Vehicle Start/Stop Electrical System Voltage Stabilization
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Solution Overview
Problem
Existing start/stop systems in motor vehicles with internal combustion engines face voltage drops in electrical systems during engine shutdown, potentially affecting vital systems like exterior lighting and chassis systems, especially with increased start/stop events and higher current consumption.
Innovation Solution
The system includes a primary battery, a secondary battery, an alternator, and a DC/DC converter in parallel with a third energy source, such as a super-capacitor or lithium-ion battery, along with bypass switches to manage voltage and energy distribution, allowing the DC/DC converter to boost voltage during engine stops and providing redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large main battery and smaller support battery are used to maintain voltage during start/stop events, then voltage stability is improved, but device complexity and cost increase
Solution Approach 1:
The battery system is segmented into a main battery for starting functions and a support battery for voltage stabilization during start/stop events. This segmentation allows each battery to be optimized for its specific function, with the support battery being smaller and less expensive than a full main battery would require
Solution Approach 2:
A DC/DC converter is introduced as an intermediary device between the support battery and the vehicle electrical system. This converter actively regulates voltage levels, transferring energy from the support battery to maintain system voltage during engine shutdown, thereby reducing the required capacity of the support battery and overall system complexity
2Productivity
If a support battery is added to supply power during warm-starts, then engine restart capability is improved, but device complexity increases
Solution Approach 1:
The system incorporates a DC/DC converter that dynamically adjusts power flow between the support battery and electrical loads based on real-time voltage and current conditions. This dynamic control allows the support battery to be smaller since the converter compensates for power fluctuations during engine restart, reducing overall system complexity
Solution Approach 2:
The DC/DC converter actively changes electrical parameters (voltage, current) during engine restart events to optimize power delivery. By adjusting these parameters in real-time, the system achieves improved restart capability with a smaller support battery, thereby reducing device complexity
3Reliability
If DC/DC converter is used to manage power during start/stop events, then voltage control is improved, but device complexity increases
Solution Approach 1:
The electrical system is segmented into distinct functional blocks: main battery circuit, support battery circuit, DC/DC converter circuit, and load circuits. This segmentation allows the DC/DC converter to be optimized for voltage control without requiring redundant components throughout the entire system, managing complexity through modular design
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 configuration prevents undesirable voltage drops, allows for downsizing of the secondary battery, and extends its lifespan while ensuring reliable power supply to vehicle electrical loads, even during increased start/stop events and high current consumption.
Implementation Method 1
a DC/DC converter in series with a third electrical energy source V3... activating the DC/DC converter to boosting voltage
Implementation Method 2
an alternator A... during a warm-start of the engine after a start/stop event, closing the starter solenoid to supply power to the starter motor
Implementation Method 3
a primary battery V1 which is selectively connectible to a starter motor S... a secondary battery V2... allows for selective bypassing the DC/DC converter and charging/discharging of the third electrical energy source
Data Source
AI summary
An electrical system for a vehicle having an internal combustion engine with start/stop capability includes a primary battery connectible to an engine starter motor; a secondary battery, an alternator, and an electrical load in parallel with one another and selectively connectible in parallel with the primary battery by a charge switch; in parallel with the secondary battery, a DC/DC converter in series with a third electrical energy source; and a bypass switch operable to selectively bypass the DC/DC converter. The bypass switch allows for selective bypassing the DC/DC converter and charging/discharging of the third electrical energy source during start/stop operation, to ensure a sufficient voltage level over the additional vehicle electrical loads when the internal combustion engine and consequently the alternator are not running.