Nickel Leaf Current Shunt for Battery Temperature Stability
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Solution Overview
Problem
Current shunts used in battery systems face challenges in maintaining accurate current measurement across varying temperatures due to resistance variations in conductive materials, particularly at high currents, where minimizing resistance is crucial to reduce energy loss, and affordable materials like constantan are expensive and not always feasible.
Innovation Solution
A current shunt formed of multiple parallel nickel leaves, which provides a substantially constant temperature coefficient of resistance over a wide temperature range, using nickel or alternative materials like stainless steel or titanium zinc, arranged in a stack with conductive plates for series coupling and adjustable thickness to manage current flow, and potentially incorporating heat sinks for temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If constantan material is used for current shunt, then temperature coefficient of resistance is substantially constant, but material cost increases significantly
Solution Approach 1:
The patent uses a composite structure of multiple nickel leaves arranged in parallel between conductive plates. This composite material approach achieves a substantially constant temperature coefficient of resistance (α20 between +0.0001 and +0.0006 per degree Celsius) while using cheaper nickel material instead of expensive constantan, thereby resolving the contradiction between measurement stability and manufacturing cost.
2Loss of energy
If shunt resistance is minimized for high current applications, then energy loss is reduced, but measurement accuracy deteriorates due to insufficient voltage signal
Solution Approach 1:
The patent transitions from a single thick shunt element to multiple thin parallel leaves. This dimensional change increases the total surface area and improves heat dissipation, allowing the shunt to maintain lower resistance for high current applications while the increased surface area compensates for heat buildup, thus maintaining both low power loss and measurement accuracy.
Solution Approach 2:
The shunt is segmented into multiple parallel nickel leaves instead of a single solid piece. This segmentation allows optimization of the resistance value by adjusting the number, width, and thickness of individual leaves, enabling precise control over both the voltage signal for measurement accuracy and the power loss characteristics.
3Ease of manufacture
If nickel leaves are used instead of constantan, then material cost decreases, but temperature stability of resistance may worsen
Solution Approach 1:
The patent carefully controls the physical parameters of the nickel leaves, specifically the thickness range (0.002 to 0.010 inches) and the number of leaves (2 to 20), to achieve the desired temperature coefficient of resistance. By adjusting these parameters, the nickel-based shunt achieves substantially constant temperature characteristics comparable to constantan while maintaining lower material cost.
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 solution allows for accurate current measurement with minimal energy loss and reduced material costs by using nickel or alternative materials, maintaining consistent resistance across temperatures and accommodating high current applications with adjustable design and calibration, thus optimizing battery management system performance.
Implementation Method 1
A current shunt may be used to measure current flow in a circuit. The current to be measured may flow through a series-connected current shunt of known resistance, and the voltage across the shunt may be measured. Utilizing Ohm's Law (I=V/R), one may calculate the current based upon the measured voltage and the known resistance.
Implementation Method 2
The current shunt may have a resistance, Rshunt, in the range of 10 μΩ's to 100 μΩ's. The voltage across the nickel leaves may be measured, and the current may be calculated utilizing Ohm's Law: I=V/R
Implementation Method 3
The resistance of many conductive materials may vary with temperature. For the current calculation to be sufficiently accurate over a range of temperatures, the resistance of the conductive material should be relatively constant over the range of temperatures. The current shunt may provide a substantially constant temperature coefficient of resistance over the useful temperature range of the battery
Data Source
AI summary
For a lithium-ion battery pack adapted to provide electrical power to a load via a conductor, a current shunt adapted to be disposed in series with the conductor is disclosed. The current shunt comprises one or more stacked leaves of an electrically conductive material such as nickel.