Battery Pack Balancing Apparatus with Over-Discharge Protection
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Solution Overview
Problem
Battery packs in electric or hybrid vehicles face the risk of continuous discharge and potential overdischarge due to failures in the control processor during voltage balancing, which can lead to safety hazards like explosions, especially in lithium-ion batteries.
Innovation Solution
An apparatus with a discharge resistor, charge pump, discharge switching unit, and voltage charging unit is implemented, where the charge pump operates only with a predetermined frequency signal, and the discharge switching unit connects the battery cell to the resistor when a specific voltage level is reached, preventing overdischarge by automatically turning off when the voltage drops below a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a control processor is used to control the discharge of each battery cell during balancing, then the battery cells can be controlled to maintain uniform voltages, but the system may fail to cut the connection at the proper time due to control processor failure or program error, leading to overdischarge
Solution Approach 1:
A discharge switching unit is introduced as an intermediary component between the control processor and the discharge circuit. This switching unit automatically cuts off the discharge path when the battery cell voltage reaches a predetermined threshold, providing a fail-safe mechanism that operates independently of the control processor's software or control signals, thus preventing overdischarge even when the control system fails
Solution Approach 2:
The discharge switching unit is designed to automatically monitor the battery cell voltage and self-actuate to cut off the discharge connection when the voltage reaches the safe threshold. This self-service mechanism eliminates dependency on external control signals, ensuring reliable overdischarge protection through autonomous operation based on real-time voltage detection
2Stability of the object's composition
If a discharge resistor is connected to battery cells with higher voltage to balance the pack, then voltage uniformity is improved, but continuous discharge current may flow due to control failure, causing overdischarge and safety hazards
Solution Approach 1:
The discharge switching unit is configured to preemptively cut off the discharge connection when the battery cell voltage reaches a predetermined safe threshold. This preliminary protective action occurs before overdischarge can occur, automatically preventing the harmful effect even if the control processor continues to send erroneous discharge commands
Solution Approach 2:
The discharge switching unit serves as a protective intermediary between the discharge resistor and the battery cell. It allows controlled discharge for voltage balancing when needed but automatically interrupts the discharge path when the voltage threshold is reached, thus mediating between the need for voltage uniformity and the prevention of overdischarge damage
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 prevents battery cells from overdischarging due to control processor failures, enhancing safety by ensuring the battery pack operates within safe voltage levels and protecting the control processor from electrical impacts.
Implementation Method 1
a charge pump for pumping charges only when a balance control signal of a predetermined frequency is input thereto
Implementation Method 2
a discharge switching unit for connecting the battery cell to the discharge resistor when a driving voltage of an effective voltage level is applied thereto such that the battery cell is discharged
Implementation Method 3
a voltage charging unit for charging the pumped charges to apply the charging voltage as the driving voltage of the discharge switching unit
Data Source
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AI summary
An apparatus balances a charging voltage of each battery cell of a battery pack. The apparatus includes a discharge resistor installed on a conductive line connected to both ends of a battery cell in parallel; a balance signal relay unit for relaying a charging voltage of the battery cell according to a balance control signal; and a discharge switching unit for receiving the relayed charging voltage of the battery cell as a driving voltage and connecting the battery cell to the discharge resistor to discharge the battery cell if the driving voltage is over an effective voltage level. This apparatus prevents overcharging of a battery cell, caused by a failure of a control processor, while balancing a charging voltage of battery cells. Also, the control processor may be protected against an electric impact by electrical insulation from a discharge circuit. Accordingly, the safety of the battery pack is improved.