The voltage of the car battery is the leading indicator, on the basis of which a competent driver should draw conclusions about the state of the battery, whether it needs to be charged or replaced. It is known that there is a direct dependence of the voltage on the level of charge of the car battery. First, we will consider the question of what voltage indicators can be used to conclude that the battery is working, why the battery loses U, and what the voltage rate means. After that, let's try to determine the battery charge by voltage: a table on the basis of which certain conclusions are drawn about the state of the battery will be attached at the end of the article.

The battery loses voltage: what is the reason?

If a charged power source is quickly discharged, there may be several reasons for this "behavior" of the battery. The battery charge level can quickly drop due to a natural reason: the battery has simply exhausted its resource in the usual way and needs to be recharged.

The alternator can also fail, which charges the battery while driving, helping it maintain the required level of operating condition. If the battery is not old yet, and the alternator is in order, it is likely that the car has serious problems with current in the form of its constant leakage.

In addition, the car's on-board network may be faulty - for example, a radio tape recorder or some other device takes too much current, and the battery simply cannot cope with this load.

In order to eliminate the voltage drop, it is sometimes enough to correct the problem by technical inspection, identifying the cause, eliminating it and re-measuring the voltage at the battery terminals after several hours of operation. It is important to evaluate indicators such as level, as well as measure the voltage under load and without it.

What does normal battery voltage mean?

For normal battery operation, its voltage should fluctuate between 12.6-12.7 volts, no less. This norm should be learned by novice drivers, like a multiplication table - in order not to miss the critical level of battery drop and not be in a position where the car suddenly “gets up”.

You should also be aware that, depending on the characteristics of the battery and the car, as well as other related conditions, the rate may vary - up to 13 volts and a little higher. This is what some battery manufacturers claim, and this factor must also be taken into account. How many volts should ideally be is a relative figure. But you always need to focus on readings from 12.6 to 13.3 volts - depending on the type and country of manufacture of the battery.

If the battery voltage drops below 12 volts, it is at least half discharged, and when it drops below 11.6 volts, the battery urgently needs to be charged.

So, the norm for the voltage indicator of most car batteries is from 12.6 to 12.7 volts, and if a non-standard battery model is used, the U norm can be slightly higher: 13 volts, but a maximum of 13.3. Some novice motorists ask what the U indicator should ideally be. Of course, there are no ideal figures, since the current level in the car network, weather conditions, and energy consumption by individual elements of the car's on-board network can change.

In order not to miss the moment when the battery charge begins to drop to a critical level, there is a so-called battery charge table. If you measured U at the terminals of your battery, you can determine the battery charge by voltage: the table will help you navigate this. It displays a directly proportional dependence of U on the level of battery charge as a percentage.

The table also shows the density of the electrolyte and the temperature at which it can freeze in the cold season - also depending on the level of charge and U in the battery.

Battery charge level table

Electrolyte density, g/cm³	Voltage (voltage) without load	Voltage (voltage) under load 100 amperes	Battery charge level, in %	Freezing point of electrolyte, in °С
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

The only source of current when starting the car is the battery. It starts the engine, which in turn starts the generator. From this moment on, the battery ceases to be a current source and becomes its consumer. During the operation of the motor, the voltage of a charged car battery rises and returns to normal.

However, during frequent short journeys, the battery does not have time to charge, there is a constant and regular decrease in charge. In this case, it is necessary to restore the current level using external devices. Consider to what level this is done, and how much time it takes for such a process.

Most situations in which a car battery is discharged are the fault of drivers. Less commonly, the reason lies in the design features or factory defects. The battery often loses its charge if there is insufficient tension on the alternator belt. Due to this, the belt slips and the generator does not work efficiently.

The same problem occurs when the door is not tightly closed or the trunk is not slammed to the end. The fault in this case will be working light bulbs. In a few hours, they can significantly lower the charge level.

Normal parameters for the battery

There are a number of parameters that a normally working battery must meet. Let's consider to what voltage a car battery can be discharged, but at the same time you need to know that too strong a discharge level contributes to a rapid deterioration in battery performance.

A battery is considered healthy if:

• open circuit - 12.6-12.8V;
• with the engine running, the "high beam" turned on and the speed about 1500 rpm - 13.8-14.2V;
• on serviced batteries, the density of the electrolyte at +20 C will be 1.28 g/ml.

There are also indicators at which it is required to raise the voltage in the battery:

• with the terminals open, the charge voltage of the car battery is less 12.6 V;
• the density of the electrolyte in the serviced battery is significantly lower 1.26 g/ml;
• the difference in density between the battery banks is more than 0.2 g/ml.

The electrolyte density level is measured under normal conditions, which are characterized by an atmospheric pressure of 760 mm r.s. and +20 C. At negative temperatures, it is desirable to increase the density of this liquid. The normal parameter for -20 C is the density of 1.4 g / ml, since 1.2 g / ml begins to freeze under such conditions.

Proper battery charging

If the measurement with a voltmeter or multimeter shows the minimum voltage of the car battery, then we recharge. For this operation, you need to configure the charging device to deliver current in the range from 0.05 to 0.1 of the numerical value of the capacitance. Accordingly, for a 55 Ah battery, an amperage of 2.75-5.5 A is used. The most gentle mode will be with lower values.

The output voltage for this operation should be at the level of 14.4-14.6 V. It is desirable that the device has the ability to set a static value. When a battery with a capacity of 55 Ah is completely discharged, it is necessary to withstand 10 hours with a current of 5.5 A.

A sign of the end of this procedure can be the invariance of the voltage at the terminals for 1-2 hours after the establishment of the specified parameters.

There may also be slight signs of boiling with slight gas formation. On automated chargers, shutdown occurs automatically. In the same way, the supply of current and voltage is regulated.

Safety regulations

You need to know that the basis for the electrolyte is acid, so the battery must be handled with extreme care. Avoid getting liquid on your hands, while protecting the skin with rubber gloves.

During boiling, toxic gases are released inside the battery. They cannot be inhaled, so it is advisable to organize the charging process in a room with good ventilation, preferably forced. It is also possible to release explosive hydrogen, so the use of open flame and sparking should be excluded. Do not leave homemade chargers unattended for a long time.

The engine is the "heart of the car", then the battery is part of its nervous system - it is its spinal cord. The operation of electrical appliances and, of course, the start of the engine depend on a normally functioning battery. Starting in cold weather is especially critical. By winter, the battery must be prepared. Any diagnostician and experienced car enthusiast knows that the key indicator in diagnosing a battery is its voltage.

Voltage is a physical quantity whose value is equal to the work of the effective electric field(including external fields), performed by transferring a unit test electric charge from point A to point B.

In simple terms, this is the accumulated energy that the battery will transfer to the starter when the key is turned. The starter will spend this energy, and then the generator will compensate. This process must be continuous. The driver must constantly monitor the voltage. In order not to get confused and do everything right, let's consider everything in order.

Normal performance with and without load

To recognize problems, you need to know how the battery works normally. To identify deviations in work, you need to know what voltage a charged car battery should show. Consider how to determine the charge battery.

It is very important to understand at what point to measure: at rest or under load. These are fundamentally different values. First of all, consider the nominal and actual voltage at rest of a charged battery without load.

• Rated (at rest) should be 12.6 - 12.7 V. This figure is written in the passports and instructions for batteries of almost any manufacturer and it indicates the full serviceability and normal operation of the battery.
• Actual(at rest) is somewhat different from the nominal. In fact, the range ranges from 12.4 to 12.8 V.

When measuring the battery voltage at rest, the value can rise to 13.2 V. This pattern will occur if measured immediately after charging, so you must wait 30 minutes and repeat the measurement. Then you will see the real figure.

Most often 12.6 volts is what the voltage should be normal battery.

Important! If the battery charge at rest fell below 12 V- this indicates an insufficient charge of the battery and it is urgent to put the battery on charge.

Now let's deal with the voltage of the battery under load. Why is it needed and what are the standards?

The load on the battery is required to check the performance of the battery. Any battery can withstand the standard voltage, but not any load. If you load the battery, the voltage will change.

This check is very simple. We load the battery with a special device.

The load should be almost twice the battery capacity. For example, if your battery has a capacity of 80 A / h, load it with 160 amperes.

The load is given to 5 seconds (no more)! Voltage should be higher 9 volt. If the charge falls below this limit, it means that the battery is discharged, or its further operation is impossible. There is one caveat to this process. After the load, the voltage should approach the norm in about 5-6 seconds.

To find out what condition the battery is in, you need to repeat the whole process after charging. If from the second time the value rises to 9 volts and above, then the battery is in a normal state, but it was discharged.

Determining the level of charge

The battery voltage is measured with a multimeter (a voltmeter or load plug is also suitable). In order to measure the voltage (whether under load or at rest), you need to switch the multimeter regulator to the "U" mode and lean the probes of the device against the battery terminals. The measurement result will appear on the display.

As mentioned above, measurements can be made at rest and under load. In the first case, and also, if we take the load from an external device - electrical circuits must be open, ignition off.

Checking the battery voltage under load using the car's on-board network is undesirable, because the network is not connected directly to the battery. Therefore, there may be measurement errors and inaccuracies.

Important! load fork must be used strictly according to the poles(plus or minus). But when measuring with a voltmeter or multimeter, you can ignore the polarity of the probes and battery terminals.

In addition to voltage, there is also the level of battery charge. These two values ​​are inseparable from each other. Knowing the normal and actual voltage of the battery, we can determine to what extent it is charged, whether it needs to be recharged again. Consider how to check the battery level.

Charge table

This table will help determine the condition of the battery and its degree of charge.

Define charge voltage level is not difficult. As can be seen from the table, when the voltage drops to 12.06 volts, we can talk about the battery being discharged by half. If the voltage drops to 11.31 volts, then it is only 10% charged. A voltage drop below indicates its full discharge. On the contrary, if the battery charge is 12.6 volts or more, then it is fully charged and no recharging is required. Voltage at 12.5 - 13 volts- exactly the one to which and needs to be charged.

It must be remembered that these data are relevant only for classic lead-acid batteries, the charge of EFB, AGM, GEL and other technological batteries must be checked according to other tables. For example in The voltage of a fully charged EFB battery is 16 volts.

Useful video

A detailed video on determining battery health by voltage:

Causes of deviations from the norm

If a charged battery loses its charge overnight, there can be a number of reasons. The battery charge level can quickly decrease due to a natural cause and a number of problems:

• The battery just ran out of power due to long service life and needs to be replaced.
• Also the generator may be broken., which charges the battery during the trip and compensates for the cost of battery energy to start the starter.
• If the battery is new and does not require replacement, and the generator works without disturbance, it is likely that the car has serious problems with current in the form of its constant leakage.

The issue of leakage current diagnostics is not considered in detail in this article, but it needs to be given close attention. In a nutshell: leakage current is the consumption of current, unforeseen by the design of the car, which systematically drains your battery. Theoretically, any device connected to the car's on-board network can be the cause of the leakage current.

All of the above causes and problems drain your battery. This explains the voltage drop, if they occur. Fortunately, normal and timely diagnosis makes it easy to identify and eliminate them.

It should be noted that the reverse situation may also occur. When the voltage exceeds 13 V and the so-called battery recharge occurs. This can happen due to a faulty generator (except when the car owner deliberately recharged the battery at the station, for example, in order to increase the density of the electrolyte). This can lead to boiling of the electrolyte and failure of the battery. Here are the main machine malfunctions that can lead to overcharging the battery:

• Device relay broken. This element turns off the generator after the battery is fully charged. If it does not work, the current continues to flow into a fully charged battery. This is a simple problem, it is not difficult to replace the relay, and it is inexpensive.
• The generator itself is broken. Repair will cost more, but the essence is the same as in the previous paragraph.
• Wrong charger selected.

Repeated measurements of the voltage at the battery terminals after the causes have been eliminated and several hours of its operation show the correctness of one reason or another. It is important to evaluate such indicators as the level of electrolyte density.

In conclusion, I would like to note that timely diagnosis and elimination of causes will extend the life of your battery and save your nerves and money in your wallet.

How many volts should a battery that is considered serviceable show? The required figures are known, although the voltage diagnostic method itself requires comments.

How many volts should a battery that is healthy and fully charged show - let's find out together, because this is the easiest way to check the condition of the battery. An ordinary voltmeter with tenths of a volt on the scale can be found, perhaps, in the garage of every self-respecting motorist, and this device can tell a lot about your battery.

measurements

- If the car was turned off a few hours ago and all this time the battery is also resting (all consumers on board are turned off), you can measure the open circuit voltage at the NRC terminals. For a properly charged battery, it should be 12.7 - 13.2 volts. In any case, a figure of at least 12.6 volts is a good result, it will also indicate the health of the car's electrical equipment. If less - the battery is discharged, and maybe even worse - it needs to be replaced.

The voltage at the battery terminals, which has spent several hours in a “resting state”, should be at least 12.6 - 12.7 volts

A half-dead battery shows about 12.0 V or slightly lower without load. If the battery terminals are only about 11.5 V, the energy reserve in it is close to zero (by the way, you can’t leave the battery in this state for a long time, because it will sulfate and lose capacity).

The charger of the old, transformer type, allows the owner to adjust the charging current at will - this is a useful feature

– Let the engine run for a few minutes after starting and without stopping it, reconnect the voltmeter to the battery. If the device shows the values ​​\u200b\u200bof 13.5 - 14.1 volts - both the battery and the generator are almost certainly in perfect order. If the voltage is higher, it means that either the battery is low (and is heavily charged by the generator), or the voltage in the network is too high due to a malfunction. Try to repeat the measurement after 5 - 10 minutes: if the readings fell below 14.2, then it was a dead battery, if not, deal with the generator and the charging circuit in more detail.

Not Just Volts

Another way to measure voltage makes it possible to assess not only the degree of charge, but also the condition of the battery as a whole - more precisely, its residual capacity. To do this, you need to measure the voltage at the terminals using the so-called load bridge - a device that measures the battery voltage under load, simulating the starter current. If at the fifth second the voltage at the terminals has not fallen below 9 - 10 volts, then the battery will still serve.

The load plug allows you to evaluate the remaining capacity and energy reserve in the battery

Of course, today there are more cunning, electronic devices that evaluate the condition of the battery by the rate of voltage drop, the response to a signal of a special form, the internal resistance of the battery, and other factors. But this is already a sphere of activity of professionals, into which we will not interfere today.

If you have an ordinary household multimeter or voltmeter on your household, do not be too lazy to measure the voltage at the battery terminals from time to time. This will allow you to notice the malfunction of electrical equipment in time and avoid the imminent unscheduled replacement of such an expensive component as a battery. After all, he is able to forgive a careless attitude towards himself for a long time, but when he finally gives up, nothing can be fixed: sulfation and crumbling plates are not “cured”.

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

The main causes of voltage drop

A car battery works on the principle of converting chemicals directly into electrical energy. When charging, the opposite happens. During the 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 voltage of the car battery is lost for the following reasons:

• battery life is completely expired;
• the generator broke down;
• there is current leakage 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 the wear of the device. Normal voltage can be restored even if the unit is used for several years. Merely measuring the current cannot be the basis for evaluating the quality characteristics of a battery.

Indicators in the normal state

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

A drop in indicators to 11.6 volts indicates a complete discharge of the device. Its use in this state is not possible. Here you will need a special recharging that can restore factory standards and get 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 realistic to determine the approximate percentage of charge. To do this, use the table below.

Readings in volts	Charge percentage

Parameters under load

The above indicated the normal voltage of the car battery without load. However, to determine the health of the battery in this way, as it turned out, is impossible. To do this, it is necessary to give the device a load twice as high by means of a special plug.

The duration of the working phase should be 4-5 seconds. The voltage should not fall below 9 volts. In case of a strong drawdown, the battery should first be charged and retested. The situation will not change if the battery life is completely exhausted.

Normal voltage on the 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 the car's 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 5-10 minutes after starting the engine. A constant increase in performance can lead to overcharging of the power source, due to which the electrolyte will boil away.

When measuring, 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), making measurements. With a faulty generator, the readings will drop by more than 0.2 V.

Influence of the winter season

Often, vehicle owners complain that battery parameters deteriorate at sub-zero temperatures. However, this is not quite true. During frost, a change in the density of the electrolyte occurs, which affects the generation of current. However, if the battery is sufficiently charged, nothing threatens. Therefore, it is not at all necessary to remove it in the cold season and bring it into heat.

Removal of indicators using special devices

The above is theoretical information that allows you to get acquainted with the basic norms. However, you also need to know how to measure the voltage of a car's battery. To take readings, special devices must be used that are connected directly to the battery terminals. The test is recommended to be carried out at an electrolyte temperature of 25 degrees.

When measuring without load, a tester is usually used. It selects a specific mode of operation. The red contact is connected to the positive pole, and the black one to the negative. The display should show the current value.

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

additional information

It is worth checking even the voltage of a new car battery after prolonged use. With a poorly functioning generator, 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 make measurements using an on-board PC, since the final result will have a significant error, which is explained by the specifics of connecting the device to the network. Rough data should not be used to identify problems.

A comprehensive check of the battery should 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 is about to expire.

Features of battery operation

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

1. Immediately before starting the engine, it is necessary to turn off the consumers of electricity. The load in one attempt should not exceed the time interval of 5-10 seconds. If the engine does not start from the fourth or fifth time, then the ignition and fuel supply systems should be diagnosed.
2. Periodically it is required to check the integrity of the wiring of the car. The current leakage in the circuits leads to a rapid discharge of the battery, and hence the loss of operating voltage. Measurement of the loss of electricity should be carried out at service stations.
3. When driving in the city in 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, generating the required current.
4. The battery must be kept clean, especially around the 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 recharging rules

The battery must be charged in a timely manner so that the voltage during the operation of the vehicle is optimal. When implementing this event, you must adhere to a number of rules.

1. Charging should be carried out at a temperature of more than 0 degrees.
2. Before connecting to the electrical network, filler plugs are unscrewed and left in the mounting holes.
3. A device capable of supplying 16 volts must be used.
4. Do not tighten the plugs within 20 minutes after completion of charging, so that the accumulated gases can freely escape.
5. The room must have supply and exhaust ventilation.
6. The criterion for the completion of the charge will be the achievement of the 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. Current measurements are recommended to be made 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

Each driver does not hurt to study the information about what should be the voltage on the car battery. With its help, he will be able to accurately determine the charge level and performance 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 accordance with the basic rules.