Dual Battery Pack Thermal Management for Power Tools
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Solution Overview
Problem
Lawnmowers powered by rechargeable lithium-ion batteries face limitations in performance and operating time due to limited energy capacity, leading to frequent recharging needs and battery overheating, which shortens their service life.
Innovation Solution
A method for operating electrical devices with two battery packs, where the pack with the lowest temperature or lowest internal resistance is prioritized for discharge, and switching occurs when temperature differences are minimal, ensuring even heating and extended usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a single battery pack is used to power the electrical device, then the device structure is simple, but the operating time is limited and the battery heats up excessively
Solution Approach 1:
The single battery pack is segmented into multiple battery packs (first battery pack and second battery pack) that can be used alternately. This allows the thermal load to be distributed across multiple units, reducing the temperature increase in each individual battery pack while extending the total operating time of the device.
Solution Approach 2:
The control device periodically switches between the first and second battery packs based on temperature monitoring. When one battery pack reaches a critical temperature threshold, the system transitions to the other battery pack, creating a periodic operation pattern that prevents excessive heating and extends operational duration.
2Duration of action of moving object
If multiple battery packs are used to extend operating time, then the operating time increases, but the device complexity increases
Solution Approach 1:
The control device automatically monitors the temperature of both battery packs and autonomously switches between them based on predefined temperature thresholds. This self-service capability eliminates the need for manual intervention, allowing the system to manage multiple battery packs without proportionally increasing operational complexity for the user.
Solution Approach 2:
The control device integrates the temperature monitoring and switching logic into a single unified control unit that manages both battery packs. This merging of functions into one intelligent controller prevents the system complexity from scaling linearly with the number of battery packs.
3Power
If continuous discharge of a battery pack occurs, then the power delivery is consistent, but the battery overheats and service life decreases
Solution Approach 1:
The system implements periodic switching between battery packs before either pack reaches damaging temperature levels. This periodic action maintains consistent power delivery to the electrical device while allowing each battery pack to cool down during its inactive period, thereby preserving battery service life.
Solution Approach 2:
The control device proactively switches between battery packs based on temperature thresholds before excessive heating occurs. This preliminary action prevents thermal damage to the batteries while ensuring continuous power supply, maintaining both power delivery and reliability.
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 extends the service life of battery packs, allows for longer operating times, and prevents overheating, enabling continuous operation without interruptions.
Implementation Method 1
Another disadvantage is the high power requirement when mowing for longer periods under difficult conditions such as tall or damp grass. This leads to strong heating of the battery, which is detrimental to its service life.
Implementation Method 2
The first battery pack and the second battery pack are alternately discharged when the temperature of the first battery pack and the temperature of the second battery pack differ from each other by less than a specified threshold. Advantageously, the two battery packs then heat up to about the same extent
Data Source
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AI summary
In a method for operating an electrical device comprising a first battery pack, a second battery pack, and an electrical load, at most one battery pack is discharged at any given time to power the load. The battery pack to be discharged is selected based on the temperature of the first battery pack and the temperature of the second battery pack, and/or based on the internal resistance of the first battery pack and the internal resistance of the second battery pack.