Battery Pack Overdischarge Control via Voltage Monitoring
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Solution Overview
Problem
Battery packs face the risk of overdischarge, leading to copper precipitation and potential internal short circuits when not used for a long time, as the battery management system may shut down, allowing further voltage drop due to self-discharge, and existing systems lack effective methods to prevent reuse of overdischarged packs.
Innovation Solution
A battery management system with a voltage sensor, comparator, and controller that measures battery voltage at set intervals, compares it with reference voltages to determine if the pack is overdischarged, and controls the charge FET to prevent charging if the pack is in an overdischarged state, ensuring the battery is not reused and potentially avoiding internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the battery management system shuts down to conserve energy, then energy consumption is reduced, but the battery voltage may drop further due to self-discharge leading to overdischarge
Solution Approach 1:
The patent applies preliminary action by setting a reference voltage threshold before the battery reaches a dangerous state. The battery management system continuously monitors voltage and compares it against this pre-established reference value, enabling early detection and prevention of overdischarge conditions before they can cause copper precipitation or internal short circuits.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the battery voltage through a voltage sensor and comparing it with the reference voltage using a comparator. When the voltage drops below the reference threshold, the system provides feedback to the controller, which then activates the charge FET to prevent further discharge, creating a closed-loop control system that maintains battery safety.
2Reliability
If the battery management system continuously monitors voltage to prevent overdischarge, then battery safety is improved, but system complexity increases
Solution Approach 1:
The patent extracts the critical safety function from the main battery management system by implementing a dedicated voltage monitoring subsystem with its own comparator and reference voltage circuit. This separate monitoring module independently evaluates battery voltage and triggers protective actions without requiring complex processing, thereby maintaining high reliability while minimizing added system complexity.
Solution Approach 2:
The patent introduces a voltage sensor as an intermediary component that bridges the battery and the control system. The sensor converts the battery voltage into a measurable signal that can be compared against the reference voltage, serving as a mediator that enables safe monitoring without directly complicating the control architecture.
3Productivity
If charging is allowed immediately after shutdown to restore battery voltage, then charging efficiency is improved, but the risk of charging overdischarged batteries increases
Solution Approach 1:
The patent applies preliminary action by establishing a voltage threshold condition that must be satisfied before charging is permitted to resume. The system checks whether the battery voltage has recovered above the reference threshold before allowing the charge FET to be activated, preventing charging of severely overdischarged batteries that could be at risk of internal short circuits.
Solution Approach 2:
The patent implements preliminary anti-action by maintaining the charge FET in a blocked state until the voltage recovery condition is met. This preliminary prevention mechanism stops harmful charging current from flowing into potentially damaged batteries, counteracting the risk of internal short circuits before they can occur.
Data Source
AI summary
A battery pack includes a battery and a battery management system to control and manage charging and discharging of the battery. The battery management system includes an external terminal connected to a charger or an external electronic device, a cell terminal connected to the battery, a charge field effect transistor (FET) and a discharge FET connected between the external terminal and the cell terminal, a voltage sensor to measure a battery voltage of the battery, a comparator comparing the battery voltage with a reference voltage to determine whether the battery pack is in an overdischarged state, and a controller controlling the charge FET to be cut off to prevent a charge operation of the battery, if the comparator determines that the battery pack is in an overdischarged state.