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Low car battery: here's what to do and how to get going again


What is the car battery and what is it for?

The car battery is a device for storing electrical energy through a chemical reaction. The part visible from the outside is in fact a container filled with electrolytic liquid, usually sulphuric acid, in which two electrodes, one positive and one negative, are immersed.

The main function of the car battery is to start the starter motor with a short but strong electrical discharge. In fact, it takes less than 3% of the battery's capacity to start the starter motor. When the starter motor starts to run, the crankshaft starts to rotate and then the engine keeps running burning fuel. We can therefore think of the starter motor as the match with which we light the coal that then lights the chimney.


The car battery then has the secondary function of assisting the alternator when the vehicle's power needs exceed those of the engine. Normally, when the engine is running, the vehicle's electrical functions are powered by the alternator and the battery is recharged. However, if many instruments are switched on while the car is stationary, for example, the air conditioning and stereo in summer, some of the electricity is supplied by the battery.

Therefore, without a good battery it will be impossible to start the car or use various electronic functions when the engine is switched off. In a modern car with a dead battery you will hardly get far.

What are the symptoms of a dead battery?

As mentioned before, a flat car battery is a common problem for all drivers. Let's take a look at what the main symptoms of a flat car battery are:


  • One of the most common symptoms is that the car starts, almost always because we forget the headlights. This problem in modern cars is avoided by means of audio-visual alerts that, as soon as we take out the key, warn us that the headlights are still on. However, a machine that won't start could be a symptom of other faults, such as a faulty starter motor. In any case, if we are used to forgetting to keep the headlights on, sooner or later the car's battery will run down.
  • The car takes longer than usual to start: if we have to keep the key turned longer than necessary or if we feel that the starter motor is idling, we may have a dead or damaged battery. In this case, even if the car can start, it is advisable to have the battery checked to avoid being stranded next time.
  • The battery/alternator light has come on - if the yellow battery light (square with + and -) appears on the dashboard, the control unit is warning us that we have a self-discharged battery or an abnormal state and therefore it is advisable to have it checked by a mechanic.

Self-discharged battery is such a common problem that there are many symptoms that indicate its presence. We have written an article on the 9 definitive symptoms of a low battery.

How to understand if it's time to change your car battery?

If we've had to recharge an empty car battery more than once and it keeps leaving us stranded, it may be time to change it.


Generally, a new car battery, used consistently and correctly, should not give problems before 4 or 5 years. If it gives problems from the first year, there may be a factory fault in the battery itself or in the alternator. It may be that you have obtained a faulty part from the factory and in this case it is covered by the manufacturer's 24 month warranty.

In general, to avoid being stranded, the lamp/alternator battery will light up to alert you to the problem and almost always to the presence of a self-discharged battery.

What to do if the car won't start because of a dead battery?

If the car won't start and we are afraid that the problem is the car's low battery, we have three (obvious) options:

  • Replace it with a new, already charged battery, purchased from an electrician or auto shop;
  • Recharge thebattery with a wall charger or cables and another working car (the procedure is explained below).
  • Start thecar by "pushing" it by getting passengers or some kind of bystander to help (read on to find out how).

How do you start the push car?

Here's how to start a push car with a low battery:

  1. Put it insecond gear and push the clutch all the way in;
  2. Turn thekey and start the engine (if the battery is dead, it may not start, just turn the key);
  3. Get someone to push you or push it downhill if you're going downhill;
  4. As soon as the car has turned over a little, release the clutch and press the accelerator.

The car should start because we have replaced the starter motor with "human" push power.


Unless you've been having fun testing the push ignition, the first place you'll need to go is to the electrostatic to change the battery or charge it properly. In this context, thinking that the self-discharged battery can be recharged with a twist is just wrong.

How to jump start a car with cables?

Almost all cars come with a set of cables for emergency battery charging. They are usually placed near the spare wheel under the trunk.

The procedure is simple but must be done with extreme caution so as not to damage the batteries of both cars or hurt yourself, there is a risk of explosion if things are not done correctly. Let's see how.

  1. Bring the two cars as close together as possible without them touching;
  2. Switch off all electrical consumers in both cars.
  3. Locate the batteries and remove the pole covers.
  4. Connect the first clamp of the red cable to the positive (+) pole of the discharged battery.
  5. Connect the second red cable clamp to the positive (+) pole of the charged battery.
  6. Connect the first black clamp to the negative (-) terminal of the charged battery.
  7. Connect the second black clamp to an exposed metal part of the chassis, or to the body of the vehicle with the discharged battery (DO NOT connect to the negative terminal of the discharged battery as sparks may fly).
  8. Start and run the engine of the rescue vehicle for 5 minutes (with all electrical consumers switched off, except the 4 arrows if it is stopped in a dangerous place).
  9. Now start the engine of the car with the low battery. Leave them on for a few more minutes.
  10. Unhook the cables in the reverse order in which you mounted them with the battery.

Once you have done this, we strongly recommend that you go and buy a new battery or take your car to an electrician to check the condition of the battery. It may need to be replaced if it is too worn. Our advice is to always replace your car battery if you have had to jump start your car.

Why won't the car battery charge?

A car breakdown, a change or recharge of a flat car battery and the problem occurs again after a few days? The problem is that the alternator is not charging the battery correctly.

If the alternator is damaged, the electric current may be transmitted at a voltage lower or higher than required by the battery, undercharging it or damaging it permanently.

In this case there will be no choice but to take the car to the garage to have the alternator replaced. Since it is not subject to a lot of wear and tear, you can usually choose to have a regenerated one fitted and save on labour, as well as making a nice gesture to the environment.

How much does it cost to replace a car battery?

The price of a car battery depends not only on the brand, but also on its starting point and its capacity (measured in Ah Amps). Typically prices range between 45 and 160 euros.

Another factor to consider when judging the price of a battery is the size of the car it will be fitted to. Obviously, a two-tonne SUV will need a larger, and therefore more expensive, battery to start its engine than a small city car, which will need a slightly larger battery than a scooter. Size counts in this context, but to its disadvantage.

With a flat car battery there is little to do and if you can't recharge it due to overly worn conditions, then you need to buy a new one.

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