Important! The battery resistance is checked either when completely discharged (and this is unsafe for some types of batteries) or using additional resistance (shunt). Only a trained specialist can make such measurements, otherwise the device can be damaged.

Actually, this value is not required at home. Battery resistance is measured to identify a shorted cell in the battery. This technique is used by battery repair and restoration specialists.

The most common need for the average consumer is to check the battery charge of a car, flashlight or other household appliance. Your tester can easily cope with this task.
Many people ask the question: “How to check the capacity car battery multimeter? The correct answer is no.

Attention! It is impossible to measure capacitance directly with a multimeter.

Battery capacity is measured in ampere hours (Ah or Ah). Under constant load, the battery provides a certain current for a certain period of time. For example, the capacity of your car battery is 60 Ah.

This means that with a load current of 1 ampere, a working battery is guaranteed to work for 60 hours, without deterioration in parameters. Accordingly, at a current of 3 amperes, the operating time before the voltage drops will be 20 hours. Important! Of course, this applies to a fully charged battery.

As can be seen from the description, it is not possible to measure the battery capacity using a universal device. We can find out the magnitude of the current, residual voltage, but not the capacitance.

However, checking the battery capacity is possible at home

Measuring the battery capacity is necessary if your battery begins to discharge noticeably faster. This test is especially relevant in a car. In order not to find yourself far from civilization with a discharged battery, do not let it reach critical wear.

How to measure voltage on a battery with a multimeter?

If your device is not equipped with a load fork, you can make one yourself or simply use a powerful consumer for measurements. It must be remembered that the load is connected in parallel to the battery terminals, and not in series with the tester, as during the test discharge.

The power source must be loaded with a device similar in power to the standard operating mode. For example, you can check a car battery using a 15-35 W lamp.
First, we connect the measuring leads to the battery terminals and record the EMF value.

For automobile starter battery this value usually does not exceed 12.85 volts. Then, without removing the multimeter wires, we connect the load to the terminals. A high-quality and fully charged battery allows a slight voltage drop, no more than 0.2-0.4 volts. If after applying the load the voltage does not drop below 12.2 volts, your battery is fine.

How to check battery charge with a multimeter?

In order for the battery to undergo charge/discharge cycles correctly, you need to ensure the quality charger. In a car, the generator and voltage regulator are responsible for this.

Important! The charging voltage should be slightly higher than the operating voltage of the battery. Working system charging the car produces a voltage of about 14.5 volts.

How to check the charge with a multimeter? Very simple. Start your car's engine and measure the voltage at the battery terminals at idle speed.

If the voltage is within 14-14.4 volts, the generator and voltage regulator are working properly. Ask an assistant to increase the speed with the accelerator pedal, or open the air damper under the hood yourself. The tension may increase, but only slightly.

If its value “jumps” sharply following the speed, check the serviceability of the voltage regulator. Excessive voltage will quickly damage your battery.

Leakage current measurement

We looked at ways to check the battery voltage, measure the EMF value, and make sure the charger is working properly. Using the tester, you can make another measurement useful for a car battery - leakage current.

Probably, every car enthusiast has encountered a situation - he returned from vacation, the car sat in the garage for a month and a half, the battery was discharged. It seemed like everything was turned off and there was no sub-zero temperature outside. Why does the battery drain?

Any modern car has service electronic modules that remain switched on even without the ignition key. Immobilizer, comfort unit, engine control module, radio tape recorder that stores station settings in memory, and much more. How to find out the cause of battery discharge?

Using a multimeter. Remove the positive wire from the battery terminal, and connect your tester to the gap in current measurement mode.

Important! The leakage current can reach several amperes, so set the measuring limit on the multimeter correctly.

Secure the wires using alligator clips and begin to remove the fuses responsible for the vehicle’s electronic modules one by one. Of course, without technical manual not enough.

When you find a module or circuit that gives the maximum leakage current value, proceed to a local check. Disconnect the connectors and use a multimeter to check the wiring resistance. You can easily find the cause of the increased leakage without contacting the service.

Conclusion: You don’t have to purchase expensive equipment to keep you in good health. You can get by with a regular multimeter.

Video for those who believe that it is better to see once than to read.

The charge level of a car battery is measured when purchasing a new battery and if problems arise during operation. And if in the summer a certain discharge of the battery is acceptable, then as the temperature drops, difficulties may arise with power supply to the equipment or even starting the engine. Determining the battery charge level is a simple procedure that you can do yourself.

Normal battery charge

When purchasing a new power source, you should check the battery charge level, which refers to the amount of energy that the battery can produce over a certain period of time. That is why the battery charge is measured in Ampere-Hours. To obtain the most accurate readings, it is worth taking several measurements: without load or with it.

For a new battery, the potential difference level must be greater than 12 volts. If the car battery voltage drops to 10.8V, then using such a battery is not recommended - it should be charged. After the battery is fully charged, the voltage reading will be approximately 12.6 volts. The electrolyte density of a fully charged battery is approximately 1.28 g/cm3.

How does the voltage change when the battery is discharged?

The direct connection of parameters such as voltage and state of chemical elements (electrolyte and plates), as well as the charging level, affects the performance of the entire system.

After a car battery is fully charged, the electrolyte has a high acid concentration and the battery voltage is at its maximum. During operation, the density decreases, and therefore the voltage value drops, hence the battery charge. It is worth noting that the potential difference of the power source changes not only from the battery charge, but also from the number of devices connected to the network.

The relationship between battery charge and battery voltage can be seen in this figure:

The voltage and capacity of the battery are closely related. The manufacturer indicates both parameters in the power supply model. They show how much energy the battery produces over a certain discharge time. High currents and rapid discharge reduce the capacity of the power source, while lower ones can help increase this indicator.

It is customary to check the remaining battery capacity:

• by voltage under power using a load plug and direct current;
• spectral analysis;
• instruments that take readings at alternating current.

All these methods are based on information about the battery resistance, which allows only a qualitative assessment of the condition of the power source. The dependence of battery capacity on voltage is not a reason to determine battery performance. This is due to the possible presence of a floating charge, which will give a completely normal diagnostic result, which will not correspond to reality. Therefore, we recommend checking the residual capacity of the battery from voltage with the help of specialists who will conduct a computer study of the battery.

How to measure battery voltage correctly

The most accurate values ​​can be obtained by performing a set of diagnostics. To do this, you need to have special devices with you (multimeter, voltmeter or load plug). To measure voltage from the battery, it is necessary to connect the contacts of the device and the battery terminals. During diagnostic procedures, it is worth understanding that the power source connected to the vehicle’s on-board system consumes energy. Therefore, the readings may be slightly lower, but they should not fall below 11-11.5 volts. Carrying out correct measurements is permissible on a completely disconnected and charged battery, that is, the electrical circuit must be open. However, this is an optional condition: if you check the voltage in a closed circuit, then take into account a certain error.

1. The battery is connected to the system of a car that is not started. Under this condition, the on-board network consumes a certain amount of energy, so the voltage indicator should be in the range of 12.5-13.0 V.
2. With the car running and the energy consumption sources turned off, the device readings should vary between 13.5 and 14 volts. Higher readings indicate that the battery is discharged and the generator is not operating normally. It is worth considering that an increase in data during the cold season is not an accurate indication of a low battery. If the voltage is within limits for some time, then the system is fully operational. Reduced readings (from 13 to 13.4 volts) indicate some discharge of the battery. Battery needs charging.
3. With the car running and power consumption sources turned on, the voltage value should be greater than 12.8-13.0 V.

Please note that working with a multimeter or voltmeter allows for an inverse relationship between the poles of the measuring device and the battery terminals. The load plug must be used strictly in accordance with the polarity.

Checking the battery charge voltage is recommended some time after the car battery is fully charged, and also in conditions operating temperature(about 20 degrees Celsius).

Below is the table “Battery charge level by voltage”.

Table 1. Battery charge level by voltage.

How does the density of the electrolyte change when the battery is discharged?

Density should be understood as the ratio of distilled water and sulfuric acid (65% to 35%, respectively), which is the most optimal for automotive electrical power sources and ensures the accumulation of an electrical charge. The lower the electrolyte density, the lower the car battery voltage and its charge level. As density increases, battery performance deteriorates.

A certain degree of battery discharge is characterized by the active absorption of sulfuric acid and its deposition on the plates. Sulfation of metal elements causes an increase in their hardness and inability to participate in the chemical process. Because sulfuric acid spent, the ratio of components changes - the liquid becomes less dense, which affects the ability of the battery in the car to hold a charge.

You can clearly see the dependence of the battery charge level on the electrolyte density in this graph:

Table 2. Battery charge level by density.

Determining the battery charge level using the built-in hydrometric indicator

Diagnosing the performance of the power source using the methods described above is necessary in cases where the battery is not equipped with a special indicator. The presence of a car battery charging indicator allows you to assess the condition of the power source without the use of additional means.

When the battery charge is over 60%, the indicator lights up green. This means the battery is in full working order and the engine can be started. The absence of a green indication and the dark color of the window indicates a low battery charge and the need to charge it. Starting the vehicle may be difficult. A light indicator informs you that the percentage of distilled water is small - it needs to be topped up.

In this article, we tried to answer all questions about the battery charge level by voltage as fully as possible. To diagnose the condition of the power supply, you will need a special tool:

• a voltmeter or multimeter, with which you can conduct research on both voltage and resistance values;
• a hydrometer that measures the density of the electrolyte;
• a device necessary to charge a battery that has a certain degree of discharge.

For ease of understanding, the text contains a table of battery charge and a table of car battery voltage.

During work, do not forget about the degree of charge of the power source, which directly affects the readings obtained. The above devices will also help you determine the degree of charge.

The battery is an important element of the car system, allowing it to function fully even when it is not running. It’s unlikely that anyone wants to be faced with the problem of a discharged power supply at an inopportune moment. We strongly recommend that you carry out battery diagnostics at certain intervals. How do you check the charge? car battery, share with us in the comments.

One of the main components of cars is the battery. With its help, you can start the engine and enjoy various amenities in the cabin, including lighting, playing music, watching TV and much more.

For this reason, every driver should know what the ideal battery voltage is, how to operate it correctly and under what conditions to charge. Below we will tell you what normal voltage car battery depending on operating conditions and time of year.

Many cars do not have the ability to view the current voltage, so it is worth getting a multimeter. It is advisable to check the voltage once a month, and in winter at least once a week, especially if the car is parked outside.

Causes of voltage loss in the battery.

Before considering methods for analyzing and charging a battery, you should analyze the main reasons why the battery discharges:

• The battery has completely used up its own resource;
• the generator has failed;
• there is a current leak;

Many of these reasons can be corrected, after which the battery restores normal voltage, even if the unit itself has been in use for many years. It is equally important to evaluate the battery before using additional recharging or a major replacement with the purchase of a new element:

• conducting a visual inspection;
• measurement;
• preliminary voltage measurement.

Merely measuring current is not a correct factor in assessing the quality of battery performance. Several indicators are taken into account simultaneously, including analysis of the unit under load, forming a complete picture of the component’s operation.

Battery standards and indicators are in good condition.

The ideal normal car battery voltage is about 12.6-12.7 volts. This is provided that the unit is fully charged and ready for use. But, depending on certain characteristics, properties and factors, the indicators may be different, up to 13-13.2 volts. Many battery companies claim that the values ​​in their products are slightly different and this factor should also be taken into account.

You should not take measurements when the battery has just been removed from charging. It is not right. Only after an hour can a measurement be taken, when the voltage drops from 13 volts to the normal value.

When readings are below 12 volts, we can say that the battery is almost half discharged. An urgent restoration of normal parameters will be required. Operation under such conditions leads to sulfation of the lead plates, after which the unit can only be thrown away.

When the engine is not resource-demanding, this voltage is enough to start. If the battery is in good condition and the generator does not require repair, natural processes are sufficient to restore normal operation of the battery.

A drop to 11.6 volts indicates a complete discharge of the unit. Its use in such a situation is not possible. Here you need professional recharging, which allows you to restore factory standards and parameters.

A small conclusion can be drawn that the normal voltage of a car battery is always kept in the range of 12.6 to 12.7 volts. It is extremely rare that, depending on the battery model, the indicator may be 13.2 volts.

Ideal indicators are only on paper, because in real life they are difficult to meet. The average battery voltage in a regular car is 12.2-12.49 volts, and this is the first signal of insufficient charging. There is no need to worry about this. Final death for the battery begins at 11.9 volts and below.

Video (checking the battery with a multimeter).

Load stress analysis.

It is necessary to consider the condition of the battery from several angles in order to determine its condition as accurately as possible. For this reason, tension includes several factors:

• nominal indicators;
• actual properties;
• voltage under load.

The main indicator for analysis and study is the nominal indicator, which is actively used to study the principles of battery operation in the literature. According to all calculations, the normal voltage of a car battery should be 12 volts, but in fact this is not correct.

After applying the load, the indicators change. This is an important parameter for analyzing the condition of the unit, because the nominal indicators can be maintained, but the load is the only correct way to analyze the quality.

For work, a “load fork” is used - this is a device that forms a load in terms of capacity. It is twice the actual capacity of the battery.

If you have a unit with a rating of 60 Am/h, the load rating should be 120 Amperes. Over the course of several seconds, a load is formed, and the voltage should be at 9 Volts. When the indicator is in the region of 5-6 volts, then the battery is not suitable for further use. A few seconds after removing the load, the rated voltage returns.

When there are problems with voltage, you need to recharge and repeat the experiment. When the voltage is kept at 9 volts, then the battery is still usable and needs a basic recharge.

Video (checking battery voltage under load).

Electrolyte is the main parameter of analysis.

Using an electrolyte, you can determine the voltage level. If discharge occurs, the acid level decreases. Its overall figure is working fluid is about 35% (more details). Restoring the charge allows you to compensate for the consumption of acid by restoring it, but at this time water is consumed, which needs to be added. As a result, the density increases and factory parameters are restored.

At the normal position of 12.7 volts, the density will be 1.27 g/cm3. All components are mutual with each other, so a decrease in one will lead to the same decrease in the other.

Table of electrolyte density in the battery.

Winter is an evil enemy for any battery.

During cold weather, many note that battery performance decreases significantly and preventive measures are to take the unit home and put it in a warm place. The bottom line is that cold affects the density of the electrolyte, and a decrease this indicator forms a decrease in voltage.

When there is enough charge, frost affects the battery by increasing its density. For this reason, if the unit is normally charged, there will be no negative effects. A discharged battery undergoes a decrease in electrolyte, making it more difficult to start the engine.

In winter, low temperatures slow down some processes, so you need to constantly monitor indicators and, if possible, correct them using available methods.

Modern vehicles may have various types of lighting, music players, televisions and other elements that create a load on the power source. Insufficient car battery voltage will not allow for full functioning of all devices and accessories. In this case, it will simply not be possible to achieve comfortable operation of the machine.

Main reasons for voltage drop

A car battery works on the principle of conversion chemical substances directly into electrical energy. When charging, the opposite happens. During operation of the device, a current is generated due to the deposition of sulfates on the plates. The electrolyte concentration decreases, and the internal resistance simultaneously increases.

Most often, the car battery voltage is lost for the following reasons:

• The battery life has completely expired;
• the generator broke down;
• there is a current leak through the wiring;
• the chain was not designed for a certain load.

The situation can be corrected in almost all cases, if we are not talking about wear and tear of the device. Normal voltage can be restored even after using the unit for several years. Current measurement alone cannot be the basis for assessing the quality characteristics of a battery.

Indicators in normal condition

Ideally, the normal voltage of a car battery should not be less than 12.4-12.8 volts. When the performance decreases, it is not able to ensure full operation of the engine, but starting it when working generator can be produced. However, it is not recommended to continue using such a device, since coarse-crystalline lead sulfate may appear on the plates, which leads to a decrease in battery capacity.

A drop in readings to 11.6 volts indicates that the device is completely discharged. Its use in this condition is not possible. Here you will need a special recharge that can restore factory standards and obtain the normal voltage of the car battery at the output.

Auxiliary table

Knowing how many volts the measuring device shows, it is impossible to know the degree of wear of the electrical power source. However, it is quite possible to determine the approximate charging percentage. To do this, use the table below.

Readings in volts	Charge percentage

Parameters under load

The above indicates the normal voltage of the car battery without load. However, as it turned out, it is impossible to determine the performance of the battery in this way. To do this, the device must be loaded twice as high using a special plug.

The duration of the working phase should be 4-5 seconds. The voltage should not drop below 9 volts. If there is a strong drawdown, the first thing you should do is charge the battery and recheck it. The situation will not change if the battery life is completely exhausted.

Normal voltage on a car battery when the engine is running

The number of volts is also measured with the engine running. Under normal conditions, the operating voltage of a car battery should range from 13.5 to 14 V. When the battery is low, the indicator exceeds the maximum value, since the generator is forced to operate in enhanced mode.

In most cases, increased voltage does not pose any danger. If everything is normal with the electrical equipment, then it returns to normal within 5-10 minutes after starting the engine. A constant increase in performance can lead to overcharging of the power source, which will cause the electrolyte to boil away.

During measurements, there is also a low voltage of the car battery. This indicates that the battery does not have time to fully charge. For testing, it is necessary to gradually turn on electrical consumers (headlights, music, air conditioning and other devices), taking measurements. If the generator is faulty, the readings will drop by more than 0.2 V.

The influence of the winter season

Vehicle owners often complain that battery performance deteriorates at sub-zero temperatures. However, this is not quite true. During frosts, the density of the electrolyte changes, which affects the generation of current. However, if the battery is sufficiently charged, there is no danger. Therefore, it is not at all necessary to remove it in the cold season and bring it into the warmth.

Taking indicators using special instruments

The above is theoretical information that allows you to familiarize yourself with the basic norms. However, you also need to know how to measure the voltage of your car battery. To take readings, special devices must be used that are connected directly to the battery terminals. It is recommended to check at an electrolyte temperature of 25 degrees.

When taking measurements without load, a tester is usually used. A specific operating mode is selected on it. The red contact is connected to the positive terminal, and the black one to the negative terminal. The display should show the current value.

Readings in a closed circuit allow you to fix the load fork. It simulates an engine starting situation by measuring the operating voltage under such conditions. The measuring device is connected to the outlets according to the same circuit. The battery is loaded for 5 seconds.

additional information

It is worth checking even the voltage of a new car battery after prolonged use. If the generator is not working well, it can gradually discharge, which means that the voltmeter readings can be much lower than normal. Recharging will be required to restore acceptable values.

It is not recommended to take measurements using the on-board PC, since final result will have a significant error, which is explained by the specifics of connecting the device to the network. Estimates should not be used to identify problems.

A comprehensive battery check must be carried out regularly. If the vehicle has not been driven for several days and the meter shows a significant drop in voltage, the power supply has reached the end of its service life.

Features of battery operation

In order for the car battery voltage to remain normal for a long time, certain rules must be followed.

1. Immediately before starting the engine, it is necessary to turn off electrical consumers. The load during one attempt should not exceed a time interval of 5-10 seconds. If the engine does not start after the fourth or fifth try, then the ignition and fuel supply systems should be diagnosed.
2. Periodically it is necessary to check the integrity of the vehicle wiring. Existing current leaks in the circuits lead to rapid discharge of the battery, and hence loss of operating voltage. Electricity loss should be measured at service stations.
3. When driving in the city in the winter, when the engine is running at low speeds and there are a lot of consumers turned on, it is advisable to recharge the battery using stationary chargers. In this case, the power supply device will last longer, producing the required current.
4. The battery must be kept clean, especially in areas near the pole terminals. It is recommended to wipe it with a rag soaked in a solution of soda ash. You can also use an ammonia mixture.

Battery charging rules

The battery must be charged in a timely manner so that the voltage during operation vehicle was optimal. When carrying out this activity, you must adhere to a number of rules.

1. Charging must be done at temperatures greater than 0 degrees.
2. Before connecting to the electrical network, the filler plugs are unscrewed and left in the mounting holes.
3. You must use a device capable of providing 16 volts.
4. The plugs should not be tightened for 20 minutes after charging is completed, so that accumulated gases can escape freely.
5. The room must have supply and exhaust ventilation.
6. The criterion for completing the charge will be the achievement of an optimal voltage or density of 1.27 g / cu. cm.
7. The temperature of the electrolyte inside the device connected to the network should not exceed 45 degrees.
8. It is recommended to measure current 8 hours after charging.
9. If there is an indicator, then the time the device is disconnected from the network is determined by it.

Final part

It would do well for every driver to study information about what the voltage on the car battery should be. With its help, he will be able to accurately determine the charge level and performance capabilities of the battery. Measurements should be carried out both in static and dynamic mode using the above-mentioned devices. If necessary, the power supply must be charged in compliance with basic rules.

(Battery) is one of the most important components of a car. It provides electricity to the starter when starting the engine, and is also responsible for the operation of many other devices when engine not running: instrument panel and interior lighting lamps, radio, signal, fuel pump etc. Normal operation of all systems is possible only with a charged battery. That is why it must be serviced and charged on time.

But often the opposite happens. You come to the garage or parking lot, try to start the engine, but in response the starter gives you either the sounds of its incredible efforts to turn the flywheel at least a little, or simply clicks A in addition to everything on dashboard The lamp is on, indicating that the battery is low.

To avoid getting into such situations, it is necessary to systematically diagnose the battery, but first, let's figure out why it is discharged.

Reasons for battery discharge

There may be several reasons why the battery drains. Here are some of them:

• the battery has completely used up its resource;
• generator malfunction;
• leakage current;
• unauthorized operation of electrical appliances when the engine is not running.

Why is this happening

Any battery has a certain resource, even with timely maintenance. Modern batteries, depending on operating conditions, can last from 3 to 7 years. After this period, the car battery voltage gradually begins to decrease. This is due to the destruction of lead plates, which, unfortunately, cannot be avoided over time. Of course, you can try to restore the battery, but it will no longer work like a new one.

When the generator malfunctions, the charging voltage of the car battery jumps, drops, or is completely absent. In this case, the battery operates in emergency mode, which can lead not only to its discharge, but also to its failure.

Current leakage is one of the main reasons for battery discharge. It is easily determined using an ammeter or multimeter turned on in its mode. By measuring the current between removed terminal mass and negative we determine the amount of leakage. If it is higher than 80 mA, you should immediately contact the service to find the leak and fix the problem.

Often, car owners independently install additional electrical appliances (speakers, subwoofers, lighting elements, various electronic devices), without even realizing that they significantly exceed the network load specified by the car’s passport data. This inevitably leads to the fact that the generator can no longer cope with this load, and part of it is covered by the battery.

It happens that unlucky drivers, sometimes leaving the car, simply forget to turn off the headlights, radio, interior lighting or other devices that consume electricity. This inattention is also the reason fast discharge battery

A battery that is not serviced on time will also never work for long. Even if your car has a maintenance-free battery, you need to constantly look after it and periodically charge it.

Ways to check the condition of the battery

It is impossible to determine the condition of the battery in one way. You should not listen to “experts” who claim that by measuring the voltage of a car battery or its current, you can draw a conclusion about its performance. This is a complex process that includes the following activities:

• visual inspection;
• determination of electrolyte level;
• determination of electrolyte density;
• battery voltage measurement.

Visual inspection of the battery

The first thing you can do to determine whether the battery is working is to inspect it. Appearance can tell you a lot.

Dirt mixed with moisture and automotive fluids on the terminals is an unacceptable phenomenon. It leads to oxidation of metal parts and loss of electrical contact. As a result, in best case scenario We may end up with self-discharge, or at worst, a short circuit. If the battery is dirty, take the time to check the self-discharge current to make sure that it is necessary to maintain cleanliness under the hood. To do this, take an ammeter, disconnect the wires from the battery, touch one of the terminals with one probe, and simply run the other along the battery body. The value indicated on the ammeter screen will be the self-discharge current.

Next, take a look at the battery case. The presence of cracks and drips on it indicates mechanical damage, which caused the leakage of electrolyte. If this happens, it is no longer advisable to use this battery. When there are leaks from under the plugs, it is necessary to check the amount of electrolyte in each of the cans and eliminate the reason for its pouring out.

How to set the electrolyte level

It is possible to check the level only in serviced batteries. It is strongly recommended not to damage the integrity of the case maintenance-free battery to carry out unforeseen “maintenance”.

If the battery is serviceable, it needs to be removed, cleaned of dirt and the plugs unscrewed. The level is measured using a special tube with a millimeter scale. It is lowered into the jar until it comes into contact with the upper plate of the separator; the hole at the top is clamped with a finger. When pulling out, you can easily determine the electrolyte level. It should not be less than 10 mm. If the electrolyte level is less than the specified value, you need to determine the reason for its decrease. It usually falls due to normal boiling and evaporation. In this case, you just need to add distilled water to the jars.

If the level has decreased due to electrolyte spillage, you need to add ready-made electrolyte. After topping up, the battery must be recharged.

How to determine the density of an electrolyte

The main factor influencing the operating voltage of a car battery is the density of the electrolyte. It can only be measured using a special device - a hydrometer. It is a large pipette with a rubber bulb at the top, a scale and a float inside. Density measurements, of course, can also only be carried out in serviceable batteries. But what should its size be?

The electrolyte density for a fully charged battery at a temperature of 20 0 C is 1.27 g/cm 3 . As the battery discharges, this figure decreases.

Battery voltage measurement

What voltage must a car battery have in order to start the engine? There is no definite answer here and cannot be.

It is known that the voltage of a charged car battery should be 12.6-12.7 V. Depending on various conditions this figure may vary slightly, but if the charge drops below 12 V, the battery can be considered 50% discharged. It urgently needs to be charged, since deep discharge will inevitably lead to sulfation of the lead plates. But even with this indicator it is quite possible. Provided that the battery does not need repairs and the generator is charging, you can safely drive. But if the voltage does not exceed 11.6 V, the battery is considered completely discharged, and its further operation without diagnostics and charging is impossible.

Measuring the battery voltage is easy. To do this, you will need to disconnect the wires from it, and connect the contacts of a voltmeter or multimeter to the terminals in its mode, setting the limit to 20 V.

What determines the voltage of a car battery? Battery discharge level

Now let's try to figure out how the main parameters of the battery are interconnected. The voltage of a car battery directly depends on the density of the electrolyte. When the acid that is part (36%) of the electrolyte is consumed. As a result, its density decreases. The reverse process occurs when charging a battery: water consumption leads to the formation of acid, as a result of which the density of the electrolyte increases.

The voltage of a charged car battery (12.7 V) corresponds to a density of 1.27 g/cm 3 . When one of the indicators decreases, the other also decreases.

Table of dependence of battery voltage on electrolyte density

Electrolyte density, g/cm 3		Battery discharge level, %

How do the electrolyte density and battery voltage depend on the ambient temperature?

Car owners often hear that the car battery voltage can drop significantly in winter. You leave the car in the cold for a few days, they say, and that’s it, then you won’t start it. That is why some of them remove and take the battery home.

What happens inside the battery at low temperatures and what can this lead to? In fact, the car battery voltage does not drop in winter. Yes, the density of the electrolyte changes, but for a charged battery it increases, and for a discharged battery it decreases. In other words, if the battery is discharged, it must either be charged or carried with you. Otherwise, not only will it not be able to start the engine in cold weather, but the electrolyte in it may freeze, which will lead to rupture of the housing.

A charged battery is not in danger of anything like this. Yes, sometimes problems arise with starting the engine, but only because at low temperatures chemical processes proceed much more slowly, so the battery may not produce the power required to start. But it’s enough to bring it into the heat and hold it for a while, and it will again be ready to work as before. Therefore, the normal car battery voltage for winter period no different from the indicators for summer.

How to charge the battery

There are four ways to charge the battery. Each of them has its own advantages and disadvantages. Let's look at them.

A car battery consists of 6 cells connected in series. Each bank has a full charge of 2.10-2.15 V, so the total voltage is summed up and is 12.6 - 12.8 V. What is the voltage of the battery after the charger is turned off? When installing the battery in a car, the voltage after charging should be 12.4 V. This is normal. The car's starter battery is discharged during engine startup and, while driving, it recovers energy from the car's generator. If the battery voltage drops to 12 V, the device requires charging from the network. A large loss of charge in banks is characterized as a deep discharge that destroys the battery.

A car operated with the advantage of long runs has time to be fully charged from the generator for the next start. But its charge will not be full. The state of charge of the battery can be determined by the voltage at the terminals. The lower the value, the weaker the electrolyte concentration in the jars.

You can check the battery charge using a multimeter. You should set the “alternating current” calibration and measure the indicator at the terminals. You can determine the charge level by the density of the electrolyte.

The degree of charge of a car battery is determined by voltage, as in the table.

To increase the battery capacity, you need to charge it with a special charger. This is a voltage converter, rectifier. Batteries are serviced, maintenance-free, gel, AGM, lithium. Their charging voltage and current differ in voltage, time, and cycle duration. There are universal chargers designed to switch modes for different models Battery, parameter regulation.

Voltage at battery terminals when charging

To charge the battery from a charger, select the mode with DC or tension. Both are equally effective, but apply to different batteries. During charging and operating the battery, it is necessary to measure the voltage at the terminals of the acid battery.

To charge a 12 V battery, you will need to set the constant voltage mode to 16 -16.5 V. Using a current of 14.4 V, you can charge the battery by 75-85%. At a constant voltage, the charging current is variable and is limited only by the charger.

What charging voltage should I set? They proceed from the achievement of a critical voltage, accompanied by “boiling” - the release of gas from the car battery cans. A battery is considered to be normally charged, with a voltage at the terminals from 12.6 to 14.5 V. Readings should be taken with the device, without relying on on-board computer. The measurements with the engine running and with the battery disconnected are different.

The permissible charging voltage at the battery terminals when the engine is running varies from 13.5 -14 V. The indicator shows the battery is undercharged if the voltage is higher. You need to repeat the measurement after 2 minutes, the battery may have been discharged during startup. If the charging voltage is low, the battery is losing its life or the problems come from car generator. Measurements must be taken by turning off the on-board systems.

By measuring the battery charging voltage with the car not running, it is impossible to identify problems with the generator, but the degree of battery charge is well determined. A voltage of 12.5 - 14 V indicates no problems. If the indicator is low, you need to check:

• electrolyte condition - the substance should be transparent, the level should be normal;
• a lot depends on the battery charge level;
• determining the possibility of recharging to the optimal voltage.

Testing will reveal problems with the battery and its performance.

Charging a battery with constant resistance

Is it possible to charge a battery with a constant resistance? From the formula I =U*R, it is clear that if you set the resistance to a constant value, then the current or voltage will become variable. But inside the battery, resistance is a variable value that affects energy absorption. The total resistance consists of the polarization resistance, which changes, and the ohmic resistance, which remains stable under the same conditions and for a particular battery.

The resistance is affected by temperature, degree of discharge, and electrolyte concentration taken into account in the characteristics of the battery discharge curves. But if in the formula resistance is a variable value over time and the state of the car battery, then current, voltage, or a combination of current and voltage can be constant during charging. To smooth out the charging current, a resistor is used - ballast resistance.

What voltage should I set when charging the battery?

Voltage is a potential difference, and the current will flow in the direction where this value is smaller. Therefore, the charger voltage is always selected higher than the charging level of the car battery. The greater the voltage difference, the faster and more fully the car battery will gain capacity after charging.

During charging at a constant voltage, the limit of the parameter set on the charger is lower than the characteristic at which the release of gases from the battery being serviced begins. What potential difference is needed to charge a car battery? The maximum voltage used when charging the battery is 16.5 V. Which parameter should be depends on the type of battery. The time and completeness of battery charging depends on the voltage. The ratio of charge voltage and capacity recovery for a 12 V battery in 24 hours is as follows:

• With a voltage of 14.4 V you can charge the battery by 75-80%;
• Using a voltage of 15 V, the charge level is 85 - 90%;
• With a voltage of 16 V, the battery is charged by 95 - 97%;
• With a maximum voltage of 16.3 -16.5 V, the batteries are fully charged.

When the battery voltage reaches 14.4 - 14.5, the charging end signal lights up on the charger.

It has been established that it is this voltage of the car battery that does not create gas emissions after and during charging. Therefore, during actual vehicle operation, the generator, through a voltage regulator, limits the maximum voltage level to this value. In summer this figure is close to 100% capacity, in winter it corresponds to 13.9-14.3 V, with the engine running, which corresponds to 70-75% capacity.

Maximum battery charging voltage

We know, modern cars high class have an on-board system operating at 16 V. What batteries are used in these batteries? To avoid gas emissions, the system must be closed.

This means that maintenance-free Ca/Ca batteries can withstand harsh operating conditions. They use a special charging mode. Using calcium instead of antimony allows the battery to be charged at higher voltage, which causes the electrolyte to boil. Maintenance free battery does not tolerate sudden changes in voltage in the on-board network. It is designed for vehicles with a good electronic voltage control system. Hybrid batteries made from low-antimony and calcium plates are more tolerant of operating conditions.

Battery voltage at the end of charging

After the battery is fully charged, the charge will change slightly. The electrolyte dissociates and the pores of the current-carrying plates are filled. A car battery installed in the engine compartment takes on the temperature environment, and the capacity will change upward in hot weather or decrease in sub-zero temperatures. Therefore, after charging, you can find out exactly what the voltage of the car’s battery is by installing it in place. Even while in the workshop, the voltage at the terminals changes. This is especially noticeable if the cycle is not completed and the charging current has not dropped to 200 mA. In this case, charge redistribution occurs, and additional energy replenishment of the device is possible.

But if, after charging the battery, the voltage drops while the car is running, this is a reason to inspect the generator or replace the battery.

Dependence of battery charging on voltage

Each type of battery is charged based on the characteristics of the types of designs used. Serviced, gel and lithium batteries. Causes: boiling over, destruction of the composition, fire hazard. If the battery being serviced can be charged with a simple charger, lithium and gel systems require compliance with a 2-stage combined energy storage mode.

All systems are designed to prevent overcharging and are equipped with automatic power off when the voltage required for a car battery is reached. When charging, the current gradually decreases due to an increase in resistance, but the voltage remains stable. After charging, the electrochemical reaction process continues in the form of a slight self-discharge.

It is important that the charging voltage always exceeds the parameters required for operating the device. For current to flow, you need a slope, which is the voltage difference between the charger and the battery.

Video

We suggest you look at expert advice on how to properly charge and maintain a car battery, what voltage should be on the battery after charging.

Normal car battery voltage and how to measure it

The battery voltage, along with the capacity and density of the electrolyte, allows us to draw a conclusion about the condition of the battery. By the voltage of a car battery you can judge the degree of its charge. If you want to be aware of the condition of your battery and take proper care of it, then you definitely need to learn how to control the voltage. Moreover, it is not at all difficult. And we will try to clearly explain how this is done and what tools are needed.

First you need to define the concepts of voltage and electromotive force (EMF) of a car battery. EMF ensures the flow of current through the circuit and provides a potential difference at the terminals of the power source. In our case, this is a car battery. The battery voltage is determined by the potential difference.

EMF is a quantity that is equal to the work expended on moving a positive charge between the terminals of the power source. The values ​​of voltage and electromotive forces are inextricably linked. If there is no electromotive force in the battery, then there will be no voltage at its terminals. It should also be said that voltage and EMF exist without the passage of current in the circuit. In the open state, there is no current in the circuit, but the electromotive force is still excited in the battery and there is voltage at the terminals.

Both quantities, EMF and car battery voltage, are measured in volts. It is also worth adding that the electromotive force in a car battery arises as a result of electrochemical reactions occurring inside it. The relationship between EMF and battery voltage can be expressed by the following formula:

E = U + I*R 0 where

E – electromotive force;

U – voltage at the battery terminals;

I – current in the circuit;

R 0 – internal resistance of the battery.

As can be understood from this formula, the EMF is greater than the battery voltage by the amount of voltage drop inside it. In order not to fill your head with unnecessary information, let's put it simply. The electromotive force of a battery is the voltage at the battery terminals without taking into account leakage current and external load. That is, if you remove the battery from the car and measure the voltage, then in such an open circuit it will be equal to the EMF.

Voltage measurements are made with instruments such as a voltmeter or multimeter. In a battery, the magnitude of the emf depends on the density and temperature of the electrolyte. As the density of the electrolyte increases, the voltage and emf increase. For example, with an electrolyte density of 1.27 g/cm 3 and a temperature of 18 C, the voltage of the battery bank is 2.12 volts. And for a battery consisting of six cells, the voltage value will be 12.7 volts. This is the normal voltage of a car battery that is charged and not under load.

Normal car battery voltage

The voltage on the car battery should be 12.6-12.9 volts if it is fully charged. Measuring the battery voltage allows you to quickly assess the state of charge. But the actual condition and wear of the battery cannot be determined by voltage. To obtain reliable data on the condition of the battery, you need to check the actual battery and conduct a load test, which will be discussed below. We advise you to read the material on how.

However, using voltage you can always find out the state of charge of the battery. Below is a table of the battery charge level, which shows the voltage, density and freezing temperature of the electrolyte depending on the battery charge.

			Battery charge level, %
Electrolyte density, g/cm. cube (+15 degrees Celsius)	Voltage, V (no load)	Voltage, V (with load 100 A)	Battery charge level, %	Electrolyte freezing temperature, gr. Celsius
1,11	11,7	8,4	0	-7
1,12	11,76	8,54	6	-8
1,13	11,82	8,68	12,56	-9
1,14	11,88	8,84	19	-11
1,15	11,94	9	25	-13
1,16	12	9,14	31	-14
1,17	12,06	9,3	37,5	-16
1,18	12,12	9,46	44	-18
1,19	12,18	9,6	50	-24
1,2	12,24	9,74	56	-27
1,21	12,3	9,9	62,5	-32
1,22	12,36	10,06	69	-37
1,23	12,42	10,2	75	-42
1,24	12,48	10,34	81	-46
1,25	12,54	10,5	87,5	-50
1,26	12,6	10,66	94	-55
1,27	12,66	10,8	100	-60

We advise you to periodically check the voltage and charge the battery as needed. If the car battery voltage drops below 12 volts, it must be recharged from a wall charger. Operating it in this condition is highly not recommended.

Operating the battery in a discharged state leads to increased sulfation of the plates and, as a consequence, a decrease in capacity. In addition, this can lead to deep discharge, which is death for calcium batteries. For them, 2-3 deep discharges are a direct path to the landfill.

Well, now about what tool a car enthusiast needs to monitor the voltage and condition of the battery.

CARS CLUB

WHAT DO VOLTAGE AND CURRENT SAY?

Many people know how to check, but not everyone knows how it should be.

Vasily SINKEVICH, Valery KIRSANOV, SKB "Kamerton" (Minsk)

Nowadays, diagnostic testing electrical systems Car testing not only in a reputable car service center, but also in many small workshops is increasingly carried out using special auto testers. Their design (as well as the price) depends on the number and accuracy of the measured parameters. For car enthusiasts, simple instruments are intended that measure voltage, current, electrical resistance, and also rotation speed. crankshaft. Almost everyone who drives is capable of performing these measurements, but not everyone knows what the data obtained indicates.

Let's consider the diagnostics of the vehicle's power supply units - the battery and generator. To assess the condition of the battery, we connect an autotester to its terminals (you can also use an ordinary autometer tester). For all cars, the voltage on the battery without load (that is, without working consumers) should be on average 12.6 V. If it is less, the battery is partially discharged or faulty, and therefore the starter will rotate more slowly. The degree of discharge can be judged from the table below.

At a service station, the battery capacity is assessed using a load fork. This, simply put, is a set of resistances (shunts) connected to the battery.

When measuring the voltage with an autotester voltmeter, you can turn on the parking lights And high beam. The discharge current at such a load (tested several times) will be 5–6 A. If the voltage does not drop below 11.5 V, the battery is fine.

The voltage at the battery terminals when starting the engine with the starter should not fall below 9.5 V. Otherwise, the starter is faulty (consumes a lot of energy). Moreover, the older it is, the more oxidized all its contacts are - brushes, relays, etc. In some cases, because of this, the starting current can reach a huge value - 150–200 A.

By the way, about current measurement. Usually, for this purpose, an ammeter is connected to the open circuit. It is undesirable to break circuits in a car, and not all devices will be able to record such large values ​​as when starting the engine. Motor testers use special overhead sensors that do not require breaking the circuit. They use the effect of changing the magnetic field strength when a current of a certain magnitude passes. The insulation of the wires does not interfere with such measurements.

We continue checking. After starting the engine, we monitor the voltage at the battery terminals and the charging current. Two more important components of the vehicle's electrical equipment are included in the work - the generator and the relay-voltage regulator. A few seconds after starting, the voltage at the terminals rises above 12.6 V. The generator begins to charge the battery. We increase the engine speed to 2000 per minute and control the charge voltage. The normal value is from 13.8 to 14.5 V.

The operation of the generator under load can be assessed by turning on the headlights. The voltage should be higher than 13.8 V. If it is lower (12.6–13 V), you need to check the tension of the generator drive belt. Low voltage may also be caused by defects in the generator itself. But if it works properly, then you should look for the reason in the relay regulator. In older mechanical relays, the voltage can be raised by adjusting its lower level. In modern electronic adjustment is impossible, so you need to check the reliability of their contacts with the circuit. They are fine - that means the relay is faulty.

If the voltage, having overcome the 14.5 V mark, continues to increase, then we adjust the electromechanical relay or replace the electronic one.

The charge current after starting the engine is usually 6–10 A and as the engine operates and the battery is charged, it drops to zero when the consumers are turned off.

Let's estimate the voltage at other points of the electrical equipment system. The difference between the voltage measured at battery, and the voltage between its “minus” and the “battery” (mains) contact on the ignition coil will indicate losses in the circuit running from the battery to the coil. They should be minimal - no higher than 1 V. If a coil is installed on the car that does not have a ballast resistor (additional resistance as in the Moskvich of previous models, IZh) or if the resistor is connected on the battery side and the difference is more than 1 V, the reason should be sought in reliability of contacts of wires with devices, primarily in the ignition switch. This would seem to be a trifle, but because of it, a high voltage less than the nominal value will be generated in the secondary winding of the ignition coil. This will lead to a decrease in spark energy and, as a result, to a decrease in engine power characteristics.

For coils with a ballast resistor (at the terminal after the ballast resistor), the voltage should be in the range of 5–9 V. If the contacts in the supply wires are poor or the resistor is faulty, the voltage may be less than 5 V. If it is higher than 9 V, then it may have occurred short circuit of the ballast resistor.

By measuring the voltage between the battery negative and the ignition coil contact that is connected to the breaker, we can assess the degree of cleanliness of the breaker contacts in our old classic car models. In mechanical breakers, you should pay attention to this when the voltage value is more than 0.3 V. If the contacts are in order, you need to check the reliability of the connection of the support board inside the breaker to ground. Possible reason An increase in voltage may also be due to an unreliable connection of the breaker to ground or a malfunction of the capacitor.

This is how, by taking measurements at just three points of the vehicle’s electrical equipment, you can evaluate the operation of current sources.

DEPENDENCE OF VOLTAGE AT BATTERY TERMINALS ON ITS DEGREE OF DISCHARGE

Battery voltage - 12.6 12.0 11.6 11.3 10.5

battery, V

Degree of discharge, % 0 25 50 75 99