Dual Power Source for Vehicle Auto Stop-Start
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Solution Overview
Problem
Auto stop-start equipped vehicles face challenges in managing power for high load devices during engine stop-start operations due to limited charge capacity of single 12V batteries, leading to potential battery depletion and customer dissatisfaction when critical features are unavailable during engine-off periods.
Innovation Solution
A dual power source system where a primary power source is used for the starter and a secondary power source supplies energy to electrical loads during engine-off sequences, with electrical isolation and monitoring to prevent depletion, ensuring sufficient power and maintaining functionality of electrical loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single 12V battery is used as the power source, then the system is simple and cost-effective, but the battery has limited charge power capability and may be depleted during engine stop-start operations when high load devices operate
Solution Approach 1:
The power source system is segmented into two independent batteries: a first battery connected to the starter motor for engine cranking, and a second battery connected to high load devices for powering electrical loads during engine-off periods. This segmentation allows each battery to be optimized for its specific function, resolving the contradiction between power capability and system simplicity.
2Ease of operation
If high load devices are allowed to operate during engine-off periods, then customer satisfaction improves, but the battery may be depleted to a point where engine re-start is not feasible
Solution Approach 1:
The electrical load system is segmented into critical loads (connected to the first battery for engine restart assurance) and non-critical high load devices (connected to the second battery). This allows high load devices to operate during engine-off periods without compromising the reliability of engine re-start operations.
Solution Approach 2:
Different quality levels of power supply are provided to different loads: critical systems receive guaranteed power from the first battery, while non-critical high load devices receive power from the second battery. This local differentiation resolves the contradiction between operational availability and restart reliability.
3Power
If both batteries are used to draw energy during engine re-start operation, then the starter motor has sufficient power, but both batteries may be depleted and voltage may drop below predetermined levels causing diagnostic trouble codes
Solution Approach 1:
The power delivery during engine re-start is segmented such that only the first battery connected to the starter motor provides energy for cranking operations. The second battery remains isolated and preserves its energy, preventing voltage drops that would trigger diagnostic trouble codes while ensuring sufficient power for starter motor operation.
Data Source
AI summary
An auto stop-start equipped vehicle power management system includes a primary power source supplying energy to an electrical starter to crank a vehicle engine and a secondary power source coupled in parallel to the primary power source. The secondary power source supplies energy to electric loads during an engine auto stop-start operation. The electrical loads maintain vehicle subsystem functionality during the engine auto stop-start operation. The energy supplied to the electrical loads is current limited during the engine auto stop-start operation. A controllable switch decouples the secondary power source from the primary power source and starter motor during the engine auto stop-start operation. Operating parameters of the electrical loads are monitored during the engine auto stop-start operation. If a respective operating parameter threshold associated with the electrical loads is exceeded during the engine auto stop-start operation, then the vehicle engine is automatically restarted and the controllable switch is subsequently closed.