THE CORRECT PROCEDURE FOR JUMP STARTING
THE CORRECT PROCEDURE FOR JUMP STARTING
First off, jumper leads do not need to made with huge cables. 6B&S ( 13.5mm2 ) is the most convenient cable size but cabling as thin as 8B&S ( 7.8mm2 ) will easily jump start a vehicle with a flat battery.
Also, you do NOT need suppression type jumper leads. These are nothing more than a salesman’s con job.
Whether the crippled vehicle’s battery is flat or faulty, it will still hold a surface charge, even if that is for just a few minutes. When jump starting a vehicle, you don’t need it to hold that surface charge for more than a few seconds.
The correct procedure for jump starting a vehicle is as follows.
Bring the donor vehicle as close as practical to the crippled vehicle.
Leave the motor running in the donor vehicle at all times.
If you turn the motor off in the donor vehicle and connect the jumper leads, while you will not flatten the donor vehicle's battery, you can cause a sufficient drop in the voltage of the donor vehicle’s battery that the motor can not be started without disconnecting one of the leads.
Make sure the PARK BRAKE is applied in both vehicles.
Turn the ignition off and remove the kew from the ignition of the crippled vehicle. This is not done to protect the vehicle’s electronics, this is done to remove any remaining current draw from the crippled vehicle’s battery.
Many vehicles can draw quite high currents with the ignition key still in the switch ( up to 40 amps ).
Note, in many new vehicle, not until you remove the ignition key will all current loads be turned off and in some vehicle, like new Land Rovers, the computers will remain active for up to 3 minutes, while they go through shut-down routines, after the key is removed.
With Keyless Entry type vehicles, make sure the vehicle’s ignition is off and take the key away from the vehicle.
Next, connect the positive lead to the crippled vehicle’s positive ( + ) battery terminal, then connect the other end of the positive lead to the donor vehicle’s positive ( + ) battery terminal.
The POSITIVE Lead is connected first as a safety precaution. If your to drop the Positive lead while trying to connect it to the donor vehicle, you will nor cause a short.
If you were to connect the NEGATIVE Lead first and dropped the POSITIVE lead as you were trying to connect to the donor vehicle’s battery, if this lead can in contact with any metal parts on the donor vehicle, there could be a considerable short.
Next, connect one end of negative lead to the donor vehicle battery’s negative ( - ) terminal.
You MUST NOT connect to the crippled vehicle battery's negative ( - ) terminal.
This again is for safety reasons. If you have been cranking the motor trying to start is with a flat battery, or if the battery dropped a cell while you were driving and you stopped the motor, say to fuel up and then went to try to start the motor again.
In these situations, the battery will most likely have been gassing. When you connect up the last lead, it will complete the circuit and can regularly cause a spark as you make the last contact.
If you connected to the crippled vehicle’s negative ( - ) terminal on the battery, there is a chance you could ignite the gas coming from the battery, causing the battery to explode.
PLEASE NOTE, if a battery does explode, it will NOT vaporise the vehicle, it will simply spray electrolyte around the engine bay, and a quick wash down with a hose will remove the electrolyte.
The danger posed if you connect to the cranking battery’s negative terminal is that if the contact causes a spark and ignites the gas, you are more than likely going to be over the top of the battery at the time and could easily end up with a face full of acid ( electrolyte ).
By making the last connection somewhere other than at the battery, while it far less likely to ignite gasses at the battery, if it does cause the battery to explode, you are in a much safer position.
Now find a suitable earthing point in the crippled vehicle’s engine bay ( if the cranking battery is located there ). This earthing point should be a bolt on the motor or something of that nature.
Do not use any body parts as the earthing point, because they are usually not thick enough to carry the startup current load.
With all connection made, leave the vehicles connected with the donor vehicle’s motor running at a high idle, for at least 2 minutes.
Once some time has elapsed, try starting the crippled vehicles motor.
If it does not start straightaway, turn the crippled vehicle’s ignition switch off and remove the key and give the crippled battery more charging time.
If the motor starts, remove the negative lead from both vehicles first, then remove the positive lead.
DO NOT switch the crippled vehicle’s motor off to test the crippled vehicles battery. If you are in the middle of nowhere and your motor is now running, don’t tempt fate.
