A Final Report
Submitted to Dr. Kevin Scoles
And the
Senior Project Design Faculty of Drexel University
The Electric Car Conversion
Project Number ECE-4
Team Members/Major:
Keith Kolkebeck ___________________
Bernard McGrath___________________
Michael Rehrman___________________
http://www.ece.drexel.edu/ev
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Submitted in partial fulfillment of the requirements for Senior Project
Design, ENGR 491
March 9, 2016
Abstract
The original goal of the SunDragon V data acquisition team was to design and
implement a data acquisition system for SunDragon V and VI. However, due to the
bleak outlook of Drexel's solar car program our team decided to redirect the objectives of
our project to the electric vehicle. An electric vehicle, a 1984 Honda CRX, was donated
to the university with the intention of having the school finish the car’s conversion to
electric power. Our team redefined its goal to include rewiring and documenting the high
and low voltage electrical systems and implementing electrical instrumentation. Thus
far, the high voltage system has been checked and documented and the low voltage
system has been torn apart, rewired and documented. The rewiring and the electrical
installation of the car are complete. The last phase of the project will include testing for
proper system functionality and efficiency.
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Table of Contents
ABSTRACT ....................................................................................................................... 2
INTRODUCTION............................................................................................................. 4
SOLUTION ....................................................................................................................... 6
HIGH VOLTAGE ELECTRICAL SYSTEM ............................................................................. 6
LOW VOLTAGE ELECTRICAL SYSTEM .............................................................................. 8
E-METER ........................................................................................................................ 10
ECONOMIC ANALYSIS .............................................................................................. 12
FINAL BUDGET ............................................................................................................ 14
DISCUSSION & CONCLUSIONS ............................................................................... 15
RECOMMENDATIONS FOR FUTURE WORK....................................................... 16
APPENDICES ................................................................................................................. 17
HIGH VOLTAGE DIAGRAM ............................................................................................. 17
LOW VOLTAGE DIAGRAM .............................................................................................. 18
E-METER DIAGRAM ....................................................................................................... 19
REFERENCES ................................................................................................................ 20
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Introduction
The original objective of the SunDragon data acquisition team was to design and
implement a data acquisition for SunDragon V and VI. However, due to the bleak
outlook of Drexel University’s solar car project, our team decided to redefine the goal of
our Senior Design project.
The new objectives were first, to correctly rewire the
electrical systems of the schools Electric Vehicle and second, to incorporate a small data
acquisition system using Cruising Equipments e-meter to gather high voltage information
and transmit the data to a computer.
The University acquired the electric vehicle, a converted 1984 Honda CRX, as an
incomplete project car donated to the Drexel University Electric Vehicle team. Our
primary goal was to make sure that all the wiring in the high and low voltage systems
were correctly wired and documented in schematics and manuals. The high and low
voltage systems were rewired with the guidance of a reference diagram. There remain
issues with the batteries, charging system, and windshield wiper switch. The car will be
road tested to check the overall system functionality. The E-meter was implemented with
the use of a Power Book laptop and a Palm Pilot to collect the data a Matlab script was
written to compile and display the data.
The dominant problem regarding the use of an electric vehicle in an everyday
application is the limit of the battery charge, thus resulting in a limited range. The total
battery usage time, for Drexel CRX EV, when the motor in use is approximately 24minutes at a constant current draw of 120 amps before a lengthy recharge of the batteries
is needed. This limits the range of the Drexel EV to a small operational area. The
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biggest draw on the batteries is during acceleration of the vehicle to operating speed. The
motor does not run while the car is standing still at a traffic light or a stop sign.
Unless a major development in battery technology or a decrease in battery cost
occurs the trend for the motor vehicle industry will be towards the use of hybrid vehicles
that run on a combination of internal combustion gas engines and electric motors. An
example of such a car is the new Honda Insight, currently on sale in the United States,
which uses an electric motor to accelerate to operating speed and a gas engine is used to
maintain speed. The gas mileage of the Honda Insight is approximately 70 miles per
gallon on the highway.
There is a need for alternative fuel vehicles in the United States to reduce
pollution and conserve the environment. In the future we will see such vehicles as a
prevalent part of our society. However, without the development of a battery that is
lighter, cheaper, and more efficient in the near future it will be rare to see a pure electric
vehicle on the streets unless it is a conversion.
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Solution
The Honda CRX conversion was broken into two large parts, the first being the
electrical systems and the second the mechanical systems. Our team was primary focus
was on the electrical systems, which included the low voltage system and the high
voltage system including battery charger, and E-meter with data logging. Both the High
and the Low voltage system were installed incorrectly from the start of the original
conversion project. However, these systems were never properly installed in the car. As
a result we needed to trace and document all wiring previously installed by the original
owners. Using the documented information, we were able to decide the best approach to
rebuilding the high and low voltage systems. We began by assessing the high voltage
system and making the correct changes, then moved onto the low voltage system.
High Voltage Electrical System
The high voltage system is the heart of the electric vehicle. Without the necessary
level of DC voltage and current, the car will not move. The Advanced DC motor is
connected directly to the original manufacturer’s 5-speed manual transmission. The high
voltage system includes the following parts:
o 10 12-volt Trojan 27TMH batteries
o 9” Advanced D.C. Motor’s 120 volt motor
o Curtis PWM Motor Controller
o Potbox to control speed via the OEM acceleration linkage.
o 200A Breaker
o K&W BC-20 Charger with LB-20 booster
o Albright Contactor
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o Cruising Equipment E-meter for voltage, current measurements, and amphour
o Shunt to measure the battery pack current.
o Red motor hi temperature indicator light
o Orange charger indicator light
The first objective of our work on the EV car was to ensure the proper setup of
the high voltage system. Tracing each of the high voltage cables throughout the car we
were able to determine that the system with the motor, motor controller, contactor, and
battery pack was properly setup. A Honda CRX
requires the motor to run in a clockwise direction
and from the motor documentation it was
determined that the motor was correctly wired as
seen in the picture to the right. A red indicator
light was wired into the instrument cluster to indicate if the motor is overheating. This
was accomplished by using a discrete temperature output provided by the manufacture of
the motor. Most of the wiring for the high voltage system was the proper gauge or was
replaced in order to carry the load.
Another issue that needs to be resolved with the system is the placement of the
two batteries that are currently located directly behind the front bumper. The current
location for these batteries is not safe and poses a great safety risk if there was a collision
involving the front end. It was decided that a good location for the batteries would be in
the trunk with the six others already there, but the final decision is to be made by the
mechanical team.
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The last issues to be addressed with the high voltage system are the battery
charger circuitry and the batteries. The car was donated with a K&W Engineering BC-20
battery charger and LB-20 line booster to raise the
voltage to 140 volts DC. However, after inspection of
the charger needed to be rewired with 10-gauge wire
as indicated in the manufacture specifications. The
charger also needs a dedicated 120V, 20A circuit to
produce the 120V DC, 12A current to the battery pack. An orange indicator light was
installed in the instrument cluster to let the driver know that the car is charging. It will
take an estimated 8-10 hours to fully charge the batteries once they are exhausted.
Low Voltage Electrical System
The low voltage electrical system provides the power to the existing low voltage
system (lights, turn signals, horn, wipers, etc…) and safety devices.
The 12-volts
necessary to run these systems is provided by means of a Sevcon DC-to-DC converter as
well as an auxiliary 12-volt battery. The low voltage system is monitored by DC volt and
ammeter mounted on the dashboard. The low voltage electrical system includes:
o Sevcon DC-to-DC converter
o 12-Volt auxiliary battery
o Original electrical system (Lights, horn, turn signals, stereo, etc…)
o Ignition Switch
o 2 relays to control the contactor and 12-volt system
o Indicator lights
o Analog Voltmeter and Ammeter
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The initial wiring was both incomplete and disorganized in both the engine
compartment and under the dashboard. In order to assure that the low voltage system
was correctly wired we determined the best approach was to completely rewire it. The
entire low voltage system was rewired, as well as interfacing to the original 12-volt OEM
system. The team also tested the low voltage system and assured that the turn signals,
headlights, and brake lights worked properly. The one problem that remains is a bad
windshield wiper switch on the steering column causing the wipers to stay on at one
speed when the key is turned. We believe that a replacement switch is necessary to
correct the problem after tracing down all connecting wires and testing the connections.
The safety features of the low voltage system include the use of two relays, a key
switch relay and a potbox relay, to provide control of the 12-volt system the motor. The
potbox relay controls the contactor
by allowing the contactor to close
only when the key is turned and the
accelerator pressed. The use of this
relay is an added safety measure
that allows the flow of current to the motor only when the pedal is used and not just by
turning the key. Therefore the motor will only get power when both the key is turned and
the accelerator is pressed.
Next the key switch relay was wired, which activates the low voltage system
when turned to either position one or two on the steering column. This allows the potbox
relay to be triggered when the accelerator is pressed. The key switch relay also activates
a green light on the lower right side of the dashboard that tells the driver the lower
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voltage system is engaged. Next the two relays were
mounted on the firewall close to the divider panel for
easy access to all the components. The key switch was
tested along with the pot-box relays by attaching a 12volt battery to the low voltage system. The key was
turned causing only the low voltage system to work, but not closing the contactor. Next,
stepping on the accelerator caused the micro switch in the potbox to close, which
activated the potbox relay, closing the contactor and allowing power to be supplied to the
motor.
E-meter
The e-meter is a voltmeter with data logging capabilities using an RS232
communications port. The E-meter is being used to take measurements of the high
voltage system in the electric car. A 500-volt prescaler, voltage divider, was used to drop
the input voltage into the E-meter from the battery pack. The E-meter monitors the
voltage, current, and amp-hours by means of an LED panel mounted in the center of the
car’s dashboard. The E-meter also has a RS232 serial communication port on the back,
which allows data to be transmitted to a computer. Any device with a serial port can
potentially be used to capture data. USB is replacing most serial connections so a USB to
RS232F can be used.
The data coming out of the E-meter in the form of a comma delimited text file. A
laptop, PowerBook 5300, and a Palm Pilot were used for testing. The computer will save
more samples than the Palm Pilot, which gives a higher sampling rate for providing good
resolution for testing. The Palm Pilot application can be used later when fine details are
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not as important. The data was output over a
serial connection tool then saved to a file for
analysis later using Excel or Matlab. The Emeter is installed in the center of the dashboard
with a serial cable located at the floor to
provide easy laptop or Palm Pilot hookup as
seen in the picture to the right.
The E-meter measures the total voltage across the entire battery pack by hooking
it up in series with the high voltage circuit. Since the voltage of the battery pack is over
50-volts cruising equipment’s 500-volt prescaler is being used to drop the input voltage
to the E-meter down. The E-meter is then programmed to adjust the display of the
voltage to reflect the actual voltage. The current is also measured, using a shunt, which is
installed on the firewall and connected in series to the high voltage circuit.
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Economic Analysis
The budget in the following section will show that it costs approximately $7,300
to convert a small vehicle not including the price of the chassis. Of course the type and
age of the car one chooses to covert will affect the overall price of the conversion. There
are also costs that one might incur during a conversion, such as chassis modifications,
various new parts, tools, etc…. However, if one decides to convert a vehicle it will take
approximately 120-180 hours to produce a working model if all goes according to plan.
The above price does not take into consideration the man-hours for the conversion. The
time of conversion can add to the overall cost.
An easier solution then converting a vehicle would be to buy one of the few
electric vehicles on the market. The big three auto manufactures have electric vehicles
on the market, but are out of most people’s price range. The General Motors EV1 is
priced around $34,0001 for a basic model, plus a $2,000 charge for the special charging
station to be installing in your home, however only a lease option is available. There is
also the option of paying an electric vehicle specialist to convert a vehicle for the owner.
However, the price also runs on the high side, around $20,000 -$25,000 for the
conversion.
The Drexel University Honda CRX’s total cost of the conversion including the
purchase of new Trojan TMH batteries was $7,000. To operate the vehicle using per
mile cost versus a gasoline engine vehicle is shown below. All formula’s are taken from
the EV 1999 senior design project and adjusted to reflect present day cost. The vehicle
uses a 120-volt battery pack, which has a capacity of 26.6 kWh 2. If the range of the
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Based on the EV homepage http://www.gm.com
Capacity=V*AH (120V*220AH)
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vehicle is approximately 60 miles depending on conditions the average energy per mile
used is 0.44 kWh/mi3. The cost of electricity per kilowatt-hour provided by PECO
Energy in the City of Philadelphia is $0.15/kWh4, thus making the operation of an EV
around $0.044 per mile. In comparison using the rough estimate that a gallon of regular
gas costs around $1.45 and the average vehicle gets around 20 miles per gallon it costs
about $0.075 per mile to operate a gas vehicle. The price comparison is not much
different and does not include the added cost of maintenance for either vehicle.
Therefore in the future we will begin to see more hybrid vehicles on the road instead of
pure electric vehicles. The Electric motor has the potential to run on the road for more
miles than any gasoline or diesel engine.
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4
Average energy=Capacity/miles (26.6kWh/60mi.)
Cost per mile=kWh/mi.*cost per kWh (0.44kWh*$0.15/kWh)
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Final Budget
The following is the budget from last years EV senior design team with the
addition of the costs incurred this year broken down by item.
Item
1984 Honda CRX chassis
9” Advanced DC Motor
CurtisPMC Motor Controller
CurtisPMC Potbox
Albright Contactor
Current Shunt
Cruising Equipment E-meter w/ 500V prescaler
Sevcon DC/DC Converter
K&W Battery Charger
K&W Battery Charger Booster
Power Brake Vacuum Pump
50mV Shunt
10-12-volt Trojan THM Batteries
Car relocation
Miscellaneous
Total Cost
Cost
$1150.00
$1623.00
$906.00
$77.00
$165.00
$22.75
$300.00
$580.00
$675.00
$195.00
$285.00
$30.00
$833.30
$155.00
$300.00
$7297.05
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Discussion & Conclusions
An electric vehicle is an environmentally friendly alternative to regular internal
combustion engine automobiles including mass transit. Electric vehicles, though they
have a limited range, are less expensive to operate and emit 97 percent less pollution than
a regular automobile including power generation for charging.
Electric vehicles are less expensive to operate than regular automobiles. At an average of
4.4 cents per mile, this beats the per mile average of regular automobiles by over 3 cents
a mile. This gives the owner a great savings over other types of transportation even
though the electric vehicle is limited in range.
Currently an electric vehicle range is limited to a local area. In areas such as
Southern California and Arizona, where General Motors has begun leasing its EV1
electric vehicle, public charging stations are provided by the local utility companies in
order to provide a means of refueling while the EV1 is not in use.
Overall, pure electric vehicles will most likely never become the prevailing form
of transportation in the United States. Research in electric vehicle and battery technology,
however, is important to provide information to engineers for further development of
transportation that is more efficient and cleaner such as hybrid electric vehicles.
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Recommendations for Future Work
The future work to be considered for the Drexel University Honda CRX-EV
includes the development and implementation of a regenerative braking system and a
comprehensive road test to create a baseline for efficiency. Further work could involve
working to improve upon that efficiency. Regeneration techniques as well as different
battery technology will allow the converted CRX to run longer and use energy more
efficiently.
In addition to the aforementioned future work suggestions, research into different
weight distributions and other mechanical factors could lead to a more efficient vehicle.
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Appendices
High Voltage Diagram
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Low Voltage Diagram
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E-meter Diagram
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References
Bob Brant. Built Your Own Electric Vehicle. McGraw-Hill, Inc. 1994.
Michael P. Brown. Convert It. Future Books. 1993.
Peter Ohler. Palm Pilot E-meter Application. www.ohler.com
K&W Engineering, Inc. BC-20 Charger Manual. http://home.att.net/~kwengineering/
Cruising Equipment Company. www.cruisingequip.com.
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