Electric Power Tool Battery Control for Low-Temperature Voltage Drop
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Solution Overview
Problem
Users face difficulty in distinguishing between battery depletion and voltage drops caused by low temperatures in electric power tools, leading to unexpected tool shutdowns.
Innovation Solution
Incorporating a drive control unit with a voltage meter and temperature meter that adjusts power supply to the motor based on predetermined voltage and temperature thresholds, allowing for differentiated operation and intermittent driving to distinguish voltage drops from battery depletion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the undercut function stops discharging when battery voltage is low (2.0V/cell), then battery protection is improved, but the user cannot distinguish between battery depletion and voltage drop caused by low temperature
Solution Approach 1:
The control unit continuously monitors battery voltage and temperature, and provides feedback to the display unit to show the cause of shutdown. When voltage is low and temperature is low, the display shows voltage drop as the cause. When voltage is low but temperature is normal, the display shows battery depletion. This feedback mechanism resolves the information loss by providing clear distinction between different shutdown causes.
Solution Approach 2:
The display unit acts as an intermediary between the battery system and the user. It translates complex electrical parameters (voltage, temperature readings from sensors) into user-friendly information about shutdown causes. This intermediary component bridges the gap between the technical battery protection mechanism and user understanding.
2Power
If large current is discharged when battery temperature is low (5°C or lower), then power delivery is improved, but voltage drop increases causing unexpected shutdown
Solution Approach 1:
The control unit dynamically adjusts the discharge characteristics based on real-time temperature readings. When temperature is low (≤5°C), the system modifies its power delivery behavior to account for increased voltage drop. The system doesn't simply reduce power, but adapts its operation to the thermal conditions, allowing power delivery while managing voltage stability through intelligent control.
Solution Approach 2:
The system changes operational parameters based on temperature conditions. When temperature drops to 5°C or lower, the control unit modifies discharge parameters to prevent excessive voltage drop. This parameter adjustment allows the system to maintain reliable operation in cold conditions by adapting to the changed electrical characteristics of the battery at low temperatures.
3Productivity
If the electric power tool operates under large load and low temperature, then productivity is improved, but the undercut function incorrectly stops operation due to voltage drop
Solution Approach 1:
The control unit performs preliminary assessment of battery conditions (voltage and temperature) before allowing operation to continue or stop. When the undercut function is triggered, the system first checks temperature to determine if the voltage drop is due to cold conditions rather than battery depletion. This preliminary action prevents incorrect shutdown decisions and maintains operation continuity when appropriate.
Solution Approach 2:
The system uses continuous feedback from temperature and voltage sensors to make real-time decisions about operation continuity. The control unit monitors whether voltage drops are within acceptable ranges for low-temperature operation and adjusts accordingly. This feedback loop ensures that productivity is maintained when the tool operates under large load and low temperature, preventing false shutdowns while still protecting against actual battery depletion.
Data Source
Figure 1~2C
AI summary
An electric power tool (10) includes a drive source (M), a rechargeable battery (21) that supplies power to the drive source (M), a voltage meter (18) that measures voltage of the rechargeable battery (21), a temperature meter (T) that measures temperature of the rechargeable battery (21), and a drive control unit (15,17) that regulates the power supplied to the drive source (M) from the rechargeable battery (21) to drive the drive source (M). If the battery temperature measured by the temperature meter (T) is lower than or equal to a predetermined temperature (Ts) when the battery voltage measured by the voltage meter (18) is lower than or equal to a predetermined voltage (Vs1), the drive control unit (15,17) drives the drive source (M) differently from normal driving that is performed if the battery temperature is higher than the predetermined temperature (Ts) when the battery voltage is higher than the predetermined voltage (Vs1).