Surely on more than one occasion you would like check the condition of the 12V car battery and know if the alternator is charging correctly so that we don't get left behind. And it is that, when the car does not start, we always think that the problem comes from the same place, from the battery. Even more so when we have changed it a few years ago. Let's face it, we all feel really bad leaving the house, getting in the car and not being able to start it.
But before stating that "we have run out of battery", we must make some checks. We can be almost sure, but be careful, we can also get a surprise. The battery may have run down, but what if the problem comes from the alternator or some other electrical system? In this article we explain how to check the condition of the battery and if the alternator is doing its job correctly.
Video tutorial to check car battery and alternator
In this video you will be able to see how check if your car battery is bad state or can still be tapped. In addition, we also talk about how to check if the Alternator charge it properly. You would be neither the first nor the last, who changes the battery when the problem is elsewhere.
Symptoms to know if the 12V battery is worn out
Cars of a certain age
Before it doesn't start from one day to the next, the car's 12-volt battery usually gives some signs that it is worn. It is not completely exhausted, but you can see a fainting. The main symptom is that it takes a few seconds longer to start the heat engine, and a somewhat lower speed can also be seen when moving the starter motor.
On the other hand, and although it depends on each model, it can be noticed that during startup the lights on the instrument panel have changes in intensity. That means the battery is very, very tight on charge. Likewise, in some cars strange movements are noticed in the speed and rev counter needles.
modern cars
These are some clear symptoms, but the negative side is that in newer cars they are not so pronounced. Especially in diesel cars and high displacement. One day you take the car in the morning and at first glance it starts normally. The next day, and without us having left any consumer on by mistake, it practically does not have the strength to move the starter motor slowly.
Check the alternator with a multimeter
We are going to start by checking the alternator because it should be done before checking the battery itself. It is much faster and it is better to rule out this problem beforehand. you will need a multimeter and the steps to follow are:
- start the engine and let the car idle for two or three minutes.
- Configure the multimeter: choose the mode voltmeter (V) and direct current and in the measurement range of 20 V (in some multimeter it will be 30 V, 40 V, etc).
- Place the test lead black of the multimeter in contact with the negative terminal of the battery and the red in the positive.
- The multimeter should read between 13,5V and 14,5V about. If the multimeter shows less than this value, it means that the alternator is not capable of charging the battery, so it is necessary to check it and replace it with a new one if necessary. If, with the engine idling, we measure more than 15 volts between the terminals, the alternator may not be working properly either. It is likely that the alternator regulator has been spoiled.
The voltage must be constant even with the lights on and accelerating the car to about 3.000 rpm. In the event that the voltage fluctuates a lot and is not constant, the problem can also be located in the alternator voltage regulator. In this case we must also check the alternator and replace it if necessary.
If can't load it properly, would break again again shortly after change battery.
Check the battery with a multimeter
The next step is to check the battery. In the workshops they usually have some machines quite precise to check if it is healthy, if it needs a slow charge or if it has to be changed directly. As individuals do not have this device, the solution is a multimeter, which can also help us to get a good idea of its status. The steps to follow are:
- Drive the car for about 45 minutes at 2.000 or 2.500 rpm. A trip that we have to do by road or highway will do. That is why we have checked the alternator before, because if it does not work, it does not matter how many laps we give the car, it will not charge it well.
- discharge the battery a little turning on the lights for a minute or two with the engine off.
- Open the hood and close the car, so that everything turns off. Otherwise the various current consumers would disturb the measurement.
- Act quickly. set up the multimeter in the same way as when checking the alternator (previous section).
- Put the black lead of the multimeter on the negative terminal and the red one on the positive (as in the image).
- The voltage shown by the battery between 12V and 13V will indicate the battery salute. More of 12,7 V is that the battery is very good. 12,5 V that already shows some sign of deterioration and when it reaches the 12,2V or 12,3V it is better to change it.
Quick visual battery check
Of course, do not forget to take a good look with a first visual check of the battery. Wearing appropriate gloves and always avoiding contact of the car battery with clothing or skin itself, we take a look. Above all, check that the terminals are not sulfated and make sure that you do not leak acid anywhere. Obviously, it should not present bumps or deformations either.
What if the problem is not with the battery or the alternator?
You can also use the multimeter to check if the problem is in the car's electrical system. Sometimes a battery discharges prematurely because the vehicle has abnormal electrical consumption when it is parked. This can occur due to deteriorated or poorly installed components and equipment. In the following video you can see how they are easily checked with a multimeter:
Check car battery amps
Many people make the mistake of trying to measure amps with a multimeter. It must be taken into account that in the starting phase, the intensity is very high. Therefore, it is most likely that this intensity blows the fuse of our multimeter, rendering it inoperative. It is not a device designed to measure such high intensities. At a particular level, it is best not to check the amps, but the volts.
Greetings. The topic and the responses they give to the news are good. My question is that I have problems with the battery charge. I made some adjustments but it does not load. I want to see if you can send me a diagram of the connection between the battery, the starter motor and the rest of the devices. I already bought a new battery but I have no charge. The problem is that I had the alternator checked and a technician told me that it was fine. here I want to see if they help me to solve my problem. Thanks a lot. Greetings from Quito, Ecuador.
To check the battery you only need a multimeter, try with the car off, and then with the car on. With the car on, it should give you a higher value.
If you have the alternator outside the car or you have bought a second-hand one and you want to check it, you can do it with a battery and a light bulb.
good .. I have a problem, I was with the vehicle stopped for 5 months due to battery ... when I put it on, a battery signal appeared and the engine was on and I couldn't get the vehicle to turn on ... what could be happening??????
it is a synchronous car