Bi-Directional Battery Cell Balancer With Compact Inductor Circuit

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing active battery cell balancing technologies are limited by unidirectional charge transfer and require significant space, leading to inefficiencies and potential thermal issues in battery packs.

Innovation Solution

A bi-directional active battery cell balancer system using a compact circuit with small inductors and MOSFETs, enabling bidirectional charge transfer and controlled voltage balancing through a controller that manages switching elements and capacitors to equalize battery cell voltages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If unidirectional charge transfer is used in active battery cell balancing, then charge transfer can be achieved, but space requirements increase and thermal issues arise

Engineering Contradiction:

Improvecharge transfer efficiencyVSAvoidspace requirements

Core Design Contradiction:

Loss of energyVSArea of stationary object

Solution Approach 1:

The battery pack is divided into multiple series-connected cell pairs, with each pair having its own bidirectional balancer circuit. This segmentation allows independent balancing of each pair, reducing the overall space required compared to a single large unidirectional balancer while maintaining effective charge transfer between cells.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements bidirectional charge transfer capability, allowing charge to flow in both directions between battery cells. This inversion of the traditional unidirectional approach enables more flexible energy management, reduces thermal issues by distributing heat generation, and decreases space requirements through more efficient circuit topology.

Inventive Principle:

Principle #13The other way round (Inversion)

2Loss of energy

If unidirectional charge transfer is used in active battery cell balancing, then charge transfer can be achieved, but thermal issues occur

Engineering Contradiction:

Improvecharge transfer efficiencyVSAvoidthermal issues

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The bidirectional charge transfer capability allows the system to reverse charge flow direction, distributing thermal load more evenly across battery cells and reducing concentrated heat generation. This inversion enables thermal management by alternating between charging and discharging different cell pairs, preventing overheating while maintaining efficient energy transfer.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If conventional active battery cell balancing is used, then voltage balancing can be achieved, but device complexity increases

Engineering Contradiction:

Improvevoltage balancingVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The bidirectional balancer circuit serves multiple functions: it balances voltage between cell pairs, enables bidirectional charge transfer, and provides thermal management capabilities. This multi-functionality reduces overall device complexity by consolidating what would otherwise require separate systems, while maintaining reliable voltage balancing through a unified control architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Reliability

If conventional battery cell balancing is used, then voltage equalization can be achieved, but energy utilization efficiency decreases

Engineering Contradiction:

Improvevoltage equalizationVSAvoidenergy utilization efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The bidirectional charge transfer capability allows the system to recover and redistribute energy that would otherwise be lost in unidirectional balancing. By enabling reverse charge flow, the system can utilize excess energy from one cell pair to charge another, significantly improving overall energy utilization efficiency while maintaining voltage equalization across all cells.

Inventive Principle:

Principle #13The other way round (Inversion)

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 system achieves efficient, compact, and scalable battery cell balancing with reduced ripple current, minimizing space requirements and improving energy utilization in battery packs.

Implementation Method 1

An inductor can be connected between a positive terminal of the first battery cell and a negative terminal of the second battery cell

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Implementation Method 2

A capacitor can be connected between a drain of the first MOSFET and a drain of the second MOSFET

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS12483043B2Bi-directional active battery cell balancer and method for bi-directional cell balancing

Publication Date: 2025.11.25 RENESAS ELECTRONICS AMERICA INC

AI summary

Systems and methods for balancing a pair of battery cells are described. A controller can determine a voltage difference based on a first voltage of a first battery cell and a second voltage of a second battery cell. The controller can determine a current difference between current of an inductor and a current limit of the inductor, where the inductor can be connected to a node between the first and second battery cells. The controller can identify at least one switching elements among a plurality of switching elements based on the voltage difference and the current difference. The controller can activate the identified switching elements to perform battery cell balancing between the first battery cell and the second battery cell.