Dual-Battery EV Charging Control Through the Motor System
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Solution Overview
Problem
Electric vehicles face limitations in driving distance due to battery voltage and capacity constraints, where increasing battery capacity requires matching both output and withstand voltage of the motor system, making it challenging to enhance driving range without increasing vehicle price or weight.
Innovation Solution
Incorporating an auxiliary battery and a controller that allows the main battery to be charged by the auxiliary battery through the motor system during driving, using boost or buck converter topologies to manage power distribution between the batteries, thereby optimizing voltage and capacity without separate voltage-raising means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the capacity of the battery is increased to extend driving distance, then the driving distance is improved, but the motor system must satisfy both output reference voltage and withstand voltage reference voltage requirements, increasing system complexity and cost
Solution Approach 1:
The battery system is divided into two separate batteries: a main battery connected to the motor system and an auxiliary battery not directly connected to the motor system. This segmentation allows the main battery to be sized for motor power requirements while the auxiliary battery provides additional capacity for extended driving distance, eliminating the need to oversize the motor system for the total battery capacity.
Solution Approach 2:
A voltage conversion device (DC-DC converter or charging device) is introduced as an intermediary between the auxiliary battery and the main battery. This intermediary enables power transfer and voltage matching, allowing the auxiliary battery to charge the main battery without direct connection to the motor system, thus maintaining motor system simplicity while extending driving distance.
2Power
If the voltage of the battery is increased to improve power performance, then the available power is improved, but the withstand voltage design of the motor system must be strengthened, increasing cost and complexity
Solution Approach 1:
The battery system is segmented into a main battery connected to the motor system with voltage matched to motor requirements, and an auxiliary battery with potentially different voltage characteristics. This allows the motor system to be designed for optimal performance without needing to withstand higher voltages from an oversized battery configuration.
Solution Approach 2:
A voltage conversion device serves as an intermediary that performs voltage matching and conversion between the auxiliary battery and the main battery/motor system. This intermediary enables the system to utilize higher voltage or different voltage configurations in the auxiliary battery without requiring the motor system to be designed for those higher voltages.
3Ease of operation
If a separate voltage-raising means is added to charge the main battery, then the charging capability is improved, but the device complexity and vehicle cost increase
Solution Approach 1:
The auxiliary battery is designed to serve multiple functions: it extends driving distance by providing additional energy storage and simultaneously provides charging capability for the main battery through the voltage conversion device. This multi-functionality eliminates the need for separate voltage-raising means or additional charging infrastructure.
Solution Approach 2:
The system enables self-charging capability where the auxiliary battery can charge the main battery through the voltage conversion device during vehicle operation. This self-service charging mechanism eliminates the need for external voltage-raising equipment or complex external charging systems in certain operating conditions.
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 approach enables efficient charging of the main battery using the auxiliary battery, optimizing voltage and capacity without unnecessary increases in vehicle price or weight, enhancing driving range while maintaining motor system performance.
Implementation Method 1
the controller may control the main battery to be charged by raising power of the auxiliary battery through the motor system during driving of the electric vehicle
Implementation Method 2
the controller may control the auxiliary battery to be charged by decreasing power of the main battery through the motor system when charging the main battery through an external power source
Data Source
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AI summary
An electric vehicle may include a motor system having a motor and an inverter, a main battery and an auxiliary battery, and a controller which controls the main battery to be charged by voltage step-up of power of the auxiliary battery through the motor system during driving of the electric vehicle, and controls the auxiliary battery to be charged by voltage step-down of power of the main battery through the motor system when charging the main battery through an external power source.