How to check the charge of a car battery with a multimeter

We check the car battery using a multimeter correctly

Sometimes in winter, car enthusiasts have problems starting their cars. This occurs due to the bad influence of negative temperatures on the liquid poured into the battery (electrolyte). To avoid troubles, you have to monitor the battery capacity at certain intervals. Let's look at how to check a car battery with a multimeter.

Methods for checking battery charge

There are several ways to check battery charge. Some can be done using devices specially designed for this purpose. And some batteries even have such a device built into them.

Existing ways to measure battery charge:

checking using a special indicator built into the car battery;
use of a “load fork”;
measurement with a conventional multimeter.

How to determine voltage using the built-in indicator

Modern cars are already equipped with built-in indicators that can help the car owner find out at any time about the current state of charge.

For the first time, such batteries came off the assembly lines of Japanese automakers. A special “green window”, which is an indicator, helps determine the degree of charging.

Its other name is hydrometer. The color of the window depends on the degree of charge:

green – charged;
gray or white – capacity is lost;
black – the battery is completely discharged, the electrolyte level is below critical.

If the car has a battery with an indicator, then there is no point in measuring the charge with a multimeter or a “load plug”.

It is worth noting that batteries of this type are not cheap. In some cases the price increases by about a third. Not every car enthusiast is willing to overpay for such a battery.

Then other methods for measuring battery charge will be suitable.

Checking voltage with a load fork

The load fork is considered a slightly outdated tool today. You can meet it more often at service stations than at private car owners. Nevertheless, such a check turns out to be the most accurate and professional.

A load fork is a specific tool that allows you to accurately determine the level of battery malfunction. It combines a multimeter and a load resistor.

the device is connected to the battery terminals, and a short circuit current occurs. This is a kind of imitation of the operation of the starter. When there is no load, the battery produces 12.7 Volts, with a load - much less;
Next you need to read the instrument readings. They will show what level the charge will be at the moment the owner starts the car.

Another nuance that needs to be taken into account when measuring in this way: it is advisable to check the voltage at a battery temperature of 20-25 degrees and not do it very often. Otherwise, you may lose a large portion of the capacity.

This method is reliable and reliable. Its only disadvantage is that the load fork is practically not found in the average garage of the average car enthusiast. For such car owners, it is worth thinking about how to check the car battery voltage with a multimeter.

Measuring charge with a multimeter

A multimeter is a device capable of measuring amperage, voltage, resistance and temperature of technical devices.

These testers are used not only to measure the battery charge of cars. They can accurately determine the voltage in the battery of screwdrivers, laptops and phones.

For example, many IPHONE devices run on lithium-ion batteries, which are very convenient to test with electronic Japanese multimeters from Sanwa or Chinese DT-830b.

For modern car owners, this is almost an ideal option. The cost of such a device is quite reasonable. It is especially convenient to use those models that are equipped with electronic displays.

There will not be such accuracy as with the first and second verification methods. However, it is quite possible to measure the charge when necessary and navigate further actions.

How to measure the voltage step by step with a multimeter on a car battery:

It is necessary to connect the multimeter using the appropriate wires. The tester must operate in the “voltage” mode (voltage measurement). To do this, it is set to a level of 20 Volts.
Using special metal probes, which are located on the wires, the device is applied to the battery terminals (red probe - to the plus, black - to the minus). In rare cases, the wires are the same color.
Next, the measurement data should appear on the electronic display.

For the convenience of car enthusiasts, a special scale of values has been developed that helps determine the degree of charge of the battery using the tester data:

More than 12.7 Volts – the battery is fully charged.
If the values are in the range from 12.1 to 12.5 Volts, then the battery is half charged.
If values are less than 11.7 Volts, the battery is severely discharged.

Based on the presented parameters, we can conclude that voltage values on the device less than 12.7 Volts indicate that the battery is partially charged. In cases where the multimeter shows less than 11.7 Volts, the battery should be charged.

Any machine constantly experiences minimal current leakage (within 50-80 mA). In particular:

25-25mA is consumed for the security alarm;
the controller takes 5mA from the injection system;
The car radio consumes 3mA;
the dashboard with the central locking unit also takes part of the current.

As a result, everything together discharges the battery within 60mA. These costs are not critical for the battery and it can be used for several more years. Another thing is that if the consumption is more than 60-80 mA, the battery will quickly discharge.

Leakage current measurement technology

How to check a battery to determine current leakage using a tester:

The car is pre-prepared for inspection. To do this, the radio, dimensions, and lights in the car interior are turned off.
Next, an ammeter is connected to the broken circuit and the data is taken.
If the ammeter detects a leakage current, you need to remove and replace a number of fuses and relays one by one in strict order. This will allow you to understand in which circuit the leak is occurring. After this, the current should normalize.

In order to learn how to correctly determine current leakage using a tester, the following video is recommended:

Quick battery check

In some cases, car owners have absolutely no time to disconnect the battery from the car, as well as “digging” with the lighting and dashboard. Such car owners determine the battery charge level without removing it, right under the hood.

The process looks like this:

When the car freezes after turning off the engine, the multimeter is connected to the battery according to the scheme: plus to “+”, minus to “minus”, respectively. It is worth considering that the indicators will have minor deviations. 12.7 Volts is a normal indicator.
Then the car starts. When the motor starts, the voltage will rise to 14.7 Volts.
It is recommended to check it under load (external lighting, window heating, medium heater mode). In this case, the norm is 14.6 Volts.

Measuring the voltage of a car battery with a multimeter is a feasible task even for a novice car enthusiast. Not everyone can afford an expensive battery equipped with a special indicator.

A practical and universal option is to measure the battery charge with a multimeter. This device, with a talking prefix “MULTI”, allows you to measure not only voltage, but also current. In addition, the multimeter can be useful for other electrical equipment, including phones, laptops, and screwdrivers. Remember that it is better to purchase such a device from trusted manufacturers in specialized stores.

How to check a car battery?

Checking the battery charge level takes little time and does not require high qualifications or expensive equipment. The operation allows you to check the condition of the battery and the need for charging. This is the first thing to do if you have problems with the starter. Also, the ability to check the charge will be useful when buying a new battery or servicing an old battery. In this article we will look at three ways to diagnose a battery: using a multimeter, an indicator and a load plug.

In this article you will learn:

Why check the battery charge?
Ways to check the car battery for performance
Video instruction

Also at the end of the article you can watch an instructive video that gives useful tips for quickly and accurately checking the performance of the battery.

Why check the car battery charge?

Lead-acid batteries, which are used in cars with internal combustion engines, have low internal resistance. This allows them to deliver the hundreds of amperes of current required to operate the starter. However, this type of battery cannot be subjected to deep discharge. Otherwise, the plates become covered with a layer of lead sulfate and the battery suddenly loses capacity.

A fully charged battery produces a voltage above 12.6 V. As the charge level drops, this figure decreases:

Given the tendency to sulfate, it is undesirable to discharge lead-acid batteries to less than half the charge. Therefore, if the voltage at the terminals drops to 12 volts, you need to immediately charge the battery.

When purchasing a new device, you should not buy severely discharged batteries. It is possible that sulfation of the plates has already begun in them. Therefore, if there is no indicator on the battery, it is worth checking it with a multimeter or a load plug.

How to check the battery charge using the indicator?

Many maintenance-free batteries have charge indicators that allow you to visually determine the condition of the battery. This option first appeared on Japanese products and quickly gained popularity due to its convenience and accessibility.

The hydrometer, as the indicator is called, is a transparent window on the battery cover. The color of the window changes depending on the condition of the battery:

Green —full charge.
Gray or white - need to be charged.

For some indicators, the window turns red when capacity is lost.

The principle of operation of the device is based on changes in the density of the electrolyte at different charge levels. It works like this:

A tube with a green float is attached to the window.

When charging the battery, the density of the electrolyte increases and the float rises, approaching the window.
If the battery is discharged, the density drops and the ball sinks in the electrolyte. As a result, the indicator window changes color to gray or black.

Some indicator models have a red ball that floats up when the density of the electrolyte decreases. This provides a red indication of the discharge.

When the electrolyte level drops, not the ball, but the electrolyte itself will be visible through the window. To prevent the destruction of the plates, you need to add distilled water to the jars and charge the battery.

The advantage of the indicator is that the device allows you to determine the condition of the battery without the use of special instruments. This is convenient when purchasing a battery or in road conditions when you need to quickly check the condition of the battery. However, indication using a float does not always allow one to draw accurate conclusions about the performance of the battery. Therefore, when in doubt, you should use a multimeter or a load fork. They are also useful when you need to check a battery that is not equipped with an indicator.

How to check battery charge with a multimeter?

To check the voltage at the battery terminals you need a voltmeter. However, instead of these specialized devices, it is easier to use universal measuring devices - multimeters. In addition to voltage, they measure current and resistance. Depending on the indication method, these devices are divided into two categories - digital and pointer . If you have a choice, it is better to buy a digital multimeter. It is simpler and more convenient to use.

On-board computers of modern cars are also equipped with voltmeters that display the voltage at the battery terminals. However, they are not connected directly to the terminals. Therefore, due to contact and wiring resistance, the on-board computer readings may differ from the battery voltage. With the engine running, the voltmeter on the dashboard shows too much voltage. If the engine is turned off, the device will give low readings.

Readings must be taken with the engine running and switched off. In the first case, you will be able to check the condition of the battery and wiring, in the second - only the battery.

Measurements while the engine is running

Place the car on a level surface, open the hood, put the handbrake on and start it. When the engine is running, the generator and voltage regulator operate, which charge the battery. Therefore, the voltage at the terminals should be within 13.5-14 volts. In some cars, when the battery is discharged and the air temperature is low, the electronics automatically increases the voltage to speed up charging. In this case, it should fall smoothly as it charges. If this does not happen, the electrolysis process is activated in the banks. The electrolyte will begin to boil away rapidly. Overcharging is especially dangerous for modern gel batteries with limited gas emissions.

A voltage of less than 13.4 volts is a sign of undercharging. Operating in such conditions promotes sulfation of the plates and shortens battery life.

When measuring voltage, you need to turn off all powerful consumers: headlights, heater, audio system. Otherwise, the power of the generator when idling will not be enough to maintain the optimal voltage level.

There are several possible reasons for low voltage at the terminals:

Poor contact.
Generator failure.
Voltage regulator malfunction.

You cannot operate a machine whose battery is in undercharge mode. The cause of the failure must be immediately localized and eliminated. If the voltage at the terminals and the output of the generator is very different, you need to clean the contacts on the battery with sandpaper or a file.

After checking without load, you need to turn on the headlights and other powerful energy consumers, add engine speed and repeat the measurements. If at high speeds under load the voltage drops to 13.4 volts or lower, diagnostics of the generator system and control unit is required.

Diagnostics of the battery with a multimeter with the engine turned off

In this state, the normal voltage on the battery is 12.5-13 volts. Lower readings on the device indicate a discharge.

How to check battery charge with a multimeter. Let's find out the readings at home + VIDEO

Sometimes you need to check your car battery for charge. Well, for example, the car was parked for a long time, the terminal was thrown off , and the engine seemed to start - but it is not clear whether the battery needs to be recharged or not? After all, “undercharging” can play a cruel joke, the density of the electrolyte will drop and your battery may simply freeze . There are no charge sensors in the interior of a modern car, and therefore you will have to check with a multimeter - now there are simply a lot of them, and this will not necessarily be an expensive option. By the way, there will be a video version below, so read and watch...

THE CONTENT OF THE ARTICLE

There are not many ways to check the battery, two methods are using third-party devices, but the latter can be built into the battery itself. If I were to list them, they would be:

Built-in indicator
"Load fork"
Regular multimeter

Today I want to talk about all three types, but I would like to start with the “built-in indicator”.

"Green Window"

Some types of batteries have a built-in indicator , this invention came to us from Japan, after which most companies began installing it on maintenance-free types.

The essence is simple, on the right or left, it also happens that there is a small peephole in the middle, in which there is a slight glow - an indicator. It has three positions, very easy to check:

Green – the battery is fully charged.
White – low electrolyte level.
Black – the battery is discharged and needs to be recharged.

As you can see, if you have this option, then you don’t actually need a multimeter and a load fork. We arrived at the parking lot, opened the hood, looked at the indicator, and made a decision. If there is no “green window”, recharge immediately.

However, these types are not cheap, they cost about 20 - 30% more than the average battery, many drivers save money, and therefore this test will not pass! Let's move on to the next methods.

Load fork

“What,” you ask? What is this anyway? YES guys, the tool is not popular, and you will probably only see it at service stations. However, testing the battery with this device is the most accurate.

The bottom line is this: this device is connected to the battery terminals and produces a short circuit current. If without load the battery can produce 12.7 Volts, then under load the voltage actually sags.

Under load, the voltage should not drop less than 9 - 10 Volts. After the load is disconnected, it is restored to 12.7 Volts. If a strong sag occurs under load, up to 3 - 5V, then the battery is “dead”! It will not start the car engine.

That is, the load fork simulates the load of the starter on the car battery; if the load is sustained, then the battery can be used. Let me emphasize once again - checking the charge on this device is the most accurate and reliable. But as you understand, in 90% of cases there will not be a load fork in a simple garage or in your home! Therefore, you can most likely only check it with a multimeter.

Checking with a multimeter

A multimeter is a device for measuring current, voltage, as well as resistance and temperature. It is used in many areas of electronics (for repairs, for manufacturing, for testing, etc.), it can determine the voltage in almost any electrical circuit (although for me the limit is 600V, it’s no longer worth measuring that way). You can also check the battery. Of course, it does not give such accurate readings as, say, the first and second methods, but you can get your bearings a little.

Now a little instruction:

We are assembling a multimeter; the wires must be connected in the “voltage” mode (measuring voltage), and not in the “amperage” mode (measuring current).

We set the rotary switch to the 20 Volt position, that is, it will show us everything below, and as we know the battery produces 12.7 - 13.2 Volts, approximately this range.
We connect the wires from the multimeter to the battery terminals - black wire to the negative terminal, red to the positive terminal (sometimes the wires are the same color).

We take voltage readings.

By voltage:

A fully charged battery has a voltage of 12.7 (rarely 13.2) Volts, which means the battery does not need to be charged.
If the voltage is from 12.1 to 12.4V, then the discharge is approximately half.
If the indicator is 11.6 - 11.7V, then this is a deep discharge ! need to charge your battery , and it’s unlikely to start the engine.

Now a short video.

Checking electrolyte density

Another way to check the battery charge, but it is also not very popular, is to measure the density of the electrolyte. But we again need one more device - a hydrometer. The thing is that a charged battery has an electrolyte density of approximately 1.24 - 1.27 g/cm3. The density is measured with a hydrometer - it is immersed in the battery “jar” and electrolyte is pumped into it, then either the “float” or the “sticks” inside float to the desired value.

1.24 – 1.27 g/cm3 your battery is fully charged
1.20 g/cm3 – discharge approximately 25%, requires a small recharge
1.16 g/cm3 – 50% discharge
1.08 – 1.10 g/cm3 – full or deep discharge, urgently needs to be charged!

The disadvantage of this method is that now many batteries are maintenance-free. That is, you cannot disassemble and immerse the hydrometer in electrolyte.

To summarize, checking the charge with a multimeter is the simplest and easiest method, however, it cannot always paint a complete picture of what is happening, because you cannot apply the load that the starter provides. The most accurate method is still a load fork, but there will be an additional article about this. So stay tuned for blog updates.

I’ll finish this, read our AUTOBLOG.

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How to check a car with a multimeter

This time we’ll tell you how and why you need to check your car with a multimeter before buying. The methods can be used directly when meeting with the seller and inspecting the car. To make things go faster, practice the day before in a friend’s or acquaintance’s car.

First of all, you need a multimeter in order to notice a current leak on the machine in time. Because of this, the engine may run unevenly and the emissions will become more smelly. The wiring may short out, which will damage the radio, electronic control unit and other devices. Or the iron horse simply won’t start.

Content

How to check current leakage on a used car with a multimeter

The check includes:

Turn off the engine, remove the key. Close the doors, but open the windows - the battery will not work continuously, and the car may be locked with a central lock.
Make sure that the additional lighting and radio are turned off.
Remove the negative terminal from the battery.
Place one probe between the negative terminal and the negative terminal of the battery - the device will show the leakage current value.

The normal value is 15-70 mA. If the numbers are higher and you and the seller have time, try to find the reason. To do this, also connect a multimeter, then start removing the relays and fuses one by one.

The readings have returned to normal - you have found the cause of the current leak. Perhaps further repair or replacement of a part, or even the entire wiring, will be required. You can confidently ask the car seller for a discount or refuse the purchase altogether.

There may be several reasons for the leak. The following may be involved:

battery;
sensors;
high voltage wires;
generator.

Each element can be checked using a multimeter.

How to test a car battery with a multimeter

Testing a car battery with a multimeter involves connecting two probes at once. Also turn off the engine before taking measurements.

Place the red probe against the “positive” terminal, the black one against the “negative” terminal. If you mix it up, it’s okay, the device will show the current numbers, just with a minus sign.

Look at the device screen. The normal battery charge ranges from 12.6 to 12.9 volts.

The operation of the battery can also be checked with the engine running. When checking the car battery with a multimeter, you will also find out how the battery works in conjunction with the generator, as well as whether the voltage regulator is working properly.

Normal numbers with the engine running are 13-14 volts. If the multimeter shows less, the battery needs to be charged, or there is a current leak.

Remember: a multimeter will show the battery charge, but will not tell you everything about its operation. There are other devices for this. For example, a load fork.

How to check car sensors with a multimeter

The reason for the “death” of the battery, voltage surges, and unnecessary values on the instrument panel can be various sensors in the car. According to the experience of motorists, 5 types of sensors most often cause problems:

You can understand where they are located from the instructions for the car, on car enthusiast websites, and various forums.

To check your car's sensors with a multimeter, you will also need information about the normal voltage readings specifically for your car. It can also be found in the instructions or on the Internet.

ABS sensor

It is checked by two parameters: voltage and resistance.

To start measuring, select the appropriate mode on the multimeter. If you want to know the resistance value, for most the norm is 1.2-1.8 kOhm. Connect the device to the sensor and start taking measurements. At the same time, shake the wires going to the element. If the numbers on the screen change and become higher or lower than normal, there is a problem with the sensor.

Measuring voltage is a little more difficult - this can only be done with a jack or in a car service on a stand. You need to spin the car wheel to 40-50 rpm and monitor the multimeter readings. On any machine it should output 2 volts.

Crankshaft sensor

An important element - without it, the car will not start at all, or you will not be able to drive it. If visually it seems to be working, take a multimeter. Connect the device to the sensor and measure the resistance. The norm is usually from 550 to 750 ohms. But be sure to check if these numbers are accurate for the car you're looking at.

Oxygen sensor

Determines whether oxygen remains in the exhaust gases. Before taking measurements, also inspect it - it may be damaged and a multimeter will not be needed at all. Then the element just needs to be replaced.

If everything is in order, measure the voltage and resistance as with the ABS sensor. The algorithm is the same. Start the car and watch the device. After start-up, the numbers 0.1-02 volts will appear on the screen. When the car warms up, the device will show up to 0.9 volts. If you didn’t notice that the indicator has changed, the sensor is most likely faulty.

If the voltage test is successful, find out the resistance readings. The norm ranges from 10 to 40 ohms.

Knock sensor

Determines the shock wave during fuel combustion. The resistance indicators for each car are individual - look for information in different sources.

It's a little easier with tension. First remove the sensor. Connect the plus probe to the signal wire, the negative probe to ground, closer to the mounting bolt. Next comes the fun part - hit the sensor against a wall, chair or table. This is the only way the multimeter will record the voltage reading. The norm on most cars is from 30 to 40 millivolts.

Speed sensor

Be sure to inspect the element before taking measurements. Perhaps it simply oxidized or melted.

Then connect the multimeter and measure. The procedure is the same as with the knock sensor.

The only thing is that they don’t need to hit anything. You can simply rotate or shake. If the multimeter does not show voltage at all, the sensor is faulty.

How to check high-voltage wires on a car with a multimeter

If you feel a loss of car power, see increased fuel consumption, the car shakes, and the idle speed fluctuates, it’s time to check the high-voltage wires. More precisely, measure the resistance in them. Remember the procedure:

disconnect the wires from the machine or disconnect one wire on both sides;
turn the device into ohmmeter mode and place the probes on both sides of the wire.

The normal resistance value is 6-10 kOhm. If the device shows less, down to zero, do not be alarmed. The multimeter numbers are influenced by many factors, for example:

quality of wire insulation;
length;
presence of microdamages;
wire type.

If your car's performance is outside the normal range, it is better to contact a car service center, where the resistance will be measured with professional and more accurate instruments.

How to check a generator on a car with a multimeter

Checking the generator is similar to measuring other elements of the car that cause current leakage.

Traditionally, turn off the ignition, take out the key, turn off the radio, and so on.
Connect the multimeter to the battery.
Measure the voltage. A fully charged battery will produce between 12.5 and 12.9 volts.
After this, start the engine, turn on the heated windows, seats, heater, and low beam.

And measure the voltage again. The norm is 13-14 volts. Maximum - 14.8 volts. In these cases, the generator works like a clock. If the multimeter shows lower numbers, the generator is not charging the battery. So, get ready to pay a decent amount for replacing or repairing the unit.

Instead of an afterword

When buying a used car, it is useful to know how to find an electrical leak and understand its cause. Take a multimeter to inspect your car - you will save yourself from unpleasant surprises, such as a suddenly dead battery, power surges or burnt wiring.

For the same purpose, check the car's history. This can be done directly during a conversation with the seller. It’s convenient to use the Autocode service - monitor information from 13 sources at once: traffic police, RSA, EAISTO, banks, tax and other services. The verification will take 5 minutes.

Afterwards you will find out the actual mileage, number of owners, history of fines, as well as information about theft, participation in an accident, restrictions on car registration and much more. Be carefull!

Having fully studied the online report, it is still worth taking a closer look at the technical nuances of the car when purchasing. And if you are not confident in your knowledge, or it is not possible to go for an inspection, order an on-site inspection service. The specialist will conduct a diagnosis for you and make a detailed conclusion from a professional point of view.

How to check the battery with a multimeter on a car?

Drivers often have to check the battery charge, this problem is especially relevant in winter. If the car has not been used for a long time, the battery may freeze even after the engine has been successfully started. Checking the battery with a multimeter will allow you to get fairly accurate information about the charge and avoid getting into an unpleasant situation.

What parameters can you check?

A multimeter is an electrical measuring instrument that combines the functions of an ammeter, voltmeter and ohmmeter. Portable devices fit in your hand and are inexpensive; it is desirable for every driver to have one in their car. To measure the battery charge, you need to measure the voltage. The multimeter is also useful for checking other parameters - current leakage, for example. This is an excellent prevention against rapid battery discharge.

In emergency situations, when electrical equipment fails, a multimeter is useful for diagnosing faults:

on-board network voltage measurement;
“continuity” of fuses, electrical wiring and light bulbs;
control over sensors, their resistance and voltage.

How to check

Before you start checking the voltage, you need to turn off the car's ignition. It is not difficult to measure the voltage and other parameters of a battery with a multimeter; working with the device requires minimal knowledge in the field of electronics. The battery itself must be disconnected from the terminals or removed.

Battery voltage

To check the voltage, the device must be switched to DC (voltage) mode, and the rotary switch set to 20 V. The multimeter has two probes: connect the black one to the negative terminal, and the red one to the positive terminal. A number indicating the DC voltage will appear on the device display. If the wires are the same color, you need to carefully inspect them for special markings.

After removing the voltage, you can obtain the following information about the condition of the battery:

A charge above 90% corresponds to a value of 12.7V (sometimes 13.2V). This means the battery does not need to be charged.
The voltage range from 12.1V to 12.4V indicates 50%-60% discharge.
If the values fall within the range of 11.6V – 11.7V, then you need to charge the battery as soon as possible.

As you can see, you can check the battery with a multimeter and measure the voltage if you have no experience.

Battery capacity

To measure the battery capacity, you will have to perform a test discharge of the battery. The battery must first be charged (fully), this point is easy to determine - use the instructions given above to measure the voltage. After this, a load of known power is connected to the battery - an incandescent lamp will do. Having marked the beginning of the study, stop it when the discharge occurs by 50%. Disconnect the light bulb and calculate the capacity: to do this, you need to multiply the current value when the light bulb is connected and the discharge time. It must be expressed in hours, and the current in Amperes. If the result is close to the nominal value, the battery is OK.

Battery amperage

In amperage measurement mode, it is important to select an external load - it should not exceed 120 W. The diagnostic mode for DC should not be confused with resistance - the switches are located next to each other. Most often, it is necessary to measure the leakage current, which will give an idea of the condition of the acid battery.

Leakage current

When the battery terminals are not connected to the elements that consume energy, it will still discharge. This independent process is not accidental; it is indicated in the documentation for the battery; the figure is higher for acid batteries. As the condition of the battery deteriorates, the leakage current also increases, which is affected by wet areas and thinner insulation. This will gradually lead to the discharge and combustion of the damaged area - and the whole process will pass beyond the driver’s sight.

This is very dangerous, so at the slightest sign of an increase in the discharge rate, you need to check the leakage current. Otherwise, there is a risk of an open fire - even one spark is enough. Before starting the measurement, you need to turn off the ignition, radio, alarm and other “side” current consumers.

After this, switch the multimeter to current measurement mode and set it to the “10 A” icon. Those. the circular switch is in amperage mode, and the red plug is in the “10 ADC” socket. Now, having connected the terminals of the device to the battery, look at the display. If there are no values, everything is in order - the leakage current is not outside the norm. But any values recorded by the multimeter indicate problems with this parameter. Detailed diagnostics of the onboard part of the machine is necessary - it is for this part that the highest leakage current is most dangerous.

Overcharging the battery is an unpleasant situation that occurs due to a breakdown of the relay regulator. Those. too high voltage is supplied to the electrical elements on board - the devices burn out. If the regulator is still functioning, albeit weakly, the breakdown may not be noticed for a long time. A multimeter will help in identifying the problem:

Connect the terminals to the AC in voltage mode.
Start with 20 V, and then increase the speed.
Idling should show no more than 14 V, medium - 13.6-14.2 V, high - up to 14.5 V.

If the specified values are exceeded, you need to disconnect the device, clean the circuit contacts, and recheck. The next line of testing is a separate measurement for the relay regulator. You need to remove it and measure the voltage using an external power source and a lamp (12 V). The source must have adjustable voltage!

The negative terminal is connected to the housing, and the positive terminal is connected to the regulator. The lamp is connected to graphite brushes; polarity is not necessary.

Gradually changing the voltage from 12.7 V to 14.5 V, observe the lamp. At first it should light up, and go out towards the maximum value. If this does not happen, the regulator is faulty and needs to be replaced.

Charge level

To determine the charge level of a car battery, it is enough to measure the voltage and compare it with the table values. The process is completely similar to that described in the first section, only before taking measurements you need to wait 4-5 hours after disconnecting the battery. This is necessary in order to eliminate the influence of discharge and charging currents. The charge values for a battery cell correspond to the voltage as follows:

100% - 12.7 V;
90% - 12.57 V;
80% - 12.47 V;
70% - 12.37 V;
60% - 12.29 V;
50% - 12.21 V;
40% — 12.13;
30 % — 12.05;
20% — 11.99;
10% — 11.95.

More accurate figures can only be obtained using special devices with microprocessors. For general diagnostics, it is enough to check the battery charge with a multimeter on the car.

The driver should know the approximate battery charge of his car - at least approximately. This way he will be able to quickly detect a possible problem, an increase in leakage current and other disturbances in the operation of the battery element. A multimeter will save time and nerves by allowing you to quickly and accurately check the voltage on the battery.