Vehicle Battery Pack Isolation Detection Using Precision Resistors
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Solution Overview
Problem
High voltage power supplies in electric and hybrid-electric vehicles can experience undesirable leakage currents due to resistance between the power supply and chassis, which existing technologies struggle to effectively detect and manage, especially in distributed battery pack configurations.
Innovation Solution
A leakage detection circuit is implemented, comprising precision resistors and switching elements connected to chassis ground, allowing for the detection of leakage currents across multiple battery packs using centrally located sense circuitry and controllers to determine the presence and magnitude of leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leakage detection circuitry is implemented in each distributed battery pack, then leakage current detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The detection circuitry is segmented such that only essential components (switching element and series limiting resistor) are placed in each battery pack, while the precision resistor and sense circuitry are centralized in one location. This segmentation reduces complexity in each individual pack while maintaining detection capability across all packs.
Solution Approach 2:
A precision resistor serves as an intermediary element that enables centralized measurement of leakage currents from multiple battery packs. The switching elements act as intermediaries to selectively connect different battery packs to the shared sense circuitry, allowing one measurement system to monitor multiple packs without requiring full detection circuitry in each pack.
2Device complexity
If precision resistors and sense circuitry are centralized, then cost and complexity are reduced, but detection coverage across distributed packs must be maintained
Solution Approach 1:
The centralized sense circuitry and precision resistor serve multiple battery packs simultaneously, performing the universal function of leakage detection across the entire vehicle. The switching elements enable this single measurement system to universally monitor any or all battery packs by selectively connecting them to the shared circuitry.
Solution Approach 2:
Each battery pack contributes its own switching element and series limiting resistor to the shared detection system, effectively providing part of the detection infrastructure itself. This self-service approach allows each pack to participate in the centralized detection system without requiring external dedicated circuitry.
3Power
If high voltage power supplies are used to increase output, then power output is improved, but leakage currents increase
Solution Approach 1:
The sense circuitry continuously monitors voltage across the precision resistor, which is proportional to leakage current flowing through it. This feedback mechanism allows the control system to detect when leakage currents exceed acceptable thresholds and take appropriate action, such as isolating affected battery packs or alerting the operator.
Solution Approach 2:
The patent replaces direct current measurement (which would require high-current sensing) with voltage measurement across a precision resistor. This substitution allows leakage current detection using low-voltage, low-current sense circuitry, making the detection system safer and more practical for high-voltage environments.
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 enables efficient detection and management of leakage currents across distributed battery packs, reducing costs and complexity by using a centralized sense circuitry and precision resistors connected to chassis ground, ensuring proper functioning of isolation detection circuits.
Implementation Method 1
a first precision resistor disposed within the first battery pack and electrically connected with chassis ground... sense circuitry configured to detect voltage across the resistor
Data Source
AI summary
A power system for a vehicle includes at least two battery packs spaced away from each other. A first battery pack includes a plurality of battery cells and a switching element electrically connected with the battery cells. A second battery pack includes a resistor electrically connected in series with the switching element, and sense circuitry configured to detect voltage across the resistor indicative of leakage current associated with the first battery pack.