Fuel Cell System Battery Charging Control
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Solution Overview
Problem
In fuel cell systems combining a fuel cell and a secondary battery, the rapid deterioration of the secondary battery due to high charging currents, especially at low temperatures, poses a significant challenge for maintaining system stability and longevity.
Innovation Solution
A control unit adjusts the fuel supply to limit the charging current to the secondary battery based on detected temperature, ensuring it remains below a predetermined maximum value, thereby reducing the stress on the battery and slowing down deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small capacity secondary battery is used to enable miniaturization, then the system size is reduced, but the maximum charge/discharge current increases causing rapid battery deterioration
Solution Approach 1:
The patent applies dynamics by making the maximum charging current value adjustable based on temperature conditions. The control unit dynamically changes the maximum charging current limit according to the detected temperature, allowing the system to adapt to varying thermal environments and prevent battery deterioration while maintaining miniaturization benefits
Solution Approach 2:
The patent changes the parameter of maximum charging current value based on temperature. By detecting temperature and adjusting the maximum charging current limit accordingly (lowering it at low temperatures), the system prevents excessive current from causing lithium metal deposition and battery deterioration, while still enabling small battery capacity for miniaturization
2Speed
If high charging current is applied to the secondary battery, then the power supply responsiveness is improved, but the battery deteriorates quickly especially at low temperatures
Solution Approach 1:
The patent changes the maximum charging current parameter based on temperature conditions. At low temperatures, the maximum charging current is reduced to prevent lithium metal deposition and battery deterioration, while at higher temperatures, higher charging currents are permitted to maintain good power supply responsiveness
Solution Approach 2:
The patent implements feedback by detecting the temperature of the secondary battery and using this information to adjust the maximum charging current limit. The control unit continuously monitors temperature and modifies the charging current constraints accordingly, creating a closed-loop control system that balances responsiveness and durability
3Productivity
If the fuel cell operates at full power, then the power generation efficiency is maximized, but the charging current to the secondary battery becomes excessive causing battery stress
Solution Approach 1:
The patent applies partial action by limiting the charging current to a maximum value that is lower than what full fuel cell power would produce. The control unit regulates the fuel supply to ensure the charging current stays within safe limits, using only the necessary portion of available power to charge the battery without causing deterioration
Solution Approach 2:
The patent changes the operating parameters of the fuel cell system by adjusting the maximum charging current value based on temperature. This allows the system to operate efficiently while preventing excessive current from damaging the battery, effectively decoupling full power generation from full power charging
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 effectively minimizes secondary battery deterioration across various temperature conditions, enabling stable operation while allowing for miniaturization of the fuel cell system, particularly by limiting charging currents and reducing acceleration of degradation at lower temperatures.
Implementation Method 1
When one of gas diffusion electrodes is set as a fuel electrode (anode) and methanol is supplied as fuel to the surface of the electrode, the methanol is degraded, and hydrogen ions (protons) and electrons are generated. Moreover, when the other gas diffusion electrode is set as an oxygen electrode (cathode) and air as an oxidant gas is supplied to the surface of the electrode, oxygen in the air and the above hydrogen ions and electrons are combined, and water is generated. By such an electrochemical reaction, electromotive force is generated from the DMFC.
Implementation Method 2
The hydrogen ions pass through the solid polymer electrolyte membrane.
Data Source
AI summary
The present invention provides a small fuel cell system including a secondary battery, in which deterioration in the secondary battery is suppressed regardless of a temperature condition. A control unit adjusts the supply amount of a liquid fluid of a fuel pump so that charging current I2 to a secondary battery becomes smaller than a predetermined maximum charging current value Imax. Consequently, for example, even in the case of using a small secondary battery, the charging current I2 is limited to be smaller than a predetermined upper limit value (maximum charging current value Imax). In addition, a temperature detecting unit detects temperature T1 of the secondary battery and the control unit controls the maximum charging current value Imax in accordance with the detected temperature T1 of the secondary battery. In such a manner, the operation of limiting the charging current I2 in accordance with the temperature T1 of the secondary battery at that time is performed.