Minimum car battery voltage

Self-checking the voltage of a charged car battery is easy

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Battery charger

The most optimal charging rate for a car battery should be about 12.65 volts; it is acceptable for the car battery voltage to be slightly less high or low, by 0.5 V. If the charge value is less, this indicates that the device is not sufficiently charged. For example, if the charge indicator is approximately 12.

42 V, this indicates that the battery is approximately 80% charged. If the car battery voltage is 12.2 V, then the charge level is 60%. In the event that this indicator is only 11.

9 V, this indicates a critically low battery level; using such a battery may make it impossible to start the engine.

Naturally, not many car batteries allow a voltage level of 12.65 V. As practice shows, on most devices the battery voltage varies around 12.2-12.4 V, which indicates a lack of charge.

As for the maximum indicator, many manufacturers assure consumers that their batteries produce a charging voltage of 13-13.2 V. This is nothing more than a publicity stunt. Of course, you can find batteries that provide about 13.

2 volts, however this is rather an exception.

Do-it-yourself battery voltage measurement

If necessary, you can measure the voltage of a charged car battery at home. To diagnose this parameter, you will need a multimeter or voltmeter.

The procedure for measuring and monitoring the charge of a partially or fully charged battery is as follows:

First you need to remove the battery from the seat of the car. Disconnect the terminals and, if necessary, clean the device terminals - if they are oxidized, the obtained values may be inaccurate. You should also clean the device body from dust and dirt. Remove the plate securing the battery, and then remove it from its seat. Inspect the case carefully - there should be no cracks or other signs of damage, otherwise the verification process will be impractical.
Before starting the procedure, make sure that the level of the electrolyte solution in the jars is normal. To do this, unscrew each can and check the volume. If it is clear that it is insufficient, that is, the liquid does not cover all the jars, distilled water should be added. Only after this can you start measuring.
First of all, the voltage level is measured without load on the device; to do this, connect the probes of a multimeter or voltmeter to the battery terminals, observing the polarity. That is, plus to plus, minus to minus. Turn on the tester and measure the value approximately 5 seconds after activation. As stated above, ideally the resulting reading should be approximately 12.6 volts. You can also test each individual bank - in this case, the tester should produce about 2.1 V.
When the first diagnostic stage is completed, you can proceed to the next one - now you should measure the same parameter, only under load.
To implement this step, you will need to additionally enter a resistance, and its value must correspond to the battery capacity. The resistance should be approximately 0.01 Ohm for batteries with a capacity of 100 Ah. When the resistance is set, the procedure is repeated in a similar way. That is, the battery should be connected to the tester, and after 5 seconds the parameters are read. On average, under load, the voltage on the banks should be approximately 1.8 V, and the total charge level should be approximately 12.2-12.6 V (author of a video on how to correctly measure battery voltage - channel VAZ 2101-2107 REPAIR AND MAINTENANCE).

If during the diagnostics it turns out that the obtained values differ from the nominal ones, and the gap is quite large, then this indicates the need to solve the problem.

If you continue to use your vehicle with a partially discharged battery, it may cause more serious problems later.

If the values differ, you need to make sure that the tester you are using is fully functional, otherwise it may produce incorrect results.

Test results do not meet the required requirements - actions of the car owner

So, if you are faced with a similar problem, then the best way out of this situation would be to replenish the battery charge using a charger. If you have the appropriate device, then you can do everything yourself at home.

There are several ways to recharge your device at home:

Accelerated option.
In most modern chargers that are sold on the car market today, this mode is called Boost. It should be noted that this method is more relevant if you urgently need to start the engine for a trip, but there is simply no time to recharge the device. The charging procedure allows you to replenish the battery capacity much faster as a result of using a higher current. Please note that this option cannot be used constantly, as this can lead to destruction of the plates installed inside the structure, and accordingly, to a reduction in the service life of the device as a whole. The accelerated charging method can only be used in extreme, exceptional cases.
Another option is with constant voltage.
This method of replenishing capacity is based on maintaining a constant volt value across the contacts. On most modern chargers, this option is used as automatic. Most experts recommend resorting to this method when the device’s discharge level is not critical, that is, it corresponds to at least 12 volts. It should be noted that this option is most often used among our compatriots. Its main advantage is that the car owner does not need to constantly monitor the process, in particular when it comes to automatic chargers. Such devices allow you to automatically determine the level of charge of the device, and if the device replenishes its charge, the device itself turns off the power. Another advantage of this method is that it does not destroy the internal structure of the battery.
The next method is with direct current.
As the name suggests, this method is based on conducting direct current through a car battery. The charging procedure is carried out in several stages, at each of which the current gradually decreases. If you urgently need to start the engine and drive somewhere, then this option will not suit you, since it takes longer than all those described above. The implementation of this method is more relevant if the battery is completely and deeply discharged - the direct current method will make it possible to more optimally replenish the battery capacity without destroying its plates. The only, but most significant drawback is that the car owner will need to constantly monitor the completion of this task and measure the voltage. And when the procedure is completed, you will need to disconnect the battery from the power supply in time.

Photo gallery “Replenishing the charge of ABC on our own”

Remember that the charging procedure must be carried out if the battery has no damage to the case and its contacts are intact. Damage to the device body can lead to leakage of electrolyte, which will cause the capacity to drop.

If using the charger does not produce results and after a few engine starting cycles the discharge problem is again diagnosed, most likely the problem lies in the device itself.

Most likely, damage to the plates inside the battery has occurred, and this problem cannot be solved at home. The only solution is to completely replace the battery.

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Video “Visual instructions for charging a car battery”

Detailed instructions on how to charge a car battery with your own hands using a charger at home are given in the video below (the author of the video is the Science Vetal channel).

Do you have any questions? Specialists and readers of the AVTOKLEMA website will help you ask a question

Source: https://avtoklema.com/akkymylyator/naprjazhenie-zarjazhennogo-avtomobilnogo-akkumuljatora-805/

Normal car battery voltage

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 the normal voltage of a car battery is, 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;
increased load on the electrical circuit.

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:

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.

Standards and indicators of the battery in normal 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 they are hard to meet in real life. 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 total indicator in the working fluid is about 35% (more details here).

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.

Battery electrolyte density table

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 in this indicator results in 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.

Source: http://autoepoch.ru/avtoazbuka/normalnoe-napryazhenie-akkumulyatora-avtomobilya.html

Car battery voltage - how to take measurements and judge the condition of the battery from them

The driver must be able to evaluate the battery. One of the important indicators is tension.

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Many car enthusiasts know how to check the voltage of a car battery, but not everyone knows what it should be. For cars, the voltage without consumers should be 12.65 V. If the readings are lower, the battery is partially discharged or faulty. A drop to 12 V still allows the car to start. You can evaluate the degree of sparseness based on the table:

They will protect the chassis and save you money, increasing ground clearance by 3 cm.

When measuring voltage, you can connect, like a load, dimensions and high beam lamps. It has been established that the discharge current will be about 6 A, as consumed by the starter. The voltage in a working battery should not fall below 11.5 V. The main load of the battery is the starter.

We check the readings on the terminals when turning it on - they should not fall below 9.5 V. If less, the starter uses too much energy due to a malfunction. More often this happens due to aging - contacts oxidize.

Sometimes the current when starting the starter reaches an unimaginable value of up to 200 A.

To continue the test, start the engine. In addition to the battery, a generator with a relay regulator works. When the engine starts, the voltage initially drops, but a few seconds pass and it begins to rise, exceeding 12.6 V.

Battery charging begins. We control the value of the charging voltage by increasing the speed to 2000. The normal value is 13.8–14.5 V. With further increase, adjustment of the mechanical relay or replacement of the electronic one is required.

Based on the voltage value, you can assess the health of the generator. We create a load for it: turn on the headlights. The voltmeter should show more than 13.8 V when the engine is running. If it is 12.6–13.0 V, check the belt tension - the reason may lie there.

The generator may be faulty, but if everything is fine with it, we turn our attention to the relay regulator. In mechanical relays that were installed on cars earlier, the contacts were adjusted and the voltage was raised. Electronic relays are not adjustable, check the contacts.

If everything is fine with them, you will have to replace the relay.

The battery voltage is measured with a tester, also called a multimeter, or a regular voltmeter is used. To check the parameters under load, a load fork is used.

The device has two contacts - a voltmeter and a resistance. With its use, you can measure voltage, creating an imitation of the operation of the starter when starting the engine.

It is created by selecting the resistance, which must match the capacitance.

To use the multimeter, switch it to the appropriate mode and touch the terminals with the probes. To take objective indicators, disconnect the battery from the consumers and remove the contacts.

We connect the red probe to the positive terminal, the black one to the negative terminal. The display will show the values.

If the probes are connected incorrectly, no disaster will occur, the display will simply display negative values.

The battery voltage is measured with a tester, also called a multimeter, or using a regular voltmeter

We connect the load plug with terminals to the battery terminals and take readings at the fifth second. A drop below 9 V indicates a loss of functionality of the current source; it must be replaced.

We first check the battery voltage with a multimeter without load. The indicators should indicate a full charge - 12.65 V. If discharged, charge, after which you can test with a load plug.

A working battery under load will first drop to 10–10.5 V, then the figure rises slightly.

Among the voltage indicators, one should distinguish between nominal, actual and loaded. It is usually assumed that the voltage is 12 V, this indicator is nominal.

It does not meet actual performance, especially under load. Normally, the value of a charged battery at rest is 12.65 V. In fact, the actual value is from 12.4 V to 12.8, it is the most reliable.

The indicator is taken on the battery disconnected from consumers.

Applying a load will change the parameters: they will be very far from nominal and actual. To find out its performance, tests must be carried out using a load.

In most cases, the voltmeter shows a normal state on a charged battery, but as soon as you connect the load, it “dies”. The load for checking the condition is created, as already noted, by a special device - a load fork.

The load should be twice the battery capacity.

The most common batteries are those with a capacity of 60 Ah

The most popular battery has a capacity of 60 A/h, for which we select a load of 120 A. It is supplied for no more than 5 seconds, and we take readings on the latter.

They should not fall below 9 V; lower values are present when the load fork test is carried out on an uncharged battery. There's nothing wrong with it - they recharged it and that's it.

But if the charge is full (outside the circuit it showed 12.6 V), and with the plug 5-6, it’s time to change it to a new one. You should also know that after a load fork, the voltage is restored to normal within 5 seconds.

The voltage is determined by the internal contents of the battery - the state of the electrolytic filler. The discharge is accompanied by the consumption of acid, which is part of it.

When discharging, the density decreases, and when charging, the process occurs in the reverse order: water is consumed, acid is formed. This leads to increased density. The required state of 12.7 V is observed at a density of 1.27 g/cm3.

The indicators are interrelated - changes in one are accompanied by changes in the other.

In winter, drivers often complain that it is impossible to turn the engine with the starter; the main parameters of the current source have dropped. Some people remove the battery at night and take it to a warm place.

In fact, in severe frost, processes occur in the battery that are completely different from those that most drivers imagine. It is absolutely not necessary to remove the battery every time and take it somewhere warm, you need to charge it well.

A good charge is a guarantee of normal density and voltage, which will be sufficient to start the car in the most severe frost.

Battery discharge is accompanied by consumption of acid, which is part of it.

What happens to the battery in severe frosts? If you leave it discharged in the cold overnight, the density level rapidly decreases, and in the morning there will not be enough voltage to start the car.

A good charge level leads to an increase in density, even in the cold, which increases the second interrelated important parameter. Therefore, in the most severe frosts, a normally charged battery does not reduce its performance.

A reduced level of density, in addition to preventing the engine from starting, can lead to freezing of the electrolyte and rupture of the housing.

If the voltage is less than 12 Volts, the battery should not be used; it should be charged. Further operation with high discharge leads to irreversible negative consequences. The process of sulfation of the plates begins and the capacity drops.

The critical norm is 10.8 V, below which a deep discharge occurs, at which the service life is greatly reduced. Maintenance-free calcium batteries especially suffer from this. 2-3 deep discharges are enough, and the capacity is lost forever.

Try to prevent further use of the battery when the voltage drops below 12 V

Another important point that is related to normal voltage. After charging, the voltmeter reads 12.6 V. We install the battery, measure the voltage and see a drop: 12.4–12.5 V. This is not a reason for concern, but to remain in a normal state. When the circuit is open, the indicators are slightly higher; this is actually not voltage, but electromotive force (EMF).

If the battery is working, but not charged, we charge it. Modern technology knows three methods:

accelerated, typical of many modern chargers;
using constant voltage;
on direct current.

The faster mode, called Boost, does not provide a full charge sufficient to start the car. This method is used when the car battery is dead and you need to leave immediately. The principle of this method is an increased charging current. It is often not recommended to use it - it greatly reduces the battery life.

Constant voltage charging maintains a constant voltage. This mode is used for a light discharge: not lower than 12 V. The process is completely automatic: connect the contacts, and you can be free - no control is required. When the required charge level is reached, the device detects this and turns off.

DC charging is the most complete and uniform. We gradually reduce the current manually. We constantly monitor the voltage and stop charging when the norm is reached. Recommended for heavily discharged batteries.

Source: http://tuningkod.ru/obsluzhivanie-avto/akkumulyator/napryazhenie-akkumulyatora-avtomobilya.html

What should the battery voltage be with the engine running: checking the battery voltage

A dead car battery is an unpleasant surprise. Especially when the battery is new and the battery has just been charged. Of course, you can start the engine “from a pusher” or “by lighting it” from another car. However, it is necessary to eliminate the cause of the problem. Information on how to check the battery voltage while the engine is running will help with this.

A little theory

First you need to understand what functions the battery performs:

Starts the engine. Namely, it provides energy (spark) for ignition and rotates the starter motor. Well, and, of course, in modern car models it provides power to all electronics. If the battery is completely discharged or absent, the engine cannot be started at all;
When the engine is not running, it powers all electronics (dimensions, electrical equipment, etc.);
Performs auxiliary functions for the generator when the load on it is too heavy.

As you can see, the role of this part in the design of any machine is very significant. For this reason, the battery must not only be charged in a timely manner (especially for those who travel short distances), but also its performance must be regularly checked. In this case, it will be able to last much longer, and the driver will be able to avoid many problems on the road.

Why do you need to check your battery?

Checking the battery should be part of a regular procedure during a routine inspection of your car for every driver. It includes several points:

Visual inspection. Here you need to pay attention to the integrity of the case (especially after extreme trips on rough roads), electrolyte leaks on the case, as well as the condition of the terminals. They need to be cleaned from time to time with sandpaper, removing the oxide film. The fact is that all these contaminants can become one of the reasons for the appearance of battery self-discharge currents.
Checking the electrolyte level and density. To perform the first step, you will have to unscrew the lids of all the cans (you will need a large flat-head screwdriver). Next, you can determine the level “by eye” (the liquid should cover the plates), or you can use a special device - a level tube. For the second step you will need a hydrometer. It has an affordable price and is desirable to have in the garage.
Measuring the voltage at the terminals when the engine is not running and when the engine is running. For this operation you will need a multimeter (preferably) or a voltmeter. By the way, we should dwell in more detail on checking the voltage on the car battery while the engine is running.

Why check the charge with the engine running?

The operation of any device or component in the machine must be stable. The same applies to the battery. More specifically, the voltage that the battery produces. Normally, when the engine is running, the voltage is 13.5 - 14.0 volts. If it is higher, this indicates that the generator is working in enhanced mode and the battery is being recharged.

This in itself is not a problem, because the battery could be discharged, for example, during a long stay. This is especially true in cases where the outside temperature is low.

During normal operation of all electrical appliances, the excess voltage will quickly drop to normal by itself.

It will be much worse if the voltage is low. This means that the car battery is constantly undercharged.

Firstly, this may indicate a problem with the generator. And secondly, the life of the battery itself is significantly reduced.

In order to identify problems in the generator and save money on buying a new battery, you need to check what the voltage of the car battery is when the engine is running.

How to check voltage

As mentioned above, this operation is best carried out using a multimeter. To do this, first of all, with the engine running, you need to turn off all electrical appliances: headlights, interior lights, radio, and so on. This way the results will be more accurate. Next, following the instructions for the device, take measurements.

After this, without turning off the engine, it is necessary to apply a load. That is, turn on electrical appliances. If the readings are within normal limits, then everything is fine. If the voltage at the battery terminals while the engine is running drops below 13 volts, this indicates that the battery is not being charged, which in turn means problems with the generator.

Of course, modern cars have on-board computers that also show voltage in numbers. However, the difference is that they are not connected directly to the battery. It becomes clear that there will inevitably be leaks along the path from the battery to the built-in voltmeter.

That is, the numbers will be somewhat inaccurate. We also recommend reading the article on how to measure the density of the electrolyte in the battery yourself. From this article you will learn about the features of measuring density, as well as what features and nuances need to be taken into account when adding acid or distilled water to jars.

From this we can conclude that it is optimal to measure the voltage directly, that is, directly at the terminals. It should also be added that a common cause of failures when charging a battery from a generator is the relay regulator.

We determine the degree of charge of the battery by voltage

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.

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.
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 in 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.
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.

We do not recommend checking your car's battery voltage using the on-board system because it is not directly connected to the battery. Therefore, certain measurement errors are allowed.

Checking the battery charge by voltage is recommended some time after the car battery is fully charged, as well as at operating temperature (about 20 degrees Celsius).

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

Battery charge level	Open circuit voltage of low-antimony (Sb/Sb) and hybrid (Sb/Ca) batteries, volts	Open circuit voltage in calcium (Ca/Ca) and AGM/Gel (Ca/Ca) batteries, volts
100%	12,516—12,663	12,666—12,813
75%	12,316—12, 463	12,466—12,613
50%	12,106—12,253	12,266—12,413
25%	11,926—12,073	11,866—12,013
0%	11,756—11,903	11,666—11,813

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.

As sulfuric acid is consumed, 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:

Battery charge level	Electrolyte density value
100%	1,249—1,297
75%	1,209—1,257
50%	1,174—1,222
25%	1,139—1,187
0%	1,104—1,152

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 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 of a car battery, share with us in the comments.

Determining the degree of battery charge by voltage Link to main publication

Source: https://AkkumulyatorAvto.ru/konstrukciya/parametry/zaryad.html