EV Battery Voltage Divider for Switch Diagnosis
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Solution Overview
Problem
High output voltage in electric vehicle battery packs makes direct voltage measurement difficult, and existing voltage dividers are not effective in scaling and diagnosing the state of switches in the battery system.
Innovation Solution
A battery system with a pack voltage divider and coupling power supply system, featuring resistances connected in series with sub-resistances, allows for voltage measurement and diagnosis by measuring voltage drops across these resistances, and includes switches to manage and disconnect components for accurate diagnosis without additional power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a direct voltage measurement is performed between the poles of the battery pack, then the measurement is straightforward, but the high output voltage (400V-800V) makes direct measurement difficult and unsafe
Solution Approach 1:
The voltage measurement is segmented into multiple sub-measurements. Instead of measuring the full high voltage directly, the patent divides the voltage measurement into smaller segments by measuring voltage drops across individual resistors in the voltage divider network, which are at safer voltage levels.
Solution Approach 2:
A voltage divider network consisting of multiple resistors is introduced as an intermediary between the high voltage battery pack and the measurement system. This intermediary scales down the high voltage to measurable levels while isolating the measurement equipment from direct exposure to dangerous high voltages.
2Measurement precision
If a voltage divider is provided between the poles of the battery pack to measure output voltage, then voltage measurement becomes possible, but the system cannot effectively diagnose the state of switches and detect insulation faults
Solution Approach 1:
The voltage divider is segmented into multiple resistive elements with different resistance values arranged in series. This segmentation allows different portions of the voltage divider to be used for different measurement purposes: overall voltage measurement and localized switch state diagnosis.
Solution Approach 2:
Different resistive elements in the voltage divider are assigned different resistance values to create local quality variations. This enables specific regions of the voltage divider to be optimized for specific functions, such as detecting voltage drops across particular switches or identifying insulation faults in specific areas.
3Reliability
If additional auxiliary voltage or current sources are added to the battery system for diagnosis, then diagnosis coverage is improved, but the device complexity and cost increase
Solution Approach 1:
The existing voltage divider resistors are made multi-functional. They serve both as voltage scaling elements for voltage measurement and as diagnostic elements for detecting switch states and insulation faults. This eliminates the need for separate diagnostic circuits or auxiliary power sources.
Solution Approach 2:
The battery system's existing voltage divider structure performs self-diagnosis. By monitoring voltage drops across different resistive elements, the system automatically detects its own operational state, switch positions, and potential insulation faults without requiring external diagnostic equipment or additional power sources.
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 precise voltage measurement and diagnosis of switch states, including detection of double insulation faults and contactor adhesion, with increased robustness and coverage, without requiring additional auxiliary voltage or current sources.
Implementation Method 1
a pack voltage divider, which has a positive pack resistance and a positive sub-pack resistance, which are connected in series with one another between the positive pole and a reference point, and a negative pack resistance and a negative sub-pack resistance, which are connected in series with one another between the negative pole and the reference point
Implementation Method 2
A positive pack voltage in the form of a voltage drop across the positive sub-pack resistance can be measured by a measuring channel. Likewise, a negative pack voltage in the form of a voltage drop across the negative sub-pack resistance can be measured by a measuring channel
Data Source
AI summary
The invention relates to a battery system (10) for an electric vehicle, comprising a battery pack (5) having a positive pole (22), a negative pole (21), at least one battery cell (2) and a pack voltage divider (25), and comprising at least one coupling network having a negative terminal (11) and a positive terminal (12), wherein the pack voltage divider (25) comprises a positive pack resistor (RP2) and a positive sub-pack-resistor (RSP2) which are connected to one another in series between the positive pole (22) and a reference point (50), and a negative pack resistor (RP1) and a negative sub-pack-resistor (RSP1) which are connected to one another in series between the negative pole (21) and the reference point (50). The at least one coupling network comprises a coupling voltage divider (15) having a positive coupling resistor (RK2) and a positive sub-coupling-resistor (RSK2) which are connected to one another in series between the positive terminal (12) and the reference point (50), and having a negative coupling resistor (RK1) an a negative sub-coupling-rcsistor (RSK1) which are connected to one another in series between the negative terminal (11) and the reference point (50). The invention also relates to a method for diagnosing a battery system (10) according to the invention, wherein a positive pack voltage (UP2) falling at the positive sub-pack-resistor (RSP2) is measured, a negative pack voltage (UP1) falling at the negative sub-pack-rcsistor (RSP I) is measured, a positive coupling voltage (UK2) falling at the positive sub-coupling-resistor (RSK2) is measured, a negative coupling voltage (UK1) falling at the negative sub-coupling-resistor (RSK1) is measured, and an evaluation of the measured voltages (UP1, UP2, UK1, UK2) is carried out. The invention also relates to an electric vehicle comprising a battery system (10) according to the invention.