Battery Electric Vehicle
Frequently Asked Questions
Updated 9/29/09

If you have any questions not listed or adequately answered here, or if you can contribute to improving the answers given, please contact chris_b_jones@prodigy.net.

Fundamental Questions about BEVs
1. What is a BEV?
2. Why BEVs?
3. How does a BEV work?
4. How fast are BEVs?
5. How far can BEVs go between charges?
6. Can BEVs go up hills?
7. Are BEVs safe?
8. Are BEVs reliable?
9. Do BEVs have all the features a gas car does?
10. How much noise do BEVs make?
11. How heavy are BEVs?
12. How long have BEVs been around?
13. Why aren't there more BEVs?
14. Are more EVs coming soon?
15. Will EVs just trade our current oil crisis for a future lithium crisis?

BEV Energy Usage
16. How much energy do BEVs use?
17. Does running your heater, air conditioning or accessories reduce your driving range?
18. How much emissions do BEVs generate?
19. How many more power plants would we need if we all started driving BEVs?
20. How much of our electricity grid is powered by renewable energy?

Owning a BEV
21. How much do BEVs cost?
22. Are there any incentives for BEVs?
23. Where can I buy an BEV?
24. How do you register a BEV?
25. How do you insure a BEV?
26. How is driving a BEV different from a gas powered car?
27. Can I tow an EV?
28. How hard is it to maintain a BEV?
29. How long do BEV batteries last?
30. Are BEV batteries recyclable?

Charging BEV Batteries
31. Can you charge BEV batteries during braking?
32. How long does it take to recharge BEVs?
33. Where can you charge BEVs?
34. Can solar panels be added to a BEV to extend its range?
35. Can a BEV tow an ICE generator to extend its range?
36. Can I put a pusher trailer on my BEV to extend my range?
37. Can generators be added to the wheels of a BEV to extend its range?
38. Can windmills be added to a BEV to extend its range?
39. Can BEV batteries that never need recharging work?

BEV Conversions
40. What type of vehicles can I convert to BEV?
41. Who can convert vehicles to BEVs?
42. Can I convert my classic car to BEV but preserve its value?
43. Will converting my car to BEV void my warranty?
44. What is the best type of battery for a BEV?
45. What is the best type of motor for a BEV?
46. What is the best type of charger for a BEV?
47. How do you determine the state of charge of the batteries?
48. How can you predict the range of a BEV conversion?
49. How can you predict the acceleration of a BEV conversion?
50. How can you predict the hill climbing ability of a BEV conversion?
51. Are wheel hub motors better than one central motor?

More Information
52. What new BEV energy storage research is going on?
53. Where can I get more information about BEVs?

Fundamental Questions about BEVs

1. What is a BEV?

A BEV is a Battery Electric Vehicle. BEVs have batteries on board that power an electric motor via a motor controller. The batteries are charged by electricity from an energy source that is not a part of the vehicle. The BEV's battery charger can either be on board or off board. On board chargers provide a means of charging at more places while away from base, extending their effective range. BEVs are different from other electric vehicles, including Hybrid Electric Vehicles (HEVs) and Plug-in Hybrid Electric Vehicles (PHEVs) which carry a liquid fuel source, and Fuel Cell Vehicles (FCVs) which typically carry a gas energy storage medium.

2. Why BEVs?

BEVs enable the efficient use of renewable energy sources such as electricity generated from solar photovoltaic panels and windmills. The shift to use of these energy sources are vital for us to achieve sustainable energy use, which includes energy independence, greenhouse gas reduction, air pollution reduction, and water pollution reduction.

3. How does a BEV work?

While driving, the accelerator is sensed and translated to a duty cycle of a Pulse Width Modulated (PWM) Switch Mode Power Supply (SMPS) DC to DC buck voltage regulator that provides current from one or more strings of deep cycle, high power, long life batteries through welding cable, lugs, fuses, and some combination of circuit breakers, main contactors and cutoff switches to the motor field windings that creates a magnetic field. Ions flow from the anode to the cathode of the batteries through the electrolyte, causing current to flow from the anode through the motor to the cathode. In the case of an AC induction motor, the motor position is sensed and the field current is further modulated to induce eddy currents and hence opposing magnetic fields to the field in the rotor that causes the shaft to turn. In a series DC motor, the current goes through brushes to the rotor that creates an opposing magnetic field to the field that turns the shaft. If AC induction, the motor probably can be used to slow down the vehicle and charge the batteries via regenerative braking. Motor torque is transferred either to a flywheel, clutch, transmission and differential system, or straight to a transmission without a clutch, or a fixed reduction gear differential system. The former offers the best efficiency and performance for a given overall weight, but the latter two are lighter which may offset some efficiency and performance; and the latter two are progressively easier to drive. Automatic transmissions are rarely used in conversions due to lower efficiency due to slip and different optimum shift points between gas and electric drive systems, although there is potential to remove the torque converter and tune the shifting, or use EV tuned semi-automatic transmissions.

While charging, electricity flows from the power source, typically through the power grid, in to the battery charger, and then in to the batteries. Ion flow from the cathode to the anode and current flows from the charger to the anode, through the battery and out the cathode, back to the charger. State of the art chargers are Isolated SMPS AC to DC converters that have a Power Factor Corrected Boost Regulator stage, an isolation transformer, and a Current Limited Voltage Regulated Buck Regulator stage. The charger increases the duty cycle of its PWM until either the current limit or voltage set point are reached.

Accessory power isolated from the main batteries is supplied usually by an accessory battery that is charged either by an on-board DC-DC converter or as a secondary output to the battery charger. The on-board DC-DC converter is typically a double isolated SMPS buck voltage regulator.

A Battery Management System will monitor each cell or module in the pack and then stop the charger when the first cell or module is full, and warn the driver or cut back the power when the first cell or module is empty.

4. How fast can BEVs go?

As of 1/30/09, the fastest EV is Killa-Cycle, a motorcycle that achieved 7.890 seconds and 167.99 MPH in the quarter mile. The fastest 4-wheeled BEV is the Current Eliminator V dragster at 7.956 seconds and 159.85 MPH. The fastest street car conversion is the White Zombie at 11.466 seconds and 114.08 MPH. See www.nedra.com for details. The fastest production BEV is the Tesla Motors Roadster with 0-60 MPH in under 4 seconds and a top speed of 125 MPH.

5. How far can BEVs go between charges?

The Nuna solar powered race car from Delft University of Technology in the Netherlands went 1877 miles across Australia at 56 MPH, only charging from the sun via on-board panels. The Power of 1 solar powered car has traveled slightly slower but over 11,000 miles solely on its on-board solar panels. The farthest a convential car has gone between charges is the Solectria Sunrise that went 375 miles at slow speed around a track. The AC Propulsion T-Zero went 302 miles at 60 MPH. The longest range production EV is the Tesla Motors Roadster which goes 220 miles between charges. Typical BEVs go between 40 and 120 miles on a charge, but new batteries and more efficient vehicle designs are under development which could increase this range. It is best to never plan to drive more than 80% of the range of an EV due to variations in efficiency and hence range, and to maximize the life of the batteries, it is best to not plan to exceed 50% of the range on a regular basis. Fast charging batteries and battery chargers are being developed that will offset the disadvantage of a limited range vehicle.

6. Can BEVs go up hills?

Most EVs can drive up short hills at the speed limit. Some BEVs may not be able to climb long, steep, fast hills because their motor controller or motor will overheat, or their batteries and drive system don't have enough power. Fixed gear DC cars may struggle with uphills.

7. Are BEVs safe?

All vehicles can be deadly, but BEVs with secured, contained and thermally stable batteries such as Lithium Iron Phosphate (LiFePO4) that are kept away from the cab in the event of a collision can be safer than gasoline powered cars that can catch fire. Lead acid batteries, particularly flooded ones, pose an explosive hydrogen gas risk and require fail-safe active ventilation on the vehicle and in the building when charging. Nickel based batteries can explode, so they need to be monitored and contained withing small cell sizes. Lithium Cobalt Oxide (LiCoO2) batteries can burn inextinguishly due to external or internal faults, so they too need to be contained within small cell sizes. Chargers and DC-DC converters need to be isolated for safety, and high voltage needs to be kept out of the cab and trunk for best results. Fuses must be used in line with the batteries to blow in the event of a short circuit, and a way to interrupt power to the wheels is necessary in the event of a short circuit, particularly with DC drive systems which can fail on. Care must be taken with BEVs when being serviced or cut open in the event of an accident due to the high voltage hazard. High voltage can flow through your heart and stop it. Always keep high voltage covered, keep conductive items such as tools away from batteries, use only one hand when servicing BEVs and work with someone whenever possible. Rescue personnel need to be trained to know how to cut open BEVs so they do not get electrocuted. If an EV is driven underwater and both the batteries and the passengers are in the conductive water, current could flow and there is an electrocution risk. However, if the batteries are placed as they usually are, far from the cab space and away from the occupants, the batteries should short out to themselves and very little or no curernt should not flow through the passengers. Like intertia switches that detect impact, Water presence sensors driving contactors could be added to an EV to break the high voltage circuit in one or more places to lower the voltage and hence the current given the conductive water medium and hence the electrocution risk. Watertight sealed battery boxes and electronics found on higher end EVs also help reduce the risk.

8. Are BEVs reliable?

Yes. There are less moving parts and less complexity. BEV components can last longer than gasoline car parts, providing the components are used within their design limits.

9. Do BEVs have all the features a gas car does?

Yes. Power brakes can be driven by a vacuum pump and vacuum tank. Conventional hydraulic power steering can be driven by an electric motor, and there is directly electrical power steering in the Prius and Civic. The heater is typically a hot water heater and pump under the hood that connects to the original heater core and hoses. An air conditioner pump can be driven by an electric motor.

10. How much noise do BEVs make?

Most are very quiet. Some have backup beepers. Legislation is being considered to have all cars be either loud enough on their own or to emit a noise for safety of pedestrians, particularly for sight impaired people.

11. How heavy are BEVs?

Short range or advanced battery medium range BEVs can have a light enough pack such that they are close or equal to their gasoline counterparts. Lead acid and long range BEVs can significantly add weight to the car and hence reduce the payload for passengers and cargo. Suspension and brake upgrades on heavier vehicles can be done to improve the ride, but the manufacturer's original Gross Vehicle Weight Rating (GVWR) should never be exceeded.

12. How long have BEVs been around?

BEVs have been around since 1834, and were higher performance and more popular than gasoline cars until the early 1900s.

13. Why aren't there more BEVs?

Despite California's Zero Emission Mandate in 1990, automakers fought and won the right to not fullfill shipping large volumes of BEVs, and some took back their leased EVs and crushed them. The movie "Who Killed the Electric Car" documented this chain of events. High performance BEVs typically cost more to purchase than their gasoline counterparts and several have limited range and long charge times, but many are working on making improvements. Many companies have announced their intention to sell EVs, but few have delivered so far. In the mean time, thousands of people have converted gasoline vehicles to BEVs themselves or with help of others.

14. Are more BEVs coming soon?

A desire to achieve energy independence and avoid volatile gasoline prices and climate change believed to be contributed in part by gasoline automobile use all appear to be driving up the demand for BEVs, and the announcements for future vehicles are increasing, so it is expected that EV choices will increase over the next few years.

15. Will EVs just trade our current oil crisis for a future lithium crisis?

Possibly, if we aren't careful. Lithium is the leading EV battery chemistry due to its high capacity and power, improving EV range and acceleration. According to stratfor.com, South America is estimated to hold 85% of the world's lithium reserves, followed by Asia at 7%, North America at 5%, Africa at 1% and Australia at 1%. Europe has no known reserves. There is estimated to be over 27 billion pounds of lithium reserves; the Lithium percent weight of a battery varies, but if it was 100% it would be enough to make about 30 million 900 pound Tesla Roadster packs that propel the 2600 lb car 240 miles. There is an estimated 600 million cars globally on the road, so if lithium takes up more than 5% of the battery weight and is not 100% recyclable or if it takes a long time to recycle them, we won't have enough to cover all of our current driving patterns. Faster charging and more fast chargers could alleviate this, reducing the range requirements of vehicles. Nanotechnology Lithium batteries such as A123 Systems or Altairnano charged by 480V 250A chargers like Aerovironment with greater than 90% efficiency can charge 25 kWH 100 mile range packs in less than 15 minutes; this fast rate could be used for long trips with only a few fast chargers along the freeways while normal charging could be done slowly at home or work over several hours. Nickel is in mass production for EV batteries, but is quickly getting supplanted by Lithium due to a 50-100% improvement in capacity per unit weight and hence driving range between charges; this could be alleviated by lighter weight, more efficient vehicles with more payload dedicated to the battery pack. Other alternative high capacity chemistries using more common materials such as Zinc Air and higher capacity nanocapacitors are being researched and may alleviate the focus on Lithium, but as of August 2009 Lithium is still the leading candidate being used for new developments in EV batteries.

BEV Energy Usage

16. How much energy do BEVs use?

BEVs use approximately 1/4 less non-renewable energy than gasoline when charged from today's grid. BEVs whose energy is offset by renewable energy generators such as wind and solar that were created on today's mostly non-renewable grid use approximately 3/4 less non-renewable energy. If the grid was renewably powered, EVs would use no non-renewable energy. It may take more energy to make the batteries than a gas engine, but the energy used to propel a vehicle far outweighs the energy it takes to make it.

17. Does running your lights, accessories, heater and air conditioning reduce your range?

Lights and accessories only draw 100s of Watts vs. 10s of kiloWatts to propel the car, so the reduction in range is only a few percent. A heater or air conditioner however can draw several kW so it could reduce range by 10s of percents, depending on setting, outdoor temperature, insulation and solar gain of the vehicle.

18. How much emissions do BEVs generate?

None while operating, but it depends on the fuel source used to provide the electricity. With solar or wind the emissions are only what it took to produce the renewable energy generators. If the grid used to create the generators was mostly renewable, it would be nearly zero emissions.

19. How many more power plants would we need if we all started driving BEVs?

Millions of EVs could be charged at night before needing to add power plants, but if for every EV added to the grid the same amount of renewable energy was added, no more non-renewable power plants would need to be added. Many people who drive BEVs added photovoltaics to their home before they got an EV that generate more energy than their BEVs use.

20. How much of our electricity grid is powered by renewable energy?

According to the US Energy Information Administration in August 2009, 3.2% of the US grid was powered by non-hydro renewable energy such as solar and wind, up sharply over the past decade from a fraction of a percent.

Owning a BEV

21. How much do BEVs cost?

The only new EV cars available for sale in the US as of August 2009 are the Tesla Roadster and the Commuter Cars Tango. Both are 2 seats, 0-60 MPH in 4 seconds, and cost $109K. Others EVs are planned for future production release, and some are currently available only to fleets. Some have 2 or 3 wheels or are limited to 25 or 15 MPH. See www.pluginamerica.org/plug-in-vehicle-tracker.html for details.

Almost any vehicle can be converted, and some companies do convert cars for hire. See www.evalbum.com for examples of converted cars. See "EV Converters" on www.eaaev.org/eaaevsforsale.html or contact your local EAA chapter at www.eaaev.org/eaachapters.html for more information.

22. Are there any incentives for BEVs?

There is a $7500 federal tax rebate. More rebates are being discussed.

23. where can I buy a BEV?

Search for websites for EVs listed above for dealer locations. Some of them have outlets in the San Francisco Bay Area.

24. How do you register a BEV?

If OEM, the dealer does it for you. If it is a conversion, you need to go to smog referee to get the fuel type changed from "G" (gas) to "E" (electricity) so you then are exempt from smog checks, which is important for cars less than 20 years old.

25. How do you insure a BEV?

Check with your insurance company first to make sure they are aware of BEVs and have a rate structure for them.

26. How is driving a BEV different from a gas powered car?

Much quieter, no smell, and smoother acceleration.

27. Can I tow an BEV?

Yes, but if it has a DC motor with a transmission you need to put it in neutral to not overrev the motor beyond its RPM limit -- this can destroy the bearings.

28. How hard is it to maintain a BEV?

Much easier than a gasoline car. Unique EV maintenance includes:
- Flooded batteries require periodic watering
- periodic battery balancing may be required, if not automatic
- the charger may need adjusting over time
- DC motors need brush replacement after approximately 80K miles
- tire pressure should be checked regularly to insure maximum efficiency and hence range
- wheel alignment toe-in should be slightly negative for maximum efficiency, but for handling safety, it should be checked and adjusted regularly.

29. How long do BEV batteries last?

If treated well, 5 to 10 years, depending on chemistry, use and ambient temperature.

30. Are BEV batteries recyclable?

Lead acid is and is being recycled >>90%, fortunately, since they are toxic. Li-Ion can be in the future once mass produced and a market need arises; fortunately they are non-toxic.

Charging BEV Batteries

31. Can you charge BEV batteries during braking?

Yes if equipped with regenerative braking. AC drive systems typically come with regen. Shunt wound DC motors can be used for regen, but are not as common as DC series wound motors, which can provide very little regen before overheating the drive system.

32. How long does it take to recharge BEVs?

Nanotechnology Lithium Ion such as Altairnano or A123 Systems can take 10-15 minutes with 480V/250A charges made by companies such as AeroVironment. 1 minute charge batteries have been experimented with in labs, but the power supply requirements would be great, possibly requiring local pre-storage. Typical is a few hours at 240V/30A and several hours at 120V/12A.

33. Where can you charge BEVs?

Home, businesses, RV parks, and public charging stations. EV Charger News lists many of these. Also portable solar generator trailers can charge EVs, such as the Solar Rover.

34. Can solar panels be added to a BEV to extend its range?

Yes, per above, the Power of 1 has gone over 11,000 miles. Regularly sized cars with solar hood, roof and trunk solar panels can add several miles to the range if left to charge during the day in full sun, for instance while the driver was working.

35. Can a BEV tow an ICE generator to extend its range?

Yes, AC Propulsion prototyped this, as have others. Up to 20 kW is needed to sustain freeway speeds. These generators can have very high emissions, be very noisy, and very heavy. And this would require a similarly rated battery charger, which can be expensive. The GM Volt PHEV plans to have an on-board generator to charge its batteries.

36. Can I put a pusher trailer on my BEV to extend my range?

It has been experimented with, but it could be dangerous and illegal.

37. Can generators be added to the wheels of a BEV to extend its range?

Yes, but only when replacing braking energy in traffic or going downhills. This is how HEVs, PHEVs and BEVs with regenerative braking systems work to increase their range 10-20%, although they typically use a single centralized propulsion motor that doubles as a generator. Capturing energy during steady speed flat driving would violate the 1st law of thermodynamics. The added system would have heat losses, hence it would take more energy to turn them than you'd get back.

38. Can windmills be added to a BEV to extend its range?

Maybe, but not much, and only if they are put in the vorticies around the vehicle that are caused by poor aerodynamics. Better aerodynamics would be more effective. Similar to wheel generators, adding a windmill far from car's airstream during steady speed flat driving would have heat losses and again take more energy to turn it than it would give back, even in a headwind.

39. Can BEV batteries that never need recharging work?

No. A fusion reactor may last a very long time, but would run out once the mass ran out. No known small scale fusion reactors exist. Virtually endless energy could have global warming implications, so seeking such power supplies is controversial.

BEV Conversions

40. What type of vehicles can I convert to BEV?

Anything -- scooters to buses and even planes have been done. But cost rises and performance drops with increasing weight and aerodynamic drag. Small vehicles may not have the space or payload to carry the large and heavy batteries required to go a reasonable distance. Search the Electric Vehicle Discussion List Photo Album for examples, www.evalbum.com.

41. Who can convert vehicles to BEVs?

You don't have to be an engineer -- there are books and kits. You may need help with welding or machining.

42. Can I convert my classic car to BEV but preserve its value?

Yes, no body or weight modifications can be done if a small pack of LiFePO4 batteries is used, mounted to where the original motor and gas tank mounts were.

43. Will converting my car to BEV void my warranty?

Only if the change affects the warranty claim. As an extreme example, if you change the motor but your upholstery unrelatedly falls apart, you can still get the upholstery fixed under warranty. Reused drive train components could be stickier, but there is a legal precedent.

44. What is the best type of battery for a BEV?

Large format high power long life deep cycle LiFePO4 is becoming more common, with fast charging nanotechnology versions being sought after next. Flooded lead acid golf car batteries are the most popular for conversions, but weigh several times more for the same capacity at high BEV discharge currents due to the Peukert effect, and have hydrogen safety and lead toxicity issues. High power AGMs are also commonly used but require module monitoring and balancing. Gel batteries are sometimes used but do not offer as much power per pound. Starter, backup and low cost wheelchair batteries won't last long in BEVs.

45. What is the best type of motor for a BEV?

AC induction is most common in OEM vehicles. Series wound DC is most common in conversions.

46. What is the best type of charger for a BEV?

One that is high power >= 3 kW but also isolated, power factor corrected, UL and FCC compliant.

47. How do you determine the state of charge of the batteries?

The voltage, temperature and cumulative amp hours extracted from the batteries can be used to predict the state of charge.

48. How can you predict the range of a BEV conversion?

There are calculations in books, but here is an example of a rough empirical estimate, based on vehicle weight and MPG. A ~3000 lb DC rear wheel drive 1966 Mustang convertible used to get ~20 MPG, and now goes ~40 miles on a ~15 kWh 400 lb pack of LiFePO4 with the same curb weight, or about 2.7 miles per kWh. It would cost about $10K for Thunder Sky batteries and an eLithion BMS and last at least 5 years, so $2K/year or ~$5 per day battery amortization and ~$1/day to charge, assuming 20 miles per day or ~7000 miles per year driving. So writing off everything in the conversion except for the batteries as a rebuild, this "pays" when gas goes above $6/gallon.

As a very crude estimate, a Cadillac weighing twice as much and getting half the mileage with about twice the motor and gas tank weight displaced with twice the batteries would go the same 40 mile distance but cost twice as much to run, but it also does on gasoline.

But an AC drive with regenerative braking, better aerodynamics, slightly lighter weight and more efficient front wheel drive might be 50% more range or 60 miles, which is the target for the AAA grant 2005 Focus sedan conversion underway at the Santa Rosa Junior College. Thermally unstable Lithium cobalt would also be 50% better, but would cost more to manage and contain for safety. 50% more pack would probably get 40% more range, but would cut your payload in half. A combination of all three would be about 200% more range or ~120 miles, similar to the AC Propulsion eBox, which is about as good as you can get on a mass produced compact car body.

Going to lead acid is about 25% the continuous range per battery pack pound due to the Peukert effect at high EV discharge rates, so the Mustang example would be around 10 mile range with lead. But if stops are made along the way and the chemistry is allowed to "catch up" and rebalance, the range would approach 50% or 20 miles. Offsetting this twofold reduction in capacity by adding more batteries can greatly reduce vehicle payload and can be a safety hazard if done to extremes, as mentioned above.

49. How can you predict the acceleration of a BEV conversion?

There are calculations in books, but here is an example of a rough empirical estimate, based on vehicle weight and horsepower. A ~3000 lb DC rear wheel drive 1966 Mustang convertible with a 1V carbeurator and a 200 cubic inch six cylinder motor with 120 HP bench/102 HP brake used to get ~12 seconds 0-60 MPH. Now converted to electric it has a 100 Ah 154V LiFePO4 pack with 72 milliohms internal resistance, a 500 amp Curtis series DC motor controller, and a 9" 28 HP continuous Advanced DC motor. The motor controller is the bottleneck, limiting the power to ~44 HP bench/37 HP brake, or only 37% of the gasoline version peak; the batteries could supply 75 HP bench or 62%, and the motor could deliver 100 HP or 83%. As an EV it takes 23 seconds to go 0-60 MPH, or 52% of the original configuration. It turns out that this is barely fast enough to keep up with traffic on the freeway, which infers that most drivers do not floor it when driving gas cars. The nonlinear reduction in acceleration rate can be explained by differences in torque and horsepower over RPM, being much wider and lower for an electric motor. Thus the HP ratio to acceleration rate "gain" of going to EV is approximately 40%. Therefore if a 900 amp controller was used to fully utilize the battery power, the 0-60 time would probably drop to about 14 seconds. If a 1200 amp controller and 50 milliohm batteries were used to fully utilize the motor power, the 0-60 time would probably drop to 10 seconds. A slightly lighter car with the same power would roughly linearly reduce the 0-60 MPH time. Power to weight ratio effects 0-60 MPH time roughly by the inverse squared, and as speeds increase, effects such as aerodynamics and gear and tire losses begin to have more of an effect.

Sealed lead acid batteries can be obtained with similar power per pound, but with far less capacity or range.

50. How can you predict the hill climbing ability of a BEV conversion?

Note that in the acceleration rate example above that great increases could be made with the 100 HP peak motor, the 3000 lb configuration is limited to only about 40 MPH up a long 6% grade since the continuous HP is only 28 HP. Continuous power to weight ratio varies roughly linearly with continuous uphill speeds, so a 40% lighter car, or 40% more battery, motor controller and motor continuous power ratings should allow 55 MPH continuous up a 6% grade, but in particular the motor could weigh significantly more, which counteracts this affect and could impact payload, and may not fit. AC induction drive systems are about 15% more efficient and have the best power to weight ratios, and being brushless can take advantage of more efficient higher voltages, so they are a good fit when trying to increase continuous power. Note however that range will be reduced significantly when going uphill, but similarly increased going downhill.

51. Are wheel hub motors better than one central motor?

Wheel hub motors eliminate long drive shafts which can help in both drive and regenerative braking efficiency and provide optimum traction control and braking performance. Announcements have been made by companies that are researching wheel hub motors. Challenges to overcome include unsprung weight, gear reduction and control system complexity.

More Information

52. What new BEV energy storage research is going on?

Stanford University is experimenting with silicon nanowires that when used for the anode and cathode may increase lithium ion capacity by 6X and have been proven to last for at least 50 cycles. MIT is experimenting with nanocapacitors that are approaching the specific energy of lithium ion batteries, but with much higher specific charge and discharge power and longer life. EEStor claims to have developed a high dielectric constant capacitor that has higher specific energy than lithium ion but so far has only shared it with the military.

53. Where can I get more information about BEVs?

See the Electric Auto Association's website at www.eaaev.org for BEV information.