Battery Cell Charge Balancing via Preliminary Voltage Sampling

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Solution Overview

Problem

Charge imbalances between battery cells in a battery pack can occur due to manufacturing differences and timing issues during the charge balancing process, leading to incomplete charge capacity and potential overcharging or undercharging of cells.

Innovation Solution

A method for balancing charge in a battery pack by using charge data from a previous balancing cycle to initiate and adjust charge balancing in subsequent cycles, ensuring that battery cell stacks with different numbers of cells are balanced simultaneously, thereby minimizing the impact of processing time on charge balancing timing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If charge balancing is performed on battery cell stacks with different numbers of cells simultaneously, then charge balancing efficiency is improved, but processing time differences cause charge imbalance to increase

Engineering Contradiction:

Improvecharge balancing efficiencyVSAvoidcharge balance accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary sampling of battery cell voltages during a first charge balancing cycle before actual charge balancing operations begin. This advance measurement allows the controller to calculate and prepare balancing strategies for multiple stacks with different cell counts, ensuring all stacks can start balancing simultaneously without waiting for voltage measurements to be completed, thus resolving the contradiction between efficiency and accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses voltage sampling data from previous cycles as feedback to adjust and optimize charge balancing operations in subsequent cycles. By continuously monitoring voltage differences between cells and adjusting balancing currents accordingly, the system maintains charge balance accuracy even when processing stacks with different numbers of cells simultaneously

Inventive Principle:

Principle #23Feedback

2Measurement precision

If charge balancing processing is delayed until data is ready, then processing accuracy is improved, but timing synchronization between battery cell stacks deteriorates

Engineering Contradiction:

Improvevoltage sampling accuracyVSAvoidcharge balancing timing delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Voltage sampling is performed in advance during a first charge balancing cycle, and the sampled data is stored for later use. This preliminary action ensures that accurate voltage measurements are captured before charge balancing operations begin, eliminating the need to delay balancing operations until sampling is complete, thus resolving the contradiction between measurement precision and timing synchronization

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The charge balancing process is divided into distinct phases: a sampling phase where voltages are measured and stored, and a balancing phase where actual charge balancing operations occur using the pre-captured data. This segmentation allows voltage sampling to be completed independently without blocking the timing-critical balancing operations, maintaining both accuracy and synchronization

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9641004B2System and method for balancing charge between battery cells

Publication Date: 2017.05.02 A123 SYSTEMS LLC

AI summary

Systems and methods for balancing charge of battery cells of a battery pack are disclosed. In one example, battery cell balancing may be improved by balancing battery cells of a battery cell stack simultaneously. The system and method may be particularly useful battery packs that may be constructed with battery cell stacks that vary in a number of series battery cells.