Multi-Cell Battery Balancing Using Resistor Ladder VCO Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for balancing voltage in multicell batteries are costly and inefficient, often relying on expensive high-resolution ADCs or complex analog circuits that are prone to inaccuracies and noise interference, which can lead to battery failure, reduced capacity, and safety risks.
Innovation Solution
A system using a resistor ladder and voltage-controlled oscillators (VCOs) with digital level shifters and a logic circuit to measure and balance battery cell voltages, allowing for accurate voltage balancing with reduced component costs and improved immunity to noise, employing a method that calibrates and corrects for inaccuracies using reference voltages and temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution ADCs (14-16 bit) are used to measure battery cell voltages, then measurement precision is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent replaces expensive, complex high-resolution ADCs with cheaper, simpler voltage sensors that have lower individual precision. However, through the resistor ladder network and differential measurement technique, the system achieves accurate relative voltage comparisons without requiring each sensor to be highly precise, thus using cheaper components to achieve the desired measurement accuracy.
Solution Approach 2:
The patent combines multiple voltage measurements into a differential comparison scheme. By measuring the voltage difference between adjacent cells rather than absolute voltages, and using a shared resistor ladder reference, the system achieves accurate balancing information with simpler, lower-cost sensors that don't require high individual resolution.
2Device complexity
If a common ADC is time-multiplexed to measure multiple battery cells, then device complexity is reduced, but measurement precision deteriorates due to load injected noise and lack of concurrent measurement
Solution Approach 1:
The patent divides the measurement system into separate parallel measurement channels, each with its own voltage sensor measuring a specific cell voltage simultaneously. This segmentation allows concurrent measurement of all cells without time-multiplexing, eliminating the noise and accuracy problems associated with shared ADCs while keeping the overall system simple through the shared resistor ladder reference.
3Ease of manufacture
If passive discharge is used to balance high-voltage cells, then manufacturing cost is reduced, but productivity decreases due to extended balancing time
Solution Approach 1:
The patent implements a feedback control system that continuously monitors cell voltages through the resistor ladder and voltage sensors, identifies imbalanced cells, and actively directs charge current to specific cells that need balancing. This active feedback-controlled charge balancing achieves faster equalization compared to passive discharge while maintaining cost-effectiveness through the use of simple switches and the shared resistor ladder reference.
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 effectively balances battery cell voltages with high accuracy, reducing the risk of battery failure and extending battery life while minimizing costs, by using a resistor ladder and VCOs to measure voltage across each cell, and digital level shifters to process signals, thus providing a cost-effective and reliable solution for voltage balancing.
Implementation Method 1
a resistor ladder including a plurality of resistors disposed in series with each other... converting the voltage across the multicell battery to a total battery output signal proportional to the total battery voltage
Implementation Method 2
a plurality of voltage-controlled oscillators (VCOs)... converting the voltage across the multicell battery to a total battery output signal
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A resistor ladder comprising identical resistors is disposed electrically in parallel with a multicell battery to calibrate voltage-controlled oscillators or analog-to-digital convertors for voltage balancing the battery cells in the multicell battery. Switches in a first state provide the voltage across each resistor as inputs to the VCOs or ADCs. The number of oscillations of the output signal of each VCO or ADC over a predetermined time period are compared to determine an offset error. Switches in a second state provide the voltage across each battery cell as inputs to the VCOs or ADCs. The battery cells with a higher relative voltage can be discharged until they are balanced. Some aspects describe temperature-adjusted and interpolated determinations of electrical quantities in the cells such as voltage and/or current.