Jump start (vehicle)
From Wikipedia, the free encyclopedia
A jump start or boost is a colloquial term for a method of starting an automobile or other internal combustion engine-powered vehicle which has a discharged battery. A second battery (often in another vehicle) is temporarily connected to the "flat" battery, to provide the initial charge required to start the engine. Once the engine is running, it will recharge the battery, so the second battery can be detached. However, if the engine stops running too soon, the battery may not have built up enough charge to restart the engine, so a further jump start may be required.
Most passenger vehicles use a standard 12-volt DC battery which provides power to a starting motor 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, such as by inadvertently leaving one's headlights switched on while parked, the car's engine will not "turn over" when the ignition key is turned.
Many motorists carry jumper cables which consist of a pair of heavy gauge wires with alligator clips at each end. Jumper cables are marked by black (-) and red (+) handles, representing the two polarities of the automobile's direct current system. Interchanging the polarities will cause a short circuit and a hazard to people and damage to one or both automobiles.
Motorists can be severly injured by a battery explosion. Operation of a lead-acid battery produces hydrogen gas which is flammable. Proper jump start procedure are usually found in the owner's manuals for the vehicles. Caution is in order to avoid a spark which may ignite the gas. The usual recommended sequence is to first connect the positive terminals of the charged and dead batteries with the red booster cable, then connect the frame of the vehicle with the dead battery and the frame of the vehicle with the charged battery, at a point away from the batteries themselves. Since automotive batteries are connected to the frame and engine block, this method avoids creating a spark at the battery terminals. The boosting vehicle must not touch the boosted vehicle.
A jump start is only effective for a discharged battery. Other faults such as a failed battery, damaged starting motor, or other mechanical problems with the vehicle cannot be overcome by a jump start. Even a successful jump start may not allow the vehicle to resume normal operation, since the reason for the dead battery may have been a failed charging system. The operator of the "boosted" vehicle should have the battery and charging system checked at once.
[edit] Battery booster and jump starter
A hand-portable battery, equipped with attached cables and charger, can be used similarly to another vehicle's battery (it is called a battery booster and jump starter). It can reach 1700 peak amps.
It generally includes technology that automatically senses the battery's polarity prior to sending power to the vehicle, eliminating the costly damage that can result from a simple jump-starting mistake.
[edit] 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 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.
Passenger vehicles with 42-volt electrical systems, and hybrid vehicles, 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 (tow truck).
[edit] External links
- AAA starter cables information
- Jump-Starting a Car — from the US Naval Safety Center
- Jump-Starting a Car — Printable Reference Sheet
