How to determine the charge of a car battery

Car battery charging voltage

A lack of charge in a car battery may be an indicator of problems with the generator or lack of timely recharging. When this indicator drops to critically low values, there is a risk that the car will “freeze” and the owner will not be able to start it. Therefore, a car enthusiast should be able to determine the battery charge by voltage; a table of indicators can help him with this.

Battery charging voltage with car charger

If the car owner drives mainly long distances, the battery manages to replenish most of the charge from the generator during the run. The degree of charge is assessed by the indicator on the terminals: the higher the indicator, the more electrolyte.

The battery capacity is replenished using a charger operating on the conversion principle. Batteries can be classified according to a number of criteria. For example, they can be maintained or unattended and use different chemical agents (gel, lithium, etc.).

You can evaluate the degree of charge using a multimeter (by setting the voltage measurement mode) or a voltmeter. The ends of the wires are applied to the terminals. Since in this case only the number is important, it is not necessary to monitor the polarity. If the user confuses the red and black wires, the device will simply show a negative value, but in modulus it will correspond to the desired one.

The optimal charge level is indicated by indicators in the range from 12 to 16 Volts. When the number drops below 12, you should not use the battery - lead sulfate will settle on its plates, and this leads to a decrease in capacity and deterioration in performance. A deep discharge of the battery (a drop below 10.8) can lead to failure.

Voltage at battery terminals when charging

The battery is powered from the charger using a program with a constant voltage or current. When it is charging, you need to measure the data on the clamps. Measurements are performed only with the engine running. The optimum is 13-14 V. If it is high, the battery needs to be recharged; if it is low, there is a problem with the generator or the battery is depleting its resource.

If the number is in the range of 12-14 V, there is no need to worry.

If it is lower, you need to check:

transparency and electrolyte level;
presence of deposits on the plates;
the ability to recharge the battery to normal condition.

Charging a battery with constant resistance

If you set the resistance to a constant, the voltage or current will take variable values. But the resistance inside a car battery is always a variable value, which is influenced by a number of factors: electrolyte saturation, state of charge, temperature. The total value is the sum of two: polarization resistance (not a constant value) and ohmic (constant for a battery).

Since resistance is an unstable quantity depending on the state of the battery, voltage, current, or a combination of both can be taken as a constant. The ballast resistance smoothes the charging flow.

What voltage should I set when charging the battery?

The charging parameter is always set to exceed the battery charge level. The more pronounced the difference, the sooner the battery will charge to the desired level.

This difference also affects the completeness of charging, and the ratio looks like this:

to charge a 12 V battery, you will need to set the level to 16-16.5 V (then the battery will be fully charged);
when using a value of 15 V, the battery can be filled to 85-88%;
a parameter of 14.5 V gives 77-80% charge.

When the indicator at the battery terminals reaches 14.5 V, the device will notify you with a signal that charging is complete. Since this level does not provoke the release of gases when recharging the battery and after its completion, after some time of operation of the machine, the generator will limit the indicator to this figure.

Maximum battery charging voltage

The highest value used on the charger when recharging the battery is 16.5 V. Setting it will allow the battery to quickly reach its maximum capacity. However, it is not advisable to use such a voltage for all batteries. Calcium maintenance-free products are designed for it, capable of withstanding intense power supply with the accompanying boiling of the electrolyte.

Battery voltage at the end of charging

When the charging process is completed, after some time the electrolyte begins to dissociate, fill the pores of the plates and adapt to the temperature of the environment, which is why the charge level changes slightly. In hot weather it rises; when the air temperature is below zero, it falls.

To find out the final voltage, you need to measure it at the terminals with the motor turned on. If the indicator on a running car after charging begins to drop sharply, you need to diagnose the condition of the generator or replace the battery.

Dependence of battery charging on voltage

To quickly assess the battery charge level and, if necessary, use the charger, the car owner must be able to determine by the voltage at the terminals how many percent the device is charged . The indicator correspondence table will help with this.

Car battery charging voltage

Before connecting the charger, the battery charge is checked by voltage; the table helps to find out its condition. Depending on the voltmeter readings, select the capacity restoration mode.

Battery charging voltage with car charger

The battery is recharged while the engine is running, when it releases energy, by a car generator. If its operation is unstable, then the capacity is not restored. When driving long distances, the battery is charged, there is enough energy to start the engine, but the capacity is not 100% filled. This is provided by design so that the battery does not overcharge.

Check the condition of the battery and at the same time the car charger with a voltmeter in voltage measurement mode. The red probe touches the positive terminal, the black probe touches the negative terminal. If you connect it the other way around, the device will simply show a negative value. The on-board voltmeter is not directly connected to the battery, so there are errors in the readings.

First, they measure with an open circuit: remove the battery or disconnect the terminals. Normally, the readings should be from 12.6 to 12.9V. If they are smaller, there is a problem with the battery or the generator does not provide it with current to restore capacity.

A more accurate picture of the degree of charge is given by measurements with the internal combustion engine running without lighting:

from 13.0 to 13.4V – a slight drop in capacity, recharging is required;
from 13.5 to 14.0V – the condition of the battery and charging equipment is normal;
above 14V - the battery is discharged (if in the winter after some time the indicators return to normal, the system is in order).

Charging is carried out using an external device.

Voltage at battery terminals when charging

Charge with constant amperes or volts on the charger. To know the charge of the battery, monitor the voltage at its contacts. It grows, the charging current drops. If measurements show that it does not increase over 2 hours, and the amperage is stable, then the battery has filled its capacity to almost 100%.

The voltage rises to the same as that of the memory. The recommended value is from 14.4 to 14.5V. When the voltage on the device and the battery terminals is equal, this means that 90-95% of the charge has been achieved. The most modern maintenance-free batteries require 16.1-16.3V. The same indicator should be on the terminals.

Charging a battery with constant resistance

Charging with a stable current is the main universal method of restoring capacity. Amps remain unchanged. You can charge in another way by applying voltage without changing. The process is faster, but the amp readings drop as the capacity increases.

According to Ohm's law, if you maintain a constant resistance, then the voltage will change during the charging process. But the battery has an internal variable resistance. It changes depending on charge, load and other factors. If the resistance is variable, then the volts or amperes will be stable.

What voltage should I set when charging the battery?

To start charging, the charger requires more voltage than is available on the battery. The more significant the difference between them, the faster the capacity is gained. There are rise limits beyond which the electrolyte begins to boil.

If you set the optimal parameter, then the most complete charge occurs, there is no gas evolution. On a car, the voltage is limited by a relay, so if the system is working properly, the battery is not in danger of overcharging and boiling of the electrolyte. If external storage is used, then the indicator is set manually.

Maximum battery charging voltage

It is affected by the type of battery. The voltage determines how quickly and how completely the capacity will be restored.

All batteries, except calcium ones, are charged primarily with a stable current or voltage. With a constant amperage, it is set to 10% of the battery capacity. Charge until the voltmeter shows 14.3-14.4V. The amperes are then halved and charging continues. When the voltage rises to 15V, the amperage is again reduced by 2 times. Charge until the volts and amperes stabilize.

Using the constant voltage method, the charger is set to the maximum value - 14.4V and wait. When the readings on the charger and terminals are equal, we can assume that the battery is charged.

In luxury cars, the on-board system operates on 16V, the battery is recharged with increased current. Acid devices are unable to withstand it, so maintenance-free Ca/Ca are used. They have a closed system, no gas emission, and can withstand harsh operating conditions. However, deep discharge and incorrect operation of the on-board network system are not allowed.

The use of calcium batteries is justified in vehicles where good equipment is installed to monitor the on-board electrical system. Such batteries need to be charged up to 16V using a special mode. A special programmable memory is used, capable of delivering 16.1-16.5V. With this voltage, the calcium battery is charged to 100%. If the device produces no more than 14.8V, then the capacity will be replenished by 50%. When limited to 15.5V Ca/Ca, the battery will be charged to 75%.

Battery voltage at the end of charging

The end of the charge is indicated by 14.4V on the tester. On factory devices this is indicated by a green indicator light. If charging is incomplete, the voltage will begin to drop after a few hours. If it changes downward while the car is running, then we can judge that the battery or generator is faulty.

Deviations from the correct voltage at the end of charging are dangerous. If the voltage is insufficient, the battery will not charge and will sulfate. And if gases escape during charging, the temperature of the electrolyte rises. The consequences can be dangerous: the resource decreases more.

Dependence of battery charging on voltage

When charging with a stable voltage, there is a direct dependence of the battery capacity on the voltage supplied from the charger:

Each battery is charged in the mode provided for by the design. The lowest voltage is required for serviceable acid and gel batteries. The highest is for calcium. Charging stops when the nominal value is reached.

Battery charge level table

The battery capacity is measured with a tester by disconnecting the charging from the network. To obtain more accurate data, readings are taken under a load of 100A. Voltage also characterizes the density of the electrolyte and its freezing point.

How to check your car battery for performance

One of the important elements of a car that requires checking is the battery, or battery. The serviceability of the battery and its performance are very important, since it is thanks to the battery that the car starts, and all systems of the car are powered by it: low and high beam headlights, media system and much more.

Content

If you have already met with the seller and want to be sure that if you buy a car, the first thing you will have to do is run headlong to the store for a new battery, which usually costs more than 10 thousand rubles, then you have several ways to check the battery by car:

Inspect the battery externally;
Measure the voltage on the battery with a multimeter;
Check the battery with a load fork;
Check the electrolyte level in the battery.

We will consider each question in detail, but we immediately note that the fourth option, with checking the electrolyte level, is only available for serviceable batteries. But one way or another, there are a number of methods for checking a car battery for performance, and in this article we will look at them.

External inspection of the battery

You met the seller and have already walked around the car, seeing how clean and beautiful it is. It's time to look under the hood, you lift the lid and see the usual contents of the engine compartment, the engine and numerous systems that keep the car running.

In most cases, here, in the engine compartment, there is also a battery - a rectangular box with electrolyte inside, to which two wires are connected - positive and negative. These wires go to the distribution block, and from this massive electrolytic “battery” the entire machine and all its systems are powered with electricity.

Even if you don’t understand anything about cars and went for an independent inspection rather as part of a formality, you can still determine by the appearance of the battery what condition it is in.

During an external inspection, attention should be paid mostly to the integrity of the elements, and whether the battery itself and contacts are clean. There are a number of external factors, the presence of which immediately indicates the need to replace or at least clean the battery.

Dirt on contacts. In order for the battery to work, both contacts connected to it by wiring must be clean. If the contacts are dirty, this indicates that the battery is not new, and dirt will interfere with the correct operation of the contacts.
Oxidation of the terminals - foreign deposits can be seen on the battery terminals with the naked eye - this is oxidation, which in most cases is associated with electrolyte leakage. Electrolyte is an acid that is found inside the battery. If it spills and gets on the contacts, it can lead to poor battery performance and a reduction in the contact area.
Cracks on the case - the battery itself should be intact. The plastic box containing the electrolyte must not be damaged. This is also clearly visible without additional equipment and in good lighting.
Dirt, dust, electrolyte leaks - all this is removed with a rag, and the car should not be allowed to drive with a dirty battery, since the conductive deposit will contribute to its rapid discharge and deterioration of performance.

In addition to the external inspection, you can start the car engine. A cold start will be especially indicative if the engine has not been started for a long time and it is cold outside. If the car starts easily, the battery is in order, but if it does not start or starts with difficulty, the headlights shine dimly, and the instrument panel is also not brightly lit, then the battery should be changed. Or, at least, check it with instruments, which we will discuss below.

Measuring voltage with a multimeter

If you do not want to check the condition of the battery “by eye”, or simply want to have accurate results in numerical terms, you will need a device such as a multimeter.

So, how to check a car battery with a multimeter: the device itself has two probes, one of which is red and the other black. In order to measure the voltage on the battery, you need to put the multimeter in measurement mode and place the red probe against the “positive” terminal, and the black probe, respectively, against the “negative” terminal.

The procedure is carried out on the battery terminals without load. If the battery is properly charged, the result on the device will be about 12.6-12.9 volts. This is the normal voltage that should be present on a fully charged battery. If you mess up the colors of the probes, the number will be the same, it will just be displayed with a minus sign.

If the engine is running, then you can also check the operation of the battery with a multimeter, but in this case it will be checked whether it is working together with the generator, as well as the serviceability of the voltage regulator. When the motor is running, the readings should be slightly higher - from 13 to 14 volts. If the indicator is lower, this will mean charging problems for the battery, and if the indicator is higher, the process of water electrolysis will begin.

There is a method to determine the degree of battery discharge by voltage. Voltage 12.5 - says that the battery is 90% charged, voltage 12.1 - 50%, and 12 - 10 percent. Although the method is approximate, it is proven.

It is also advisable to measure with the device “cold”, since a car that has recently been running can give higher values and be misleading. The multimeter checks the degree of charge, but does not provide comprehensive information about its performance. To do this, it is better to use a load fork.

Checking the battery with a load fork

The load fork is a very precise tool, but is rarely used in “manual” use, as it is used mainly in service stations. The beauty of this method of verification is that thanks to it an absolutely accurate result will be known.

The load plug works in a similar way to a multimeter: it is also connected to the battery terminals, but produces a short circuit current. As we already said, without load the indicator should approach 13 volts. The load fork imitates the operation of a starter, which is why the voltage “sags” at the moment of use.

The drop should be no more than 9 volts. Otherwise, it will mean that the battery is very discharged. After removing the load, the indicator again “rolls back” to its original value. If under load the voltage “sags” to 5 or even 3 volts, this means that the battery will not be able to start the car engine.

It is recommended to think about changing the battery even if the voltage when using the load plug drops below 9 volts.

An extremely important note: the load plug supplies approximately 200 amps of voltage to the battery and is not recommended for use in low temperatures. The ideal conditions for “field” use of this device is a temperature of +20-25 degrees Celsius.

If you apply voltage to a cold battery, there is a risk of severely discharging it.

Checking the electrolyte level in the battery

Another convenient and reliable method, which, however, is only suitable for checking serviced batteries, is checking the electrolyte level. The method is a little more complicated than the previous ones, but it gives a good idea of the condition of the battery and tells you what’s inside it.

First, remove the battery and completely clean it of dirt. Let us remind you that it is better to do this with a rag; dirt and minor corrosion can also be cleaned off using an ammonia-based glass cleaner.

Next you need to open the two filler plugs. They need to be easily pryed with a screwdriver and unscrewed; six filler holes are hidden under them. The electrolyte level in them is checked by eye and can be seen with a flashlight. If the liquid level is the same everywhere, then everything is in order, if somewhere the liquid does not cover the plate, you need to add distilled water.

In general, this procedure must be carried out regularly, since each time the battery is charged, the electrolyte decomposes in small proportions into hydrogen and oxygen. Without regular maintenance, the battery will simply fail.

The norm is considered to be a level exceeding the height of the plates by about one centimeter, or below the neck of the filler hole by three millimeters. If necessary, it is worth adding distilled water to the battery being serviced, but we remind you once again: if the battery is marked “maintenance free”, or the manufacturers of this particular battery model do not recommend adding distilled water to it, you can only resort to the previous testing methods and, if necessary, replace the battery.

Knowing how to properly check a battery is important when buying a used car. Often, car sellers want to save money on small things, including selling a car with a dead battery, which can lead to negative consequences for the new owner. Always be alert and fact-check what the seller says about the health of your car.

And don't forget to check the car's history before purchasing. This can be done using the Autocode online service using VIN or state registration number. number. The system checks the car in more than 12 official databases: traffic police, EAISTO, RSA, taxi and bank registers, Federal Tax Service, Federal Customs Service and others. From the report you will find out: actual mileage, whether there are traffic police restrictions, compulsory motor liability insurance data, customs history, history of fines, participation in road accidents and much other important information.

If you do not have the opportunity to go for an inspection or you simply doubt your experience, order the Autocode on-site inspection service. An expert will come for an inspection and conduct a comprehensive diagnosis of the car, leaving no doubt about your choice of vehicle.

How to check the charge of a car battery at home?

The battery is the most important thing in any car. It is this element that provides the starting current to the starter. It is thanks to the battery that the engine starts quickly and without problems. But this doesn't always happen. To avoid difficulty starting, you need to periodically check its charge level. There are several ways to do this.

How to check the charge of a car battery at home? You will find out the answer to this question further in our article.

There are several ways to check the charge of a car battery:

by indicator;
using a loading fork;
multimeter;
by measuring the density of the electrolyte.

Each of them has its own characteristics. Let's look at the listed methods in more detail.

Built-in indicator

Most imported batteries have a built-in indicator that can be used to check the charge. For the first time such batteries appeared in Japan. Then European manufacturers began to practice a similar trick.

What is its essence? There is a transparent window on the battery cover (a kind of peephole). If you look at it, you can see that it is colored green. But this doesn't always happen. The green tint in the window will only appear if the battery is fully charged. If the window is transparent or white, it means the battery has lost part of its charge. The worst case is a black window. In this case, the battery has run down and needs to be charged urgently.

For your information, this is one of the easiest ways to check the charge of a car battery without a voltmeter and other devices. After all, all you need to do is open the hood and look through that very window. But it is worth noting that not all batteries have such a peephole (especially when it comes to domestic ones). Therefore, to determine the charge level, you need to know other methods.

Load fork

This is perhaps the most professional way to check the condition of the battery. Typically this method is used at service stations. What is its essence? The device is connected to the battery terminals and provides short circuit current.

That is, the load fork simulates the operation of the starter and shows how many volts the battery drops when the driver tries to start the engine. To date, this is the most accurate scheme for checking the condition of the battery. To read the readings correctly, remember that after loading the battery voltage must be at least 10 Volts. If the battery drops to 9 and below, it means it is already weak. Such a battery will discharge quickly in winter.

We use a multimeter

This is an indispensable device that every motorist should have. Allows you not only to check the battery voltage level, but also the resistance of the sensors, the load of the on-board network in real time and many other important parameters. You can purchase this device for 300-700 rubles, which is 2-3 times cheaper than a load fork. This device is very easy to use.

How to check the charge of a car battery with a multimeter? First you need to assemble it. We perform the following actions:

We connect two wires with positive and negative polarity to the corresponding connectors.
There will be probes at the ends of the wires. We apply them to the battery terminals.
First, set the device to voltage measurement mode and set the rotary switch to 20 Volts.
We connect the multimeter leads to the battery and look at the result. In this case, the car ignition must be turned off.

Reading data from a multimeter

What is normal for a battery? Experts note that a fully charged battery must produce a voltage of at least 12.5 Volts. If the multimeter shows exactly 12V, it means the battery is half discharged. A reading of 11.5 Volts or lower indicates that the battery urgently needs to be charged.

Electrolyte

There is another way to check the charge of a car battery with your own hands. It is especially relevant on the eve of winter. As is known, with a drop in temperature, the density of the electrolyte decreases. Accordingly, the charge and performance of the battery decreases. How to check the charge of a car battery? For this we need a hydrometer. Below are detailed instructions:

So, open the hood and, using a negative screwdriver, unscrew the battery “banks” one by one. There are only 6 of them.
We immerse our hydrometer inside and wait until it is filled with electrolyte.
Next, we take the device out and look at the readings.
After a short time, the float will float to the desired level. There will be several divisions on the scale. A figure of 1.23-1.27 grams per cubic centimeter is considered normal. If the electrolyte density is 1.2 grams, then the battery is about a quarter discharged. A deep discharge is indicated by a reading of 1.1 or less grams per cubic centimeter.

It is also worth checking the electrolyte level itself in each of the “cans”. If it is insufficient, it should be renewed. This can be done with distilled water (coolant is also diluted with it).

Do not ignore insufficient electrolyte level in the battery. This can cause frequent loss of charge and shedding of lead plates. As a result, the battery will become unusable, and during any attempts to recharge, the liquid will boil.

How to check the charge of a car battery with a charger?

Each charger has a scale that determines the battery voltage. If you don’t have a multimeter, a load fork and a hydrometer, you can use them. How to check the charge of a car battery in this way?

Everything is very simple - we connect the charger terminals to the battery terminals and press the test button. There is no need to connect the device to a power outlet - in this case it will charge, and the readings will not be lower than 13 Volts.

Can I charge at home?

If there is no garage, it is possible to recharge the battery in the apartment. But it’s better to do this on the balcony. During this process, the electrolyte releases sulfur dioxide and oxygen chloride, which are harmful to humans. Inhaling it may cause dizziness and nausea. Therefore, we charge in the most remote and well-ventilated area. Also monitor the electrolyte condition.

Do not allow the battery to boil. This reduces its resource. On average, a 60-amp passenger battery charges in 7-8 hours. In this case, the charger must be set to the minimum current strength. Stress loads are harmful to the battery. If the battery takes a long time to charge, or one of the cans boils after half an hour, it means it has become unusable.

Finally

So, we found out how to check the charge of a car battery. One of the easiest ways is to use a multimeter. As for the hydrometer, this is already a preventive measure. Yes, such a device can measure the “remaining life” of the battery. But, for the most part, it is a diagnostic device (as well as a load fork). Therefore, each device is good in its own way.

What is the charge rate of a car battery and how to check it

The battery (rechargeable battery or battery) is one of the key components of a car. The main role of a car battery is to supply current to the starter when the engine starts. In addition, when the engine is not running, the battery ensures the functioning of various devices (lighting, sound system, signal and other current consumers). When parked, the battery powers the security system. And during a trip, when the generator cannot cope with the load, the battery comes to its aid. Normal functioning of the vehicle's on-board network is only possible with a battery that has a normal charge. Therefore, today we will discuss what the charge rate for a battery is.

Battery charge rate

One of the main parameters of the condition of a car battery is voltage. Using voltage, a certain battery charge level is checked. Therefore, the car owner needs to know what the normal value of the battery voltage is.

The normal voltage of a six-cell battery in a charged state is 12.6-12.9 volts. That is, the voltage of one fully charged element is 2.1─2.15 volts. A lower value indicates that the battery is low.

But that doesn't mean it can't be used.
Ideally, of course, you need to keep the battery fully charged. But in practice, this can only be done if the battery is fully charged and then a current equal to self-discharge is applied to the terminals. So the battery is rarely in a fully charged state. Below you can see the relationship between voltage and battery charge level.

As for the charge rate, in most cases it is not recommended to operate a battery with a voltage of less than 12 volts. In this case, it needs to be charged. Operating the battery in this condition negatively affects the condition of the battery. This contributes to an increase in sulfation of the plates and, as a result, leads to a decrease in battery capacity.

The critical voltage norm can be called 10.8 volts. The voltage should not fall below this value. This is called deep discharge of the battery, which is very harmful to the battery and greatly reduces its service life. Deep discharge is especially harmful for maintenance-free calcium batteries. For them, 2-3 such deep discharges lead to failure. After such a voltage drop, they irreversibly lose part of their capacity.

As you saw in the table above, the density of the electrolyte is inextricably linked with the degree of charge. This is true. The charge level of the battery can be checked not only by the voltage at its terminals, but also by the density of the electrolyte. A fully charged battery should have a density value of 1.27─1.29 g/cm 3 . The density of the electrolyte is measured with a special device - a hydrometer. Read more about the electrolyte in the battery at the link provided.

EMF, like voltage, is measured in volts and represents the work expended on moving the positive charge between the terminals of the battery. Without electromotive force, there will be no voltage at the battery terminals. Voltage and EMF are present at the terminals of the power source, even without current flowing in the circuit.

What does this mean in practice?
Let's say you charged the battery and the emf at its terminals is 12.6 volts. After installation on the car and measuring the voltage, the value will be 12.4─12.5 volts. This is normal and there is no need to worry about it. Now let's talk about the tools for measuring battery voltage. We also recommend reading the article about why the generator does not charge the battery. Return to content

How to check the charge of a car battery?

To check the battery voltage, use a voltmeter or multimeter in voltage measurement mode.

In order to measure voltage with a multimeter, you need to switch it to voltage measurement mode. Then apply the probes to the battery terminals and the device will show the voltage value. Polarity is not necessary in this case, since you only need the magnitude. If you put the red probe on the minus and the black probe on the plus, the device will simply show a negative value. By the way, you can read more about what straight battery polarity is. But the photo below shows the result of measuring the voltage of a dead battery.

Voltage measurements with a multimeter

Before performing the test, the battery must be fully charged. To perform a load plug test, connect the terminals to the battery terminals and apply a load for five seconds. At the fifth second, note the voltage value on the voltmeter. If it drops below 9 volts, then it's time to think about replacing the battery. The norm for a working battery is a voltage drop to 10-10.5 volts. After the drop, the voltage value should increase slightly. In the video below you can see the testing process clearly.

In principle, there is another way to estimate the battery charge rate. You can measure the average density of the electrolyte in the banks, and then look at the degree of charge using the table above. But usually no one does that. It is much more convenient to use a voltmeter. The density of the electrolyte is usually measured after charging the battery to assess the efficiency of this process.

What to do if the battery charge is not normal?

The answer to this question is simple. If the battery charge is not normal, the battery needs to be charged. The charging process was described in detail in the article “How to properly charge a car battery with a charger.” Here I would like to note some nuances.

accelerated This mode is often called Boost and can be found on many modern chargers (chargers). In this mode, the battery charge is not fully charged, but it is quite enough to start the engine. This type of charging is used when you need to go urgently and the battery is low. This mode is not recommended to be used continuously. Here, the charge is accelerated by increasing the current strength, which increases the battery life;
with constant voltage. This type of charging involves maintaining a constant voltage across the terminals. This mode is used in the automatic charge mode on most chargers. It is recommended to use it when the battery is not very discharged (not lower than 12 volts). Read more about car battery voltage in the article at the link. The advantage of this mode is that you don't have to control it. The charger itself will determine when the charge is normal and stop the process;
with direct current. This charging option involves supplying constant current to the battery. The process is carried out in several stages, in which the current gradually decreases. This mode is recommended when charging a deeply discharged battery. It allows you to charge the battery most fully and evenly. The downside is that you will have to constantly monitor the process, measure the voltage and stop the process when the battery charge is normal.

Battery charging process

In conclusion, I would like to remind you about the safety rules when charging a battery. The process must be carried out in a ventilated area. It is better not to charge in residential areas. There should be no open flames or sparks near the battery being charged. During the charging process, hydrogen is released, which in combination with oxygen forms an explosive mixture!