Battery Module Balancing With PWM-Controlled Constant Discharge Current
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Solution Overview
Problem
Existing battery pack balancing methods, particularly passive balancing, face inefficiencies due to decreasing discharge currents as voltage differences are reduced, prolonging the time required to equalize battery module voltages.
Innovation Solution
A system comprising a driver unit with PWM-controlled drivers, a control unit, and a sensor unit that generates and adjusts PWM control signals based on detected module voltages to maintain a constant average discharge current, thereby accelerating the balancing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive balancing is used to equalize battery module voltages, then the battery modules are discharged to reduce voltage differences, but the discharge current decreases as voltage differences are reduced, prolonging the balancing time
Solution Approach 1:
The patent applies dynamics by making the discharge current adaptive rather than static. The control unit continuously adjusts the discharge current based on real-time voltage differences between battery modules. When voltage differences are large, higher discharge currents are applied; when voltage differences are small, the current is reduced. This dynamic adjustment maintains balancing effectiveness throughout the process without the current degradation problem of passive balancing.
Solution Approach 2:
The patent changes the parameter of discharge current from a fixed or naturally decaying value to a controlled variable that is actively adjusted based on voltage difference measurements. The control unit modifies the discharge current parameter in response to changing battery module states, enabling the system to maintain optimal balancing performance throughout the equalization process.
2Reliability
If passive balancing discharges battery modules to equalize voltages, then voltage equilibrium is established, but the process is slow due to decreasing discharge currents
Solution Approach 1:
The patent implements feedback control by continuously measuring the voltages of individual battery modules and using this information to adjust the discharge current. The control unit receives voltage measurements, compares them against target values, and modifies the discharge current accordingly. This closed-loop feedback mechanism ensures both voltage equilibrium is achieved and the process occurs at optimal speed.
Solution Approach 2:
The system transitions from the static, naturally decaying discharge current of passive balancing to a dynamic, actively controlled discharge current. The control unit adjusts the current in real-time based on voltage measurements, enabling the system to maintain high balancing speed while achieving complete voltage equilibrium.
3Reliability
If individual battery modules are discharged to predetermined voltage values, then voltage differences are equalized, but the process requires monitoring and controlling multiple modules separately
Solution Approach 1:
The patent applies universality by using a single control unit that can manage and coordinate the discharge of multiple battery modules. Rather than requiring separate control systems for each module, one multi-functional control unit performs voltage measurement, comparison, and discharge current regulation for all modules, simplifying the overall control architecture while maintaining individual module control.
Solution Approach 2:
The patent merges the control functions for multiple battery modules into a single integrated control unit. This consolidation combines voltage monitoring, current regulation, and equilibrium management into one system, reducing the number of separate components needed while maintaining the ability to individually control each module's discharge process.
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 approach allows for faster and more efficient balancing of battery modules by maintaining a constant discharge current, reducing the time required to reach a predetermined voltage, thus enhancing the battery pack's performance and lifespan.
Implementation Method 1
Each driver is configured to regulate the electrical charge of a battery module according to a pulse width modulated, PWM, control signal
Implementation Method 2
a resistor unit with several electrical load resistors... wherein the load resistors each provide electrical resistance between the driver interface and the system interface
Data Source
AI summary
The present invention relates to an apparatus, system and method for controlling a charge of a battery pack having a plurality of battery modules connected in series, each battery module including at least one battery cell, such that a constant average discharge current can be enabled.