Introduction

This device will be marketed toward current electric vehicle owners as well as individuals who are looking for a battery backup system for their house. The applications for this device are seemingly endless. In essence wherever an individual needs power, the SEVI can be used. A key application is for the construction industry. A contractor with a switch vehicle that is equipped with the SEVI will be able to use power tools in remote locations where power isn’t usually available.

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Literature Review

The concept of using a car to power external devices is not new. All of the major car companies including Toyota, Ford, Chevy, and Dodge offer a 110v ac outlet in the bed of their larger trucks. However the outlets in those trucks only support 1.5 amps of current. Also they are installed in a combustion powered vehicle. The Switch Electric Vehicle Inverter (SEVI) will be supporting 30 amps of current, which is twenty times more power than that of the existing trucks. This opens up the ability to connect more devices and a broader range of devices. Furthermore the battery in an electric vehicle has a much larger capacity so it can provide power for a longer period of time. For this project, the Inverter will be constructed so that it can power household appliances such as a refrigerator. Another existing similar product is a portable Inverter that plugs into the cigarette lighter of a vehicle. A product like this can be purchased on amazon for around $40, but only produces 5 amps of current. Even if an individual wanted to purchase a more expensive cigarette lighter powered inverter, it is still limited by the amount of power the outlet can support. An average 12v cigarette lighter is limited by a 10 amp fuse, so again, the main drawback power limitations.

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Problem Statement

There are currently no devices that can produce enough power to support an individual's power needs in a time of need without reverting to gasoline sources. The SEVI will be marketed toward current electric vehicle owners as well as individuals who are looking for a battery backup system for their house. The applications for this device are seemingly endless. In essence wherever an individual needs power, the SEVI can be used. A key application is for the construction industry. A contractor with a switch vehicle that is equipped with the SEVI will be able to use power tools in remote locations where power isn’t usually available.

 

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Methodology

Our team will be creating an inverter that can support devices that require large amounts of current.  This will be done using existing inverter designs and altering them to fit our situation, and will also include additional safety features to ensure the device will operate properly every time. The Inverter will essentially connect to the existing large DC battery in an electric vehicle and convert the power to usable AC power that any household appliances can use. The safety features are peripheral to the main unit that will monitor temperature and voltage.  If the values deviate too far from the safe operating range then a relay will be activated and the power will be cut off from the inverter.  

 

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Key Components

1. Pic Microcontroller

2. Temperature sensor

3. GFCI Outlet

4. Inverter Components

5. Switch Vehicle's battery and Battery Management System

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Challenges

Although there are similar products to the SEVI, it will be a significant challenge to build an inverter capable of supplying more than 10 amps of current. Efficiency is another challenge that will be anticipated. Without a decent efficiency percentage, the SEVI will drain batteries quickly, defeating the whole purpose of the device. The technology to build the SEVI already exists, it is just a matter of combining and adapting existing technologies for our needs.

 

 

Engineering Requirements:

1. Device must accept dc input voltages between 76v and 144v as this is the range of the battery packs.  

2. Device must support 220v and 110v AC output at 60Hz.

3. Device must be able to supply 20 amps - 30 amps nominal output.

4. Device must have an inline 30 amp AC fuse to protect devices.

5. Device must automatically shut off if battery level reaches 50% to preserve battery longevity.

6. Device must have a physical switch to prevent standby power drain.

7. Device needs to have a large aluminum heatsink for passive cooling to ensure no overheating under strenuous loads.

8. Device housing needs to be constructed out of aluminum sheet metal to reduce weight and increase durability.

9. Needs to have a lcd screen to display battery information.

10. Device must be contained in a sealed container to prevent weather damage.

11. Device must include a thermal auto-shut off if temperatures rise above 95 Degrees Celsius.

 

Marketing Requirements:

1. Device needs to be offered as both a built in option for new customers, and as a portable module to be added onto existing vehicles.

2. This will be sold for an additional $100 if installed in the vehicle, or $250 for a stand alone unit.

3. Advertise that this device can be used with solar panels in addition to electric vehicles.

4. Use renewable environmentally friendly branding on the product to appeal to a wider audience.

5. Advertise that the inverter is warranted for the first year for parts and service. Also that it’s under warranty for five years with limited coverage on manufacturer's errors.

6. The device will be marketed as a future proof piece of tech because of  the expanding market for electric vehicles.

7. Product needs to perform continuously until battery has drained.

8. The EV needs to have proper shielding to prevent from shorting or damage to the user. This includes insulating the wires. Weather proofing the box.

9. The product needs to have built in storage for the display so that usage records can be saved.

10. The device needs to have two outlets, 110v and 220v.

11. The device requires two steps before operation. First turn the switch to the on position, then plug the external device in.

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Design Approach

The architecture of the SEVI will be fairly simple. The device will connect into the existing DC electrical system of an electric vehicle and convert the DC power to 110V or 220V AC power to be utilized for simple household appliances. Unlike existing car DC to AC inverters, the SEVI will be able to supply a large amount of current and power in order to be used with larger household appliances, such as a refrigerator or a television. The SEVI  will also be a smart device, and will be capable of monitoring itself in case of a power overload or battery failure.

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Testing

1. Temperature displayed on LCD.

2. Voltage Displayed on LCD.

3. Physical Switch (Ghost Drain Protector).

4. Breaker test.

5. Outlet test.

6. Output frequency test.

7. Voltage step down test.

 

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Results

LCD testing (Temperature): For the testing on the display for the temperature, we used a 2x20 LCD and sent values from a 1k potentiometer into the ADC port of the PIC MCU (PIC18F45K20).  This represents the values we will be receiving from the temperature sensor that will be used in the project. Also, there's a button implemented in the design to allow for multiple functions.  When the button is pressed, it switches back and forth between reading values from the ADC and turning on an LED.  In the future the button will switch between reading temperature and reading voltage.

 

LCD testing (Voltage):  For the display testing for voltage, we used the same 2x20 LCD as from the temperature readings. This was simulated through showing a range of values that represents voltage drop over time. For instance, the display shows low voltage when the battery is at its lowest allowed capacity. Alternatively, the display shows full when the battery is fully charged. This is a critical test because it will be used for detecting when the device is automatically shut off to prevent from excessive power drain.

 

 

Engineering Ethics

As responsible Electrical Engineering students, we will produce our own unique work and do so as specified.  We will strive to use our own ideas, as well as improve on existing ideas to provide the best final product we can. This includes the software required to complete the project.The deadlines stated in the gantt chart will be met to the best of our ability.  It’s very important for us to take responsibility for any mistakes that may occur, especially when working with the expensive test equipment at Switch Electric Vehicles. We will be completely honest and upfront with our advisors. We won't attempt to cover up any mistakes or blame our faults on others. The project is ethically sound when it comes to the environmental aspect due to its use with electric vehicles. The use of our project will help lessen the environmental impact that current gas generators create. Lastly, we will never accept gifts or bribes that may compromise our relationship with Switch Electric Vehicles. Safety will be a very high priority for us and will not be taken lightly. This extends to the inverter being safe to operate on the consumer end as well as during the construction of the device. The high power that we will be working with will be extremely dangerous. It will be crucial for us to follow the safety procedures set forth by Switch Electric Vehicles.

 

 

References

1] S. Vehicles, "Welcome," in Switch Vehicles. [Online]. Available: http://www.switchvehicles.com/ .Accessed: Oct. 4, 2016.

[2] "Toyota Tacoma owners manual: Power outlet (120 VAC)∗ - other interior features - interior and exterior features," in Toyota Tacoma Owners and Service Manuals, 2011. [Online]. Available: http://www.ttguide.net/power_outlet_120_vac_8727_-114.html.  Accessed: Oct. 4, 2016.

[3] S. Electric, "Pure sine wave Inverters," in xantrex, 2013. [Online]. Available: http://www.xantrex.com/power-products/power-inverters/overview.aspx. Accessed: Oct. 4, 2016.

[4] "400W Power Inverter Owners Manual," in Northern Tool. [Online]. Available: http://www.northerntool.com/images/downloads/manuals/457400.pdf. Accessed: Oct. 4, 2016.

[5] "How Inverters and Converters work in Hybrids and EVs," in About Autos. [Online]. Available: http://alternativefuels.about.com/od/researchdevelopment/a/inverterconverters.htm. Accessed: Oct. 4, 2016

[6] N. Mohan, T. M. Undeland, and W. P. Robbins, Power electronics: Converters, applications, and design, 3rd ed. New York, NY, United States: John Wiley and Sons (WIE), 2002

[7] J. Doucet, D. Eggleston, and J. Shaw, "DC/AC Pure Sine Wave Inverter,"

[8] "800VA Pure Sine Wave Inverter’s Reference Design," in www.TI.com, 2013. [Online]. Available: http://www.ti.com/lit/an/slaa602/slaa602.pdf. Accessed: Nov. 6, 2016.