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{{Short description|Power in cars}}
{{More citations needed|date=June 2021}}
[[Image:Energy flows in car.svg|thumb|right|450px|Example energy flows for a late-model midsize passenger car: (a) urban driving; (b) highway driving. Source: U.S. Department of Energy [http://www.fueleconomy.gov/feg/atv.shtml/]]]
'''Automobile accessory power''' can be
An engine has one or more devices for converting energy it produces into a usable form, [[electrical|electricity]] connection through the alternator, [[hydraulic]] connections from a pump or engine system, [[Pneumatics|compressed air]], and engine [[vacuum]]; or the engine may be directly tapped through a [[Machine|mechanical]] connection. Modern vehicles run most accessories on electrical power. Typically, only 2% of a vehicle's total power output
▲'''Automobile accessory power''' can be produced by several different means. However, it is always ultimately derived from the [[automobile]]'s [[engine|internal combustion engine]].
▲An engine has one or more devices for converting energy it produces into a usable form, [[electrical|electricity]] connection through the alternator, [[hydraulic]] connections from a pump or engine system, [[Pneumatics|compressed air]], and engine [[vacuum]]; or the engine may be directly tapped through a [[Machine|mechanical]] connection. Modern vehicles run most accessories on electrical power. Typically, only 2% of a vehicle's total power output goes towards powering accessories.<ref name=autogenerated2>[http://www.trb.org/publications/sr/sr286.pdf TRANSPORTATION RESEARCH BOARD SPECIAL REPORT 286 TIRES AND PASSENGER VEHICLE FUEL ECONOMY Fig 3-1, p.63 of pdf, p.40 of report]</ref>
==Mechanical==
Some automobile accessories are connected directly to the engine through [[gear]]s or [[belt (mechanics)|belt]]s. These usually require large amounts of power. The [[air conditioning]] [[Gas compressor|compressor]]
==Electrical==
Early automobiles used a [[
The first electrical accessory connection was supplied by a [[Direct current|DC]] [[Electrical generator|generator]]. Voltage varied with engine speed and because of technological limitations, complicated mechanical devices were used to regulate it. Even so, voltage at idle was too low to be useful. A lead-acid [[Battery (electricity)|battery]] was used to provide proper voltage when the generator could not, and was recharged at higher engine speed or lower electrical load. The [[automobile self starter]] was an early engine system to use this.
Lighting, which had previously been
Early systems
Starting, lighting and ignition systems of most gasoline-powered vehicles remain as 12 volt systems. Diesel-powered vehicles, including mobile construction equipment and heavy trucks use 24 volt electrical systems, as do many military vehicles. Research is ongoing into adopting a [[42-volt electrical system]] standard for automotive electricity, but the entire electrical system will have to be redesigned and new components manufactured to work with the higher voltage. The main advantage of higher voltage is that electrical components can be made with less metal, saving weight and cost, and improving [[Efficient energy use|energy efficiency]]. As such an [[48-volt electrical system]] has been introduced.
Most modern systems, such as [[power window]]s, [[power seat]]s, and [[power door locks]], are electrically powered. Electrically driven [[power steering]] systems have been developed and are used in numerous models.▼
▲Most modern systems, such as [[power window]]s, [[power seat]]s, and [[power door locks]], are electrically powered. Electrically driven [[power steering]] systems have been developed and are used in numerous models. High-efficiency all-electric refrigerant compressors for air conditioning are starting to be used, especially in hybrid or all-electric vehicles.
The [[cigarette lighter receptacle]] serves as a de facto standard for use of portable 12 volt equipment in or near an automobile.
==Hydraulic==
The engine generally has a hydraulic pump
In passenger cars, the most common use of hydraulic power
The French company [[Citroën]]
▲In passenger cars, the most common use of hydraulic power is the [[power steering|steering system]]. [[Convertible]] tops may be raised and lowered using hydraulics. [[Windshield wiper]]s were sometimes hydraulically driven, although this use mostly ceased after the late 1960s. On vehicles with little or no engine vacuum, Hydraulic systems are generally adapted in place of vacuum systems.
The 1999–2004 Jeep Grand Cherokee had a hydraulically driven radiator fan, powered by the SUV's power steering pump.
▲The French company [[Citroën]] has devised a high-pressure hydraulics system for cars which was used for all manner of systems, even power-adjustable seats.
In vehicles such as heavy [[truck]]s and [[tractor]]s, hydraulic systems are much more common. [[Hydraulic ram]]s are used for accessories such as dump truck beds, cranes, loaders, and [[three-point hitch]]es.
==Vacuum==
A commonly available source of power from an internal combustion engine is the partial [[vacuum]] available at the [[Inlet manifold
Manifold vacuum varies depending on engine load and [[throttle]] position, and automobiles use [[vacuum reservoir]]s or "vacuum canisters" to provide a usable source under
Reservoirs and devices connected to the engine through [[check
The most ubiquitous vacuum-powered accessory is the booster for the power [[Hydraulic brake|brake system]]. The vacuum is only an assist and the brakes can still function, requiring greater force, if the booster vacuum is used up.
Many older vehicles used vacuum-powered [[windshield wiper]]s. Loss of manifold vacuum when the engine was working hard, or at wide open throttle, necessitated using a vacuum booster pump which was usually part of the fuel pump.
Automotive vacuum systems reached their height of use between the 1960s and 1980s. During this time a huge variety of [[vacuum switch]]es, [[Vacuum delay valve|delay valves]] and [[List of automotive vacuum devices|accessory devices]] were created.
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* Power [[brake]]s
* [[Transmission (mechanics)|Transmission]] shift control
* Doors for the [[hidden
* Remote trunk latch release
* Rear cabin vent control
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Such systems tend to be unreliable with age as the vacuum tubing becomes brittle and susceptible to leaks.
==
Pneumatic (compressed air) systems are rarely found in passenger cars.
Larger vehicles often use [[air brake (road vehicle)|air brakes]] and the pressure may be used to drive other systems. Windshield wipers, automatic gear boxes, and other common hydraulic or vacuum powered accessories are often adapted. On buses where the engine is often at the rear of the vehicle, compressed air may be used for the throttle and clutch.
[[Bus doors]] are typically air powered, as well as the steps and the [[suspension (vehicle)|suspension]], allowing the bus to lower itself or "kneel" at stops to allow passengers on or off.
==References==
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{{DEFAULTSORT:Automobile Accessory Power}}
[[Category:Automotive
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