that depends on battery charge level. When battery charge exceeds a threshold, full delayed shut-off is applied; when charge drops below the threshold, the delay is reduced or eliminated, thus preventing exhaustive discharge while maintaining user-friendliness when possible.
2Reliability
If fixed delayed shut-off is used for control electronics, then dead times during restart are prevented, but battery charge threshold cannot be avoided leading to exhaustive discharge
Solution Approach 1:
The system implements feedback control by continuously monitoring battery charge level and using this information to adjust the shut-off delay behavior. The control unit receives feedback about battery state and modifies the delay parameter accordingly, creating a closed-loop system that prevents exhaustive discharge while maintaining restart reliability. This feedback mechanism allows the system to adapt to changing battery conditions in real-time.
Solution Approach 2:
The shut-off delay transitions from a fixed static parameter to a dynamic one that responds to battery charge conditions. The system actively adjusts the delay duration based on real-time battery state, ensuring reliability when charge is sufficient while preventing damage when charge is low, thus resolving the contradiction between maintaining restart reliability and avoiding exhaustive discharge.
3Reliability
If immediate shut-off is used when battery charge is low, then battery damage is prevented, but dead times occur during restart reducing user-friendliness
Solution Approach 1:
The delay time parameter is adjusted based on battery charge level. When battery charge is high, a longer delay is applied for user-friendliness. When battery charge drops below a threshold, the delay parameter is changed to zero or minimal value, immediately prioritizing battery protection while accepting the trade-off of potential dead times during restart.
Solution Approach 2:
The system dynamically switches between two operational modes: a user-friendly mode with delayed shut-off when battery charge is sufficient, and a protection mode with immediate or minimal delay when battery charge is low. This dynamic switching resolves the contradiction by adapting the shut-off behavior to current battery conditions, prioritizing user-friendliness when safe and battery protection when necessary.
Data Source
AI summary
The invention relates to a handheld electrical machine tool having at least one electrical drive, at least one electrical device requiring electrical energy for its operation, a shut-off delay apparatus for the electrical drive and/or the electrical device and having at least one rechargeable battery for the electrical supply to the drive and the electrical device. Provision is made for the handheld electrical machine tool to have an exhaustive discharge protection apparatus (8), which predetermines the delay time (t) of the shut-off delay apparatus (3) as a function of the state of charge of the rechargeable battery (9) detected by it. In addition, the invention relates to a corresponding method.