How to check the capacity of a car battery

Checking the car battery - when else can you fix it?

When the key is turned in the ignition, it is the battery that provides the impulse to start the engine. If the battery is completely discharged, the car is unlikely to move. It is for this reason that it is important to check the car battery in a timely manner (with a multimeter, for example), because problems noticed in time will not only allow you to avoid searching for someone to light a cigarette, but will also save you from much larger problems. Checking a car battery should be comprehensive and thorough and include both an external inspection and a check of the “inner world”, as well as electrical indicators.

Visual inspection

First of all, carefully inspect the battery: normally it is dry, clean and without signs of damage. It's bad when:

the surface of the battery is heavily contaminated;
terminals are oxidized;
the battery case is damaged;
There are traces of electrolyte.

Any of the items listed will lead to rapid discharge of the battery, and therefore increase the risk of getting into unpleasant situations. What to do?

The same solution will help deal with terminal oxidation - apply the mixture to contaminated areas, wait a couple of minutes and thoroughly clean with a brush (not a metal one!). After the procedure, rinse the cleaned surfaces with distilled water.

If the oxidation is extensive, then the first step is to resort to mechanical cleaning, the main thing is not to damage the wires.

Exploring the inner world

The battery check should continue with electrolyte measurements. It is he who is responsible for most of what happens to the car. The electrolyte is checked according to the following parameters: density and level.

To check the level you will need a glass graduated tube. Unscrew the washers covering the so-called banks - sections in the battery. Lower one end of the tube all the way down and close the upper end with your finger. Pick up the tube.

It is optimal if the solution covers the upper edge of the plates by 10–15 mm. The total liquid content should be 30–40 mm. So check each section.

The next step is to check the density of the electrolyte using a hydrometer. The normal value is 1.26–1.28 g/cc. see at above-zero temperatures. The indicator will be lower if measurements are taken at zero temperature, but this indicates a low battery charge.

If the density of the electrolyte is higher than the required values, and its level is lower, then it is worth adding distilled water. It is important that it is not any other water, since only the distillate does not contain impurities of salts and metals that can damage the battery.

If the density is slightly lower (1.24–1.25 g/cc), then the electrolyte is added. You can either make it yourself or purchase it in specialized stores. Excess liquid is removed using a “pear”. Any leaks of electrolyte must be removed from the housing!

Making electrolyte at home

For this recipe you will need a well-ventilated area, personal protective equipment (at least gloves), non-metallic utensils, distilled water and 360 ml battery (sulfuric) acid.

First, water is poured into the container, then acid is poured in small portions and carefully. The mixture is thoroughly mixed at all stages. Then the resulting mixture is left to stand for several hours, and the electrolyte is considered ready.

After the completed manipulations, but before repeated measurements, the battery must be charged using a low current. This is the moment when longer is better. After charging, the measurements are repeated.

If during measurements the readings differ in only one section, this indicates damage to the plates. Maintaining life in such a battery will cost much more than purchasing a new one.

Using a Multimeter

A common question is: “How to test a car battery for performance with a multimeter?” First, it’s worth understanding what is measured using this device:

Even the simplest multimeters will help in measuring air temperature and other indicators. Hence the name: “multi” translated as “many”, which means that the device can measure a lot of things. However, when it comes to the battery, it is the first three indicators that will tell you about its health. Let's take a closer look.

Voltage check

This manipulation will allow you to assess the current state of battery charge. To carry out the measurement, the multimeter is switched to the voltage measurement mode at around 20 units. Connect the red wire of the device (also known as “plus”) to the positive terminal of the battery, and the black (sometimes blue) wire to the negative terminal.

If the car is not started, then the optimal indicators will be numbers in the range from 12.4 to 13 V. In this case, a higher value indicates a 100% charge, and a lower value indicates an incomplete charge. It is better to carry out such a check when the car has been parked for a long time (at least several hours), in which case the measurement will be the most informative.

If the numbers are slightly less than 12, then the situation is bad - the battery is close to natural death. There is a chance to try charging it with a low current. Numbers close to 11 mean the death of the battery, and it is better to take care of purchasing a new one.

When checking with the car running, the readings will be different: from 13.5 to 14 V, the readings are good. If the figure is greater than 14.2 V, then we can judge that the battery is being recharged by the generator. However, if measurements are taken in winter, you should wait 15 minutes and repeat the procedure - perhaps the generator was intensively recharging the dead battery.

Capacity check

The battery capacity is usually indicated on the accompanying sheet. Another thing is that over time the capacity decreases, and it is important to keep track of this point. In this case, checking the car battery with a multimeter will be a good help.

To check, you will need:

disconnect the car battery from the generator;
connect an energy consumer with fixed consumption to the circuit (for example, a 12 V light bulb);
The operation of the circuit is observed for several minutes (here it is important to see whether the light of the light bulb becomes noticeably dimmer, whether there are any interruptions in its operation, etc.);
the consumer is switched off, battery readings are measured in voltage mode.

If the measurement result is 12.4, then this indicates that the battery is fully operational. If the readings are in the range from 12 to 12.3 V, then soon the battery may “forget how to work”.

Another method is the control discharge method. The steps are similar to the previous method, however, before starting the test, charge the battery to 100%, then connect a light bulb to the circuit, noting the exact time of switching on, and, under the control of an ammeter, wait until the battery charge is reduced by exactly half.

Next is the question of calculations: the time spent discharging the battery is multiplied by the current in the circuit. The result should be the same as in the technical passport or close to it. If this does not happen, then the battery capacity has already suffered greatly.

Resistance check

To understand what is happening, you can also check the internal resistance of the battery. To do this, you will need the same 12 V light bulb. It is connected to the battery terminals, and the voltage at the terminals is immediately measured. After the measurement, the light turns off and the measurement is repeated. If the difference in measurements is within 0.05 V, then the battery is working. If the difference is greater, then the battery has problems.

Checking with a load fork

To obtain the most accurate measurement results, a load fork is used. Of course, this equipment is rarely seen in private hands, much more often in professional workshops or at technical diagnostic stations. However, if it does exist, then why not use it.

The load plug is a device that, like a multimeter, is connected to the battery terminals. It then supplies a short circuit current to the battery, which simulates the operation of the starter. As you know, without load the readings are about 13 V.

At the moment of turning the ignition key, which is simulated by the load fork, the readings normally “drop” down. The maximum normal drop can be up to 9 V and return to the initial reading after the voltage is removed. In this case, the battery can be considered serviceable.

If the readings drop below 9 V, then even if they return to their original state, such a battery is unlikely to start the car. It is important to remember that testing with a load fork should be carried out only in the warm season (optimally at a temperature of +20... +25 degrees), otherwise it is possible to drain the battery charge during testing.

A little theoretical knowledge

Knowledge of how to test a car battery should also be combined with knowledge of normal values and readings and why they change.

The density of the electrolyte can change due to temperature fluctuations - overheating or hypothermia. In this case, in case of overheating, the electrolyte may boil, in which case the distilled water will partially boil away, and the electrolyte will become more dense.

In the case of cold, the electrolyte, on the contrary, often begins to have a reduced density. In both cases, the conductivity becomes worse, and therefore there are problems with the establishment, rapid “landing” and work on its last legs.

But why is any liquid so important? The thing is that the battery only looks like a small box. In fact, it consists of many parts, the main of which are conductive plates, positive and negative, which make up 6 elements connected in series. They are in contact with the electrolyte, so the electrical impulses move with the necessary force.

For what other reasons could a battery suddenly stop working? For example, just from time to time. On average, batteries work stably for 3–4 years. Of course, many work longer, but their capacity and ability to hold a charge still decreases.

Another reason is frequent battery overcharging, undercharging, or complete discharge. It is very important for a car battery to maintain some kind of average state, without strong changes.

The next reason is hidden in the generator, or rather, in its breakdown. In this case, it may either constantly recharge the battery, giving too much current, or, conversely, may not even be able to maintain the existing charge. Both options indicate the need for urgent replacement of the generator.

The last on the list of unpleasant situations is current leakage: something in the car consumes too much energy even when the car is turned off and parked. This can be determined using the same multimeter. To do this, you will need to turn off the car and remove the negative terminal of the car from the battery. Turn the multimeter into current measurement mode, set the switch to 10 or 20 units. Connect one wire to the negative terminal of the car, and the other to the negative terminal of the battery.

Conclusion

Simple car diagnostics are available to any car owner. Careful attention to the battery will save a lot of effort and nerves, especially on long trips, in winter or at low temperatures.

The simplest thing that anyone can do is remember to inspect the battery every time you lift the hood. Quickly inspect the integrity of the case, wipe it with a rag to remove dirt, make sure that the terminals fit tightly and there are no signs of oxidation.

Once a month it is a good idea to check the level and density of the electrolyte, this is especially true in winter, during severe cold or long trips.
If suddenly the car begins to behave strangely when starting up, the starter turns sluggishly, and the engine does not start the first time, serious problems are not far off, and you need to check both the battery and the car’s alternator in the near future. To do this, you will need a multimeter, which can be purchased at almost any auto store for a fairly modest amount. Timely attention to detail often helps to avoid serious troubles.

How to check the actual capacity of a car battery

A car consists not only of mechanical elements, but also of electronic ones. And their basis is a car battery. It is he who ensures the operation of all electronics in the car, accumulating charge and providing it as needed. It is based on a chemical reaction, so it tends to gradually reduce its technical characteristics as it is used.

Since the battery does not last forever, it is necessary to regularly check its performance. This will avoid troubles associated with its discharge or insufficient voltage to start the car. It is better to carry out a comprehensive check using the services of a service station, but this is not always available. In such cases, it is possible to independently check using available tools.

Signs of breakdown

Electronics are a complex thing, so it is quite difficult to determine a battery failure based only on external signs. But, if you initially know the main signs of a power failure, then this task becomes much easier. Therefore, it is worth remembering the main signs indicating an insufficient charge or breakdown of the car battery. Among them:

no light from the battery charge indicator;
clicks when starting the starter;
slow starter operation;
weak headlights.

All car electronics malfunction if the battery has a weak charge. Although the problems may be due to other reasons, a set of these signs clearly means a battery problem.

If one of these symptoms occurs, it is recommended to check the car battery using available methods. It is also recommended to conduct an external inspection, including searching for damage, as well as checking the reservoirs and electrolyte.

Checking the charge

The first step in case of problems with the batteries is to check the charge level. After all, this is what determines the efficiency of the device and the operation of all electronics in the car. In addition, an undercharged battery may be a sign of a generator failure. Therefore, it is worth monitoring this factor and checking if possible.

Modern battery models have special indicators that change color to check the charge level. But often there is no such element on the device, so you need to check using old and accessible methods.

You can use a multimeter or voltmeter to check the charge. The testing process is simple - you just need to measure the voltage at the battery terminals, having first disconnected it. Based on the result, the current state of the device and the possibility of its further operation are determined.

The optimal battery voltage indicator is 12.6 V. It indicates a fully functional device with a full charge. If the indicator drops to 12.2 V, then this indicates a slight discharge. If the voltage is even below 12 V, then such a battery requires urgent charging.

If it drops below 11 V, there is a high chance of device failure. You should try to charge it if the problem is a malfunction of the generator or other batteries. If they work normally, but the voltage cannot be increased, then using such a battery is dangerous. This may adversely affect the operation of the vehicle and damage other electronic components of the system.

This indicator is the basis for a car battery. It reflects the time that the battery can operate without loss of current. It is measured in ampere hours and is an important factor when purchasing such devices.

The amount of energy that a battery can contain gradually decreases during its operation. This is an important factor for the operation of the car, so it needs to be monitored and measured periodically. There are several methods for this:

control digit;
calculation using a multimeter;
using special equipment.

Although the first two methods are quite complex, they allow you to determine the battery capacity at home. The latter requires special equipment, which is often available at service stations. If you find such equipment, then independently checking the capacity is greatly simplified.

An important nuance is that checks are carried out only on a fully charged battery. Otherwise, the result will be incorrect.

Checking with a multimeter

The method of checking capacitance using a multimeter or voltmeter is quite complex, although quick. To measure this indicator, you will need the following equipment: a multimeter, as well as a device that will consume approximately half of the declared capacity of the device. In other words, with a capacity of 7 A/h, the consumption should be about 3.5 A.

It is worth considering the voltage at which the device operates. It should be 12 V. For such tasks, a regular lamp from a car headlight is suitable, but you should still select the consumption according to your battery.

The disadvantage of this method is that it cannot be used to tell the exact capacity of the battery. You can only find out the current percentage of capacity from the original. In other words, this test determines the wear and tear of the device.

The method is similar to the previously mentioned method of checking the battery charge. After connecting a certain device, you need to wait a couple of minutes and then measure the voltage at the terminals. Afterwards, you need to check the following parameters, which determine the percentage of the original capacity:

more than 12.4 V - 90-100%;
between 12 and 12.4 V - 50-90%;
between 11 and 12 V - 20-50%;
less than 11 V - up to 20%.

However, even if the capacity is less than 50%, you cannot drive with such a battery. This comprehensively harms the entire car.

The result obtained must be compared with the percentage, and then compared with the declared capacity. This will allow you to approximately determine the current capacity and make an appropriate decision regarding the further operation of the device.

It is much easier to determine the battery capacity using a control discharge or special testers. Using the second option will allow you to get quick results, which is why they are used in various services and workshops. The first method is to measure the rate of battery discharge based on current strength.

The capacity of a car battery is an important factor that should be taken into account and checked regularly, since over time the life of the device decreases and the capacity rapidly decreases. A significant decrease affects the operation of the car’s electronics, so you should carefully monitor this.

As for the test charging method, this video describes the nuances of this method. This will allow you to find out the exact capacity of the battery using only available tools:

How to determine the capacity of a car battery and extend the battery life

Automobile and other batteries are characterized by simply a huge number of very different parameters by which their selection is made. The most important is the capacity - an indicator that determines the duration of the battery under load until it is completely discharged. The capacity of a battery can be determined in a variety of ways, each of which is selected depending on its design features.

Calculations carried out

You can determine the capacity of a car battery by taking into account the information indicated by the manufacturer on the label, as well as by simple calculations. The minimum output voltage when fully discharged for a car battery is 10.8 volts. A full discharge cycle takes about 10-20 hours.

If a car battery indicates a capacity of 72 Ah, then it is capable of delivering a current of 3.6 Amps throughout the entire discharge period. After removing the load, the output voltage should be 10.8 volts or more.

To calculate the capacity, a special formula Cp = I k * t is used, which takes into account the discharge time (t) and the Peukert coefficient (k) - a constant parameter for a certain type of battery. For lead models the figure ranges from 1.15 to 1.35.

When making calculations, it is worth taking into account the division of capacity into nominal and reserve. The features of these two indicators include the following points:

The rated capacity is determined by discharging with a small current, for example, during prolonged use of various electrical equipment. When starting the engine, a current arises that exceeds the minimum by several times.
The reserve capacity determines how long the battery can function without the use of a generator. In this case, the discharge current is 25 amperes.

The nominal parameter of a car battery is determined taking into account its technological and design features. The capacity is influenced by the conditions of use of the battery.

Dependence of capacity on various parameters

You can determine the battery capacity of a car or other devices using various methods. Before making calculations, you need to take into account that the indicator can be influenced by several different factors:

Electrolyte composition. The appearance of impurities can lead to a significant drop in capacity.
Volume of active mass. Chemical processes that take place inside the structure lead to the evaporation of liquid. As a result, the mass of the electrolyte decreases and the acid concentration increases.
The thickness level and condition of the plate determine the operating life of the device and the capacity indicator. Operation with a low mass of electrolyte causes damage to the plates: they begin to crumble, the thickness becomes smaller. In addition, small metal particles entering the liquid cause bridges to form between individual plates, which leads to a short circuit.

The rate of loss of capacity is influenced by the temperature of the electrolyte and the magnitude of the discharge current. Too high a load can cause the liquid to evaporate and the mass of the active substance to decrease.

Application of a multimeter

You can determine the capacity of a car battery by using a multimeter. This measuring device is widely used and can be used to take a wide variety of indicators from a battery. There are several ways to determine the indicator in question. The features of the procedure include the following points:

Capacity measurements in most cases are carried out at a load that takes half the battery current.
To perform the test, you need to remove the power source from the car. The surface of the housing is cleaned of various contaminants. For this, a rag and a special solution are used. If you take an indicator with oxidized or contaminated terminals, the data obtained may differ significantly from the real ones.
The density of the electrolyte largely determines the result obtained. When fully charged, the density of the liquid chemical is 1.24 g/cm3. When the battery is half discharged, the electrolyte density decreases to 1.16 g/cm3.
It is recommended to carry out measurements when difficulties arise when starting the engine. This is due to the fact that a fairly large starting current is required to rotate the crankshaft. When the capacitance drops, the voltage drops to a value that is not enough to start the motor.
Before using the measuring device, you need to take into account the nominal capacity, which is indicated by the manufacturer on the label. It determines what load needs to be applied at the time of testing. With a capacity of 7 Ah, the load should be 3.5 V. For this, you can use a car headlight bulb.
The load is connected, after which it will take a few minutes. It is recommended to use a light bulb as a load because it immediately allows you to determine the state of the power source. If it starts to glow dimly immediately after connection, the battery can no longer be used.
In bright light from the lamp, you can measure the required indicator. If the multimeter shows 12.4 V, then the energy source is in good technical condition and the capacity is full. If the engine does not start with the battery in question, the problem lies in its technical condition.
A voltage reading of less than 12.4 V indicates that the battery will have to be replaced in the near future. Experts say that when the voltage at the terminals is less than 12 V, the device is completely discharged. If the indicator is less than 11 V, then the battery should not be used.

You can determine the battery capacity within just a few minutes. That is why, to extend the life of the purchased battery, it is recommended to carry out tests periodically, since deep discharge leads to damage to the structure and its rapid wear.

Types of measuring instruments

Before carrying out the test, you should purchase a more suitable measuring device. All multimeters are divided into two main groups:

Analog - a design option in which a special scale with arrows is used to indicate indicators. This type of device is one of the cheapest, but they are characterized by errors when taking readings.
Digital are measuring instruments that have become very widespread. Information is displayed on the screen, the device is characterized by high accuracy.

Restoring the capacity indicator

To ensure long-term battery life, periodic maintenance is recommended. The amount and density of the electrolyte can be restored if necessary. Recommendations for carrying out restoration work are as follows:

To restore the value, a fresh electrolyte is used, the density of which is 1.28 kg/cm3. The solution used must contain a desulfating additive. It takes about 48 hours for it to completely dissolve, during which the battery should not be used.
At the time of pouring, you need to measure the density using a hydrometer. This device is designed to determine the indicator in question.
The next step is to restore the battery level. To do this, unscrew the plugs, after which the charger is connected and the appropriate mode is selected.
In order for the replenished electrolyte to return to its properties, it is recommended to carry out several charging and discharging cycles. The charger applies a minimum current, which should be no more than 10% of the maximum.
At the time of charging, the power source should not heat up, as this will damage the installed plates. When the capacitance value increases to 13.8 V, the density of the water is checked, since too high an acid concentration leads to damage to the main structural elements.
Next, it is recommended to adjust the electrolyte density, since it may change during several charging cycles.
The next step is to discharge the battery. To do this, a light bulb or resistor is used as a load. Discharge is carried out until the voltage drops to 10.2 V. In this case, it is recommended to note the time from the moment the load is connected.

After restoring the battery capacity, it is recommended to add an additive that significantly increases its performance and service life. You cannot use a power source if the readings of the multimeters are far from the recommended ones.

Recommendations for use

Following certain operating recommendations can significantly extend battery life. As practice shows, it is when the battery is used incorrectly that it fails within a year. Recommendations for use are as follows:

Multiple full discharges should not be allowed. This is due to the fact that Ca-Ca batteries begin to quickly deteriorate when fully discharged. If you allow several such cases, you will have to replace the power source.
In winter, it is recommended to carry out periodic charging even if there are no problems. This is due to the fact that driving in the city at low speed when all consumers are turned on leads to a rapid loss of capacity, since the generator cannot cope with the high load.
Do not allow water or contaminants to come into contact with the surface of the terminals. This is due to the fact that a decrease in their conductivity leads to an increase in resistance.
Do not use the battery if the vehicle electronics are faulty. Even a small current leakage during long-term operation of the battery leads to an acceleration of the process of capacity loss.
In addition to the charge level, the electrolyte density is checked once a year. This indicator also determines the battery life. Too high a density leads to corrosion of the main elements, too low an indicator leads to a decrease in voltage.
Do not allow the battery to heat up. This is due to the fact that too high a temperature leads to a change in the basic properties of the electrolyte.

When choosing power sources, it is recommended to give preference to batteries from well-known manufacturers. This is due to the fact that their products are characterized by higher performance characteristics.

What is the capacity of a car battery?

The capacity of batteries that have been in use for 2–3 years gradually decreases. This provokes deterioration in the operation of the main components and the engine. There are problems starting the engine in winter. Therefore, every driver should know how to check the battery and which method to use.

Checking the car battery charge

Checking a modern car battery is simplified. After all, they include sensors that help determine the charge level. Such sensors are used by drivers to determine the approximate state of the power source.

A more accurate check of the battery capacity is carried out using a multimeter. This device is equipped with 2-3 operating modes. To check the battery voltage, perform the following steps: Setting the voltmeter mode. Measurements are carried out in the range of 0–20 V.

Disconnecting electrical wiring of vehicles and conductive terminals from the power source.
Connecting cables with clamps to the appropriate terminals.
The set voltage is recorded.

Checking the battery charge with a multimeter is easy. But at the same time, it is very important to follow the procedure established by experienced craftsmen. After all, it depends on how accurate the result will be obtained.

A working battery produces a voltage of 12.5–12.6 V. If lower values are displayed on the monitor, then recharging is performed. After this, the voltage must be measured again.

If the charge of the battery being tested is 11V, then its operation is not allowed. After all, dead car batteries affect the performance of the generator and power units of vehicles.

Before checking the charge of the power source, it is disconnected from the mains. It should be at rest for 4-6 hours.

How to check battery capacity?

What is battery capacity? How significant is this parameter?

The capacity of a car battery shows how much energy the unit produces in a certain time period. Knowing the actual battery capacity, it is easy to determine how long the device will operate.

Checking with a tester

Testers are used to check the functionality of the power source and establish the capacity. After all, these devices are distinguished by their extensive functionality. They are used to test various power sources.

Before using the tester, you need to learn how to measure battery capacity.

The tester includes a button with which various parameters are measured: capacity, load, current. Before testing, the required mode is selected.

The value obtained during the measurement process is considered approximate. To establish the exact value, mathematical formulas are used.

Application of a multimeter

Checking the battery capacity with a multimeter is easy. After all, this device is distinguished by its simple design and several operating modes.

To check the battery capacity with a multimeter, several methods are used.

Load testing

A light bulb acts as a load when measuring the battery capacity. If during testing the brightness of the light bulb decreases, it dims, and the test stops. After all, this indicates the inoperability of the power source.

Amperage is taken into account when determining the load required to measure battery capacity. If the rated capacity is 7 A/h, then the load value is 3.5 Volts. With such indicators, you can use a car headlight for testing.

To install the battery capacity, perform the following steps:

Disconnecting the power source from the generator.
Supplying the load. Under load, the battery operates for 1–2 minutes.
Load shedding.
Connecting to a multimeter device. The battery capacity is measured with a multimeter within 10–20 seconds.
Recording of readings.

A voltage of 12.4–12.5 Volts indicates that the car battery is functioning normally. If a value of 12 Volts or lower is determined, then there is a need to replace the power source.

Control discharge technique

To check the battery with a multimeter using the test discharge method, the load is first calculated. It should be equal to the strength of the discharge current. This parameter is recorded in the technical documentation that comes with the power source.

How to check the battery capacity if the passport is missing? The data is easy to find on the manufacturer's website.

The multimeter remains connected until the current drops to 50-60%. The value that was obtained is compared with that stated in the technical data sheet. If they differ significantly, it is recommended to replace the power supply.

Checking other parameters of the car power supply

A modern multimeter is multifunctional. With its help, not only the residual capacity of the battery is measured.

Voltage measurement

To calculate the voltage, the car battery is switched to voltmeter mode. If a unit whose load is 20 volts or more is used for testing, then enter the corresponding indicator. After adjustment, a black wire is connected to the negative terminal, and a red wire is connected to the positive terminal. Within 1-2 seconds, the monitor will display the voltage value (at constant current).

The voltage of a working power supply is 12.5-12.7 V. The state of the electrolytic composition in this case is normal. Therefore, the car battery is operated in standard mode.

This measurement method is used for alkaline-acid, lithium-ion and other batteries.

Internal resistance testing

The performance of a car battery largely depends on the value of internal resistance. To measure this indicator, you will need a light bulb (power - 12V) and a multifunctional multimeter.

The following list of actions is performed:

Connecting to the lamp power source. At the same time, charging the car battery is prohibited.
After 1–2 seconds, probes are connected to the conductive terminals, with the help of which the voltage is determined.
Turning off the lamp.
Repeated voltage measurement.

If the battery is in good condition, then the difference in the obtained values will not exceed 0.04–0.05 V. If the difference is more significant, then a more thorough assessment of the technical condition of the power source is required. After all, internal resistance is higher than normal.

Leakage current test

If you are aware of how to find out capacitance, you need to familiarize yourself with the features of determining leakage current. After all, the capacity also depends on this parameter.

The permissible self-discharge is specified in the technical data sheet that comes with the battery. Maximum energy losses are observed in acid-base power sources, which have different powers.

An increase in battery capacity leakage occurs due to the fact that there are areas in the circuit with poor-quality insulation. If the situation is not corrected, the car battery will discharge quickly. Sometimes poor insulation causes a short circuit or fire.

To determine current leakage, use a multimeter, which is switched to the appropriate mode. The indicator moves to 10 A.

There are two probes coming off the multimeter. The red probe is connected to the positive conductive terminal, and the black probe is completely disconnected. There should be no readings on the monitor at this moment. If the readings are present, then a leakage current is observed. In this case, the on-board system of the vehicle is checked.

How to restore battery capacity?

To ensure the operability of all vehicle components, it is not enough to know how to determine capacity. Motorists should explore ways to restore charge.

Preparation

Before restoring the charge and capacity of the battery, the power source is inspected. Electrolytic leaks are removed from the body. Conductive terminals are cleaned of dust, dirt and oxides.

The contaminated electrolytic composition is drained. It is also mandatory to wash the tanks and cans that are included in the composition.

Lead plates are checked. If the integrity of the elements is compromised, it is not worth restoring the charge. After all, these actions will not bring any results.

Control training cycle

Carry out to reduce the effect of sulfation and restore charge. What is the essence of this cycle? So, the battery is charged and discharged 2–4 times.

To control the process use:

Hydrometer. With its help, the density of the electrolytic composition is controlled.
Bulb. With its help they create a certain load.
Voltmeter or multimeter. Such devices are used to estimate current, voltage, and other parameters.

The frequency and duration of charging is set individually.

Multiple charging

Between charging and discharging cycles, breaks of 12–16 hours are established. The charging time is 7–8 hours. A more precise period is set taking into account the current strength, rated capacity, and other parameters.

A break between cycles is necessary to ensure that there is a uniform potential on the surface of the lead plates.

The number of restoration processes reaches 4–5. During this period, the degree of density of the electrolytic composition increases. If the density has increased excessively, the electrolytic composition is diluted. For this purpose, distilled water is used.

Chemicals

The essence of this technique is to pour sodium solution into the power source. This is done after draining the distilled water and washing the housing. The special solution is poured 2-3 times.

Monitoring the capacity of a car battery helps extend its service life. After all, even minor deviations provoke a rapid discharge, destruction of lead plates, and the formation of oxides. Every motorist can easily choose a way to check this indicator that is ideal.

Video on car battery capacity

How to check the capacity of a car battery?

The battery is a reusable current source that serves for autonomous power supply of various devices, and in this case, a car. Therefore, over time of use, the volume of the capacity may decrease, as a result, its operating time without additional charge decreases.

Battery Units

Rated capacity - this unit is most often used to determine the electrical charge of power supplies. The nominal capacity of a car battery is expressed in Ah, that is, in ampere-hours, or Ah (Ah – ampere – hour in the English abbreviation).

Electrical voltage is measured in volts, V. Batteries used in passenger cars most often have a standard value of 12 V. This is a characteristic indicated in the technical data sheet. And the voltage value is often indicated after the brand, for example, BOSCH 63 Ah, where 63 is the capacity of the car battery, Ah.

We check with a tester

So, to begin with, the car enthusiast is wondering how to determine the residual capacity of a car battery.

To determine the volume of the container and understand how functional it is, special testers are used. These are indispensable devices for testing all types of batteries; their functionality is enormous. The tester is not at all difficult to operate and in most cases has only one button, with which the indicators of various parameters are determined, for example, both the capacity volume and the current strength. The results obtained will not necessarily accurately reflect the condition of the battery, but if desired, using simple formulas, you can make a final calculation of the capacity of the car battery.

Application of a multimeter

A multimeter (or avometer, from the word ampere-voltmeter) is also a combined instrument used to measure the performance of electrical appliances.

It also has several operating modes and is not difficult to use.

There are several ways to take measurements and find out the capacity of a car battery.

Load testing

The load will be an ordinary light bulb. If during measurements the level of its brightness decreases, then testing will stop immediately, since this will indicate poor performance of the battery - there is not enough charge or the device circuitry is broken.

To calculate the required load for the capacity of a car battery, the first step is to take into account the number of amperes. If the capacity rating is, for example, 7 Ah (Ah), then the corresponding load value will be 3.5 Volts. If you don't have the right light bulb at hand, a regular car headlight will do just fine.

Measuring process

Every car enthusiast should know how to determine the capacity of a car battery!

To determine battery capacity measurements, carry out the following steps, in exact order:

First you need to disconnect the battery from the generator.
Next, connect the load in the form of a light bulb and let the battery run for just a couple of minutes. Then turn it off.
Then a multimeter is connected to the battery and measurements are taken for 20 seconds.

If the voltage is 12.5 Volts, then the battery is in good condition. But if the readings are 11.5 or even lower, then the battery needs to be replaced.

Check discharge method

In order to measure the capacity of a car battery in this way, you need to know the discharge current of a specific power source. To do this, you can look at the technical documentation attached to it. The capacity discharge current will be equal to the required load level that will be applied to the battery.

In this type of capacity volume measurement, the multimeter should remain connected to the battery for as long as possible until the current drops to 60, or preferably 50%. The result will be a value that must be compared with the value in the battery technical data sheet. Most likely, they will not coincide, since each charge/discharge of the battery gradually reduces its working capacity, but the numbers should not differ greatly! If the discrepancy is large, there is only one conclusion - replace the battery.

Measurements of other indicators

A modern multimeter is a device with great functionality. It is suitable for measuring other parameters of the power source.

Voltage measurement

If the battery type is alkaline-acid or lithium-ion, then you can measure the battery voltage by switching it to voltmeter mode. Depending on the load level of the device being measured, adjust the multimeter by setting the appropriate indicator. After this, a black wire is connected to the negative terminal of the battery, and a red wire is connected to the positive terminal. Literally within the next 2 seconds, the voltage indicator will be displayed on the multimeter screen.

If the battery is working properly, then the indicator value will be 12-12.5 Volts. This will indicate that the state of the power supply is normal.

Internal resistance test

Here again you will need a 12 V light bulb and, of course, a multimeter.

The internal resistance of the battery is also an important indicator of performance.

To take measurements, a car enthusiast or master proceeds in the following order:

A light bulb is connected to the battery. The battery is never charged!
After a couple of seconds, a multimeter is connected to the battery terminals and the first voltage measurement is taken.
The lamp turns off.
And a second voltage measurement is made.

If there is a difference in the obtained numbers, but it is not higher than 0.05 V, then the battery is considered to be in good condition. If the difference is higher, then either replacement or inspection and additional tests are required. Internal resistance must not exceed the norm!

Leakage current

If the above measurements are not so difficult to understand and remember the steps, then you need to move on to the question of how to check the capacity of a car battery for current leakage. This is an indicator on which the volume of the battery capacity itself, and therefore its “life”, directly depends.

The level of self-discharge allowed for a battery at rest is specified in its technical documentation. However, it is worth knowing that alkaline types of batteries have the highest level!

Any leak implies a break or poor sealing in the battery power circuit. And if the measurements revealed a leakage level much higher than the technically permissible level, then the battery will discharge even faster. But not only battery discharge can become a problem, since poor insulation of individual sections of the power circuit can lead to a short circuit or fire!

To test the level of battery current leakage, the multimeter is switched to the appropriate mode, and the voltage indicator is set to 10 Amps. The multimeter is connected in this way: the red wire is connected to the positive terminal, and the black wire is disconnected completely.

The leakage indicator is determined as follows: if nothing is displayed on the device monitor, it means that the test of the car battery capacity was successful, there is no leakage! If there are any indications, then it is urgent to check the entire on-board system.

Restoring power supply capacity

After taking all the necessary measurements, the next logical step is to learn how to restore the “size” of the battery capacity. Indeed, in any case, especially during long-term use of the vehicle, the battery loses some of its capacity.

How to restore the capacity of a car battery?

Preparation for restoration begins with inspection and superficial cleaning of the battery. It is necessary to remove all possible internal leaks, dirt and oxidation from the terminals. Before washing the tank itself, the contaminated electrolyte is drained. Lead plates must be checked for integrity, since otherwise the restoration procedure simply will not yield anything.

Next, a control cycle is carried out to completely discharge and further charge the battery. It is better to carry it out at least 4 times.

To control this cycle, you can use:

hydrometer - to determine the density of the internal composition of the battery;
light bulb - to create the required load;
voltmeter or multimeter.

Directly between the cycle of discharging and further charging the capacity of the car battery in mAh, a break of about 12-14 hours is set. The charge duration must be at least 8 hours. The technical documentation indicates the exact parameters of the required current strength and charging time; they must be taken into account in each specific case.

A period of rest between cycles is needed so that a single potential is established on top, on the surface of the lead plates.

For each complete discharge-charge cycle, the density of the electrolyte composition will increase. If it becomes very high, you can use distilled water to dilute it.

After the distilled water has been drained and all containers have been thoroughly washed, a sodium solution is poured into the battery. Its filling is also done in several approaches, 2-3 times.

Rules of manipulation

When working with any electrical appliances, everyone should be aware that voltage surges caused by forced disconnection from the power circuit will adversely affect the device itself. Therefore, all operations should take place, if possible, with the engine turned off. If there is a need to replace the battery while the engine is running, then to minimize voltage surges, you need to turn on all electrical appliances in the car (heated rear window, headlights, radio). And connect/disconnect each terminal as quickly as possible, without multiple touches. In this way, unwanted voltage drops will be kept to a minimum.

If there is a need to charge the battery from other equipment, then the devices must be connected with great care. Otherwise, this may also cause the devices to malfunction.

Interesting Facts

The concept of “best battery” simply does not exist. Different types serve different purposes. For example, calcium batteries have a low current leakage, but at the same time they almost cannot withstand deep discharges, especially in winter. At the same time, for standard “maintained” batteries, for example, lead-acid batteries with a capacity of 18Ah car battery, such a discharge will not be critical, but you will constantly have to take measurements and wash and top up with distilled water.

If the temperature is low, the battery's ability to “charge” is sharply reduced. Therefore, short trips in cold weather can lead to faster discharge. Even if the battery is new! And this will lead to the impossibility of starting the engine!

In winter, a heated design will be a good help for the battery, which will accelerate the increase in the temperature of the internal composition of the battery. After all, it has a certain viscosity, so its temperature decreases or increases following the ambient temperature, with a delay. And in order to help the battery receive a charge from the generator more efficiently, it is necessary to provide an additional source of warm air. And this in turn will help slow down the battery drain during rest. You can also take the device home and charge it after warming up to room temperature.

The more regularly the performance indicators of the power supply and the state of the “size” of its capacity are checked, the more timely it is possible to notice an increase in current leakage, and therefore carry out restoration. The more minor the deviations, the easier it is to carry out this procedure and the more likely it is to regain the lost volume. After all, using a battery inevitably leads to the destruction of lead plates and the formation of electrolyte leaks, and all this contributes to its slow failure.