Late model cars are generally more dependent on complex electronics to function and any voltage spike can damage the delicate electronic circuitry. Quality jumper leads fitted with a 'spike guard' or 'surge protector' should always be used and are available online or from any Supercheap Auto store.
If the vehicle will not start, the charge indicator shows a fault or the alternator light is on, you should stop what you are doing immediately and contact your local auto club or local mechanic. In these circumstances the issue may not be battery related.
Tips and Warnings
The following precautions should be read and understood before any jump starting attempt is undertaken.
- Ensure the ignition switch is in the OFF position on both vehicles
- Turn off the lights and power draining functions (such as the stereo and interior light) to help ease the strain off the donor battery
- Ensure the donor battery is the same voltage as the flat battery
- Ensure the two vehicles are not touching in anyway
- Make sure the vehicles are in either Neutral (Manual) or Park (Auto) with the handbrake on
- Remove any vent caps on non-maintenance free batteries – be very careful as battery acid is highly corrosive
- Only run the engine in a well-ventilated area to ensure toxic exhaust gas does not build up
- Don't leave either engine running unattended
With all precautions checked, connect the red coloured jumper lead to the (+) positive terminal of the flat battery and the other end of the red jumper lead to the (+) positive terminal of the charged battery.
Connect the black jumper lead to the (-) negative terminal of the charged battery and the other end of the black jumper lead to a good earth point (solid metal component of the engine) on the disabled vehicle.
DO NOT connect the black cable to the negative terminal on the discharged battery as this may cause a dangerous spark.
The engine block is typically the best place for a good earth.
Attempt to start the engine with the flat battery.
If the charged battery doesn’t have enough capacity to do this, start the engine with the charged battery and try it again.
The vehicle should now start.
Let the vehicle with the previously flat battery idle with the headlights on to prevent a possible voltage spike, damaging electrical equipment.
Disconnect the jumper leads in the reverse order of connection. Remove the black negative lead from the ground, then from the donor vehicle.
Then remove the red cable from the already charged battery and lastly disconnect the red positive cable from the vehicle you have just started.
The car has now been started and after any caps and covers have been replaced it is ready to be driven. If the charging system is working correctly and the battery is in good condition the battery will be recharged whilst the car is running.
Drive the vehicle for 30-40 minutes to recharge the vehicle battery. Unless the cause of the flat battery is known, for example lights left on, the battery and electrical system condition should be checked for problems and rectified as soon as possible.
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