Series Battery Modules with DC-DC Balancing for Fast Charging
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Solution Overview
Problem
Existing battery systems in electric vehicles face issues with cell imbalance due to differences in capacity, internal resistance, and chemical degradation, leading to decreased storage capacity, lifetime, and potential damage from overcharging and overvoltage, while existing balancing techniques are either slow or expensive and complex.
Innovation Solution
A battery system design comprising first battery modules connected directly in series and second battery modules connected via power electronics units with DCDC converters, allowing flexible charging and discharging, with high-energy and high-power cells used separately for different performance needs, and a smart battery management system for optimal voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing techniques are used, then cell voltage can be balanced, but the balancing process is slow and charging time increases
Solution Approach 1:
A DC-DC converter is introduced as an intermediary device between battery modules to enable active power transfer balancing. The converter acts as a mediator that can rapidly redistribute energy between modules with different states of charge, achieving voltage balancing without the slow passive resistor discharge method, thus resolving the contradiction between balancing reliability and charging time.
2Loss of time
If active balancing techniques are used, then charging speed is improved, but system cost and complexity increase
Solution Approach 1:
The DC-DC converter is designed to perform multiple functions: it enables active balancing between battery modules, provides voltage matching for different module configurations, and supports flexible charging/discharging operations. By making the converter multi-functional, the patent reduces the need for separate dedicated balancing circuits, thereby lowering overall system complexity while maintaining fast charging capability.
3Adaptability or versatility
If DC-DC converters are assigned to each battery module, then flexible charging and discharging is achieved, but device complexity and heat generation increase
Solution Approach 1:
Instead of assigning individual DC-DC converters to each battery module, the patent merges the balancing function into a single centralized DC-DC converter that can manage power transfer between multiple modules. This consolidation reduces the total number of power components, decreases system complexity, and lowers heat generation while preserving the flexibility to charge and discharge different modules independently.
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
Enhances battery lifetime by up to 30% and overall efficiency with flexible charging options, supports recycling, and allows for a wide range of DC link voltage from 400V to 800V, while ensuring even load distribution and cell balancing.
Implementation Method 1
each second battery module comprises a power electronics unit having a DCDC converter
Data Source
AI summary
A battery system including a number of first battery modules each including a number of battery cells, and a number of second battery modules each including a number of battery cells. Each second battery module includes a power electronics unit having a DC/DC converter. The first and second battery modules are connected in series. The first battery modules are connected directly in series and the second battery modules are connected via their power electronics units.