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Frequently Asked Questions 

(about electric & hybrid-electric buses)

Although most of the questions focus on electric and/or hybrid-electric buses, the answers can often be applied to all electric vehicles.

How far (or how long) will the bus operate on a single charge?
What are the benefits of operating electric buses?
Do electric buses have transmissions?
How long do batteries last?
Can cells in a battery pack be replaced?
Are components in an electric bus easy to replace?
Is an electric vehicle more energy efficient than an ICE vehicle?
Can you get electrocuted by riding in an electric vehicle when it floods?
How fast can an electric bus go?
How long does it take to charge the batteries?
How much does it cost to charge the batteries?
What is a hybrid-electric bus?
What kind of batteries are normally used on electric buses today?
What is a fuel cell bus?
Do electric buses have the same accessories as other types of buses?
Are electric buses more expensive to purchase?
Is special training required for drivers and mechanics?
What is regenerative breaking?
Can electric buses operate up hills?
Are all hybrids utilized for range extension?
What is the difference between an electric bus with an AC motor and one with a DC motor?
What happens if you run out of energy before returning home?
What about increased emissions through additional power generation necessary to charge electric vehicles?
What is the difference between "grid connected" and "non-grid connected" electric vehicles?
What is better...conductive charging or inductive charging?
What is a thermal management system?

How far (or how long) will the bus operate on a single charge?
Variables such as weather, speed, capacity of the batteries, performance of the driver, efficiency of the propulsion system and terrain can all impact the range of a bus. For planning purposes, most electric buses with conventional lead-acid batteries will operate between 40 - 80 miles on a single charge.

There are a number of methods that can be followed to increase the amount of time an electric bus can be operated in service. The first is to perform battery change outs. Many systems, including Chattanooga, regularly swap battery packs. In a span of 10-15 minutes, the bus can be back in service.

The second way to increase the amount of time an electric bus can be operated is to fast charge the batteries. Several research projects are underway utilizing this process. The Cape Cod National Sea Shore utilizes a fast charger on their trams to keep them running throughout the day.

Another method for increasing the amount of time an electric bus can be operated is to purchase advanced technology batteries, such as nickel-cadmium batteries. Although much more expensive, ni-cads can double the range of electric buses and have a longer life span than conventional lead-acid batteries.

A final method for increasing the amount of time an electric bus can be operated is to integrate an auxiliary power unit (or APU) on the bus for range extension. By utilizing a second fuel and an engine/generator, electricity can be created that can significantly add to the range of the bus. Electric vehicles that use two fuels are referred to as "hybrids"

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What are the benefits of operating electric buses?
The most obvious is that electric buses are quiet as well as being zero-emission at the tailpipe (which, of course, an electric vehicle does not have.) They are more economical to operate and are fueled by domestic sources. Transit and fleet operations have also learned the tremendous public relations value of operating zero-emission and quiet buses; a major change from the buses operating on fossil fuels and even most other alternative fuels.

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Do electric buses have transmissions?

No, although some have a transaxle system. Because there is no transmission, acceleration is "seamless"; no jerking or noise....just nice and smooth.

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How long do batteries last?
Depending on the type of battery (lead-acid, nickel-cadmium, etc.), the length varies from 800 to 3,000 cycles (charges and discharges.) It should be noted that maintenance of the battery, and how the battery (bus) is operated, will have a tremendous impact on cycle-life.

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Can cells in a battery pack be replaced?

Yes. Most electric bus battery packs contain a number (up to 250) two-volt cells. When one cell is damaged, it can impact performance battery and battery life. With proper preventative battery maintenance, the damaged cell can be identified and replaced.

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Are components in an electric bus easy to replace?
As with all motor vehicles, this varies by manufacturer. However, because there are so few components in an electric bus compared to a conventional bus (including those using alternative fuels), placement for quick access is more easily accomplished. Thus, components on electric buses are normally very easy to replace.

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Is an electric vehicle more energy efficient than an ICE vehicle?

An electric vehicle is much more efficient than a conventional vehicle. A conventional vehicle's engine typically wastes over 80% of its energy output in areas not associated with propelling the vehicle. Mechanical losses associated with the hundreds of moving parts are the largest energy consumers while cooling and accessory systems make up the rest of the losses. Electric vehicles have few moving parts, so mechanical losses are eliminated. Because electric vehicles have a ready supply of electricity, no generator is needed to power vehicle accessories. There are also no mechanical losses associated with a transmission because an electric motor is used to propel the vehicle.

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Can you get electrocuted by riding in an electric vehicle when it floods?
No. The accessories in an electric vehicle, including an electric bus, are powered through a 12-volt DC battery or a converter that steps down the voltage from the traction battery to 12-volts, just as the 12-volt battery in your automobile or truck powers your accessories. Therefore, the risk of electrocution is no different.

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How fast can an electric bus go?
An electric bus can operate at whatever speed is necessary to perform the transit service. Higher speeds do translate to slightly less range, and the range of electric buses somewhat inhibits their use on the longer, and therefore high speed, routes. Thus, most electric buses operate on routes that do not exceed 40 or 45 miles per hour and average in the teens.

The 22-foot bus, which is the predominant electric bus in operation today, is governed around 45 miles per hour. The 40-foot hybrid-electric bus operating in New York is governed at 55 miles per hour.

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How long does it take to charge the batteries?
For electric buses, six hours is a good rule of thumb for a complete charge. Equalizing the batteries, which involves a steady but low power charge after the batteries are "filled", normally adds two hours to the process.

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How much does it cost to charge the batteries?
Most fleet operations charge the buses overnight at a time when electricity rates are at their lowest. And, because an electric bus is inherently more efficient than a bus with an internal combustion engine, the cost per mile of "fueling" a bus is normally 1/3 the cost of fueling a diesel or gasoline bus. As most other alternative fuels are more expensive than diesel fuel, savings on fuel costs compared to other alternative fuels is significant.

It should be noted that "fuel" costs can vary based on battery size and/or the efficiency of the battery charger, along with local electricity costs of course.

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What is a hybrid-electric bus?
A hybrid-electric vehicle utilizes two fuel systems; the primary fuel being provided by batteries. The second fuel propels an engine/generator that provides fuel to the batteries. The second fuel can be any of the fuels that propel motor vehicles today, including diesel, gasoline, compressed natural gas, propane, natural gas, ethanol, and methanol, to name just a few.

There are three different types of hybrids; series, parallel, and dual-mode. Today, most of the hybrid-electric buses are series hybrids with propulsion power coming from the batteries with the engine/generator fueling the batteries. Most of the hybrid automobiles, however, are parallel hybrids; the vehicle can be moved by either the batteries or the engine; whatever is most efficient.

A third type of hybrid is emerging, one that will operate on both the batteries and the engine at the same time. This is referred to as a dual-mode hybrid.

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What kind of batteries are normally used on electric buses today?
The most common battery in use today on electric buses is a deep-cycle, flooded lead-acid battery. However, sealed lead-acid batteries that do not require maintenance (watering) are beginning to grow in popularity. Advanced batteries, such as nickel-cadmium batteries, are also becoming more popular. Although much more expensive to purchase, the longer life and increased range of advanced batteries provide a choice of batteries for fleet operators today.

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What is a fuel cell bus?
A fuel cell is an electrochemical engine (no moving parts) that converts the chemical energy of a fuel, such as hydrogen, and an oxidant, such as oxygen, directly to electricity. Research continues on fuel cells, however, there are three fuel cell buses operating in Chicago now.

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Do electric buses have the same accessories as other types of buses?
Yes. Most of the accessories (windshield wipers, lights, etc.) operate off of a 12-volt battery or a dc-dc converter. Although the traction battery provides energy to the 12-volt battery or the converter, energy draw for most accessories is not significant.

Energy draw for air-conditioners and heaters is more significant. Therefore, many electric buses do operate the AC and heat through a separate system that is powered by an alternative fuel such as compressed natural gas or propane. There are a number of efforts underway to produce low energy and high efficient air-conditioning systems.

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Are electric buses more expensive to purchase?
At this time, because most electric buses and almost all of their components, are being built by hand, electric buses are more expensive than their diesel counterparts. However, as with all new technologies, economies of scale will reduce the purchase price of electric buses; and electric vehicles in general.

Although electric buses are more expensive to purchase than comparable sized diesel buses, remember that the cost of fueling the bus is significantly less. Additionally, because there are fewer components and daily maintenance is normally limited to batteries, regular maintenance costs are also much lower. Thus, the life cycle cost of an electric bus (including purchase and operating costs) is, today, equal to or even lower than comparable diesel buses.

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 Is special training required for drivers and mechanics?

Although an electric bus operates like a diesel bus, the manner is which an electric bus is driven has a great impact on the vehicle's range. Training, therefore, is very important. However, it is even more important to ensure that the operators maintain the driving habits necessary to maximize range once the training is completed. This includes gentle acceleration and utilizing the regenerative breaking system as much as possible.

Maintenance training on electric buses is extremely important. Electric buses are not any more complicated than buses with internal combustion engines, but they are different. An alternative fueled bus utilizes all of the same components as a diesel bus with the exception that the fuel is different (and some fuel delivery components). An electric bus utilizes a propulsion system that is unlike any other motor vehicle. Thus, understanding the unique elements of electric propulsion systems is critical to ensure dependable operation.

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What is regenerative breaking?
One of the most unique elements of electric buses occurs during the braking process. As an electric vehicle slows down, the motor turns into a generator, adding electricity to the battery. Bringing an electric bus to a sudden stop reduces, or eliminates, energy generation. Slowing down gradually, and in many cases allowing the bus to come to a halt without actually breaking fully utilizes the system allowing the greatest amount of energy being produced that, in turn, increases the range of the electric bus. One of the ancillary benefits of regenerative braking is an increase in brake life.

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  Can electric buses operate up hills?

Most electric buses have the torque necessary to operate up most hills that conventional buses can traverse. However, range is normally reduced when an electric bus operates up a steep grade. Thus, the terrain that an electric bus is operated in becomes very important in terms of range...and life of the batteries.

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Are all hybrids utilized for range extension?
No. Hybrid-electric vehicles can either be charge sustaining or non-charge sustaining; a product of the size generator and the operating demand of the service. A charge sustaining hybrid-electric bus will operate as long as fuel is available to operate the auxiliary power unit (APU). The generator is large enough to provide the necessary amount of electricity to propel the bus, regardless of its application.

A charge non-sustaining hybrid utilizes a generator that may or may not maintain the batteries, depending on the application. Thus, if the bus runs out of the fuel necessary to operate the APU, and the batteries are depleted, the bus will not operate, even if more fuel for the APU is added.

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What is the difference between an electric bus with an AC motor and one with a DC motor?
The major difference in design between an alternating current (ac) motor and a direct current (dc) motor is the lack of brushes in an ac motor, thereby eliminating the need, and cost, of replacing them every few years. AC motors cost more, however, somewhat offsetting the reduction in maintenance cost. Regeneration appears to be easier to capture with a AC motor than a DC motor. However, the controller itself is less complex with a DC motor as it is not necessary to change the energy from DC (batteries) to AC (motors) with a DC system.

AC and DC motors come in different sizes with different torque curves. As each have different characteristics and advantages, it is important to discuss the types propulsion systems available during the purchase of an electric bus.

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What happens if you run out of energy before returning home?
Like any fueled vehicle, an electric bus can run out of fuel. Interestingly, the type of battery used impacts how the bus will react to low fuel. Electric buses with lead-acid batteries will slow down before stopping, often providing the operator with the ability to return to the "fueling" station. Nickel-cadmium batteries, however, react the same as diesel or gasoline fuels; when they run out of power the bus will stop until the batteries are recharged.

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What about increased emissions through additional power generation necessary to charge electric vehicles?
Electric vehicles do not pollute at the source. Energy production does require fuel and, as such, there could be additional emissions from a power plant to produce the electricity for electric vehicles. However, these emissions are extremely small and dwarf the savings in emissions by operating electric vehicles. In a study completed in 1994, it was determined that total savings in emissions by operating electric vehicles exceed 98%, even when including the increased power plant emissions for providing electricity to the electric vehicle as well as emissions caused by the manufacture of the vehicle, batteries, and recycling of batteries.

And, of course, power plants are not located where people live and work. Additionally, it is easier to scrub for emissions at the relatively low number of power plants then the millions of motor vehicles traveling our streets.

It should be noted that the way the electricity is created will play a major role in determining this percentage. Clearly, power generated from water or wind will result in a 100% reduction in emissions.

And one other point must be made. Power plants which operate on coal or similar types of fuels have made great strides to reduce emissions. It is much easier to maintain and police the few power plants then the millions of cars, trucks, buses, etc., used by the public.

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What is the difference between "grid connected" and "non-grid connected" electric vehicles?
Hybrids which are charge sustaining, which means that the generator used in the propulsion system is large enough to provide the necessary energy to maintain vehicle movement, can operate without ever being connected to the electrical grid (a battery charger.) These are "non-grid connected" hybrid-electric vehicles. Most of the hybrid-electric cars will probably never have to be plugged in.

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What is better...conductive charging or inductive charging?

Both systems are safe and will provide efficient energy transmission. Inductive charging, which transfers energy across a magnetic field (reducing no direct metal-to-metal contact) is favored by automobile manufacturers such as General Motors and Toyota. Inductive chargers use a paddle that is easily slipped into a port, normally on the front of the car.

Conductive chargers are used by many other automobile manufacturers and use the more traditional electrical plug concept.

For electric vehicles to become more viable, a single type of charging connection will need to be agreed on.

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What is a thermal management system?
Batteries do not do well in cold weather. A thermal management system helps maintain an acceptable level of heating to keep batteries "happy" by supplying heat to the batteries using their own energy. (A thermal management system can also be devised to use electricity from external sources to heat the batteries.)

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