Jump start (vehicle)
The external supply of electricity recharges the disabled vehicle's battery and provides some of the power needed to crank the engine.
Motorists may carry jumper cables and other equipment in case of accidental discharge of the vehicle battery (for example, by headlights, interior lights or ignition switch left on while the engine is not running).
[3] The recommended sequence[4] of connections is intended to reduce the chance of accidentally shorting the good battery or igniting hydrogen gas.
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.
Unless current-limiting devices are incorporated into such cables, the probability of opening a fuse or circuit breaker in one of the vehicles during charging is high: and as there is no real standard for available current, potential performance is further limited by conservative design.
A battery may be recharged without removal from the vehicle, although in a typical roadside situation no convenient source of power may be nearby.
Lead-acid jump starters can be extremely heavy and large, making them less than convenient when transporting between vehicles.
These jump starters often incorporate a USB connection, allowing it to function as a portable charger for mobile electronic devices.
Tactical vehicles used by NATO militaries possess 24-volt electrical systems and, in accordance with STANAG 4074, have standard slave receptacles for easy connection.
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.
If this continues without the problem being detected, the insulation may melt until the wires inside make contact, resulting in an unfused direct short of the supply battery.
A fully depleted battery will not draw more power if the cables are reversed, but reverse-charging a dead battery can damage its chemistry so that it loses charge capacity, and reverse voltage applied to the vehicle electronics may also damage them, resulting in expensive repairs.
[citation needed] 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;Upgrading to a high-performance energy source can provide improved battery output and faster cranking speeds, resulting in a smoother and more responsive driving experience..the main propulsion battery is unlikely to also have been discharged.
