Pre-Charge Voltage Balancing for Parallel EV Battery Connection
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Solution Overview
Problem
Connecting large numbers of EV batteries in parallel to a common bus is challenging due to differences in state of charge and voltage, leading to potential overheating and damage from high current flows, with existing solutions struggling to effectively manage current and heat limitations.
Innovation Solution
A resistive current limiting system using switched resistors, linear current limiting with metal oxide semiconductor field-effect transistors, and switchmode current limiting with inductors and switches, which allow for controlled current and heat management, enabling safe and efficient connection of batteries with different states of charge and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If large numbers of EV batteries are connected in parallel to a common bus, then the storage capacity of the battery system can be scaled up, but high current flows occur due to differences in state of charge and voltage, leading to overheating and potential damage
Solution Approach 1:
The patent applies preliminary action by implementing pre-charge circuits that activate before main battery connection. These circuits gradually charge disconnected batteries to match the common bus voltage, preventing high current flows when batteries are connected in parallel. The pre-charge process occurs in advance, ensuring voltage matching before the main connection is made.
Solution Approach 2:
The patent uses pre-charge circuits as intermediary components between the common bus and disconnected batteries. These intermediary circuits include current-limiting resistors and control logic that mediate the connection process, gradually equalizing voltages and limiting current flows to safe levels during the transition from disconnected to connected state.
2Reliability
If pre-charge circuits are implemented to limit current during battery connection, then overheating and damage are prevented, but system complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing pre-charge circuits that serve multiple purposes: voltage matching, current limiting, and safety protection. The same circuitry that limits current during connection also provides ongoing protection and can function as part of the battery management system, reducing the need for separate dedicated protection components.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting resistance values in the pre-charge circuits based on voltage differences and current conditions. The control logic modifies circuit parameters in real-time to optimize the pre-charge process, transitioning from high resistance during initial connection to lower resistance as voltages equalize, thereby simplifying the overall control strategy.
3Object-affected harmful factors
If switched resistors are used to limit current in pre-charge circuits, then current and heat are controlled, but the system requires additional components and control logic
Solution Approach 1:
The patent merges the pre-charge control logic with the existing battery management system architecture. The same microcontroller or control circuitry that manages battery charging and discharging also controls the pre-charge switches and resistors, eliminating the need for separate dedicated control hardware and reducing overall system complexity.
Solution Approach 2:
The patent implements dynamics by using switched resistors that can dynamically change their resistance values based on real-time voltage and current measurements. The control system adjusts which resistors are active and their switching timing to optimize current limiting during the pre-charge process, adapting to changing battery conditions rather than using fixed resistance values.
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
The proposed systems effectively limit current and heat, preventing overheating and damage, while allowing for rapid and safe connection of batteries, with the switchmode approach reducing heat dissipation challenges and enabling efficient battery balancing and scaling.
Implementation Method 1
A pre-charge circuit is utilized to limit current and heat between a newly added battery and existing batteries during connection, and between individual batteries during normal operation
Implementation Method 2
A linear current limiting system for paralleling high voltage batteries comprising at least two linear pass elements, wherein the at least two linear pass elements are positioned to limit current in both directions. Preferably, the two linear pass elements are metal oxide semiconductor field-effect transistors connected in a common source, back-to-back configuration
Implementation Method 3
A switchmode current limiting system for paralleling high voltage batteries, the system comprising at least on inductor, at least two main switches and at least two rectifiers
Data Source
AI summary
A resistive current limiting system for paralleling large high voltage batteries, the system comprising a plurality of switched resistors and at least one controller, wherein the plurality of switched resistors are driven by the at least one controller to maintain current and heat below pre-set limits. The system allows a connection between batteries to rapidly occur in a manner that does not exceed pre-set current limits of both the high voltage batteries being connected and existing batteries within the system.