Vehicle Isolation Switch Control for Dual Battery Voltage Matching
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Solution Overview
Problem
The electric isolation switch in vehicle electrical systems experiences degradation due to high current flow during engine starting, which can lead to reduced lifespan and abrupt changes in system voltage levels.
Innovation Solution
Reducing the voltage of the low voltage primary electric energy storage device using a controller before closing the electric isolation switch, thereby reducing current flow through the switch, is implemented to mitigate these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric isolation switch is closed to charge both electric energy storage devices via the starter/generator, then both devices can be charged simultaneously, but high current flow through the switch causes degradation and reduces its lifespan
Solution Approach 1:
The controller reduces the voltage of the primary electric energy storage device before closing the electric isolation switch. This preliminary voltage reduction prevents high current flow through the switch when it closes, thereby protecting the switch from degradation while still enabling efficient charging of both energy storage devices
Solution Approach 2:
The controller actively adjusts the voltage parameter of the primary electric energy storage device to a reduced level before switch closure. This parameter change ensures that when the switch closes, the voltage difference across it is minimized, reducing current flow and protecting the switch from high-stress conditions
2Reliability
If the electric isolation switch remains open during engine cranking to protect the switch, then switch degradation is prevented, but the accessory electric energy storage device cannot be charged simultaneously
Solution Approach 1:
The controller performs voltage reduction on the primary electric energy storage device before closing the isolation switch, enabling the switch to be closed safely without experiencing high current stress. This preliminary preparation allows the system to achieve full charging capability while protecting the switch
Solution Approach 2:
The voltage reduction action counteracts the potential harmful effect of high current flow before the switch closes. By preemptively reducing voltage, the system prevents the harmful current surge that would otherwise occur when connecting the two energy storage devices
3Productivity
If high current flows through the electric isolation switch during engine starting, then the primary electric energy storage device can be charged quickly, but the switch experiences degradation and voltage levels change abruptly
Solution Approach 1:
The controller changes the voltage parameter of the primary electric energy storage device to a reduced level before switch closure. This parameter adjustment ensures that when the switch closes, current flow is limited to safe levels, preventing switch degradation while still enabling effective charging
Data Source
AI summary
Systems and methods for supplying electrical power between two electric energy storage devices are disclosed. In one example, an electric isolation switch is held open after engine starting until a voltage of a first electric energy storage device and a voltage of a second electric energy storage device are within a threshold voltage of at least one predetermined voltage level.