BatteryPowered Electric Vehicle Conversion:

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Battery-Powered Electric Vehicle Conversion
(BEVC) Final Design Review December 2,
2004 Presented By Ryan Bohm 1355 N. 400 E.
1 Logan, UT 84341
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BEVC Project Summary
Project Stage Final Design Review Objective
To convert a conventional gas-powered vehicle to
battery-powered electric and observe public
reaction to electric vehicles as an alternative
form of transportation. Principle Most
commuter vehicles use an internal-combustion
engine which is fueled by gasoline. Gasoline
combustion engines are inefficient, noisy,
require frequent maintenance, and require
non-renewable resources to power. Electric
motors are virtually maintenance free, quiet,
efficient, and can use renewable resources as a
power source. A gasoline combustion engine can
be replaced by an electric motor. Project
Lead Ryan Bohm Finish Date December 2004
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• Welcome / Introduction 1 min.
• Executive Summary 2 min.
• Project Objective
• General Theory of Operation
• Dismantling of Internal Combustion system
  1 min.
• Drivetrain 2 min.
• Coupling motor shaft to flywheel
• Coupling motor to transmission
• Cooling motor
• Batteries 1 min.
• Battery Racks 1 min.
• Galvanic Corrosion 1 min.
• Power Brakes 2 min.
• Vacuum pump
• Vacuum tank
• Power Steering/Air Conditioning 1 min.
• Mounting bracket 1 min.

4

• Heater 2 min.
• Building heater housing
• Hall-effect sensor unit
• Motor Controller 2 min.
• Mounting
• Cooling
• Connecting
• Throttle control
• Tach sensor
• Controller interface
• Battery Charger 2 min.
• Battery Regulators
• Charging connector
• Accessory Electronics 12V system 1 min.
• Isolation of High-Voltage and 12V system 1
  min.

5

• Circuit Breaker and Main Fuses 1 min.
• Battery Voltage Monitoring 2 min.
• Block diagram
• Programming/calibrating
• Current Sensing Unit 1 min.
• Block diagram
• Programming/calibrating
• Conclusion 1 min.

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Project Objective

• Convert a 1984 Nissan 200sx conventional
  internal-combustion vehicle to battery powered
  electric.
• Display to the public the feasibility of
  battery-powered electric vehicles for
  short-distance commutes.
• Fulfill the requirements for Computer-Engineering
  Senior Design Project and Utah State University.

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Theory of Operation
Battery Bank
Adapter
Controller
Transmission
Charger
Motor
Electronics Box
High-Current Cables
Charging Cable
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Drivetrain Electric Motor

• A series wound DC motor with the following
  characteristics will be used
• 20 HP (continuous rating)
• Series wound
• 96 Volts (will be run at 144, which is within
  working range)

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Coupling Motor to Flywheel

• Motor shaft coupler and adapter plate were
  designed and manufactured by Electro Auto. The
  motor coupler is a critical component of the
  drive train through which all torque is
  transmitted.

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Coupling Motor to Transmission

• The flywheel is attached to the motor shaft with
  a new clutch installed. The motor and
  transmission have been installed in the vehicle.

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Cooling Motor

• An external 12V blower will force air through the
  motor to keep it cool.
• A 12V relay will switch on the blower.

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Batteries

• Twelve Exide Orbital 12V batteries are wired in
  series to produce 144V operating voltage.
• All battery terminals are crimped onto 2/0
  welding cable capable of handling the 1000 amp
  surges of current.
• A tool was made for high-pressure crimping.

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Battery Racks

• Total battery weight is 492 lbs.
• 10 of the 12 batteries are located in a metal
  rack built into the rear seat.
• The remaining 2 batteries are secured to the
  electronics rack in the engine compartment.

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Galvanic Corrosion

• When in contact with steel, aluminum will break
  down over time.
• All locations where steel and aluminum come in
  contact will be treated with paint or silicon
  sealer to minimize the effects of galvanic
  corrosion.
• This is not considered a threat to the integrity
  of the vehicle. It can affect the longevity and
  appearance of several of the components.

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Vacuum Pump

• A 12v, 9 amp vacuum pump replace the vacuum
  provided by the internal combustion engine.
• An adjustable vacuum switch will turn on the pump
  when vacuum falls below the set value.

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Vacuum Tank

• The vacuum pump alone will only provide about 1
  assisted actuation of the brakes. By using a
  vacuum tank, multiple assisted actuations of the
  brakes can be made.

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Power Steering/Air Conditioning

• The air conditioning compressor and power
  steering pump will be run off of the 1.5 hp
  accessory motor.
• Pump and compressor will rotate at approximately
  2500 rpm.
• Accessory motor will be switched on/off by a
  relay. A snubber diode will be placed across the
  motor leads to prevent voltage spikes when the
  motor is turned off.

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Mounting Bracket

• A mounting bracket secures the power steering
  pump, air conditioning compressor, and accessory
  motor. It is mounted to the front face of the
  traction motor.

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Heater Theory of Operation

• The electric heater elements are positioned where
  the existing coolant-heated core was located.
  High-voltage DC relays are controlled by a
  circuit which determines if the fan switch is
  turned on, and the heat selection control switch
  is in the half or full on position.

Gnd L.V.
1
1
Fan Speed Sw.
Control Circuit
Temp. Select
2
Air Flow
Gnd H.V.
144v
Gnd H.V.
2 Gnd L.V.
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Building Heater Housing

• The 2 electric heater elements come with a
  special plastic housing capable of withstanding
  the high temperature of the element.
• This housing will be modified to accommodate the
  elements in a sandwiched configuration.
• An aluminum housing will be manufactured to fit
  in the footprint of the original heater core.

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Hall-effect Sensors

• Heater element selecting will be performed by two
  Hall-effect sensors mounted on the back of the
  heater element housing box.
• Magnets are embedded in a control arm which
  previously opened/closed a coolant valve and was
  actuated by moving the temperature control lever.

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Controller Mounting

• The motor controller will be mounted inside an
  electronics box which will reside in the engine
  compartment.
• This electronics box will keep moisture, dirt,
  and dust from the controller and other
  electronics.

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Controller Cooling

• The motor controller is cooled using a pump and
  small radiator. This allows for optimum
  performance of the controller.
• A 120VAC pump is powered by a small AC inverter.
  
• The coolant passes through the coolant lines to a
  small radiator.

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Controller Connections
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Throttle Control

• The motor controller throttle input is a 5K Ohm
  variable resistor (potentiometer).
• A pre-built unit from Curtis has been used.
• An additional return spring will be used for
  safety.

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Tach Sensor

• A tachometer sensor converts the motor
  revolutions to a signal the dash gauge and
  controller recongize.
• The controller tach signal must be pulled low 4
  times per revolution.
• The tach sensor output will feed both the dash
  gauge and motor controller.

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Tach Sensor Construction

• The tach sensor is a Hall-effect sensor and 2
  capacitors epoxied in a copper cap housing.
• Magnets are embedded in a nylon collar which
  mounts on the motor tail-shaft.

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Controller Interface

• Controller parameters, such as motor voltage and
  current, can be adjusted through a serial
  connection to the controller.
• A Palm IIIe PDA is used for the interfacing
  device. A 12v to 3v converter board provides
  constant power from the vehicle 12v system.

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Charging Connector

• The battery charger plugs into the 120 or 240 AC
  grid using a permanent twist-lock connector
  located where the gas fueling door resided.
• A Hall-effect sensor and magnet on the fuel door
  will send a signal to the motor controller to
  indicate if the fuel door is open or closed.
• The controller will not allow the motor to turn
  if the fuel door is open to prevent driving away
  with the charging cord connected.

Hall-effect sensor
Stationary Plug
Magnet
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12V System

• The existing 12 volt system will remain to power
  accessory devices such as headlights, horn,
  radio, and dashboard instruments.
• During normal operation, the 12 volt system will
  be powered and the 12 volt battery charged by 2
  IOTA DLS-55 DC/DC converters (actually
  dual-purpose battery chargers), with a maximum
  rating of 2 x 55 110 amps. This exceeds the
  original alternator output of 60 amps.

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Isolation

• The 12V chassis ground must be isolated from the
  144V system. This is to ensure that through
  error, or accident, the chassis ground cannot
  complete a 144V potential loop. The 144V system
  has no common grounded chassis like the 12V
  system.

12V
144V
-
-
Chassis Ground
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Fuses Circuit Breakers

• The main 144V feed line has a fast semiconductor
  fuse for protection of the system.
• The 144V line will also have a high-current
  circuit breaker within easy reach of the driver
  to disconnect power in case of an emergency.

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Battery Voltage Monitor

• The existing dashboard fuel gauge displays the
  battery state-of-charge (SOC).
• A battery voltage monitor unit interfaces with
  the dashboard fuel gauge.
• The battery voltage monitor calculates the SOC
  and also interfaces with the low-fuel dashboard
  light and charge warning light (previously the
  alternator error light).

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Voltage Monitor Block Diagram
Outputs
Inputs
Program. Buses
HV
Low Fuel Light
Current (from current sensing unit)
Temp. Sensor
Fuel guage
voltage bus
5V
Battery Error Light
12V
12V Gnd
Temp. Sensor
HV
5V
HV Gnd
12V
Bat. Reg. Signal
Bat. Reg. Signal Out
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Programming Voltage Monitor

• The voltage monitor unit contains two PIC
  microcontrollers.
• These microcontrollers can be reprogrammed
  in-circuit to change the software.
• Code for the microcontrollers is written in PIC
  C.

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Current Measurement Gauge

• Instantaneous current will be displayed on the
  oil-pressure gauge of the existing dashboard.
• It was discovered that the motor controller has a
  current measurement output option. This will be
  used instead of the previously planned
  Hall-effect sensor unit.
• A PIC will still be necessary to convert the
  controller current signal to one the dashboard
  gauge recognizes.

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Current Sensing Block Diagram
Programming Bus
to dash gauge
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Programming Current Sensing Unit

• The current sensing unit will be programmed in
  the same fashion as the voltage monitor unit.
• It is unlikely that the software will require
  much modification after the initial design.

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Control Boards

• All PCBs will be reduced to heat-shrink packages
  where possible to reduce costs and space
  requirements.
• The PCBs that are necessary (voltage monitor,
  current sensor converter) will be housed in a
  metal case.

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Conclusion

• We're ready to roll!