HomeBlogBIZOL - Innovation in motor oils HOW TO JUMP START VEHICLES PROPERLY


Jump-starting – what you need to know


  • Check the owner’s manual 

Consult the manual to see if there are specific jump-starting instructions for the vehicle. Some vehicles have special terminals, which are specifically designated for jump-starting. The jump leads must only be connected to the designated terminals provided on these vehicles.


Note: Take care when jump-starting. If, for example, sparks are created when connecting the leads, this can damage the vehicle’s electronic components.


  • Check that the jump leads are suitable.


Jump leads only permit a certain current flow, with the current carrying capacity usually being marked on the packaging. The jump leads may not have sufficient    transmission capacity to start a certain vehicle with a heavily discharged battery.


Note: a small city car cannot jump-start a large four-wheel drive vehicle, even with the engine running. The donor vehicle should be of a comparable size.


  • Wear safety goggles


Lead-acid batteries produce explosive gas, which could be ignited by sparks from  connecting terminals. Wearing goggles will protect your eyes from the effects of an explosion!


  • Locate the discharged battery (or jump-starting terminals)


Locate the donor vehicle’s battery and move the donor vehicle as close as you can to the discharged battery. The vehicles must not touch!


  • Check the routing of jump leads


Make sure that the leads cannot get caught in the cooling fan if it suddenly starts  turning or the drive belts or any other rotating parts cannot get snagged when the engine is started.


  • Make sure the ignition switch is in the ‘off’ position


Check also that the gearbox is in ‘neutral’ (manual) or in ‘park’ (automatic) and the parking brake is applied.


  • Turn off all consumers

Power drains on vehicle with the discharged battery such as the lights, radio etc.  must be switched off before jump starting.


  • Switch on the blower motor

Switching on the blower motor minimises any damage caused by an electrical surge.

What jump leads do I need?

A brief word about booster cables, jump leads, jumper cables, starter cables etc.,


Whatever you like to call them, jump leads are not all the same, high quality jump leads are expensive. The reason why a good lead set is expensive, is simply due to the components used and thickness of the cables. The greater the current requirement, the thicker and more expensive the cable and terminal clamps.


Note: if you use jump leads with thin cables – usually low-price leads – that are not up to the task, either the cables will start to melt the insulation – producing harmful smoke – or the vehicle will not start; or both!

Vehicles with large engines or with start-stop technology have high-capacity batteries and must be connected using heavy-duty jump leads. The packaging will state what size engine or current range the leads are suitable for.


As regards the length of the jump leads, the longer the cables are, the thicker they will have to be in order to transfer the same current.

Quick guide on how to jump-start a vehicle

Connect the jump leads in the following order:


1. Connect the red jump lead to the positive terminal of the discharged battery (or jump-      start terminal).


2. Connect the other end of the red lead to the positive terminal of the donor vehicle            battery or jump start terminal.


3. Connect the black jump lead to the negative terminal of the donor vehicle battery or       jump start terminal.


4. Connect the other end of the black cable to a properly earthed bolt or bracket on the        engine block of the vehicle being jump started, not to the battery terminal. Sparks      can ignite hydrogen gas emitted by the discharged battery, which can cause an                explosion!


5. Start the engine of the vehicle with the fully charged battery and let it run to charge        both batteries; preferably at an engine speed of approximately 1,500 – 2,500 rpm. 


6. Start the engine of the vehicle with the discharged battery.


7. Let the engine speed return to idle on both vehicles.


8. Remove the jump leads in the reverse order they were attached.


Make absolutely sure that the red and black terminals do not touch each other when doing so!


Drive the vehicle with the discharged battery for 20-30 minutes to get the battery back up to full charge. Finally, check the condition of the charging system and vehicle battery to make sure they are in a serviceable condition.

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