Lithium-Polymer Tool Battery Pack Layout for High-Current Output
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Solution Overview
Problem
Existing battery packs for handheld power tools face challenges in delivering high current and voltage while maintaining compactness and light weight, with traditional lithium-ion cells having high internal impedance and inefficient use of housing volume.
Innovation Solution
A lithium-polymer based battery pack with a housing containing multiple flat lithium-polymer battery cells interconnected for high output voltage and current, using a resiliently deformable substrate to accommodate cell thickness variations and enhance mechanical support, and a compact design that maximizes battery volume utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional lithium-ion cells are used to deliver high current and voltage, then the power output is sufficient, but the internal impedance is high and the housing volume utilization is inefficient
Solution Approach 1:
The battery pack is divided into multiple individual lithium-polymer cells (e.g., five 3.7V cells) that are interconnected through a circuit board. This segmentation allows each cell to contribute to the overall power output while maintaining low internal impedance, as each cell operates independently with optimized electrical characteristics.
Solution Approach 2:
The patent uses lithium-polymer chemistry which combines lithium-ion technology with polymer electrolyte materials. This composite approach enables the cells to achieve both high power output and low internal impedance, overcoming the limitations of traditional lithium-ion cells while maintaining safety and performance.
2Weight of moving object
If the battery pack is made compact and lightweight, then the portability is improved, but the housing volume utilization becomes inefficient
Solution Approach 1:
The battery cells are arranged in a stacked configuration rather than a linear arrangement, utilizing vertical space within the housing. This dimensional change allows for more efficient packing of cells, maximizing the use of available housing volume while keeping the overall footprint compact and the weight distributed evenly.
Solution Approach 2:
The circuit board is designed to nest between the stacked battery cells, with connection tabs extending through designated openings. This nesting arrangement optimizes space utilization by integrating the electrical connection structure within the existing cell arrangement, eliminating the need for separate mounting spaces and reducing overall housing volume requirements.
3Power
If multiple battery cells are interconnected to increase power output, then the current and voltage are sufficient, but the mechanical support and cell thickness variation accommodation become challenging
Solution Approach 1:
The circuit board incorporates resilient tabs with elastic properties that can flex and adapt to thickness variations in the stacked battery cells. This dynamic characteristic allows the electrical connection structure to accommodate natural dimensional variations in the cells without requiring rigid, complex mechanical support, simplifying the overall design while maintaining reliable electrical contact.
4Volume of stationary object
If the battery cells are stacked to maximize housing volume utilization, then the compactness is improved, but the thermal management and mechanical protection become more difficult
Solution Approach 1:
The circuit board serves as an intermediary structure between the stacked battery cells, providing both electrical connection and thermal management functions. The board's material properties and design allow it to conduct heat away from the cells while maintaining electrical connectivity, thus managing thermal effects in the compact stacked arrangement without compromising cell safety or performance.
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
The lithium-polymer battery pack achieves a high average discharge current of over 10 amps and low internal impedance, enabling efficient power delivery to handheld tools while being compact and lightweight, with improved mechanical protection and thermal management.
Implementation Method 1
a resiliently deformable substrate located between the adjacent battery cells
Data Source
AI summary
A lithium-polymer based battery pack for power a hand held power tool or a garden tool, the battery pack has a plurality of battery cells located within housing that is selectively connectable to and supportable by a hand held power tool or a garden tool. The battery cells have a lithium-polymer based chemistry and a nominal charged internal impedance of less than or equal to approximately 5 milliohms. In one embodiment the cells are think cells are stacked within the housing such that each sell is layered over or under an adjacent cell and a resiliently deformable substrate located between adjacent battery cells. In another embodiment the cells may be interconnected to have a combined output voltage of at least 9 volts and to produce a combined average discharge current of greater than 20 amps. A lithium-polymer tool battery and a battery powered tool are also part of the invention.