Jump start (vehicle)
Encyclopedia
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
or other vehicle powered by an internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
when the vehicle's battery
Rechargeable battery
A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to...
has been discharged. A second battery (often in another vehicle) is temporarily connected to provide starting power to the disabled vehicle. Once the disabled vehicle's engine is running, its alternator
Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...
or generator should recharge the dead battery, so the second battery can be disconnected after the engine starts.
Most passenger vehicle
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s use a 12-volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
car battery
Car battery
An automotive battery is a type of rechargeable battery that supplies electric energy to an automobile. Usually this refers to an SLI battery to power the starter motor, the lights, and the ignition system of a vehicle’s engine...
that provides power to a starting electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
for the engine. When the engine is running, electrical power from its alternator restores the charge to the battery in preparation for the next start. When a battery is discharged, as for example by headlights left on while the engine is off, the car's engine will not "turn over" when the ignition key is turned and the vehicle will not start.
Jumper cables
Wire gauge
Wire gauge is a measurement of how large a wire is, either in diameter or cross sectional area. This determines the amount of electric current a wire can safely carry, as well as its electrical resistance and weight per unit of length...
, insulated wires with alligator clips at each end. Jumper cables are available in various lengths. The size of copper conductors varies from about #10 AWG
American wire gauge
American wire gauge , also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in the United States and Canada for the diameters of round, solid, nonferrous, electrically conducting wire...
for light duty sets, to #1 AWG. The alligator clips generally have color-coded, vinyl-coated (PVC) insulation to prevent electrical short circuits. Most clips fit both top- and side-mounted battery terminals. Top-quality clips are made of solid copper; lesser-quality are made of material such as copper-plated steel. Jumper cables are marked by black (-) and red (+) handles, representing the two polarities
Electrical polarity
Electrical polarity is present in every electrical circuit. Electrons flow from the negative pole to the positive pole. In a direct current circuit, one pole is always negative, the other pole is always positive and the electrons flow in one direction only...
of the automobile's direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
system. Interchanging the polarities will cause a short circuit
Short circuit
A short circuit in an electrical circuit that allows a current to travel along an unintended path, often where essentially no electrical impedance is encountered....
and a hazard to people and damage to one or both automobiles, possibly including blown electrical fuses and circuit boards. Car manuals recommend connecting the negative (black) cable last and disconnecting it first, since otherwise the battery may be shorted by the tool used to loosen the cable clamps. Connecting the positive (red) cable while the negative cable is connected can also cause a spark, resulting in battery explosion.
Limitations
Operation of a lead-acid battery may, in case of overcharge, produce flammable hydrogenHydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas by electrolysis of water
Electrolysis of water
Electrolysis of water is the decomposition of water into oxygen and hydrogen gas due to an electric current being passed through the water.-Principle:...
inside the battery. Jump start procedures are usually found in the vehicle owner's manual. The recommended sequence of connections is intended to reduce the chance of accidentally shorting the good battery or igniting hydrogen gas. Owner's manuals will show the preferred locations for connection of jumper cables; for example, some vehicles have the battery mounted under a seat, or may have a jumper terminal in the engine compartment.
Motorists can be severely injured by a battery explosion. In the United States in 1994, a research note by the National Highway Traffic Safety Association estimated that about 442 persons were injured by exploding batteries while attempting a jump-start.
Current from the boosting vehicle will charge the dead battery. After several minutes enough energy is transferred to allow cranking of the engine. If the connections are good and the cables are large, the boosting vehicle battery may also supply part of the cranking current. In an extreme case, it is possible to crank and start a vehicle with no battery in it if the cables are heavy-duty. Cranking current drawn through light-gauge cables in this way will damage them by overheating; electrical resistance of a smaller wire is higher than that of a larger wire, and resistance dissipates electrical energy into heat.
If the discharged battery case is cracked, or the battery has a low electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
level, or is frozen, a jump start will not restore normal operation. A jump start is only effective for a discharged battery and cannot resolve other faults including a lack of fuel, a failed battery, or other mechanical problems. Even after a successful jump start a vehicle may not be able to resume normal operation if the reason for the dead battery is a failed charging system. Loss of voltage from the vehicle battery may have wide-ranging effects—from a trivial loss of radio receiver preset stations to a significant loss of security codes or engine control parameters.
Motorcycles
Many very old motorcycles (and cars) have 6-volt systems and cannot be jump started safely with a modern car, but newer designs with 12-volt systems may be jump started with a 12-volt car or truck. Car batteries can generally jump start a motorcycle easily without any help from the car's alternator. An alternative is to push startPush start
Push starting, also known as bump starting, pop starting or crash starting is a method of starting a motor vehicle with an internal combustion engine by engaging the manual transmission through the motion of the vehicle...
the motorcycle.
Cigarette lighter outlet
An alternative to jumper cables is a cable used to interconnect the 12 volt power outlets (cigarette lighter outletsCigar lighter receptacle
The cigarette lighter receptacle in an automobile, initially designed to power an electrically heated lighter, became a de-facto standard DC connector to supply electrical power for portable accessories used in or near an automobile...
) of two vehicles. While this eliminates concerns with incorrect connections and generation of arcs near battery terminals, the amount of current available through such a connection is small. This method works by slowly recharging the battery, not by providing the current needed for cranking. The engine cranking motor current draw will exceed the fuse
Fuse (automotive)
Automotive fuses are a class of fuses used to protect the wiring and electrical equipment for vehicles. They are generally rated for circuits no higher than 24 volts direct current, but some types are rated for 42-volt electrical systems...
rating in a cigarette lighter outlet. Many vehicles turn off the cigarette lighter outlets when the key is turned off, making the technique unusable unless the ignition key is turned to the accessory or on position to connect the cigarette lighter outlet to the battery.
Battery booster and jump starter
A hand-portable battery, equipped with attached cables and charger, can be used similarly to another vehicle's battery.Portable boosters may automatically sense the battery's polarity prior to sending power to the vehicle, eliminating the damage that can result from reversing the connection.
Battery charger
Motorists and service garages often have portable battery chargerBattery charger
A battery charger is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it.The charge current depends upon the technology and capacity of the battery being charged...
s operated from AC power. Very small "trickle" chargers are intended only to maintain a charge on a parked or stored vehicle, but larger chargers can put enough charge into a battery to allow a start within a few minutes. Battery chargers may be strictly manual, or may include controls for time and charging voltage. Some chargers are equipped with "boost" settings that supply a large current to assist in cranking the engine. Battery chargers that apply high voltage (for example, more than 14.4 volts on a 12 volt nominal system) will result in emission of hydrogen gas from the battery, which may damage it or create an explosion risk. A battery may be recharged without removal from the vehicle, although in a typical roadside situation no convenient source of power may be nearby.
Push starting
A vehicle with a manual transmissionManual transmission
A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...
may be push started. This requires caution while pushing the vehicle and may require the assistance of several persons or another vehicle. If the vehicle battery cannot provide power to the ignition system, push starting will be ineffective. Most vehicles with automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...
s cannot be started this way because the hydraulic torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...
in the transmission will not allow the engine to be driven by the wheels.
Voltage problem
Formerly, especially in cold climates, some jump starts were done with two series-connected batteries to provide 24 volts to a 12 volt starting motor. However, such overvoltage can cause severe and expensive damage to the electronic systems on modern automobiles and should never be used.Heavy vehicles such as large trucks, excavation equipment, or vehicles with diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
engines may use 24-volt electrical systems. These cannot be boosted from a 12-volt motor vehicle and must not be used to boost a 12-volt motor vehicle.
Vintage cars may have 6-volt electrical systems, or may connect the positive terminal of the battery to the chassis. The methods intended for boosting 12-volt, negative-ground vehicles cannot be used in such cases.
Passenger vehicles with 42-volt electrical system
42-volt electrical system
In automobiles, a 42-volt electrical system was a proposed electrical power standard in the late 1990s intended to allow more powerful electrically driven accessories, and lighter automobile wiring harnesses...
s may not be possible to "boost" from other vehicles; professional assistance would be required to prevent severe damage to the vehicle and possible personal injury (see tow truck
Tow truck
A tow truck is a vehicle used to transport motor vehicles to another location , or to recover vehicles which are no longer on a drivable surface.Towing services are generally provided by an emergency road service operator...
). Hybrid vehicle
Hybrid vehicle
A hybrid vehicle is a vehicle that uses two or more distinct power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles , which combine an internal combustion engine and one or more electric motors.-Power:...
s may have a very small 12 volt battery system unsuitable for sourcing the large amount of current required to boost a conventional vehicle. However, as the 12-volt system of a hybrid vehicle is only required to start up the control system of the vehicle, a very small portable battery may successfully boost a hybrid that has accidentally discharged its 12-volt system; the main propulsion battery is unlikely to also have been discharged.
Military vehicles
STANAG
STANAG is the NATO abbreviation for Standardization Agreement, which sets up processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance. Each NATO state ratifies a STANAG and implements it within their own...
4074, have standard slave receptacles for easy connection. A slave cable is plugged in to the receptacle on each vehicle, and the dead vehicle is started with the live vehicle's engine running.
See also
- Crocodile clipCrocodile clipthumb|Standard clipthumb|Pair of standard clipsA crocodile clip is a simple mechanical device for creating a temporary electrical connector, and is named for its resemblance to an alligator's or crocodile's jaws...
used in the cables - Kick startKick startKick start refers to a method of starting an internal combustion engine by pushing a ratcheting lever with one's foot. Kick start mechanisms were almost universally a part of motorcycle engines before the mid-1970s, and were phased out of production over the next twenty years or so as electric...
External links
- Breakdown Advice : using jump leads safely - The AA (United Kingdom)
- AAA starter cables information
- Jump-Starting a Car - by the US Naval Safety Center
- do-it-yourself jump start
- Official Car Talk Guide to Jump Starting Your Car - by Car TalkCar TalkCar Talk is a radio talk show broadcast weekly on National Public Radio stations throughout the United States and elsewhere. Its subjects are automobiles and repair, and it often takes humorous turns...
's TomTom MagliozziThomas Louis "Click Tappet" Magliozzi is an American radio talk show host. He and his younger brother Ray Magliozzi, also known collectively as Click and Clack, The Tappet Brothers, are the hosts of National Public Radio's Car Talk. -Biography:Thomas Louis...
and Ray MagliozziRay MagliozziRaymond F. "Clack Tappet" Magliozzi is a co-host of NPR's winning weekly radio show, Car Talk. They are known as "Click and Clack, the Tappet Brothers"...
, "Click and Clack, the TappetTappetA tappet is the noise made by a worn cam follower, however the term is widely used to represent the cam follower itself. In mechanical engineering it is a projection which imparts a linear motion to some other component within an assembly...
Brothers" - Quick & Easy Directions to Jump Start by Car Care Council