Pre-Charging Circuit Balancing for Parallel Battery Pack Voltage

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Solution Overview

Problem

Existing battery packs connected in parallel face issues with voltage imbalance leading to potential overcharge, damage, or explosion due to differing charging speeds, and require frequent manual connection of charging devices, impacting user experience.

Innovation Solution

A pre-charging circuit and battery management system that uses relays and capacitors to balance voltages between battery packs, ensuring safe and efficient power distribution by sequentially adjusting voltages and pre-charging capacitors to equalize battery states before supplying main power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If battery packs are connected in parallel to increase power output, then power delivery capability is improved, but voltage imbalance between packs causes overcharge risk and safety issues

Engineering Contradiction:
Improvepower delivery capabilityVSAvoidovercharge risk
Core Design Contradiction:
PowerVSReliability

Solution Approach 1:

The patent applies preliminary action by measuring voltages of all battery packs before connection and calculating voltage differences in advance. The system determines whether voltage imbalance exceeds a threshold value before allowing parallel connection, preventing overcharge conditions from developing. This proactive voltage verification and control mechanism ensures safe parallel operation while maintaining improved power delivery capability.

Inventive Principle:
Principle #10Preliminary action

2Reliability

If cell balancing circuit is applied to prevent overcharge, then safety is improved, but system complexity and cost increase

Engineering Contradiction:
ImprovesafetyVSAvoidsystem complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the pre-charging circuit multi-functional by having it perform both its traditional pre-charging function and a new voltage balancing function. The same circuit measures voltages, calculates differences, determines threshold violations, and controls charging based on imbalance conditions. This eliminates the need for a separate dedicated cell balancing circuit, reducing system complexity and cost while maintaining safety improvements.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system implements self-service by having the pre-charging circuit automatically measure voltages, calculate differences, and control charging without requiring external balancing equipment. The battery management system autonomously monitors voltage imbalance and adjusts charging parameters based on measured values, eliminating the need for manual intervention or additional specialized balancing hardware.

Inventive Principle:
Principle #25Self-service

3Manufacturing precision

If manual connection of charging devices is required for balancing, then voltage control is improved, but user convenience and productivity deteriorate

Engineering Contradiction:
Improvevoltage control precisionVSAvoidcharging efficiency
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The patent implements self-service by automatically measuring voltages of all battery packs, calculating voltage differences, determining threshold violations, and controlling the pre-charging circuit without user intervention. The system autonomously manages the entire balancing process, eliminating the need for manual connection of charging devices while maintaining precise voltage control through automated monitoring and adjustment.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system applies feedback by continuously measuring voltages of battery packs, calculating voltage differences, and using this information to control the pre-charging circuit. The measured voltage values feed back to the battery management system, which adjusts charging parameters based on the calculated imbalance, creating a closed-loop control system that maintains precise voltage control while operating automatically without manual intervention.

Inventive Principle:
Principle #23Feedback

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

Ensures safe and efficient power delivery to motors and inverters by maintaining balanced voltage levels, reducing the risk of damage and enhancing user convenience by eliminating the need for constant manual charging device connections.

Implementation Method 1

A pre-charging circuit, of the one or more pre-charging circuits, may be connected to the plurality of battery packs

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP4395114B1Method for balancing parallel battery packs using pre-charging circuit and apparatus and system for the same
Publication Date: 2025.12.31 HYUNDAI MOTOR CO LTD
  • EP4395114B1 patent drawingFigure 1
  • EP4395114B1 patent drawingFigure 2
  • EP4395114B1 patent drawingFigure 3

AI summary

Provided is a method in an electricity-driven apparatus to be driven by receiving power through a plurality of battery packs in a parallel type. The method includes detecting a state of charge (SOC) of each of the plurality of battery packs, calculating a voltage difference between the plurality of battery packs based on the detected SOC, and performing battery pack balancing based on the calculated voltage difference exceeding a threshold value. The battery pack balancing is performed by a pre-charging circuit including a balancing relay.