Virtual Simultaneous Sampling Single ADC Battery Voltage Balancing
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Solution Overview
Problem
Multi-cell battery packs, particularly in EVs and HEVs, face challenges in accurate cell voltage balancing due to temporal displacement errors in existing sensing methods, leading to cell damage and increased costs from premature failures.
Innovation Solution
A system that uses a multiplexer and controller to take sequential pairs of voltage readings from multiple cells within a common time window, averaging these readings to estimate virtually simultaneous voltages, thereby reducing measurement errors and improving balancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage sensor is added for each cell to simultaneously sense all cell voltages, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple voltage sensing operations into a single ADC core by using a multiplexer to sequentially connect different cell voltage sources to the same converter. This consolidation reduces the number of sensors from one per cell to a single shared sensor, eliminating temporal displacement errors while maintaining cost-effectiveness.
Solution Approach 2:
The system uses periodic sequential sampling where the multiplexer cycles through different cell voltage sources in a predetermined sequence, taking measurements at specific time intervals. This periodic action allows a single ADC to capture voltage data from multiple cells across different time points, which are then processed to determine accurate balancing parameters.
2Device complexity
If sequential voltage sensing is used for multiple cells, then device complexity is reduced, but measurement precision deteriorates due to temporal displacement errors
Solution Approach 1:
The controller receives sequential voltage measurements from the ADC and uses feedback processing to compensate for temporal displacement. By analyzing the timing and sequence of measurements, the system calculates accurate voltage differences between cells, transforming the raw sequential data into precision balancing parameters that account for the time delays inherent in sequential sampling.
3Quantity of substance
If cells are charged to maximum capacity, then energy storage is maximized, but cell reliability deteriorates due to overcharging risks
Solution Approach 1:
The patent replaces physical overcharge protection mechanisms with an electronic control system based on accurate voltage measurement and processing. Instead of relying on mechanical cutoffs or conservative charging limits, the system uses the controller to precisely monitor voltage differences between cells and dynamically adjust charging parameters, maximizing energy storage while preventing overcharge damage through intelligent control.
Data Source
AI summary
Voltage balancing in multi-cell battery packs is improved by estimating instantaneous voltages on the cells. In accordance with one embodiment, an apparatus for reading voltages from multiple voltage sources includes a first multiplexer coupled to multiple voltage sources and a controller. The controller is programmed to output from the first multiplexer a sequential pair of voltages read from each of the multiple voltage sources. The multiple sequential pairs of voltages all have a common midpoint in time. The multiple sequential pairs of voltages are all read within a small time window, such as 100 microseconds. In one embodiment, the multiple voltage sources are Li-ion or other high-voltage cells, though other types of cells can also be used.