How to measure car battery voltage 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The load fork is considered a slightly outdated tool today.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 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.

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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 measure the voltage and capacity of a car battery with a multimeter

This device, popular among car enthusiasts, is also called a tester, or less often an ampere-voltmeter. Based on the latter, it is obvious that the product is intended for testing voltage (U), current (I), resistance (R). The multimeter is powered by AA, AAA or Krona batteries. There are many models of devices, but by and large they can be divided into two categories:

Analog. How to measure battery voltage with this type of multimeter? Look at the marked scale and the pointer arrow, which deviates during testing, indicating any value of the selected mode. These are relatively accurate instruments, but there is a drawback - the inability to test values that are too small, for example, 0.2 Ohm is almost impossible to measure.
Digital. These testers have wider functionality. But using them will also not be difficult, even if you are completely ignorant of radio electronics. The device consists of a panel with a switch and symbols, two probes (red for positive contacts, black for negative ones), and a display on which the measured parameters are visible. Each probe is connected to its own socket on the device.

How to check battery voltage

First, about the letters (abbreviations) on the instrument panel. Direct voltage is marked as DCV, alternating voltage - ACV. On an inexpensive device, when measuring U and I, you should not confuse (+) and (-). If an error has occurred, a (-) will appear in front of the number on the screen. How to check the battery voltage with a multimeter: higher quality products have special electronic protection against such incidents (even if you confuse DCV with ACV). Therefore, to obtain data, it is enough to move the switch to position V (volts).

The numbers on the panel indicate the maximum value. How to measure battery voltage accurately with a multimeter? If, for example, you are supposedly testing a 12 V battery, then set the switch to the 20 V position. If you do not know what the final value will be, you should start with a higher limit. Further:

Disconnect the negative wire from the battery terminal, wait a few hours (for example, overnight), touch the red tester probe to the (+) battery, the black probe to the (-) battery (the air temperature should be +18–20 degrees).
On a charged battery with normal electrolyte density (1.27), the device will show U = 12.6–12.7 V, for gel batteries - 13 V.
Lower readings (up to 12 V) indicate that the battery is partially discharged.
If the display readings do not reach 12 V, the battery needs to replenish energy through a charger powered from the mains.

How to measure the voltage of a car battery with a multimeter under load: start the engine and touch the probes of the device to the battery terminals. With consumers disconnected, U = 13.8–14.1 V (readings on different brands of cars may vary slightly). Then turn on the most powerful electrical devices: high beams, heater (at maximum), heaters (seats, steering wheel, rear window), multimedia. The tester readings should change slightly compared to the previous ones (by 0.1–0.2 V). If this is not the case, you should check the charge level of the battery and the generator.

How to check battery amperage

If you know how to measure the voltage of a car battery with a multimeter, do not forget about the current. The first step is to check for leakage. This is quite an important procedure. Testing will show how much current your car draws when the engine is off and the ignition is off. Even in this situation, energy is consumed: for example, to power the alarm system (and not only). Of course, cases where the car owner, leaving home, forgot to turn off the side lights or the radio are not taken into account. The latter, even in the absence of sound, consumes a lot of energy and can greatly discharge the battery in a few days.

Algorithm for measuring leakage current:

Take out the ignition key, open the windows, close the doors. When testing, the battery will have to be periodically connected to the on-board network and disconnected, which can cause a reaction from the central locking, so it is necessary to provide access to the inside of the car.
Turn off all energy consumers: do not forget about the lamps in the trunk and glove compartment.
Open the hood and disconnect the wire from the battery terminal with the (-) sign.
Switch the tester to current measurement mode with a maximum measurement of 100 mA.
Connect the probes of the device between the negative terminal of the battery and the removed wire. At the same time, touch the (-) battery with the black probe of the device.
Look at the display: readings should be in the range of 15–70 mA.

Inconsistency with this data indicates a leak. It may be due to a faulty electronic component or a short in the wiring. You can find the “guilty” consumer by removing the fuses one by one (symbols of the electrical components for which this protection is responsible are drawn inside the cover). If, when removing one of the fuses, the tester readings become “standard”, then the “culprit” has been found. In a situation where it was not possible to find the cause using this method, it is necessary to test the electrical wiring. Ignoring such a recommendation is dangerous: it not only leads to a constant discharge of the battery, but also risks a fire.

How to check the capacity of a car battery with a tester

It’s worth noting right away that there are two methods that can give an approximate correspondence of the battery capacity to the value declared by the manufacturer. Both testing methods are available at home (garage or even outside). It is only important that the temperature is within +18–20 degrees.

Test under load (voltage is measured)

First, the battery is fully charged (U = 12.6–12.7 V) and verified using a hydrometer that the density corresponds to 1.27. Next, you will need a multimeter, which needs to be switched to voltage measurement mode, and a 40–45 W headlight lamp. It is connected directly to the battery terminals and left to shine for 3 minutes. Then look at the voltage on the battery. Its value is not lower than 12.4 V. If this is so, everything is in order with the capacity.

Current Testing

As practice shows, this method, called a control discharge, gives the best results. The procedure time depends on the load power. For example, if a current of 0.1 A is obtained, it will take at least 8 hours. You can increase the load, then the time will be reduced. But the measurement accuracy will decrease due to the influence of internal resistance. Algorithm of actions:

As in the previous case, the battery must have a standard density and be fully charged.
Place the device in current measurement mode with a limit of 10 A.
Connect a 24 W car lamp in series (to the break of any wire). In this case, the positive or negative probe of the device must touch the battery.
Connect the light bulb to the battery for a few seconds and note the amount of current consumed.
Disconnect the multimeter and connect the load to the battery directly, noting the start time.
From time to time, check the voltage at the terminals with a tester: when it reaches 10.8 V, stop the procedure.

Now you need to remember Ohm's law. If the lamp has a power P = 24 W, the current is equal to W/U, i.e. 24/12 = 2 A. The resistance is calculated: R = U/I. In this case it is equal to 12.6/2 = 6 Ohms. When the voltage drops to 10.8 V, we perform the calculations again: I = U/R, i.e. 10.8/6 = 1.8 A. If we add these 2 current values, divide in half, we get the average: 1.9 A. To calculate the capacity, you need to multiply this value by the time elapsed until complete discharge (reaching 10.8 V). For example, the process lasted 30 hours. We get: 1.9x30 = 57 A/h. This is the required capacity.

How to measure the internal resistance of a battery using a multimeter

This technique allows you to determine the internal resistance of the battery and, at the same time, its performance. Prepare a 60 W car lamp. It will consume a current of 5 A (60/12 = 5). In a normal battery, with an output current of 100 A, no more than 1 V will be lost. This means that in this case the loss is 0.05 V (1/20). That is, the internal resistance R = U/I will be equal to 0.05/5 = 0.01 Ohm.

Now connect the lamp and tester to the battery terminals and note the readings of the device in volts. Disconnect the load and check the value of U again. Estimate how much the voltage has risen: if it is, say, 0.02 V, the battery can be considered ready for operation, but a reading of 0.2 V indicates a battery malfunction. That is, in a good battery, when starting the engine and using a current of 100 A, the voltage loss is only 0.4 V (0.02x100).

Knowing how to check the voltage of a car battery with a multimeter, you can test other parameters of the battery. This will give the most complete picture of the condition of the battery and allow us to draw a conclusion about the possibility of its further operation.

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.

Checking the battery with a multimeter

A multimeter is a universal device for accurately determining voltage, current or resistance and more. Using even inexpensive Chinese models allows you to effectively test any type of battery. This article will describe the basic ways to use the tester to determine battery health.

Which batteries can be tested with a multimeter?

All types of batteries are characterized by parameters such as capacity, current or voltage, so using a measuring device you can easily check any battery for performance.

Most often, due to its widespread use, it is necessary to measure the performance of car batteries, Ni-Cd, Ni-MH, Li-Pol and Li-Ion batteries in this way.

Even if a car or gadget is equipped with standard programs for measuring battery charge, in many cases, such utilities show general information about the amount of charge. At the same time, the accuracy of such utilities cannot always be trusted.

Checking battery parameters using a multimeter

To carry out measuring work, in many cases, it is impossible to do without dismantling the battery. If it is necessary to test a car battery, it should also be removed from the car.

Voltage

All batteries produce direct electric current at the terminals, so to measure it, the multimeter mode switch should be set to the DC position. The battery voltage can differ significantly depending on the type of battery, so in order to get the most accurate readings, you must correctly select the maximum voltage that the device can measure.

The multimeter switch has several modes that can be used to measure DC voltage. For most batteries, it is enough to set the limit to 20 V. Almost all AA batteries and phone batteries are capable of delivering significantly lower voltage.

The only exception to this rule is the measurement of 24 V car batteries, and some laptop batteries, which, when fully charged, can have a voltage exceeding 20 V at their terminals.

Note. In the same way, you can measure the voltage in industrial batteries or in an outlet, only in this case you need to switch the switch on the multimeter to a higher voltage, for example 200 V.

Now the value is set to 20V, but if the source voltage is higher, then you need to set it to 200 or 1000 depending on the source voltage.

When measuring, it is important to maintain polarity, that is, connect the red probe to the battery positive, and the black probe to the negative. When reversing the polarity, devices equipped with a digital display will inform you about the polarity violation with a minus sign in front of the number.

On pointer instruments, such a connection will cause the needle to move in the opposite direction, which will completely prevent correct voltage measurements. Although in general there is nothing wrong with this.

In order to measure the current strength of a low-power battery, it is enough to switch the device to the mode for measuring this parameter (A). By touching the probes of the device to the battery terminals, you can get the exact value in milliamps.

When taking measurements on a battery of higher power, the device is switched to the “10A” position, and the positive output of the multimeter is moved to the adjacent cell.

If you need to measure the current on a car battery, then these two methods are not suitable, because the discharge current of such batteries can reach several hundred amperes. Such measurements can only be carried out using a special tester, for example, Bosch BAT-131.

Using a multimeter, you can approximately calculate the actual battery capacity. In addition to the tester, you will need to assemble or purchase a voltage stabilizer, which must correspond to the rated voltage of the battery.

Then you should select a load that can be powered from the battery for a sufficiently long period of time. To calculate the capacity, you should also prepare a stopwatch.

The measurement process is carried out in the following sequence:

The multimeter is switched to current measurement mode (10 A).
The measuring device is connected in series to a circuit consisting of a current source, a voltage stabilizer and a load.
The stopwatch starts.

After turning on the circuit, you should record the values of the multimeter, and use a stopwatch to determine the amount of time it will take to completely discharge the battery. After multiplying the current by the time, you can get the actual battery capacity, measured in amps/hours.

The use of this method for measuring the capacity of many acid batteries is not recommended, due to the negative impact of completely discharging the battery on its performance.

Example! If we know in advance that the device connected to the battery consumes 10 Ah, then depending on how many hours it works, this will be the battery capacity. If in our case the device operates for 10 hours, then the battery capacity will be 100 Amperes.

Internal resistance

Using a multimeter, you can easily measure the internal resistance of a current source. To perform this operation you must:

Measure the voltage at the battery terminals.
Connect the load and measure the voltage drop and current in the circuit.
Carry out calculations using the formula R = U/I, where R is the internal resistance, U is the voltage difference at the battery terminals before and after the load is turned on, I is the current strength in the circuit.

This method is suitable for measuring almost any type of battery.

High leakage current

Leakage current

Measuring the leakage current is very simple. To determine this parameter, you need to switch the multimeter to current measurement mode, connect the negative terminal of the battery to the device, and connect the positive output of the battery to the connected cable through the tester.

The amount of leakage current will be displayed on the digital display. When measuring leakage current on a car, the multimeter should be switched to resistance measurement mode (10 A), and all electrical consumers should be turned off.

To determine overcharge, the multimeter should be switched to voltage measurement mode. After determining the voltage, you should compare the nominal value of the battery with those obtained as a result of the measurement. If the latter are more than 20% higher than normal, this will indicate that the battery is overcharged.

Overcharging a battery is quite dangerous. Acid batteries, in this case, begin to boil with the formation of explosive gas. Lithium-ion batteries may catch fire or explode if overcharged.

Charge level

For many types of batteries, the state of charge is checked by voltage. As in the previous case, you need to know the battery voltage at 100% charge. A fully charged lead battery should have a voltage of 12.7 volts at its terminals.

Fully charged car battery

A complete discharge of the battery will correspond to a value of 10.5 V. It is easy to determine in this way the degree of charge of the battery if the voltage readings deviate from these values.

Similarly, knowing the nominal voltage values, you can measure the voltage with a multimeter to approximately determine the state of charge of a AA battery or battery for a mobile phone or laptop computer.