Jump start (vehicle)

Jump start

A jump start, also called a boost, is a procedure of starting a motor vehicle (most commonly cars or trucks) that has a discharged battery. A temporary connection is made to the battery of another vehicle, or to some other external power source. The external supply of electricity recharges the disabled vehicle's battery and provides some of the power needed to crank the engine. Once the vehicle has been started, its normal charging system will recharge, so the auxiliary source can be removed. If the vehicle charging system is functional, leaving the engine running will restore the charge of the battery.

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). Safe procedures for connecting and disconnecting cables are given in the vehicle manual.

Battery booster and jump starter

Some AC battery chargers have a boost, engine start, or engine assist feature. Despite being able to assist in jump starting a dead vehicle battery, these types of battery chargers perform their task over a longer period of time, rather than an instantaneous boost. Boosting a dead battery through a battery charger can take anywhere from five to twenty minutes depending on the depth-of-discharge (DOD), health of the vehicle battery, and type of engine (engine displacement). AC power is not usually available for a roadside boost.

Jump starters are portable battery devices that allow for jump starting of vehicles. These devices operate similar to jumper cables but do not require an additional vehicle to provide the power needed to boost the dead vehicle battery. Jump starters using lead-acid batteries claim 300−⁠1700 amp ratings. The main disadvantage of lead-acid jump starters is weight, size and battery chemistry. Lead-acid jump starters can be extremely heavy and large, making them less than convenient when transporting between vehicles. Lead-acid batteries may self-discharge if they develop a condition called sulfating, which permanently decreases battery capacity. It is entirely possible to destroy a new lead-acid battery within months, requiring a replacement.

Jump starters using lithium-ion batteries began appearing in the market around 2013. Most lithium jump starter brands use a high discharge lithium polymer or lithium-ion battery. Lithium jump starters are compact and lightweight compared to their lead-acid equivalents. These jump starters often incorporate a USB connection, allowing it to function as a portable charger for mobile electronic devices.