Battery Pack Sizing Using Equivalent Short-Circuit Modeling

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Solution Overview

Problem

Existing battery system management methods unnecessarily limit the number of batteries due to overestimation of total short-circuit current, leading to increased design costs and reduced energy density, which weakens product competitiveness.

Innovation Solution

A battery system management device that defines an equivalent model for the battery system, calculates short-circuit currents based on the connection structure and time constant characteristics, and determines the optimal number of batteries to prevent exceeding the limiting current of protection elements, thereby minimizing design costs and maximizing energy density.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the number of batteries is increased to satisfy required capacity for medium-to-large sized devices, then the energy source capability is improved, but the short-circuit current increases causing protection elements to be overloaded

Engineering Contradiction:

Improvenumber of batteriesVSAvoidshort-circuit current

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent segments the battery system into multiple connection paths with distributed protection elements. Instead of using a single protection element for the entire battery system, protection elements are placed at different locations (input/output terminals, connection points of batteries, connection points of battery groups), dividing the current protection responsibility and allowing more batteries to be connected safely.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an equivalent circuit model as an intermediary tool to accurately calculate and predict short-circuit current. By using the equivalent model that includes time constant characteristics of connection elements, the system can determine the optimal number of batteries before actual deployment, preventing overestimation of short-circuit current.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the number of batteries is limited due to overestimation of short-circuit current, then the protection element safety is improved, but the design cost increases and energy density decreases

Engineering Contradiction:

Improveprotection element safetyVSAvoiddesign cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent performs preliminary calculation of short-circuit current using the equivalent circuit model before finalizing the battery system design. By calculating the actual short-circuit current characteristics in advance and comparing with protection element ratings, the optimal number of batteries is determined beforehand, avoiding unnecessary limitations and reducing design costs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the approach from using conservative estimates to using calculated parameters based on equivalent circuit models. By incorporating time constant characteristics of connection elements into the calculation, the short-circuit current parameter is accurately determined, allowing optimization of battery quantity without compromising protection element safety.

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If the number of batteries is reduced to limit short-circuit current, then the protection element overload is prevented, but the energy density of the battery system is reduced

Engineering Contradiction:

Improveprotection element overloadVSAvoidenergy density

Core Design Contradiction:

Object-affected harmful factorsVSQuantity of substance

Solution Approach 1:

The patent establishes a feedback mechanism where the equivalent circuit model continuously evaluates the relationship between battery quantity and short-circuit current. By comparing calculated short-circuit current with protection element ratings, the system provides feedback to determine the optimal battery configuration, maximizing energy density while preventing protection element overload.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent adopts a dynamic approach to determining battery quantity based on actual system characteristics. Instead of using fixed conservative limits, the system dynamically calculates the optimal number of batteries by considering time constant characteristics of connection elements and actual short-circuit current behavior, allowing maximum energy density within safety constraints.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20250004054A1Battery System Management Device and Method for Determining Optimal Number of Batteries

Publication Date: 2025.01.02 LG ENERGY SOLUTION LTD

AI summary

A battery system management device includes at least one processor, and a memory that stores at least one command executed through the at least one processor. The at least one command includes: a command to define an equivalent model for a battery system having a predefined connecting structure including a plurality of batteries and at least one protection element; a command to calculate a short-circuit current generated in the battery system when a short circuit is generated at a location in the battery system using the equivalent model; a command to compare the calculated short-circuit current with a limiting current of the protection element; and a command to determine the number of batteries provided in the battery system based on the result of comparison.