How to test a car battery: simple step-by-step guide

how to test a car battery (1)

Simple steps for how to test a car battery, and how to test a car battery with a multimeter, plus ways to start if the charge is low.

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Winter is the natural enemy of your car battery. Cold and moisture are really tough on her. In addition, your heating usually runs at full throttle, you drive with lights on and maybe you even have the heated seats on. This puts a lot of strain on your battery and can sometimes give up the ghost – especially if it is a bit older. How do you know if your battery just needs to be charged or if it blesses the temporal? We tell you how to test a car battery in several ways.

Signs of a defective car battery

Even a layperson can recognize a weak battery in good time because there are some signs. While driving, pay attention to whether you recognize any of these typical symptoms:

  • The engine does not start immediately when it is started, but rotates a little longer
  • The car radio and other electrical consumers have a few dropouts after a cold start

These are all typical signs of a weak battery. After a few minutes of driving, the problems usually go away as the battery recharges. You think everything is all right now? Unfortunately it is false! The problems are only getting worse every day. You should take the steps for how to test battery power.

Simple battery test with a wall

First, we’ll tell you the simplest trick to test whether your battery is giving up: Park your car in the dark in front of a wall. Then turn on the low beam and turn off the engine. Now it’s time to observe: does the light get weaker after a short time? Then the battery is weak! However, this simple test is not accurate and is more of a rough indicator. Even if you notice that the engine is struggling to start when you start the engine, it is most likely time for a new battery.

How to test a car battery with a multimeter

With a multimeter, the state of charge of the car battery can examine more closely. However, if possible, the test should not be carried out immediately after a long journey. Then the battery is usually well charged. However, it is important that the state of charge is maintained over a longer period of time. Therefore it is better to connect the measuring device to the battery after a few hours of rest. 

The red cable goes to the positive pole, the black to the negative pole. The battery is in good condition when the voltage is between 12.4 and 12.7 volts. If the measured value stays below 12 volts, the battery should be charged or replaced.

Steps for how to test a car battery with a multimeter

Step 1: expose the car battery

First of all, the car battery must be exposed. As a rule, this is installed in the engine compartment in the front part of the car and can be reached by opening the bonnet. In some vehicle models, for example those of the brands BMW and Volvo, the battery can also be installed in the rear of the car and accessible by opening a service flap.

Once the car battery has been located and made accessible, both poles (positive pole and negative pole) must be exposed . Depending on the vehicle model, it may be necessary to unscrew a plastic panel attached to protect the poles. If both poles are freely accessible, the actual measurement of the car battery can begin with the multimeter.

Step 2: set up the multimeter

Before the test leads of the multimeter are brought into contact with the battery, the multimeter must be set correctly. Since the voltage (volts) of the battery is to be measured, the corresponding measuring function must be selected. The multimeter must be set to direct current (DC) and a measuring range in which 12 volts can be displayed with the measuring range selector switch . If a measuring range that is too low is selected, the device will display an infinite value. If a measuring range that is too high is selected, no correct result can be read.

Step 3: Apply test leads to the battery

If the multimeter is configured correctly, the two test leads can be connected to the poles of the battery. The test cables must be in the correct socket on the multimeter: the red cable in the “V / Ohm” socket and the black cable in the “COM” socket . Both test cables must always be applied to the measuring device first and then to the object to be measured. Now you can connect the red cable of the multimeter with the positive pole of the battery and the black cable with the negative pole of the battery.

Step 4: Read and interpret measurement data

Once the connection between the multimeter and the battery has been established, the voltage is shown on the display of the measuring device. This should be over 12 volts. If the voltage is below this value, the battery must be recharged or this is an indication that the battery is no longer fully functional. Since there is a possibility that the car will not start as a result, the battery should be completely replaced.

Regular maintenance of the battery

As a constant source of electricity, the battery is the lifeblood of every car. Accordingly, she is often responsible for vehicle breakdowns. But that doesn’t have to be the case: with annual maintenance and timely replacement, a lot of trouble can be avoided. When choosing a replacement battery, you should always refer to the vehicle’s operating instructions. There it is usually noted that only a certain type of battery may be used.

A car battery lasts five years

A professionally installed car battery has a service life of around four to five years ( ADAC). It is particularly stressed during the cold season. Just then the required starter a powerful battery, to overcome the friction in the engine and to start the engine easily. Later when driving, the various heaters for the front and rear windows, seats, exterior mirrors, the fully turned on ventilation and the lights need a lot of electricity.

Hard times for the car battery

Most of our cars are not yet electric, but they are already heavily electrified. There are many power consumers in the car, the car battery, or rather, the battery, and while driving the alternator must supply. Since the headlights, heated rear window, heated seats, sound system and more, some options, such as a wireless door lock, draw power permanently. All of these are consumers that suck on the capacity of the battery. 

Tips when the battery is low

They are the number 1 cause of breakdowns. Starting problems are particularly common at the beginning of winter. The usable capacity of the car battery, also known as the starter battery, decreases with the temperature. The exposure to the cold is high. Even below freezing temperatures, the capacity is reduced to a little more than half. In the end, the battery will no longer be able to start the engine. So that this doesn’t happen and you always stay ready to go, we offer some tips as first aid for weak batteries.

Use a charger

If you always pay attention to a fully charged battery, you can prevent failures. We recommend purchasing a battery charger for your home socket. Good devices can be had for less than $100. And many devices are very powerful, for example, they can automatically switch from charging power to trickle charging, display defective batteries and even cause desulphation of older batteries. This can save the performance of the car batteries and they stay fit for years. Well-maintained batteries can last for over 5 years and sometimes even 7 years.

The easy start

So that all energy is available for the start available and the battery is spared all unnecessary consumers how should lighting , radio, navigation, fan , rear window defroster, etc. off. If a start attempt remains unsuccessful, please cancel it after ten seconds at the most, then pause for about half a minute and then try again. A clean battery housing is particularly important in winter in order to avoid leakage currents.

This is how a jumpstart works

Whom it should happen that the car does not start, you can get a jumpstart from another vehicle. Prerequisite: Both batteries must have the same voltage and jump start cables must be available. The engine of the car providing the current should be running during jump start, possibly at a higher speed. The following sequence should be observed when connecting the jump leads. 

  1. The clamp of the red cable to the positive pole (+) of the discharged car battery.
  2. The other end of the red cable to the positive terminal of the battery providing the power.
  3. The black cable to the negative pole (-) of the battery supplying the current.
  4. Connect the other end of the black cable to the engine or body ground and not to the negative terminal of the discharged battery.
  5. After starting help, disconnect the cables in reverse order.

After that, we recommend a longer journey to recharge the battery.

Get a regular checkup if problems persits

Check the car battery regularly at a qualified auto repair shop. Since the car battery is connected to other electrical vehicle components, when changing the battery, special tools and special skills are required. An interruption in the circuit between the battery and the vehicle computer can result in a loss of data in the vehicle control units and infotainment systems. Reprogramming of electronic components such as radios and power windows may be required.

Causes of Battery Failure

Extreme temperatures

In summer, high temperatures under the hood can also cause the car battery to lose its starting power. Unfortunately, the problem is often only recognized when it is too late. Next you can do things to avoid starting problems:  Park  your car if possible,  not in the sun.  

Irregular vehicle use

Many drivers think that the battery does not have to provide energy when the engine is switched off. But that’s not true. Systems such as alarm systems, door locks, keyless go functions and navigation systems also require energy when the car is parked. This contributes to the discharge of the battery. After your car has been idle in the garage for several weeks, the battery may not have enough power to start the engine. This problem is more common in cold weather and with older batteries. By driving your car  for at least 10 minutes once a week, you can avoid starting problems.

Short trips

If you drive only short distances, the alternator perhaps does not fully charge the battery. In winter, power-hungry consumers, such as the heated rear window and heated seats, further discharge the car battery. Take your car  for longer trips once a month to fully recharge the battery.

Vehicle age

As the vehicle ages, battery performance decreases as corrosion and sulfation prevent full charging. Motorists should their battery  checked regularly  can to ensure a proper charge level and high performance.