Hybrid Vehicle Electrical System Isolation Switch
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Solution Overview
Problem
In hybrid electric vehicles (HEVs), the divergence between high power density and energy density requirements for propulsion and accessory systems leads to battery longevity issues and performance limitations, with high power density batteries suffering from reduced longevity and high energy density batteries compromising performance and flexibility.
Innovation Solution
A vehicular electrical system with a high voltage electrical system and a low voltage electrical system, interfaced via a DC to DC converter, includes a control switch that toggles between open and closed positions to isolate the low voltage system from the high power electrical energy storage device, preventing parasitic currents from draining the low voltage battery and maintaining the high power device's state of charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high power density battery is employed in HEV to meet propulsion requirements, then power delivery capability is improved, but battery longevity deteriorates due to deep discharges from accessory loads during engine off idle
Solution Approach 1:
The patent divides the electrical energy storage system into two separate batteries: a high voltage battery dedicated to propulsion power delivery and a low voltage battery dedicated to accessory loads. This segmentation allows each battery to operate within its optimal performance range, preventing the high voltage battery from suffering deep discharges that would reduce its longevity.
Solution Approach 2:
The patent extracts the accessory load power consumption from the high voltage battery system by introducing a separate low voltage battery. This removes the harmful factor (parasitic discharge on the high voltage battery) while maintaining the necessary power delivery capability for propulsion.
2Use of energy by moving object
If a high energy density battery is employed to extend operation during engine off idle, then energy storage capacity is improved, but HEV performance and operational flexibility deteriorate
Solution Approach 1:
The patent segments the energy storage function into two specialized batteries: a high voltage battery optimized for power delivery and propulsion flexibility, and a low voltage battery optimized for energy storage during accessory loads. This allows each component to excel at its specific function without compromising overall system performance.
Solution Approach 2:
The patent applies local quality by optimizing each battery's characteristics for its specific role: the high voltage battery is designed for high power output and rapid response to propulsion demands, while the low voltage battery is designed for sustained energy storage during idle periods. Each battery's properties are locally optimized for its designated function.
3Ease of operation
If the low voltage system remains connected to the high voltage system during engine off idle, then accessory power availability is improved, but parasitic currents cause high power electrical energy storage device discharging
Solution Approach 1:
The patent segments the electrical systems into electrically isolated low voltage and high voltage systems, with dedicated power sources for each. This prevents parasitic currents from draining the high power electrical energy storage device while maintaining accessory power availability through the low voltage battery.
Solution Approach 2:
The patent extracts the accessory power consumption path from the high voltage system by providing a dedicated low voltage battery and control switch. This removes the harmful parasitic current path while preserving the ability to power accessories during engine off idle.
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 effectively prevents low voltage battery draining and high power electrical energy storage device discharging, optimizing battery life and HEV performance by isolating accessory loads from propulsion systems, eliminating the need for combination batteries, and enabling bi-directional energy recovery and charging.
Implementation Method 1
a control switch that toggles between an opened and a closed position to control the flow of current flowing between the low voltage power source and the HPD
Implementation Method 2
A vehicular electrical system with a high voltage electrical system and a low voltage electrical system, interfaced via a DC to DC converter
Data Source
AI summary
A vehicular electrical system for a hybrid electric vehicle provides a high voltage electrical system having a high power electrical energy storage device (HPD) and a power inverter that cooperate to provide power to a hybrid electric vehicle propulsion system; and a low voltage electrical system having a low voltage power source, at least one accessory power load, and a control switch that toggles between an opened and a closed position to control the flow of current flowing between the low voltage power source and the HPD. A method of using the vehicular electrical system provides the step of using the HPD and power inverter to provide power to the electric vehicle propulsion system; and opening a control switch to isolate the low voltage system from the high voltage system and closing a control switch to charge the HPD.