Multi-Cell Battery Voltage Balancing With Resistor Ladder Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solutions for balancing voltages in multicell batteries are costly and inefficient, often relying on high-resolution analog-to-digital converters (ADCs) that are expensive and prone to inaccuracies, which can lead to battery failure, reduced capacity, and safety issues like explosions.
Innovation Solution
A system using a resistor ladder and voltage-controlled oscillators (VCOs) with switches and digital level shifters to measure resistor and battery cell voltages, allowing for accurate voltage balancing and self-calibration, reducing the need for high-accuracy ADCs and minimizing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution ADCs (14-16 bit) are used to measure cell voltage, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the voltage measurement task into multiple lower-resolution ADC measurements taken at different time intervals, rather than using a single high-resolution ADC. Each ADC measures a portion of the total voltage, and the results are combined to achieve the required measurement precision.
Solution Approach 2:
The patent implements periodic switching between different ADC measurement channels, where each ADC is activated at specific time intervals to measure different cell voltages. This time-multiplexed approach allows lower-resolution ADCs to achieve effective high-resolution measurement through multiple sequential readings.
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 noise and floating issues
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary buffer between each battery cell and the ADC input. This buffer isolates the ADC from direct connection to multiple voltage sources, eliminating floating issues and reducing noise interference while maintaining the ability to measure multiple cells using a single ADC.
Solution Approach 2:
The patent performs preliminary voltage buffering and signal conditioning for each battery cell before the ADC measurement occurs. By preparing stable, isolated voltage signals in advance through operational amplifiers, the system ensures accurate measurements when the ADC samples each cell at its designated time interval.
3Measurement precision
If multiple ADCs are used to measure each battery cell simultaneously, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the measurement function across multiple lower-resolution ADCs, where each ADC handles a specific time window or subset of measurements. This segmentation allows the system to achieve comprehensive voltage monitoring without requiring each ADC to be simultaneously high-resolution and high-channel-count.
Solution Approach 2:
The patent employs periodic switching and time-multiplexed measurement sequences, where multiple ADCs are activated in a coordinated periodic fashion. Each ADC measures specific cells during its active period, and the combined data from all ADCs over time provides complete voltage information with improved precision.
4Ease of manufacture
If passive discharge is used to balance cell voltages, then cost is reduced, but productivity decreases due to extended charging time
Solution Approach 1:
The patent implements a dynamic balancing approach where the system continuously monitors cell voltages and adjusts the balancing strategy in real-time. When voltage differences are small, the system allows faster charging; when differences exceed thresholds, passive discharge is selectively applied to specific cells, optimizing the balance between cost and charging speed.
Solution Approach 2:
The patent applies passive discharge resistance selectively to specific battery cells that exhibit voltage imbalances, rather than uniformly to all cells. This localized application of balancing resistance minimizes the impact on overall charging speed while effectively correcting voltage differences in problematic cells.
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 approach enables accurate voltage balancing across multicell batteries, preventing overcharge and over-discharge while reducing costs and complexity, ensuring safer and more efficient battery operation.
Implementation Method 1
voltage-controlled oscillators (VCOs) with switches and digital level shifters to measure resistor and battery cell voltages
Data Source
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.