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EV101: Owning and Operating an Electric Vehicle

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  1. EV101: Owning and Operating an Electric Vehicle Gary Graunke Oregon Electric Vehicle Association (Oregon chapter of the Electric Auto Association) December, 2007

  2. Gratefully acknowledging many slides fromSteve HeckerothDirector of BIPV, ECD OvonicsChair Renewable Fuels and Sustainable Transportation Division of the American Solar Energy Society

  3. 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

  4. 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 Charger Traction Batteries DC-DC Contactors Speed Pedal Motor Controller Aux. Battery Contactors Motor Differential Just like a toy car, but high voltage and high current (danger!)

  5. Throttle Linkage Zap Throttle Linkage Converted Honda Insight Linkage Electric Output S10 Electric Pickup Linkage Mechanical Input

  6. 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) Contactors (ZAP) CafeElectric Zilla 1K Electricity is the only alternative fuel you can create when you go downhill

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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)

  13. 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 full 2.16V voltage empty 1.75V overcharge full voltage empty Periodic rebalancing improves battery pack longevity

  14. Capacity Variance with Aging Overdriving • 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 full 2.16 voltage empty 1.75 0 volts overcharging full voltage empty Check aging pack batteries for varying capacity

  15. Use Appropriate Batteries 12V batteries need sufficient power to stay above 10.5V (short bursts ok)

  16. Past Time for a New Pack 2V differences indicate exhausted or reversed cells

  17. 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

  18. 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

  19. 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

  20. 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 Costs of EV Operation EV owners replace batteries when heat engine owners replace vehicle

  21. 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

  22. 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

  23. Electric Motor Torque and Power Siemens 5105WS12 at 312 Volts Insight torque 79 ft lbs at 1500 RPM Insight power 54.4 KW at 5700 RPM

  24. Solar Powered Electric Vehicles

  25. The Clean Power/Transportation Solution 2 kW of PV per parking space 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. Almost Half a MWh of storage in the parking lot Photo courtesy Donald Aitkin

  26. 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

  27. 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.

  28. The real measure of efficiency It 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 1.2x1012TWh Solar Energy=1 TWh Oil Energy Using direct solar energy is 1,200,000,000,000 X more efficient than using oil

  29. Renewables Forever terawatthours/YEAR Global Energy Potential Direct Solar Radiation350,000,000 Wind 200,000 Ocean Thermal 100,000 Biofuel 50,000 Hydroelectric 30,000 Geothermal 10,000 Tidal/Wave 5,000 Energy Stored in the Earth (Use it once and it’s gone) terawatthoursTOTAL Coal 6,000,000 Natural Gas (US Peak 2004) 1,500,000 Uranium 235 (US Peak 2008) 1,500,000 Petroleum (US Peak 1970, World Peak 2010) 1,000,000Tar Sands 800,000 World stored energy consumption = 70,000 terawatt hours/year

  30. 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

  31. Backup

  32. The fossil fuel age on the scale of human history In 150 years of burning fossil fuel the Earths 3 billion year store of solar energy has been plundered Native Americans lived on this land for12,000 years without diminishing its bounty

  33. “ America is Addicted to Oil” US Oil Discoveries Peaked in 1930US Oil Extraction Peaked in 1970 US Oil Consumption Will Peak200? • 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.

  34. World Peak Oil Gray Area Shows the Range of Forecast Peak Conventional Oil Reserves Source Peak Date 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.

  35. Advantages of Sustainable Energy Fossil Fuel Dependence Solar Independence • 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

  36. QUALITY OF LIFE FUSSIL FUEL USE RENEWABLE ENERGY USE Combustion Economy combustion depletes stored energy resources, reduces the quality of essential resources and will cause conflict and economic collapse Agrarian Economy Reliance on fossil energy has allowed population growth that can not be sustained by manual labor or beasts of burden Solar/Electric Economy Moving toward reliance on clean energy from the sun will stabilize the quality of essential resources and allow positive evolution