Hybrid EV Battery Output Control for Power Demand and Aging
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Solution Overview
Problem
Current electric vehicles using single high energy density lithium batteries face issues such as low power density, high current resistance, slow charging, and battery aging due to rapid internal resistance increases, especially under varying driving conditions, leading to inefficient energy consumption and battery degradation.
Innovation Solution
A hybrid battery system integrating high energy density and high power density batteries with a global search algorithm to optimize energy distribution, using boundary conditions and an energy consumption objective function to minimize equivalent energy consumption and extend battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single high energy density lithium battery is used, then energy storage capacity is improved, but power density and charging speed deteriorate
Solution Approach 1:
The battery system is segmented into two distinct battery modules: a high energy density battery module and a high power density battery module. Each module serves specific functions - the high energy density module handles energy storage and low-power operations, while the high power density module handles high-power demands and fast charging. This segmentation resolves the contradiction by allowing each battery type to operate in its optimal performance range without compromising the other.
2Quantity of substance
If a single high energy density lithium battery is used, then energy storage capacity is improved, but charging speed deteriorates
Solution Approach 1:
The charging function is segmented between two battery modules. The high power density battery module is specifically designed to accept high charging currents rapidly, while the high energy density battery module handles slower charging. The control system dynamically routes charging current to the appropriate module based on charging speed requirements, thereby achieving both high energy storage capacity and fast charging capability.
3Use of energy by moving object
If high current is applied to recover electrical energy during braking, then energy recovery efficiency is improved, but battery aging accelerates due to excessive current
Solution Approach 1:
The regenerative braking energy recovery function is segmented to the high power density battery module, which is specifically designed to handle high current rates. This module absorbs the high current during braking without suffering from rapid aging, while the high energy density battery module continues to operate at lower current rates. This segmentation allows aggressive energy recovery without compromising the longevity of the energy storage battery.
Solution Approach 2:
The high power density battery module acts as an intermediary between the regenerative braking system and the high energy density battery. It temporarily absorbs high current during braking, protecting the high energy density battery from excessive current stress that would cause rapid aging. The control system manages the current flow through this intermediary to optimize both energy recovery and battery longevity.
4Power
If the battery operates under varying driving conditions requiring large instantaneous current, then power demand is met, but the battery module overheats and life is shortened
Solution Approach 1:
The battery system is segmented into thermal management zones with different characteristics. The high power density battery module has thermal design optimized for high current discharge with better heat dissipation capabilities, allowing it to handle instantaneous power demands without overheating. The high energy density battery module operates in a more thermally stable regime. This thermal segmentation allows the system to meet peak power demands while protecting the energy storage battery from thermal stress that would shorten its life.
Data Source
AI summary
A method of hybrid battery electrical energy output distribution control for an electric vehicle. The method has steps comprising: (A) providing battery data of a high energy density battery and a high power density battery; (B) setting a boundary condition comprising (a) the highest and lowest boundary values of the state of health (SOH) of the batteries, (b) the highest and lowest boundary values of the state of charge (SOC) of the batteries, (c) the highest and lowest boundary values of the charge and discharge rate (C-rate) of the high energy density battery; (C) setting an energy consumption objective function; (D) using a global search algorithm to search and calculate the minimum equivalent energy consumption value under various driving conditions to establish a minimum equivalent energy consumption multi-dimensional table to achieve the output of minimum energy consumption under different driving conditions.