Active Balancing H-Bridge Circuit for Series Battery Packs
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Solution Overview
Problem
Large battery systems composed of multiple cells in series are limited by the weakest module or cell, leading to suboptimal performance and potential damage due to uneven charge distribution among cells, which existing battery management systems struggle to address effectively.
Innovation Solution
An active balancing apparatus utilizing an H-bridge circuit and step-down transformers generates a differential alternating square wave voltage to balance cell voltages across multiple packs, with a charge balancing circuit and diodes controlling current flow to equalize charge levels among cells, allowing for both internal and external power sources to achieve balanced states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If battery systems are divided into multiple packs connected in series to achieve higher voltages, then system voltage and power are improved, but the system becomes limited by the weakest module or cell due to uneven charge distribution
Solution Approach 1:
The battery system is divided into multiple packs, each containing multiple cells arranged in series. Each pack is further segmented into individual cells that can be independently monitored and balanced. This segmentation allows the system to maintain high voltage through series connection while addressing individual cell imbalances through separate balancing circuits for each cell.
Solution Approach 2:
Individual balancing circuits are introduced as intermediary components between the series-connected cells. These balancing circuits include switching elements and resistors that act as mediators to redirect current from overcharged cells, thereby equalizing charge distribution across all cells in the high-voltage series configuration.
2Ease of manufacture
If passive load balancing is used to balance cells, then implementation is simple, but balancing efficiency is low and optimal battery condition is not maintained
Solution Approach 1:
The balancing circuit employs dynamic switching elements (such as MOSFETs or transistors) that can rapidly switch between different balancing modes based on real-time cell voltage measurements. This dynamic control allows the system to actively adjust current distribution and achieve faster, more efficient balancing compared to static passive resistive balancing.
Solution Approach 2:
The system incorporates voltage sensing circuits that continuously monitor individual cell voltages and provide feedback to the control logic. Based on this feedback, the balancing circuit dynamically adjusts which cells receive balancing current, enabling precise control and high balancing efficiency while maintaining system simplicity.
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
This solution enables efficient active balancing of battery packs, maintaining optimal performance by ensuring all cells reach a uniform state of charge, preventing overcharging, overdischarging, and extending battery lifespan by dynamically adjusting system voltage and pack configurations.
Implementation Method 1
an H-bridge generates a differential alternating square wave voltage output
Implementation Method 2
a plurality of step-down transformers each associated with a pack and where the plurality of step-down transformers provide an active balancing voltage of about the associated nominal pack voltage
Implementation Method 3
a plurality of diodes coupled between the plurality of secondary windings and the respective discrete portion of the battery pack
Implementation Method 4
a transformer including a primary winding and a plurality of secondary windings with the primary winding coupled across the battery system and the plurality of secondary windings each connected across a respective discrete portion of a battery pack
Data Source
AI summary
An active balancing and battery charging system for a battery including a plurality of packs made up of cells. An H-bridge circuit having a nominal system voltage as an input generates a square wave output to a plurality of step-down transformers each associated with a pack, where the plurality of step-down transformers provide an active balancing voltage of about the nominal pack voltage. Each pack may include a balancing transformer including a common primary coil receiving the active balancing voltage from the associated step-down transformer or the pack itself. The balancing transformer also includes a plurality of secondary coils each associated with the respective plurality of cells of the pack. A voltage induced in the secondary coils causes a discrete charge current to flow to any cells in the pack that are undercharged relative to other cells.