ev101: owning and operating an electric vehicle gary graunke oregon electric vehicle association...
TRANSCRIPT
EV101: Owning and Operating an Electric
Vehicle
Gary Graunke
Oregon Electric Vehicle Association(Oregon chapter of the Electric Auto Association)
December, 2007
Gratefully acknowledging many slides from
Steve HeckerothDirector of BIPV, ECD Ovonics
Chair Renewable Fuels and Sustainable Transportation Division
of the American Solar Energy Society
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation vs fossil fuels
• Questions and Answers
How Electric Cars Work• Throttle variable resistor tells
motor controller desired speed – Like radio volume control
• Motor controller varies pulse width to motor– Rapidly switches battery
voltage on and off• Contactors (relays) may be
used to reverse motor– Other contactors used for
safety disconnect• Charger recharges batteries
from grid• DC-DC converter charges low
voltage “starter” battery from high voltage pack
Motor
Differential
SpeedPedal
MotorController
TractionBatteries
Charger
Contactors
Contactors
Aux.Battery
DC-DC
Just like a toy car, but high voltage and high current (danger!)
Throttle Linkage
Zap Throttle Linkage Converted Honda Insight Linkage
S10Electric PickupLinkage
Mechanical Input
Electric Output
Motor Controllers
• DC motor controllers pulse high voltage to motor– Pulse width controls speed– Relays used to reverse motor
• Some motor controllers do regenerative braking– Slows vehicle by generating
electricity from motion– Recharges batteries
Curtis 1231C (ZAP)
CafeElectric Zilla 1KContactors (ZAP)
Electricity is the only alternative fuel you can create when you go downhill
Series Chargers• Proper charging is important for
battery life!• Each battery has its own
protocol– Initial bulk charge usually
constant current (max power)– Finishing charge is constant
voltage (power decreases)DeltaQ charger (ZAP)
Brusa NLG512 charger Manzanita Micro PFC
DC-DC Converters
• Most EV’s have small 12V aux. battery– Runs lights, horn, etc– Runs motor controller logic
—needed to start– Small: no engine to start!
• DC-DC charges aux battery from high voltage pack– Voltage change– Isolation (safety)
• Some are integrated with motor controller
Zap DC-DC
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation vs fossil fuels
• Questions and Answers
EV Maintenance• Tires and brakes are the same as gas cars
– Regenerative braking reduces brake wear
• No filters, mufflers, oil changes, engine valves, rings, pollution control, fuel pumps
• Care and feeding of (lead acid) battery pack– Ideally charge when 50% and 70% left– Avoid discharge < 20% state of charge
• Leaving discharged causes sulfation in lead batteries– Keep lead-acid batteries topped up
• Batteries self-discharge (charge periodically if not in use)
– Avoid overcharging (good chargers won’t do this)
Running batteries down and letting them sit discharged is very bad for them
Managing Safety Issues
• Service disconnects to break HV battery string into small parts– Voltages must be below 60V to be “safe”– High voltage, high current shorts can cause plasma fires – Maintain isolation of HV pack and chassis
• Need two connections to form circuit—don’t give up this advantage!• Remove rings while working on battery pack
– High currents can weld objects• Batteries must be securely fastened down• Use DC-rated fuses, switches, relays
– DC ratings are typically 1/3 of AC ratings• Flooded batteries may explode--wear eye protection• Flooded batteries can spill H2SO4, KOH• Overcharging (mostly flooded) may produce explosive H2 • Nevertheless, electricity has safety advantages
– Does not leak into air and explode/catch fire– Easily stopped by fuse or switch anywhere in circuit
Proper Tools for Safety
• Electrical tape on metal sockets and other wrenches
• Rubber handle wrenches• Rubber gloves
– Certified if higher voltages
• Fiberglass shaft screwdrivers / nutdrivers
• Certified and isolated test equipment (meters and scopes)
Battery Balancing• Relative cell state of charge varies
over time – Manufacturing variance– Different operating temperature– Series charging increases differences
in state of charge• Individual chargers is one solution
• Stop driving when lowest cell is empty
• Stop charging when highest cell is full (5% overcharge ok)
• But charger and instruments measure total pack voltage– Ideally measure individual cell
voltages– Measuring highest, lowest batteries is
good approximation
voltage
full 2.16V
empty 1.75V
voltage
full
empty
overcharge
Periodic rebalancing improves battery pack longevity
Capacity Variance with Aging
• As batteries age capacity variances increase– More imbalance!
• Easier to overdrive– Weakest cell voltage plunges and
may even reverse polarity!– Best case: shorter range
• Low temperatures also reduce effective capacity
– Eventually it’s time for a new pack!
• Lowest capacity cell is also overcharged
• Active automatic battery balancers mitigate extremes voltage
full
empty
overcharging
voltage
full 2.16
empty 1.75
Overdriving
0 volts
Check aging pack batteries for varying capacity
Use Appropriate Batteries
drive from downtown charge at aloha
7.000
8.000
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440
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880
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1757
1977
2197
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3993
4213
seconds
volt
age
101(VDC)102(VDC)103(VDC)104(VDC)105(VDC)106(VDC)107(VDC)108(VDC)109(VDC)110(VDC)111(VDC)112(VDC)113(VDC)114(VDC)209(VDC)210(VDC)211(VDC)212(VDC)213(VDC)214(VDC)
12V batteries need sufficient power to stay above 10.5V (short bursts ok)
Past Time for a New Pack
0.000
2.000
4.000
6.000
8.000
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52:0
2.0
52:5
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56:1
2.1
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58:4
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00:2
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08:4
2.0
09:3
2.0
time
volt
s
101(VDC)102(VDC)103(VDC)104(VDC)105(VDC)106(VDC)107(VDC)108(VDC)109(VDC)110(VDC)111(VDC)112(VDC)113(VDC)114(VDC)209(VDC)210(VDC)211(VDC)212(VDC)213(VDC)214(VDC)
2V differences indicate exhausted or reversed cells
Battery Management Add-ons
• Hart Batt-Bridge is an “idiot light” costing <$10– LED lights when two halves of
pack differ by > 2v– One cell empties/reverses first– Charge now or go “turtle mode”!
• PowerCheq modules – Keep each two adjacent batteries
voltage difference < .1V– Works 24X7 while driving,
charging, parked– Limited current—keeps balanced
pack balanced– Requires N-1 modules for N
batteries
More Battery Management Aids• Manzanita Micro MK3
regulator prevents overcharge – Backs off charger when
individual battery full– Limits battery voltage– Data logging
• Hart balancer relay module (30A capacity)– Scans batteries to measure
voltage– Connects any battery to
isolated “flying” battery or DC-DC
– Can take charge from higher state-of-charge batteries
– Gives charge to lower state-of-charge batteries
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation vs fossil fuels
• Questions and Answers
Costs of EV Operation
• Top EV cost is battery wear– 3 to 15 cents / mile– Assumes proper care!
• Fuel cost 2-3 cents/mi– 10 cents/KWH and 4-8
mi/KWH– 1 US gal gas = 33 KWH
• S10: 66 mpg equivalent• NEV: 245 mpg equivalent
• Electric motors last!– AC motors: 1 moving part– DC motors: brushes
• Top heat engine cost is maintenance– 28 cents / mile (CARB)– Engine/drive train wear
• Currently 10 cents/mi – $3.00/gal and 30 mpg– Geologists, investment
bankers say global oil production has peaked
– Expect unlimited price increases
EV owners replace batteries when heat engine owners replace vehicle
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation vs fossil fuels
• Questions and Answers
Uses for Electric Vehicles• Pure electric vehicles
– Daily commuting and in-town driving– Great for circular business delivery routes (e.g., mail carriers)– Excellent for short trips (no engine warm-up needed)
• Efficient and non-polluting even when “cold”• Prius gets 25 mpg for first 5 minutes!
– Some vehicles may have speed limits• Freeway capable EV’s exist (mostly conversions for now)
– Range is only limiting factor (may be reduced in winter)• Low battery specific energy vs heat engine fuel• Lack of rapid recharging/battery swapping infrastructure
• Hybrid (HEV) and Plug-in Hybrid Electric Vehicles (PHEV)– Better (+50%) range for long trips + efficiency– Honda Insight (EPA 70 mpg) owners often report 1000 miles/tank– Plug-in Prius (Hybrids Plus) 1620 mi on 9.27 gal (171 mpg + electricity)
Consider Budget/Flexcar for those infrequent long trips
Electric Motor Torque and Power
Torque and mechanical power vs. rotation speed
0.0
10.0
20.0
30.0
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0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Shaft rotation speed, RPM
To
rqu
e (f
t/lb
s)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
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Mec
han
ical
po
wer
(
KW
)
Max torque Rated torque Max power Rated power
Siemens 5105WS12 at 312 Volts
Insight torque 79 ft lbs at 1500 RPM Insight power 54.4 KW at 5700 RPM
Solar Powered Electric Vehicles
PV charging infrastructure combined with plug-in vehicles tied to the grid (V2G) will provide peak shaving, load leveling and backup power. EVs and PVs in the parking lot or garage can power a factory or home.
The Clean Power/Transportation Solution
Almost Half a MWh of storage in the
parking lot
Photo courtesy Donald Aitkin
2 kW of PV per parking space
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation vs fossil fuels
• Questions and Answers
Fuel Efficiency and Climate Change
Assumptions: $3.50/gal, $.05/kWh nighttime rate, 40kWh/gal, 23#sCO2/gal * This column includes upstream CO2 emissions for exploration, extraction, transport, refining and distribution of gasoline,
as as well as CO2 emissions from the California mix of power plants that produce electricity to charge electric vehicles.
Vehicle Type$ Gas
25 Mi.
/Day
kWh 25 Mi.
/Day
$/year25 Mi. /Day
Gal/yr25 Mi.
/Day
Tons ofCO2/YrTailpipe
*+ Tons of UpstreamCO2/Year
10 MPG Gas 8.75 100 $3200 915 10.5 13.7
20 MPG Gas 4.37 50 $1600 460 5.3 6.8
30 MPG Gas 2.93 34 $1050 305 3.5 4.5
40 MPG HEV 2.20 25 $800 230 2.6 3.4
50 MPG HEV 1.75 20 $640 180 2.1 2.8
Plug-in HEV 25 Mile range
0 5 $100 0 0 .7
Battery EV 0 3 $65 0 0 .4
Solar/Electric 0 1 0 0 0 ZERO
The real measure of efficiencyIt took 3.5 billion years and rare geologic events to sequester hydro carbons and build up O2 in the atmosphere
3.5x109 Years X 3.5x108 TWh/year Solar Energy = 1x106 TWh Oil Total
1.2x1012 TWh Solar Energy = 1 TWh Oil Energy
Using direct solar energy is 1,200,000,000,000 X more efficient than using oil
Global Energy PotentialRenewables Forever terawatt hours/YEAR
Direct Solar Radiation 350,000,000 Wind 200,000 Ocean Thermal 100,000 Biofuel 50,000 Hydroelectric 30,000 Geothermal 10,000 Tidal/Wave 5,000Energy Stored in the Earth
(Use it once and it’s gone)terawatt hours TOTAL
Coal 6,000,000Natural Gas (US Peak 2004) 1,500,000Uranium 235 (US Peak 2008) 1,500,000Petroleum (US Peak 1970, World Peak 2010) 1,000,000 Tar Sands 800,000
World stored energy consumption = 70,000 terawatt hours/year
Agenda
• How electric cars work
• Maintenance on an electric car
• Costs of operation
• Uses for electric cars
• Sustainable transportation v.s. fossil fuels
• Questions and Answers
Backup
The fossil fuel age on the scale of human history
Native Americans lived on this land for 12,000 years without diminishing its bounty
In 150 years of burning fossil fuel the Earths 3 billion year store of solar energy has been plundered
US Oil Discoveries Peaked in 1930 US Oil Extraction Peaked in 1970
“ America is Addicted to Oil”
Reality Check:• This is not a projection it is historical data from the petroleum industry.• In a more perfect world the US might have noticed a trend after discoveries peaked in 1930.• In a less than perfect world the US would have responded to peak extraction around 1975.• Ignoring the realities of finite resources puts future generations at risk.• We are the future generation.
US Oil Consumption
Will Peak 200?
World Peak Oil
Gray Area Shows the Range of Forecast Peak
Conventional Oil Reserves
Source Peak Date
Source Peak Date
F. Bernabe, ENI SpA 2005
C. Campbell, Petroconsultants 2005-2010
J. Mackenzie, WRI 2007-2014
International Energy Agency 2010-2020
US DOE < 2020
Petroleum Industry 2020-2040
US Oil “production” has been declining at an average of 2%/year since 1985. US Oil imports have been increasing at an average of 4%/year since 1985.
Advantages of Sustainable Energy
• Finite fuel supply• Ugly infrastructure• Polluted air / Climate change• Extraction site devastation• Polluted land • Spills and polluted water• Energy resource wars• Susceptible to terrorism
• Unlimited energy source• Aesthetically superior• Clean air / Zero emissions• No extraction sites• Healthy land • No water pollution• No conflict over free sunshine• National and individual security
Fossil Fuel Dependence Solar Independence
Combustion Economy
Agrarian Economy
Solar/Electric Economy
combustion depletes stored energy resources, reduces the quality of essential resources and will cause conflict and economic collapse
Reliance on fossil energy has allowed population growth that can not be sustained by manual labor or beasts of burden
Moving toward reliance on clean energy from the sun will stabilize the quality of essential resources and allow positive evolution
QUALITY OF LIFE
FUSSIL FUEL USE
RENEWABLE ENERGY USE