Battery Management System Pre-Charge Control
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Solution Overview
Problem
Existing battery management systems fail to accurately determine if a capacitor is fully pre-charged, leading to potential damage from inrush currents when the main contactor is activated, as incorrect assumptions about pre-charge completion can cause high instantaneous currents.
Innovation Solution
A battery management system that includes voltage sensors, high-side and low-side drivers, a malfunction prevention circuit with a safety switch, and a control circuit to determine threshold voltages, ensuring the safety switch is only activated when the capacitor is fully pre-charged, thereby preventing inrush currents from damaging the main contactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple voltage check is used to determine pre-charge completion, then the control system is simple, but pre-charge completion may be erroneously determined leading to inrush currents
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the voltage difference between battery terminals and capacitor terminals during the pre-charge process. The control circuit compares the detected voltage difference with a predetermined threshold value and only determines pre-charge completion when the threshold is met, providing accurate feedback on the actual charge status rather than relying on simple time-based or assumption-based control.
Solution Approach 2:
The patent replaces simple voltage checking with a more sophisticated detection mechanism that measures the actual voltage difference across the main contactor terminals. This substitution of the detection method ensures accurate determination of pre-charge completion status by directly measuring the electrical parameter that determines whether inrush current will occur, rather than using indirect or simplified checks.
2Productivity
If pre-charge is performed without double-checking, then the system operates quickly, but the main contactor may be damaged by inrush currents
Solution Approach 1:
The patent performs preliminary action by pre-charging the capacitor through a pre-charge contactor before closing the main contactor. This preliminary charging action raises the capacitor voltage close to the battery voltage, thereby preventing large voltage differences and subsequent inrush currents when the main contactor closes. The system executes this preliminary charging step as a mandatory prerequisite before main contactor operation.
Solution Approach 2:
The patent implements a feedback verification mechanism that continuously monitors the voltage difference during and after pre-charge. The control circuit only permits main contactor closure when the detected voltage difference confirms that pre-charge completion criteria are met. This feedback loop ensures that the preliminary action has successfully reduced the voltage difference to safe levels before main power connection.
3Measurement precision
If voltage threshold checking is implemented, then pre-charge status is accurately determined, but additional voltage sensors and control circuits are required
Solution Approach 1:
The patent achieves multi-functionality by using the same voltage sensing circuitry and control logic to perform both the pre-charge control function and the pre-charge completion detection function. The control circuit that manages the pre-charge contactor also monitors the voltage difference and determines when pre-charge is complete, eliminating the need for separate dedicated detection hardware and reducing overall system complexity.
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 solution effectively reduces the likelihood of main contactor damage by double-checking the pre-charging status of the capacitor, ensuring the safety switch is only engaged when the capacitor voltage meets or exceeds the predetermined threshold, thus preventing inrush currents.
Implementation Method 1
a first voltage sensor configured to detect a first voltage between a first terminal and a second terminal of a first battery, a second voltage sensor configured to detect a second voltage between a first terminal and a second terminal of a capacitor
Implementation Method 2
a main contactor installed between the first terminal of the first battery and the first terminal of the capacitor
Implementation Method 3
a capacitor provided on a side of an electrical load
Data Source
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AI summary
A battery management system according to the present disclosure protects a main contactor from inrush currents, wherein the main contactor opens and closes a charge/discharge path connected between a first battery and an electrical load before pre-charging of a capacitor provided on the side of the electrical load is completed. The battery management system double-checks whether the pre-charging of the capacitor is completed based on a voltage across the capacitor and a voltage across the main contactor. The battery management system keeps a contact of the main contactor in an open operational position when the voltage across the capacitor is less than a first threshold voltage or the voltage across the main contactor is equal to or higher than a second threshold voltage.