If your car battery has ever gone flat and you didn’t know how to restart it, here’s what to do, with or without cables, and how to recognise the warning signs
A flat battery is a problem that all drivers will probably face at some point: it is possible that the battery, which powers the car’s entire electrics, could reach the end of its useful life all of a sudden and needs to be replaced. So what do you do when your car battery is flat and what are the signs that it might be about to happen?
Often, we only realise that our car battery is flat when it’s too late: we go to start the car and there are no signs of life. In some cases, the dashboard might light up but the engine will not start, but it is also common for the key to not even switch on the typical warning lights – this happens when the battery suddenly stops working without any signs that it is reaching the end of its useful life.
It is also possible that the car will not start when it has been stationary in the sun for too long because the excessive heat can stick the starter motor. This should not be confused with a flat battery but it can resolved by loosening the motor by tapping it to then restart the car. In principle, the warning signs of a flat battery can be problems starting the car, dim lights, sounds similar to crackling in the silencer and the battery warning light turning on, all of which should be dealt with before they cause the car to break down.
If the car battery gives off signals such as those described above, the best solution is to head to the nearest garage and have the battery replaced. It is a different matter when the car will not start: unless you contact an auto electrician that can come to you and replace the battery, the only options are to push start it or connect it to another car with cables. The latter option is preferable because push starting it can cause damage, especially with cars with a catalytic converter.
If you have cables available, simply position the two cars in such a way that it is easy to connect the two batteries, connect the red cable to the positive terminals and the black cable to the negative terminals and recharge the car. After a few minutes, you should be able to start the car and continue charging for around ten minutes. At that point, you can firstly disconnect the black cable and then the red, leaving the engine running for around half an hour and avoiding turning on accessories that could use up electricity.
If you do not have any cables available, the only possible solution is to push start the car, which you can do by inserting the key and turning it on to switch on the electrics. In second or third gear and with the clutch depressed, the car should be pushed to a certain speed, then the clutch can be released once the engine has started.
Even in this case, it is best to leave the car on for at least half an hour so the battery can recharge itself.
If the car does not start after following the advice above or if that cannot be done safely, we recommend contacting roadside assistance. If you are driving a hire car, the contract usually includes free roadside assistance available 24 hours a day, which will solve any problems you have as quickly as possible.
Here are some tips on how to avoid a flat car battery, whether your car is diesel or petrol. The first useful tip is to monitor the age of the battery as batteries last approximately three years on average but sometimes better batteries can last more than five years. However, beyond a certain threshold it would be best to have the battery checked periodically by an auto electrician.
Especially if there are signs of trouble when starting the car or other minor problems during startup, it is always advisable to have the problem checked and replace the battery in good time, which could cost between €50 and €100.