So you are running out the door in the morning figuring that you have left early enough that you'll make it to work just in time. As you jumping into the driver's seat you wonder if your wipers will be enough to move the thin layer of frosty ice on the windscreen. Unfortunately you don't get the chance to find this out because when you turn on the car you get barely more than half a crank out of the engine, then nothing. This wintertime scenario is all too frequently played out at the most inconvenient times - the car's battery is dead flat!
Of course there are several possible reasons for this. Leaving the head lights or an interior light on will do it. Or if the the battery is old and ailing then a spot of cold weather make the engine just that little bit harder to start and the electrical current required is more than the battery has to give. Whatever the reason, the net effect is the same - you are going nowhere in a hurry!
Your options are:
make that call for roadside assistance but depending on how many others are in the same predicament on this chilly morning, you could be waiting a while.
start considering public transport options (heaven forbid!).
luckily before option 2 becomes a reality, the bloke across the street realising your dilemma wanders across and offers to help. He says has a set of jumper leads somewhere in the boot but has never had to use them. You gratefully accept - crisis averted.
However there are important steps to follow when jump starting a vehicle with a dead battery.
Manoeuvre the two vehicles into such a position that the batteries can be connected with the jumper leads. Ensure that the vehicles are not touching, both are turned off and out of gear.
Inspect the jumper leads . If they haven't been used in a while and have been sitting in a puddle of water in the boot, important connecting surfaces may be rusty. The clamps and cable connections need to be in good condition for the operation to be successful. Only use jumper leads with a built in surge protector (that's the little box attached to the cables) . This will help protect the modern motor vehicle's delicate electronic systems from being fried as you attempt to get mobile. Burnt out computer modules can be very expensive to replace - a lot more than an AA membership or the cost of getting a taxi to work!
Now here's the critical bit. What do you hook up the leads up to and in what order?
Connect one end of the red (positive) jumper lead to the positive terminal on the dead battery.
Then connect the other red (positive) lead clamp to the positive terminal of the good battery.
Connect one end of the black (negative) jumper lead to the negative terminal of the good battery.
Then connect the other black (negative) lead to a clean, unpainted metal surface under the disabled car’s bonnet. This is harder said than done with all the plastic covers used in the engine bays of modern cars but somewhere on the engine block is a good place. Unless you want to see flying sparks and a possible explosion, do not connect the negative cable to the negative terminal of the dead battery!
Start the donor car (the one that’s doing the jumping), and allow it to run for about 2 to 3 minutes before attempting to start the dead car.
All going well the dead car will fire into life and you will still make that 8.30 meeting. It is important to remove the leads in the reverse order.
Keep the jumped car running for at least 30 minutes to give the battery sufficient time to recharge itself. Even this may not be enough to fully recharge the battery. A car battery that was previously in good condition may need a decent long run on the open road without other drains (headlights, aircon etc) being placed on it to get back to a fully charged state.
Of course if there is not a blindingly obvious reason for the battery going flat i.e. lights left on, then it may be nearing the end of its useful life. Unless you want to replay this event tomorrow morning it is advisable to get it checked and recharged or replaced by a professional.