Series Battery Pack Relay Switching for Shorter Precharge Time
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Solution Overview
Problem
The precharge time of battery packs connected in series is increased due to the high resistance value caused by a precharge resistor, leading to longer charging times.
Innovation Solution
A battery management apparatus that includes an information obtaining unit to measure voltages and a controller to generate control signals for the precharge relay and main relay, allowing for the optimization of their operations to reduce precharge resistance and time by short-circuiting or opening relays based on calculated voltage values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precharge resistor is serially connected to battery packs connected in series, then the resistance value increases and current magnitude decreases, but precharge time increases
Solution Approach 1:
The patent applies dynamics by making the precharge resistance adjustable rather than fixed. The controller dynamically changes the resistance value based on real-time voltage differences between battery packs. When voltage difference is large, higher resistance limits current; when voltage difference decreases, resistance decreases to allow faster charging, thus adapting the resistance to the changing system state
Solution Approach 2:
The patent changes the resistance parameter dynamically during the precharge process. The precharge resistor's resistance value is adjusted based on the voltage difference between battery packs, transforming from a static component to a dynamically controllable element that optimizes both safety and speed
2Reliability
If a precharge resistor is used to control current flow, then current magnitude is reduced for safety, but charging speed decreases
Solution Approach 1:
The patent makes the current control dynamic by adjusting resistance based on voltage difference. Initially, high resistance provides safety by limiting current when voltage difference is large. As charging progresses and voltage difference decreases, resistance is reduced to increase current and charging speed, thus dynamically balancing safety and productivity
Solution Approach 2:
The controller continuously monitors the voltage difference between battery packs and uses this feedback to adjust the precharge resistance. This closed-loop control ensures that current is limited when needed for safety but allowed to increase when safe, optimizing both reliability and charging speed
Data Source
AI summary
A battery management apparatus according to an embodiment disclosed herein includes an information obtaining unit configured to obtain a first voltage measured in an output terminal of each of a plurality of battery packs connected in series and a second voltage that is a battery module voltage value of each of the plurality of battery packs and a controller configured to generate a control signal for controlling operations of a precharge relay and a main relay included in each of the plurality of battery packs, based on the first voltage and the second voltage.