Carole Nash
Content Writer
Published: 7th February 2020
author

Jump starting a car may not be something that every car owner has had to do, but it’s certainly a concept that most of us are familiar with: Your car won’t start so you get another one that will, connect the jump leads to your engine, start it up and off you go right?

Well, we read a story in the Telegraph recently that might make you rethink grabbing the jump leads – especially if your car happens to be classic.

A guy’s Aston Martin DB7 had a flat battery a day after a 200-mile run. Luckily he had a BMW 730i on hand to jump start to the Aston. However, after connecting the jump leads to both batteries, and starting both cars, an almighty fire broke out.

So what went wrong?

After a frantic call to the RAC and a thorough assessment of the situation, it was revealed that the jump leads had been connected correctly. But the problem was something else.

The aluminium cores on the leads could not handle the amps generated by a modern alternator. And the Aston’s battery was too flat to cope with the huge charge-up generated by the BMW, which had (rightly so) detected a flat battery and was firing out the amps to charge it up.

Both prized cars could have quite literally gone up entirely in smoke. Luckily both cars survived and could be repaired, but it’s a story worth considering next time your classic car has a flat battery.

Advice on jump starting a classic car safely

  • Check the condition of the jump leads and both batteries for signs of rust, corrosion or damage. If any of these are present don’t attempt a jump start as you could hurt yourself or damage either one of the cars.
  • Connect everything without the cars started and allow the battery to acclimatise.
  • If you are trying to jump start an old, classic car, be very careful that you are dealing with the same wiring polarities, as many of them have positive earths.
  • Run the engine of the working car and switch off after 10 minutes. Then disconnect the leads and try to start the car with the poor battery to avoid overloading it.
  • It’s always worth checking a cars voltage before you attempt to jump start as the vehicle must be started with a battery with the same voltage.