Battery Pack Voltage Measurement Circuit for 400 V/800 V Switching

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Solution Overview

Problem

Existing battery pack voltage measurement circuits face challenges in accurately measuring high voltages using low-specification relay switches, leading to voltage deviations, potential damage, and increased manufacturing costs due to the need for high-specification components, and leakage currents when using parallel resistor configurations.

Innovation Solution

A battery pack voltage measurement circuit that branches the voltage into two paths with different resistances, using low-specification relay switches and controlled switches to prevent leakage currents, allowing measurement of both 400 V and 800 V voltages with a single circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a low-specification relay switch is used to reduce costs, then manufacturing cost decreases, but the relay switch cannot stably operate at 800 V and voltage measurement reliability deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidvoltage measurement reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The voltage measurement circuit is segmented into multiple relay switches (first relay switch and second relay switch) that operate at different voltage levels. The first relay switch handles 400 V measurement while the second relay switch handles 800 V measurement, allowing each relay to be optimized for its specific voltage range rather than requiring all relays to be high-specification 800 V rated devices.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The circuit dynamically selects which relay switch to use based on the detected voltage level. When 800 V is detected, the second relay switch is activated; when 400 V is detected, the first relay switch is activated. This dynamic adaptation allows the system to use cost-effective low-specification relays for 400 V applications while maintaining reliability for 800 V applications.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a high-specification relay switch is used to ensure stable operation at 800 V, then voltage measurement reliability improves, but manufacturing cost increases

Engineering Contradiction:

Improvevoltage measurement reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the circuit have different quality requirements matched to their actual needs. The first relay switch (for 400 V) uses lower-specification components while the second relay switch (for 800 V) uses higher-specification components. This local optimization ensures reliability where needed while reducing costs where full high-voltage capability is not required.

Inventive Principle:

Principle #3Local quality

3Reliability

If parallel resistor configuration is used with low-specification relay switch, then the relay switch can handle 800 V, but leakage current occurs after relay switch turns off

Engineering Contradiction:

Improvevoltage handling capabilityVSAvoidleakage current

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The harmful leakage current path is extracted and isolated by using a separate second relay switch for 800 V measurement. When the first relay switch turns off, the leakage current is prevented from affecting the measurement circuit because the second relay switch configuration isolates the problematic current path, allowing the use of low-specification relay switches without suffering from leakage current issues.

Inventive Principle:

Principle #2Taking out (Extraction)

4Device complexity

If single circuit design is used to measure both 400 V and 800 V, then device complexity decreases, but measurement precision deteriorates due to voltage deviations

Engineering Contradiction:

Improvecircuit configurationVSAvoidvoltage measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The measurement circuit is segmented into separate measurement paths for 400 V and 800 V, each with its own optimized relay switch and resistor configuration. This segmentation allows each path to be precisely calibrated for its specific voltage level, preventing the voltage deviations and measurement errors that would occur in a single unified circuit design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The circuit dynamically switches between different measurement configurations based on the detected voltage level. For 400 V measurement, the first relay switch and associated components are activated with appropriate resistor ratios; for 800 V measurement, the second relay switch and associated components are activated. This dynamic reconfiguration maintains measurement precision across different voltage levels while keeping the overall device design relatively simple.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20260079186A1Battery Pack Voltage Measurement Circuit

Publication Date: 2026.03.19 LG ENERGY SOLUTION LTD

AI summary

A battery pack voltage measurement circuit including a relay unit controlling battery pack voltage measurement, first and second branching units provided between a battery pack voltage input terminal and the relay unit, and branching a battery pack voltage into different paths according to the battery pack voltage and then supplying the branched voltage to the relay unit, and a voltage distribution unit dividing the battery pack voltage supplied through the first or second branching unit and the relay unit and outputting the divided battery pack voltage to an output terminal.