ELECTRIC VEHICLE TECHNOLOGY

David Brandt, P.E.

The Basics:

• EV: electric vehicle• Are EV’s practical? Golf courses and

airports have thought so for many years.• But what about on the road? Are there

EV’s among us? Yes, and not just in California!

• Is there actually technology available to you and me to allow us to operate a practical EV? Yes!

OEM EV’s (you may have heard of some of these):• GM EV1

OEM EV’s:

• Solectria Force

OEM EV’s

• Corbin Sparrow PTV

Hobbyists?• The hobbyist says “If I can’t buy

one, I’ll build my own…• Honda Civic

More Hobbyist EV’s

• My Escort

More hobbyist EV’s• Ford Ranger

Components• What is out there that you need to have to

build an EV (besides batteries)?– Motor– Controller– Charger– DC/DC Converter– Heater– Instrumentation– Contactor(s)– Safety Equipment

Motors

• OEM’s: typically AC drive– Fail-safe design– Low initial torque, higher at speed– requires complicated electronics

package• AC speed control (similar to industrial)• Inverter (convert DC to AC)• High voltage (240-350 VDC)• Bearings only mechanical maintenance item

Motors• Hobbyist: typically brushed DC series

wound– Motors are available and inexpensive– 100% torque at 0 RPM– Controllers are dirt cheap compared to AC– No inverter stage required– Lower voltage system (72-156 VDC)– Bearings and brushes are potential

maintenance items (change brushes every 100,000 hours or so)

Motors• “Advanced DC” 9” diameter motor• Others include GE, Prestolite

Controllers• In General, Volts = Speed, Amps =

Torque– Curtis

• to 144 VDC, 500 Amps

– Auburn Scientific• to 192 VDC, 1200 Amps

– DCP• to 336 VDC, 600/1200 Amps

– EVCL• “GODZILLA” to 336 VDC, 1200 Amps

Controllers• All use PWM technology.

Chargers• OEM: uses weird connectors like inductive

“paddle” or AVCON “gas pump” nozzle.• Hobbyist: How about something everyone

already has, like 120 VAC household outlets and 240 VAC dryer outlets?

• Simple (voltage regulated) to complicated (computer controlled charging algorithms)

• More advanced charging required for advanced batteries (AGM)

DC/DC Converters

• Uses PWM to step traction pack voltage down to 12V to run car accessories.

• Common in electronics use• Not widely available in the

voltages required

Heater

• Ceramic - Self-regulating temperature of about 180° F.

• As temp. increases, resistance increases, decreasing power and stabilizing temp.

• Therefore, more air across the element = more heat.

• Typically 1500W. Can be stacked for more heat.

Heater

• The right type can be “harvested” from an AC ceramic heater.

Instrumentation

• Instrumentation can be as simple as an expanded scale voltmeter, but can be sophisticated, and include:– Traction Pack Voltmeter– Battery Current Ammeter– Motor Current Ammeter– Amp-hour/kWh meter (“E-Meter”)

Contactors

• BIG relays for switching traction pack

Safety• Inertia switch to deactivate contactor(s)

– same as is used to shut off fuel pumps in ICE cars

• AGM batteries - no spillage• Service disconnects - BIG circuit breakers• Fuses, of course• Traction pack is electrically isolated from

frame• 8 G crash load rating recommended for

battery boxes

Performance

• Acceleration and speed – About the same as ICE– Ranges from “economy car” to

“muscle car”.– DC motors great for drag racing– Current NEDRA record 8.801 seconds

in the 1/4 mile by “Current Eliminator”

Performance• tZero by AC Propulsion

Performance - tZero

• AC Propulsion's tzero out-accelerated a Ferrari F355, a new Corvette, and a Porsche Carrera 4 in a series of impromptu 1/8 mile drag races held on January 22, 2000 at Moffett Field in Mountain View, California, and at Calstart's northern facility at the former Alameda Naval Air Station.

Performance - tZero

• tZero mfg. By AC Propulsion versus Corvette

tzero_corvette_drag1.mov

Performance

• Range - typically 30-60 miles– somewhat dependent on if you have a lead

foot– great for commuting, which is where

people use the most gas anyway.– Use an ice vehicle for long trips - the right

tool for the right job.

• Over 100 miles attainable with purpose-built EV’s or using advanced batteries

Performance• John Wayland’s 120 mile range

“Red Beastie”

Performance• “Red Beastie’s” battery pack

Emissions

• Common claim is EV’s just move the pollution

• Point taken, but power plant emissions are scrubbed to a point not possible on a vehicle.

Emissions

• Belfast electric bus project (4 year duration of monitoring)

Fuel Consumed (kWh/mile)Diesel Electric Savings

4.9 2.2 55%Pollutants (gms/mile)

Diesel Electric SavingsCO2 1331 1058 21%CO 7.64 0.18 98%NOx+SO2 19.96 11.52 42%Hydrocarbons 2.74 0.18 93%Particulates 5.1 0.2 96%