Dual Li-Ion Vehicle Power Supply for Cold Engine Starting
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Solution Overview
Problem
Lithium-ion batteries used as low voltage batteries in vehicles experience reduced output at very low temperatures, leading to insufficient engine starting performance, particularly at temperatures between −20° C. and −30° C.
Innovation Solution
A vehicle configuration utilizing a lithium-ion battery for both low voltage and high voltage systems, where the high voltage battery with a higher output voltage powers a second rotating electrical machine to ensure reliable engine starting, and a DC-DC converter for voltage conversion between the batteries, allowing the low voltage battery to be charged by the high voltage battery when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lithium-ion battery is used as a low voltage battery to improve reliability, then the reliability of the power supply system is improved, but the output decreases at very low temperatures causing insufficient engine starting performance
Solution Approach 1:
The patent combines a high voltage lithium-ion battery and a low voltage lithium-ion battery into a unified power supply system. The high voltage battery (48V) and low voltage battery (12V) work together, where the high voltage battery compensates for the low temperature output deficiency of the low voltage battery through voltage boosting capability, while both maintain reliable power supply for different system requirements.
Solution Approach 2:
The patent changes the voltage parameter by introducing a high voltage battery (48V) to compensate for the low output of the low voltage battery (12V) at very low temperatures. The voltage conversion device transforms voltage between the two batteries, enabling the high voltage battery to provide additional power when the low voltage battery's output is insufficient due to cold temperature conditions.
2Power
If a high voltage battery is introduced to improve engine starting performance at low temperatures, then the power output is improved, but the device complexity increases
Solution Approach 1:
The high voltage lithium-ion battery serves multiple functions: it acts as the main power source for the rotating electrical machine during vehicle operation, and simultaneously serves as a backup power source for engine starting when the low voltage battery's output is insufficient at very low temperatures. This multi-functionality reduces the need for separate dedicated starting batteries or complex heating systems.
Solution Approach 2:
The voltage conversion device acts as an intermediary between the high voltage battery and low voltage battery, enabling bidirectional power transfer and voltage transformation. This mediator allows the system to flexibly allocate power from either battery depending on temperature conditions and power requirements, simplifying the overall system architecture compared to having separate power sources for different functions.
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
Enables reliable engine starting at very low temperatures by leveraging the higher output voltage of the high voltage lithium-ion battery, improving the reliability and efficiency of the power supply system while reducing the need for high-performance DC-DC converters and maintaining backup power for vehicle components.
Implementation Method 1
a high voltage battery constituted by a lithium-ion battery, the high voltage battery having an output voltage higher than an output voltage of the low voltage battery
Implementation Method 2
a DC-DC converter for voltage conversion between the batteries, allowing the low voltage battery to be charged by the high voltage battery when necessary
Data Source
AI summary
A vehicle includes: a low voltage battery constituted by a lithium-ion battery, the low voltage battery supplying an electric power to an electric component mounted to a vehicle; a high voltage battery constituted by a lithium-ion battery, the high voltage battery having an output voltage higher than an output voltage of the low voltage battery; a first rotating electrical machine that operates by an electric power supplied from the high voltage battery, the first rotating electrical machine generating a torque for driving the vehicle; and a second rotating electrical machine for starting the engine. The second rotating electrical machine operates by an electric power supplied from the high voltage battery.