Auxiliary Battery Reverse Charging for Engine Start Reliability
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Solution Overview
Problem
In mild-hybrid electric vehicles, insufficient state of charge in the main battery prevents engine start, leading to increased noise, longer start-up times, and inability to move the vehicle, especially when power electronic components are not operational.
Innovation Solution
An apparatus and method that include a controller monitoring vehicle components, generating diagnostic information, and issuing a reverse charging control command to supply power from an auxiliary battery to the main battery, using a first motor connected to the crankshaft to start the engine and a second motor as a dedicated starter when components are abnormal, with a bidirectional DC-DC converter regulating power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main battery capacity is increased to ensure sufficient charge for engine start, then the reliability of engine start is improved, but the weight of the vehicle and the number of wirings/harnesses increase
Solution Approach 1:
The power supply system is segmented into two independent batteries: a main battery (140) for normal power supply and an auxiliary battery (150) specifically for engine starting. This segmentation allows each battery to be optimized for its specific function, enabling the main battery to be smaller while still ensuring reliable engine starting capability through the auxiliary battery's support.
Solution Approach 2:
A bidirectional DC-DC converter (210) is introduced as an intermediary device between the main battery and auxiliary battery. This converter enables automatic power transfer from the auxiliary battery to the main battery when the main battery's charge level is insufficient, ensuring reliable engine starting without requiring the main battery to be oversized.
2Reliability
If the main battery capacity is increased to ensure sufficient charge for engine start, then the reliability of engine start is improved, but the complexity of the electrical system increases
Solution Approach 1:
The auxiliary battery (150) is designed with multi-functionality: it serves as a starting battery for engine cranking, a power source for electrical loads during engine-off periods, and a backup power source that can automatically charge the main battery through the bidirectional DC-DC converter. This universal design reduces the need for additional dedicated components.
Solution Approach 2:
The bidirectional DC-DC converter (210) acts as an intelligent intermediary that automatically manages power flow between the two batteries based on charge levels and system requirements. It enables the auxiliary battery to charge the main battery when needed, providing a simple yet effective solution that maintains reliability without significantly increasing system complexity.
3Reliability
If the conventional starter is used when main battery charge is insufficient, then the engine can be started, but noise and start-up time increase
Solution Approach 1:
The bidirectional DC-DC converter (210) serves as an intermediary that detects when the main battery charge is insufficient and automatically transfers power from the auxiliary battery to the main battery before engine starting. This ensures the main battery has sufficient charge to operate the first motor (130) for quiet, efficient engine starting, preventing the need to use the noisier conventional starter.
Solution Approach 2:
The system performs preliminary charging of the main battery from the auxiliary battery through the bidirectional DC-DC converter before the engine starting process begins. This preliminary action ensures the main battery is adequately charged to power the first motor, thereby avoiding the need to use the conventional starter and reducing both noise and start-up time.
4Use of energy by moving object
If the auxiliary battery supplies power to electrical loads, then the power consumption requirements are met, but the engine may not start when main battery charge is insufficient
Solution Approach 1:
The bidirectional DC-DC converter (210) acts as an intermediary that continuously monitors the charge levels of both batteries and automatically manages power flow. When the main battery charge becomes insufficient after supplying power to electrical loads, the converter automatically transfers power from the auxiliary battery to the main battery, ensuring the main battery retains sufficient charge for engine starting while still meeting electrical load power requirements.
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
Prevents engine failure to start due to insufficient main battery charge, reduces engine start noise and time, and allows vehicle movement even when power electronic components are not operational by ensuring sufficient power through reverse charging and torque assistance.
Implementation Method 1
an auxiliary battery configured to supply the reverse charging power to the main battery according to the reverse charging control command
Implementation Method 2
generating a reverse charging control command to supply the reverse charging power to the main battery
Implementation Method 3
with a bidirectional DC-DC converter regulating power
Implementation Method 4
a first motor connected to a crankshaft by a first connecting device to start the engine
Data Source
AI summary
An apparatus for controlling a start of an engine may include the engine, a first motor connected to a crankshaft by a first connecting device to start the engine, a main battery supplying a start power to the first motor, a controller configured to monitor components of a vehicle according to a start command for the engine to generate diagnostic information and generating a reverse charging control command to supply the reverse charging power to the main battery as the determination result of the diagnostic information, and an auxiliary battery supplying the reverse charging power to the main battery according to the reverse charging control command.