Series Battery Charging with Stepwise Constant-Current Control

Solution Overview

Problem

Series-type charging and discharging devices for lithium secondary batteries face prolonged charging and discharging times due to difficulties in controlling voltage uniformly across batteries with varying capacities and internal resistances, especially in constant voltage mode.

Innovation Solution

A series-type charging and discharging device with a multi-step constant current charging algorithm that gradually decreases current values and includes switches to cut off current to battery cells reaching a target voltage, allowing for simultaneous charging and discharging of multiple cells in series while preventing overcharging/overdischarging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If constant voltage charging mode is used for series-connected battery cells with different capacities and internal resistances, then each battery cell can be charged at its optimal voltage, but the charging time is prolonged due to the need to control each channel separately and the exponential current decay characteristic

Engineering Contradiction:

Improvevoltage control accuracyVSAvoidcharging time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The charging process is segmented into multiple constant current stages with progressively decreasing current values. Instead of using a single constant voltage mode that requires individual channel control, the system divides charging into N stages (where N is an integer from 2 to 10), each stage using a different constant current value. This segmentation allows series-connected batteries to be charged efficiently without requiring separate control for each battery channel.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The charging current parameter is changed stepwise across multiple stages. The controller implements a charging algorithm that adjusts the current parameter from a higher initial value to progressively lower values across N stages. This parameter change approach transforms the charging process from constant voltage mode (which causes exponential current decay) to multi-stage constant current mode, significantly reducing charging time while maintaining safety for series-connected batteries with varying characteristics.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If series-type charging device controls all battery channels with equal current in constant voltage mode, then energy efficiency is improved, but it becomes difficult to control voltage uniformly across batteries with different characteristics

Engineering Contradiction:

Improveenergy efficiencyVSAvoidvoltage control precision

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The charging process is segmented into multiple constant current stages with progressively decreasing current values. Instead of using a single constant voltage mode that requires individual channel control, the system divides charging into N stages (where N is an integer from 2 to 10), each stage using a different constant current value. This segmentation allows series-connected batteries to be charged efficiently without requiring separate control for each battery channel.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The charging system transitions from a static constant voltage approach to a dynamic multi-stage constant current approach. The controller adaptively adjusts the current parameter across N stages based on the charging progress, creating a dynamic charging profile that accommodates the varying characteristics of series-connected batteries while maintaining uniform control across all channels.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If relay switching is used to control charge/discharge of each cell channel in constant voltage mode, then individual battery control is achieved, but the charging and discharging time increases significantly

Engineering Contradiction:

Improveindividual battery controlVSAvoidcharging and discharging time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The invention extracts and eliminates the relay switching mechanism from the charging system. By removing the need for relay switching between constant current and constant voltage modes, the system achieves individual battery control through a simplified multi-stage constant current algorithm. This extraction of the relay component directly addresses the time loss issue while maintaining the ability to control each battery channel appropriately.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The charging process is segmented into multiple constant current stages with progressively decreasing current values. Instead of using a single constant voltage mode that requires individual channel control, the system divides charging into N stages (where N is an integer from 2 to 10), each stage using a different constant current value. This segmentation allows series-connected batteries to be charged efficiently without requiring separate control for each battery channel.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20240413661A1Serial type charging and discharging device, and charging and discharging method using same

Publication Date: 2024.12.12 LG ENERGY SOLUTION LTD

AI summary

The series-type charging and discharging device according to the present technology for charging and discharging a plurality of battery cells in series, includes trays, a cooling fan, a power source, a charging and discharging control board, and a control unit, and the charging and discharging control algorithm includes a first to N (N is an integer from 2 to 10) charging and discharging steps, and each charging and discharging step is configured to charge and discharge in a constant current mode, but characterized in with a stepwise decrease in the value of the charging and discharging current.