There are times when the battery discharges itself and we don't know why. The car hasn't been sitting for long, we didn't leave anything on, it's not an old battery and yet the car won't start. The problem that may be behind it are the known current leaks or parasitic or abnormal consumption battery.
Here we are not the ones who have abused electrical consumers with the engine off. Nor is it that we constantly start and stop the car, without letting the battery get charged. It is that some component of the car continues to consume energy with the car stopped and closed.
When this happens, the car battery discharges unexpectedly quickly. It is a common breakdown in vehicles that are older or in which the electrical system has been touched. For example: to place a new sound system, a Bluetooth hands-free, a universal central locking...
How to know if there are current leaks or parasitic consumption?
In the next video After 6 minutes, we explain each step in detail:
Or if you prefer, here are the steps in writing to locate current leaks:
- The first is locate the fuses. The most common is to find them in the engine compartment itself. But there may also be another fuse box on the left side of the dashboard, behind the glove box, or at the bottom of the center console.
- check that he has not stayed in the car nothing on that can alter the measurements: radio, lights, ignition on, open doors... Lock the car with the key so that it turns off completely. If we are going to look at fuses inside we will have to leave a door open, so we have to trick the car by pressing the door button to make it believe that it is closed. Even if the interior lights did not turn on, there could be a witness or on-board computer that consumes and deceives us in the measurements.
- Next, we must disconnect the negative terminal of the battery, (with the positive it is easier to cause a short circuit). For this we will need a small wrench, fixed or ratchet of the appropriate size. It is easy to have some of them at home.
- The next step is to get into the skin of an electrician. Us you will need a multimeter to detect current leakage. There are many prices but for 15 or 20 euros you already get a suitable one. In the measuring instrument we will place the black cable in the common port (COM) and the red one we will put it in the plug that allows the greatest intensity to be measured (Amps), normally identified with the inscription 10A, 20A, 30A ó 40A.
- Then we will put one of the measuring tips of the tester in contact with the cable that we have released. While the other will be placed on the battery terminal that we have left free. This is done this way, because to measure intensity it is necessary to do it in series. In other words: opening the circuit and interposing the multimeter to measure the intensity of the current that passes through it.
- At this point, the multimeter will already give us a measurement. A normal value of consumption with the car stopped, it should be around 0,05 A. If it shows a value greater than this, it means that there is some parasitic consumption draining your battery.
- The way to proceed below is simple. It's time to remove the fuses one by one to check whether the intensity value decreases. We put it and remove another. So with all until the ammeter shows a normal value or we see that the intensity drops (it could be that there were several current leaks).
- If when removing a fuse, consumption returns to a normal value (current leaks disappear), we have located the problem. It will suffice to consult which system corresponds to the fuse that we have removed, in the car manual.
Car battery consumption by alternator
What if we check all the fuses and we don't find the problem? In that case. it would be quite likely that what was eating dinner every night at the expense of our battery it was the alternator, due to a fault in the rectifier diodes. To check it, we will connect the battery terminals as they were before starting all the checks.
the best you can do first is to check if it is capable of charging the battery. This will completely rule out the possibility of it being an undercharging problem, rather than a battery discharge problem. Something that can be caused by the alternator itself or just its voltage regulator. In the article how to check the battery and the alternator you have everything.
Once this is ruled out, the steps are simple:
- configure the multimeter in Amps and DC
- The check consists of releasing the alternator terminal (which goes directly to the battery positive, red), to open the circuit and be able to put the multimeter in series. That is, a measurement point on the alternator terminal and another on the cable, so that the current passes through the multimeter.
- In this way, if we have a current leak greater than 0,5 A, it means that we will have to go through the workshop to repair or replace the alternator.
If you do not have time to follow these steps and you want an immediate solution, we will explain below how to start car with dead battery and what is its price if you finally decide to change it in case it is in poor condition.
Starting with a discharged battery due to current leakage
In case you have run out of battery and you have to start the car yes or yes, there are several options to achieve it. It will depend on the conditions you have at the moment.
Jump start a car with a dead battery
If you have some pliers and a good samaritan who will let you connect them to his car battery, you are in luck. This is the easiest and least damaging method for the different parts of the car. Just follow the steps in order:
- Park both cars with the engine compartment close without touching any part of its bodywork.
- Place the cars in such a way that the cables of the battery clamps reach the battery.
- Open both hoods. Normally your batteries will be covered with a cover, so discover both batteries.
- Once you have the cars ready, it's time to use the clamps. You should first connect the positive poles of both batteries. Take the red clips and hook them to the pole with the “+” symbol on each battery. First in the car that is loaded and then in the unloaded one.
- Put the black cable in the negative pole (“-”) of the car that has a charged battery.
- Start the car that will donate energy.
- Put the black cable in the negative pole (“-”) of the car with a discharged battery.
- Start the car of the discharged battery.
- Remove the tweezers:
- First, those of the negative pole. Start with the unloaded car and then remove it from the loaded one.
- Second, those of the positive pole in the same order. That is, first the unloaded car and then the loaded one.
- Recover the two batteries with their covers and close the two hoods.
Keep in mind that if your car has a discharged battery it will have to work for a while to load it again. If even doing this it does not start again, it means that the battery is not in good condition and must be replaced.
Start the car by pushing
If you don't have clamps or there is no other car to connect your battery to, you are left with the option of start the car by pushing. It is less advisable because the catalytic converter or some part of the engine can be damaged, although we have tried it and have not had any problems. you will have to be at least two people to do it comfortably. Follow these steps:
- The person behind the wheel must leave the ignition key turned to the on position.
- You should also depress the clutch and put second. leave the clutch depressed
- The outside person or persons must push the car
- When you reach enough speed you should release the clutch and accelerate a little.
- Once turned on, do not turn it off because your battery is still discharged. It will only charge after driving for a while.
Nota: You have to take into account that in diesel engines it is more difficult because they work with a higher fuel compression ratio and you have to exert more force to reach that point by pushing the car. It will be of great help to put the car downhill, but always keeping safety in mind, since with the car off the brakes will not work properly.
Starting the car downhill with a dead battery
The steps to start the car downhill are the same as pushing, but you have to take into account a couple of things so as not to take any risks. The slope will do the work of people pushing, but don't forget that If the car won't start, the brakes won't work right. (something not recommended if you go downhill). Normally, when the car is off, there is brake fluid left in the circuit that connects the pedal to the brake calipers, so you will have one or two stops before it empties, the pedal becomes hard and you can no longer brake.
For us the most important thing is road safety, so we advise against using this method except in highly controlled environments. That is to say, a private space, where no one passes and there is enough flat area after the slope. It is better to call a friend with a car and pliers or a tow truck. The most normal thing is that your insurance includes this type of assistance. We repeat the steps adapted to this method:
- Leave her ignition key turned on.
- Step on the clutch and put second. leave the clutch depressed
- Take off the parking brake for the car to go down the slope
- When you reach enough speed you should release the clutch and accelerate a little.
- Once turned on, do not turn it off because your battery is still discharged. It will only charge after driving for a while.
How to charge a dead battery
The fact that your car battery has been discharged does not mean that it has to be replaced directly. It may be the result of leaving the lights on all night or, as detailed at the beginning of this article, having abnormal electrical consumption with the car off. If your case is any of these, start the car with pliers (or one of the other methods) and circulate for a while to charge it.
To be sure, the best way is circulate at constant revolutions for a quarter of an hour. For example, take a ride on the road or highway 2.000 rpm or more would be fine. Another option to charge it without having to start the car is to use an external battery charger. You can buy one for little money.
If after doing this, the battery still has no power to start the car, it means that it is no longer in good condition and needs to be replaced. In some cases, liquids can also be refilled, but there are batteries cheap enough to avoid this method, such as the ones we show you in this buying guide to choose from best car battery charger.
price of a car battery
The price of a car battery varies a lot depending on the type we need. From the battery needed for a small car that can be from 50 euros to 250 euros or more for large displacement cars. It also affects its price, if it is intended for a car with Start / Stop system. If so, you will need a higher capacity battery, to be able to start at each traffic light where the car stops. We recommend the article What battery do I put in my car?, to choose the most suitable for your model.
The fact that the engine is diesel can also affect the price of the battery, since by requiring more force to start you need a battery with more capacity. We recommend that you call and compare prices between workshops so as not to pay more than the bill. It won't take you more than a few minutes.
How to change a battery damaged by current leaks
If your battery has had abnormal electrical consumption for a long time, the most common thing is that it ends up deteriorating. We recommend the article How to check car battery and alternator, to make sure that the time has come.
If it is indeed time to change it and you want to do it yourself, it is one of the easiest operations in most models. You just have to take into account the security measures and, if necessary, how to maintain the car's memories. Take a look at the article How to change the car battery.
