Modular EV Battery Pack With DC-DC Balancing for Mixed Cell Loads
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Solution Overview
Problem
Existing battery systems for electric vehicles face challenges in maintaining cell balance, leading to reduced storage capacity and lifetime due to differences in cell capacity, internal resistance, and temperature, which can result in overcharging, overdischarging, and incomplete charging, and are often complex and costly to manage.
Innovation Solution
A battery system comprising first and second battery modules, where first modules are connected directly in series and second modules are connected via power electronics units with DCDC converters, allowing flexible charging and discharging, and enabling the use of high-energy and high-power cells, with smart battery management for optimized voltage control and balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive balancing techniques are used, then cost is reduced, but balancing speed decreases
Solution Approach 1:
The battery system is divided into multiple independently controllable modules, each with its own DC-DC converter. This segmentation allows individual module balancing without affecting the entire battery system, enabling faster and more flexible balancing operations while maintaining cost-effectiveness through modular architecture.
Solution Approach 2:
A DC-DC converter is introduced as an intermediary device between battery modules to enable active balancing. The converter acts as a mediator that can transfer charge between modules, achieving fast balancing while avoiding the need for expensive direct high-voltage balancing circuits across the entire battery system.
2Productivity
If active balancing techniques are used, then balancing speed is improved, but cost increases
Solution Approach 1:
The battery system is divided into multiple independently controllable modules, each with its own DC-DC converter. This segmentation allows individual module balancing without affecting the entire battery system, enabling faster and more flexible balancing operations while maintaining cost-effectiveness through modular architecture.
Solution Approach 2:
A DC-DC converter is introduced as an intermediary device between battery modules to enable active balancing. The converter acts as a mediator that can transfer charge between modules, achieving fast balancing while avoiding the need for expensive direct high-voltage balancing circuits across the entire battery system.
3Adaptability or versatility
If DC-DC converters are assigned to each battery module, then charging and discharging flexibility is improved, but device complexity increases
Solution Approach 1:
The battery system is divided into multiple independently controllable modules, each with its own DC-DC converter. This segmentation allows individual module balancing without affecting the entire battery system, enabling faster and more flexible balancing operations while maintaining cost-effectiveness through modular architecture.
Solution Approach 2:
The DC-DC converters are designed with multi-functionality, serving both as voltage matching devices for charging/discharging operations and as balancing devices for cell voltage equalization. This universal design reduces overall system complexity by combining multiple functions into a single component.
4Adaptability or versatility
If DC-DC converters are assigned to each battery module, then charging and discharging flexibility is improved, but the number of power components increases
Solution Approach 1:
The DC-DC converters are designed with multi-functionality, serving both as voltage matching devices for charging/discharging operations and as balancing devices for cell voltage equalization. This universal design reduces overall system complexity by combining multiple functions into a single component.
Solution Approach 2:
The charging/discharging control function and the cell balancing function are merged into the same DC-DC converter unit. This consolidation reduces the total number of power components needed in the system while maintaining full flexibility for both charging operations and cell voltage balancing.
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 enhances battery system efficiency, extends cell lifetime by up to 30%, allows for flexible charging from 400V or 800V stations, and facilitates recycling by enabling the use of various cell types, while ensuring even load distribution and high utilization of cells.
Implementation Method 1
each second battery module comprises a power electronics unit having a DCDC converter
Data Source
Figure 1
Figure 2
AI summary
Battery system (1) for an electric vehicle, comprising - a number of first battery modules (2) each comprising a number of battery cells (4), - a number of second battery modules (3) each comprising a number of battery cells (5), wherein each second battery module (3) comprises a power electronics unit (14) having a DCDC converter, wherein the first and second battery modules (2, 3) are connected in series, wherein the first battery modules (2) are connected directly in series and the second battery modules (3) are connected via their power electronics units (14).