Secondary Battery Voltage Measurement Using Capacitive Storage
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Solution Overview
Problem
Secondary batteries used in electric cars face challenges in accurately measuring the voltages of individual battery cells due to slight differences in characteristics, which affects their performance and lifespan.
Innovation Solution
A secondary battery system that includes a capacitive device connected to battery cells via a relay and an A/D converter, allowing sequential voltage measurement without discharging the capacitive device, and featuring a switching device to discharge over-charged cells and a reference voltage source for accurate initialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional voltage measurement methods are used for battery cells, then the measurement process is simple, but the measurement speed is slow and accuracy is reduced due to voltage changes during measurement
Solution Approach 1:
The capacitive device stores the voltage of each battery cell immediately when the relay connects it, before the battery cell voltage can change. This preliminary action of capturing and storing the voltage snapshot ensures accurate measurement without waiting for the voltage to stabilize or change, thereby improving both measurement speed and accuracy simultaneously
Solution Approach 2:
The capacitive device acts as an intermediary between the battery cell and the A/D converter. It captures the voltage from the battery cell through the relay and holds it steady for conversion, isolating the measurement process from voltage fluctuations in the battery cell, thus improving measurement accuracy without increasing measurement time
2Measurement precision
If a relay sequentially connects battery cells to a capacitive device for voltage measurement, then measurement accuracy improves, but the system complexity increases
Solution Approach 1:
The capacitive device serves multiple functions: it stores voltage from any battery cell sequentially, acts as a buffer between the relay and A/D converter, and maintains voltage stability during conversion. This multi-functionality reduces the need for additional components, thereby improving measurement accuracy without proportionally increasing system complexity
Solution Approach 2:
The patent replaces complex mechanical switching mechanisms with an optical MOS relay, which uses light to control switching. This substitution reduces mechanical wear and contact resistance, improving measurement accuracy while maintaining relatively simple system architecture through solid-state technology
3Productivity
If battery cells are measured sequentially without discharging the capacitive device, then measurement speed increases, but voltage leakage may occur
Solution Approach 1:
The capacitive device continuously holds the captured voltage without discharging it between measurements, maintaining a steady state ready for immediate A/D conversion. This continuous voltage holding enables rapid sequential measurement of multiple battery cells while preserving voltage integrity, thus improving measurement speed without compromising reliability
Solution Approach 2:
The measurement system extracts and isolates the voltage signal from the battery cell into the capacitive device through the relay, separating it from the battery cell's ongoing voltage fluctuations. This extraction allows the voltage to be measured in a controlled environment, improving both measurement speed and reliability by preventing voltage leakage and interference
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
Enables quick and accurate measurement of battery cell voltages, preventing leakage currents and ensuring balanced charge states, thereby extending the life and performance of battery cells.
Implementation Method 1
a capacitive device connected to the battery cells to sequentially store the voltages of the battery cells
Implementation Method 2
The relay may be configured with an optical MOS relay
Data Source
AI summary
A secondary battery includes a plurality of battery cells and measures voltages of the battery cells. The secondary battery includes a capacitive device, a relay and an A/D converter. The capacitive device is connected to the battery cells to sequentially store the voltages of the battery cells. The relay is between the battery cells and the capacitive device, and sequentially connects the battery cells to the capacitive device. The A/D converter is connected to the capacitive device to receive and convert the voltages of the battery cells.