# Title Team Members TA Documents Sponsor
48 Dual plug EV charging power distribution device
Haochen Zhang
Shuchen Wu
Taiyuan Hu
Hanyin Shao design_document2.pdf
# Team Members
- Shuchen Wu(sw18)
- Taiyuan Hu(taiyuan2)
- Haochen Zhang(hz18)

# Background
At present, with the increase in the number of electric vehicles, most of the vehicle charging happens at night. In addition, as every families’ property accumulates, many families have two or more electric vehicles. The majority of the existing AC charging pile can provide a maximum charging current of 32A, but there is only one plug. When the electric vehicle is charged, the charging object can only be changed manually, which is difficult to meet the charging needs of a larger number of electric vehicles. What’s more, in order to protect the battery cells from overheating, the output current of the EV charger decreases and causes a waste of resources.

# Solution
Ideally, in order to solve this problem, we want to design a dual plug EV charging conversion device, which includes an EV charger interface, charging plug, control module, button module, and user interface module. We want to create two charging modes. One is the average charging mode, that is, each output plug allocates the same charging power. When one of the outputs does not need charging anymore, the device allocates the excess power to the other output plug; The other one is the limit mode. The user can manually choose to set the output current with the first priority. After the preferential output completes charging, the power will be allocated to the next priority output plug.

Because it is hard to actually test with an EV charger and Electric car. We decided to simplify our device to a level that can be tested based on the lab device. We want to directly use a 120V and 32A power electronic device as our design input. For electric vehicles, it is hard to manipulate the EV battery’s behavior, which is requesting lower power output from the device as the EV battery is filling. We decided to include loads like resistors in our design to control the output current amount, as mentioned previously in the limit mode of our design. In addition, the current's amplitude decreases as the battery charges, so to test the limit mode, we will decrease one of the outputs' current and see if the other output's current increases.

# Safety
We can make our device’s output total current to be 32A, as intended and voltage up to 120V. However, as we consider the safety of our design, we can either lower the tested voltage and current to lower the risk, or we can add a certain heat-radiating metal plate to prevent resistors from overheating and causing hazards. In addition, the resistance of the resistors in our design depends on the range of current that we want to control, the lower the range is, the smaller the number of the resistors we use, the less chance of causing overheating, and the safer our design is. So we can also minimize the range of our current output of the limit mode to guarantee our safety.

# Components

**EV charger interface(Input)**

Connect our device to the charging dock, the EV charger. We will directly utilize a 32A current generator to test our design.

**Charging plug(Output)**

Two plugs that output desired current and voltage.

**Control module**

The module allocates the total output power in either one of the two modes described above in the Solution section.
The rough outline of the sub-components in the module are listed below:


The microcontroller unit(MCU) would control most of the other components in our device to achieve the goal of user-device interaction, relays’ control, and current measurement.


AC Current Monitor Circuits: A Hall-Effect transistor will be employed in the circuits to monitor the current output of each port.

Current distribution Circuits with certain heat-radiating devices: A circuit consists of relays and loads to control different amounts of current output. We decided to first use a heat-radiating metal plate to prevent overheating due to high power. If further heat-radiating is needed, wind-cold or water cold devices can be taken into consideration.

Power Supply Circuits: A circuit that supplies 5V power for our MCU, and uses transistors to increase the small current in PCB as the power supply of relays.

**User interface Module:**

**_LED Monitor:_**

The LED monitor module would display the feedback from the control module which would provide a better user-device interaction.

**_Button Module:_**

The button would allow users to set the working modes manually and control the power distribution as desired. The input signal would be delivered to the Control module which would be processed by the MCU.

# Criteria for Success

- Able to generate steady current output in the charging end, which can be tested through measuring the currents.
- Able to perform both modes, average charging mode and limit mode, properly.
- The LED monitor displays correct information as designed.
- What's more, our overall design focus is on the power distribution of the device, namely, how to accurately adjust output power based on current and time(to simulate battery's behavior). Even though our origin design is related to power electronic devices, we do not think we need to test our device with respect to high voltages, up to hundreds of volts, which is much riskier.

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