Jump start

from Wikipedia, the free encyclopedia

The jump start is to start an internal combustion engine if your own starter battery fails . It is a common measure of professional breakdown assistance and can also be carried out by laypeople.

In general, "jump start" is reduced to starting engines in motor vehicles , but jump start is also used for boat and aircraft engines , rail vehicles , mobile and stationary systems with motor drives and in model making .

Jump start with jump leads

If the starter battery no longer supplies enough current to start the internal combustion engine with an electric starter at sufficient speed, an external power source can be used, provided that its nominal voltage is the same and it can provide sufficient power . In the development of motor vehicles, starting aid with an incompatible nominal voltage is sometimes taken into account. Colloquially, one also speaks of “bridging”. The start-up problem should actually only be due to the battery charge level being too low , as other sources of error persist even after the start attempt.

Jump-start by donor vehicle

  • Receiver : non-startable vehicle with discharged starter battery.
  • Donor vehicle : startable vehicle with charged battery.

The operating instructions for the donor and recipient must be observed, as some vehicles have their own connections in the engine compartment for jump start, but the battery is located in the trunk, for example.

  1. Position vehicles as close as possible to each other and apply the parking brakes on both.
  2. Start the donor vehicle and switch on a larger consumer (e.g. rear window heater).
  3. Connect the positive poles of the batteries with the red cable. See image.
    Jump start cables: The sequence when connecting must be observed. When loosening it is reversed.
  4. First clamp the black cable to the negative pole of the donor battery and then to a bare metal part in the engine compartment of the receiver.
  5. Switch off large consumers and bring the donor vehicle to medium speed in order to charge the receiver battery with the generator for a few minutes.
  6. The donor battery, partially charged receiver battery and donor generator are now ready to start the receiver motor.
  7. Before disconnecting the circuit (in reverse order - starting with Schwarz-am-Metall) the vehicles should run for a certain time to ensure that the receiver battery is charged. Switching on consumers on the receiving vehicle or on both vehicles dampens voltage peaks when the cable is removed.
  8. After starting the receiver battery has to be charged e.g. B. by driving for half an hour. If the battery voltage drops again instead, the generator is usually defective.

Remarks

  1. ↑ Red-before-black sequence: If the black cable were laid first, all metal parts of the donor and recipient vehicle would be conductively connected to one another. If the red cable accidentally touches a metal part while it is already connected to a battery on one side, an electrical short circuit occurs . If the black cable has not yet been laid, this cannot be done.
  2. ↑ The second minus terminal should be connected to a metal part instead of the minus pole of the battery:
    When charging, the battery generates oxyhydrogen which could be ignited by flying sparks when the minus terminal is loosened.
    In the Swiss driving test, however, the answer is expected that "the negative pole of the donor battery is connected to the negative pole of the receiver battery".
    The batteries must not be disconnected: an interruption can destroy the alternator rectifier.
  3. ↑ A deeply discharged battery initially has a high internal resistance and only consumes little electricity . This can lead to overvoltage from the charge regulator of the alternator .
    The voltage peak is less if both vehicles remain connected for a few minutes.

Jump leads

Older jump starter cable with non-insulated pole clamp jaws

The external battery (usually from a helping vehicle) is connected to the battery of the receiving vehicle ( connected in parallel ) with the help of a jump start cable (also known as “starter cable”, “transfer cable” or “bridging cable” ).

A jump start cable consists of two insulated electrical lines with a large clamp on both sides. One line connects the positive poles , the other the negative poles of the batteries. For a better differentiation, the colors red (plus) and black (minus) are common.

Special forms are possible, for example in the military with a plug / socket system and combined cables. Only cables with a sufficient cross-section (at least 16 mm² copper or 25 mm² aluminum ) should be used. The cable cross-section depends roughly on the size of the displacement , more precisely on the required cold start current of the starter.

Cables with a larger cross-section are generally also suitable for weaker motors.

Cables with a cross-section of 25 mm² copper or 40 mm² aluminum are recommended for engines with a displacement of approx. 2 liters or more and for diesel engines (the engine must also be preheated with 20–40 amps per cylinder ). A particularly large displacement or diesel engines with a displacement of more than 3 liters require cables with 35 mm² copper or 55 mm² aluminum.

Many cables are made of aluminum because, with the same resistance, they are only a fifth of the material costs of copper and half the weight, although the cross-section is 1.6 times as large, because the density is far lower. However, aluminum cable is not as flexible and the wires break more easily.

If the external energy source is small compared to the receiver battery or the jump-start cable is weak, it is advisable to pre-charge the exhausted battery for about 15 minutes. The engine has to run so that the alternator can charge the exhausted battery, because a full battery does not sufficiently charge an empty battery.

The longer the cable, the larger the cross-section - because of the electrical resistance - must be . A large cable cross-section also reduces the risk of overheating.

DIN 72553 (edition: 1994-04, jump-start cables for road vehicles with internal combustion engines - dimensions, requirements, testing) and ISO  6722 (edition: 2006-08, road vehicles - 60 V and 600 V single-core connecting cables - dimensions, test methods and Conditions).

Fast charging via the cigarette lighter socket

A starting aid that is not recommended is to use cables to connect the vehicles via a cigarette lighter socket ( on-board power socket ). Since the current is limited by the small cable cross-sections and the fuses of the vehicle sockets (usually 10 to 20 A ), the receiver battery must be charged for many minutes while the donor vehicle is running before it can start the engine again by itself. This type of battery charging only works if the cigarette lighter on the receiving vehicle is connected to the battery even when the ignition is switched off, otherwise the switched on ignition and the units connected to it sometimes use more than the charging current.

Alternative electrical jump start

  • Vehicles with a second battery and battery cut-off relay (e.g. mobile homes , off-road vehicles and emergency vehicles ): jump start as between two vehicles.
  • Workshops often use large starter batteries, sometimes several connected in parallel, to give jump starters.
  • Battery packs ( power banks ) with high-current lithium batteries, but with greatly reduced performance at low temperatures
  • Chargers that contain a starter battery.

Other automotive techniques

Jump start by pushing

Pushing is possible if the broken-down car has a manual gearbox or an automated manual gearbox. Vehicles with automatic transmission (fluid transmission) can only be pushed or towed if the transmission is equipped with a secondary oil pump.

For successful pushing or towing, the battery must at least be able to supply the ignition current and the ignition and fuel supply must be OK. In diesel engines too, the battery must be able to open the fuel valve.

The ignition key is turned to the ignition position and the steering wheel lock disengaged. One or more people get the car going. In engines with a carburettor , unburned fuel can damage the vehicle's catalytic converter .

Motorcycles with a larger displacement should be pushed in a higher gear, otherwise the rear wheel will lock. In this way, the load in the drive train builds up slowly and does not immediately “block”; when you let go of the clutch lever it is advisable not to push any more so that a greater weight presses on the rear wheel.

Jump start by towing

For this purpose, the towing vehicle and the vehicle to be towed are connected with a rope or a tow bar . The ignition of the vehicle to be towed is switched on. Now it is carefully towed as possible without jerking (the rope). A higher gear is to be used for this. When the vehicle is rolling, briefly engage the clutch, disengage it when starting, accelerate and, if necessary, brake and signal the driver of the towing vehicle briefly with the horn that the attempt to start was successful.

Trucks with spring-loaded brakes can only be towed if the pressure in the air-pressure brake system is still sufficient to release the parking brake . With trucks, however, there is usually the option of having the brake system of the vehicle to be towed also supplied by the towing vehicle (connect the red couplings with a suitable hose).

When towing, as with pushing, vehicles with catalytic converters may only be towed if the engine does not start because the battery is discharged, i.e. the ignition system must be fully functional. Otherwise, unburned fuel can get into the catalytic converter and damage it.

Towing or pushing is not only problematic for vehicles with catalytic converters - all vehicles with exhaust gas aftertreatment systems and filters can be damaged by towing.

Jump start with a crank

Some classic cars such as the Renault 4 or the Citroën 2CV have, in addition to an electric starter, a crank in the on-board tool kit with which the engine can be started. The crank is attached to a claw clutch partly with freewheel on the crankshaft or the main shaft of the transmission. There were holes in the bumper and in the frame or in the bonnet for inserting the crank. The claws are milled out like a one-way slotted screw so that the crank is ejected when the engine starts up instead of turning.

Jump start spray

By spraying jump start spray into the intake can bring a start unwilling engine running, provided that the starter, battery and ignition system work. An application behind the air filter is most effective.

Jump-starting hybrid vehicles

Hybrid vehicles use the electric drive motor to start the combustion engine, which is operated with the higher voltage of the traction battery . Such vehicles have a 12-volt electrical system, but not for starting the engine, but for control units that are required for starting and the vehicle lighting.

Jump-starting motorcycles

A car can help jump start a motorcycle if the batteries of the two vehicles have the same nominal voltage (usually 12 V).

  1. Attachment of the positive cable to the positive pole.
  2. Attachment of the earth cable to the minus point of the car and to an earth point on the motorcycle; a fixed, non-insulated / non-painted metal part, for example on the engine.

See also

literature

  • Rudolf Hüppen, Dieter Korp: Car electrics all types. Motorbuchverlag, Stuttgart, 1968, ISBN 3-87943-059-4 .
  • Dieter K. Franke: VAG manual, Do it yourself, used car purchase-accessory installation-care. 1st edition. ADAC Verlag GmbH, Munich 1984, ISBN 3-87003-227-8 .

Web links

Individual evidence

  1. ^ Ford Motors Company: Development Requirements ; Page 84: in the case of jump start with 24 volts (a truck battery), the functionality of the on-board electrical system should continue to function (no damage) (for vehicles from 2020).
  2. ↑ Jump-start tips. ADAC, accessed on April 27, 2015 .
  3. ↑ jump start. Accessed November 5, 2019 (German).