Dual 400V Traction Battery Balancing for 800V EV Powertrains
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Solution Overview
Problem
Existing electric vehicle power systems face challenges in transitioning from 400V to 800V DC bus voltage, requiring redesign of components like on-board chargers and generators due to limited high-voltage MOSFET options, leading to increased expense and performance issues.
Innovation Solution
The proposed solution involves using two or more 400V battery packs in series to form an 800V traction battery, with existing 400V inverters, on-board chargers, and generators, and employing four switches or two switches with an inductor to manage power transfer and balance states of charge, enabling direct application of 800V DC fast chargers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If 800V DC bus voltage is implemented, then charging speed and power delivery are improved, but component redesign expense and complexity increase due to limited high-voltage MOSFET options
Solution Approach 1:
The patent divides the 800V battery system into two separate 400V battery packs connected in series. Each battery pack can be independently managed and charged, allowing the use of existing 400V components (inverters, chargers, MOSFETs) without requiring redesign for high-voltage applications. This segmentation resolves the contradiction by maintaining 800V system power delivery while avoiding the complexity of developing new high-voltage components.
2Productivity
If 800V DC bus voltage is implemented, then charging speed is improved, but development time and costs increase due to component redesign requirements
Solution Approach 1:
By segmenting the 800V system into two 400V battery packs, the patent enables direct use of existing 400V chargers and powertrain components, eliminating the need for time-consuming development of new high-voltage components. The dual-battery architecture allows one battery to charge while the other powers the vehicle, achieving fast charging capability without extending development timelines.
Solution Approach 2:
The patent employs charge balancing circuitry and control systems that are prepared in advance to manage the dual battery configuration. The charge balancing functionality is built into the system architecture from the outset, allowing seamless operation and charging without requiring subsequent modifications or delays for system integration and testing.
3Ease of manufacture
If two 400V battery packs are used in series to form 800V traction battery, then existing 400V components can be used reducing development costs, but charge balancing complexity increases
Solution Approach 1:
The patent introduces charge balancing circuitry as an intermediary mechanism between the two 400V battery packs. This circuitry includes switches, capacitors, and controllers that actively manage power transfer and voltage equalization between the batteries. The intermediary charge balancing system resolves the contradiction by automating the complex charge management tasks, making the dual-battery configuration easier to manufacture and maintain despite the inherent complexity.
Data Source
AI summary
A power system includes an inverter, a pair of traction batteries electrically in series, and collectively in parallel with the inverter, a plurality of switches electrically in series, and collectively electrically in parallel with the traction batteries and inverter such that the switches are connected between the traction batteries and inverter, and one or more controllers programmed to operate the switches during charge of one of the traction batteries or operation of the inverter to balance states of charge of the traction batteries.