The car battery does not charge from the charger - what to do?

Car battery is not charging (5 reasons). 8 decisions what to do

If a battery that is more than 5-7 years old is not charging , then the answer to the question is: “ why ?” most likely lies on the surface. After all, any battery has its own service life and over time loses some of its basic performance characteristics.

But what if the battery lasted no more than 2 or 3 years, or even less? Where then should we look for reasons why the battery does not want to charge? Moreover, this situation occurs not only when recharging from a generator in a car, but even when it is replenished from a charger.

Answers must be sought depending on the situation by performing a series of checks followed by procedures aimed at eliminating the problem.

Most often, you can expect 5 main reasons that manifest themselves in eight different situations:

To understand in detail all the possible malfunctions due to which the car battery does not charge, first of all, clearly define the situation:

The battery quickly discharges and dies

or he

does not charge at all (does not accept charge)

In general, when the battery refuses to charge, the following options are allowed:

plate sulfation;
destruction of plates;
terminal oxidation;
decrease in electrolyte density;
short circuit

But you shouldn’t worry so much right away, everything is not always so bad, especially if such a problem arose while driving (indicated by a red battery light). It is necessary to consider special cases in which the car battery does not take charge only from the generator or from the charger as well.

Please note that sometimes the battery, although fully charged, runs out very quickly. Then the reason may be hidden not only in its failure, but primarily due to current leakage! This could happen through: lights not turned off, interior lighting or other consumers and poor contact at the terminals.

The charging system of a car battery contains a number of external devices, on which the performance of the battery itself and the charging process can also greatly depend.

To check all external devices, you will need a multimeter (tester); it will allow you to measure the voltage at the battery terminals under different engine operating modes. You will also have to check the generator. But this is only true when the battery does not want to be charged from the generator.

If the battery does not take a charge from the charger, then it is advisable to also have a hydrometer to check the density of the electrolyte.

The battery does not charge from the generator . The first signal that the battery is not charging is a lit red battery light! And to make sure of this, you can check the battery voltage. There should be 12.5... 12.7 V at the battery terminals.

When the engine is started, the voltage will rise to 13.5 ... 14.5 V. With consumers turned on and the engine running, the voltmeter readings, as a rule, jump from 13.8 to 14.3 V.

No changes on the voltmeter display or when the indicator goes beyond 14.6V indicates a generator malfunction.

When the generator runs but does not charge the battery, the cause may lie in the battery itself. Apparently it was completely discharged, which is called “zero”, then the voltage is less than 11V. A zero charge may occur due to sulfation of the plates. If the sulfation is insignificant, you can try to eliminate it. And try charging using a jump charger.

How to understand that the battery is not charging from the charger ? When a battery is connected to a charger, evidence that it is fully charging is a constantly changing voltage at the terminals and jumping voltage or current readings on the device dial. If there is no charge, there will be no change. When the battery is not being charged from an Orion type charger (which has only indicators), you can very often observe a buzzing and rare blinking of the “current” light.

Frequent reasons when the battery does not charge from the generator are:

Oxidation of battery terminals;
Stretched or broken generator belt;
Oxidation of wires on the generator or vehicle ground;
Failure of diodes, voltage regulator or brushes;
Sulfation of plates.

There may also be 5 main reasons why a car battery does not want to be charged not only from the generator but also from the charger:

Deep battery discharge;
Short circuit of one of the cans;
Battery hypothermia;
Very high or low electrolyte density;
Foreign impurities in the electrolyte.

The first step is to find out the cause, and only then take action to eliminate it. To do this, you need to measure the voltage at the battery terminals, check the level, density of the electrolyte and its color. It is also, of course, necessary to visually inspect the surface of the battery, the car wiring, and also to determine the current leakage.

Let us consider in detail the possible consequences of each of the reasons for poor battery performance, and also determine what needs to be done in a given situation:

Oxidation of contact terminals both prevents good contact and contributes to current leakage. As a result, we get a quick discharge or unstable/absent charging from the generator. There is only one way out - check not only the condition of the battery terminals, but also the condition of the generator and the ground of the car. Heavily oxidized terminals can be removed by cleaning and lubricating the oxides.

Malfunction in the generator (belt, regulator, diodes).

a broken belt , but the fact is that even a slight loosening of the tension can contribute to slippage on the pulley (as well as oil ingress).

Therefore, when powerful consumers are turned on, the light on the panel may light up and the battery will discharge, and on a cold engine a squeaking sound can often be heard from under the hood.

This problem can be eliminated either by tensioning or replacement.

Diodes in their normal state should pass current only in one direction; checking with a multimeter will make it possible to identify the faulty one, although often the entire diode bridge is simply replaced. Improperly functioning diodes can cause both undercharging and overcharging of the battery.

When the diodes are normal, but they get very hot during operation, it means the battery is being overcharged. The regulator is responsible for the voltage . It is better to change it immediately. In a situation where the battery is not fully charged, you need to pay attention to the generator brushes (after all, they wear out over time).

With a deep discharge , as well as with a slight shedding of the active mass, when the battery does not want to be charged not only in the car from the generator, but even the charger does not see it, you can reverse the polarity or apply a high voltage so that it grabs the charge.

This procedure is often carried out with AVG batteries when there is less than 10 volts at its terminals. Reversing the polarity allows you to start a completely discharged battery. But this will only help if the poles on the battery have actually changed, otherwise it can only cause harm.

The change of battery poles (both lead-acid and calcium) occurs in the event of a complete discharge, when the voltage of some battery banks, which have a smaller capacity than the others connected in series, decreases much faster than others.

And having reached zero, as the discharge continues, the current for the lagging elements becomes charging, but it charges them in the opposite direction and then the positive pole becomes minus, and the negative pole becomes positive.

Therefore, by briefly changing the charger terminals, such a battery can be brought back to life.

But remember that if the polarity change on the battery does not occur, then if there is no protection on the charger from such a situation, the battery can be permanently damaged.

Polarity reversal should be carried out only in cases of the formation of a white coating on the surface of the plates.

This process will not work if:

the plates crumbled and the electrolyte became cloudy;
one of the cans is closed;
There is no required electrolyte density in the battery.

The polarity reversal method works well for desulfation, but only no more than 80-90% of the capacity can be restored. The success of this procedure lies in the thick plates; the thin ones are completely destroyed.

Electrolyte density is measured in g/cm³. Checked with a densimeter (hydrometer) at a temperature of +25°C, it should be 1.27 g/cm³. It is proportional to the concentration of the solution and inversely dependent on the ambient temperature.

If you operate a battery discharged by 50% or less at sub-zero temperatures, this will lead to freezing of the electrolyte and destruction of the lead plates!

Please note that the density of the electrolyte in the battery should be the same in all sectors. And if in any of the cells the voltage is greatly reduced, then this indicates the presence of defects in it (in particular, a short circuit between the plates) or a deep discharge.

But when such a situation is observed in all cells, it is a deep discharge, sulfation, or simply obsolescence. A very high density is also not good - it means the battery was boiling from overcharging due to the failure of the generator. Which also adversely affects the battery.

To eliminate problems caused by uneven density, you need to service the battery.

Sulfation causes deterioration or lack of contact between the electrolyte and the plates. Since plaque blocks access to the working fluid, the battery capacity drops significantly , and recharging it does not give any result. The voltage either increases very slowly or does not change at all. This process is irreversible .

But sulfation at the initial stage can be overcome by a series of cycles of full charge with low current and full discharge with minimal current (for example, by connecting a 12V 5W light bulb).

The short circuit of one of the cans is a consequence of destroyed plates and the appearance of sludge at the bottom of the battery. When trying to charge such a battery, strong bubbling of the electrolyte will occur, as if it were fully charged. The defective section will boil, but will not recharge. There is nothing to help here.

The average service life of modern batteries is from 4 to 6 years.

The service life of a battery discharged by 25% is significantly reduced if:

malfunction of the generator and voltage regulator;
starter malfunctions leading to an increase in current or an increase in the number of attempts to start the engine;
oxidation of power wire terminals;
constant use of powerful consumers during long periods of idle time in traffic jams;
repeated cranking of the crankshaft with the starter on short trips.

A reduced electrolyte level during battery operation is also a key reason for rapid battery failure. Therefore, the cause of the malfunction may be:

Rare electrolyte level monitoring. In summer, checking should be done more often because high temperatures promote rapid evaporation of water;
Intensive use of the car (when the mileage is more than 60 thousand km per year). Requires checking the electrolyte level at least every 3-4 thousand kilometers.

Source: https://etlib.ru/blog/703-ne-zaryazhaetsya-akkumulyator

The battery does not take charge from the charger: reasons, what to do

Various chargers are used to charge a car battery. Which, on average, in 15-20 hours, will provide the battery with a full charge.

If the battery does not charge, there are two possibilities: the charger or the battery itself . If the car owner, through testing, is convinced that the charger , then, logically, the problem is in the car battery itself .

There is a possibility of damage to the new battery while charging it. When charging a recently purchased battery, you need to remember that you cannot leave it charging “unattended”, as there is a possibility of damaging it. Charging a new battery should occur gradually and with low current.

In order for the battery to charge well and extend its service life , it is necessary to carefully monitor the electrolyte level in the battery.

Increased self-discharge may also be the reason why the battery cannot be charged.

Most often this occurs due to the presence of harmful impurities in the electrolyte; undistilled water was used for topping up. To fix this problem, you need to discharge the battery to a voltage of 1.1V.

Next, get rid of the old electrolyte (pour it out), rinse the battery with distilled water, and add new electrolyte.

Short circuit . It can be caused by the resolution of the separator and the contact of the plates, as well as charging the battery with a high current. To solve this problem, it is necessary to disassemble the battery and replace damaged separators and electrodes. After the repair has been completed, charge the battery.

Oxidation of the plus and minus pins. The malfunction can be eliminated by stripping the terminals and pins.

The so-called “warping” of electrodes in a car battery . Usually they say that the electrodes are “warped”, i.e. they were “led.” This process occurs when the temperature of the electrolyte increases, due to the high current strength of both charging and discharging. To save the battery, you may need to replace the electrodes when repairing the battery.

If everything is in order with the battery, there are no visible damages or malfunctions, but it still refuses to charge, apparently its service life has come to the end.

You need to go to the car market or auto supply store and purchase a new battery. It is recommended to change the battery in a car every 3-4 years.

This will save the car owner from an unpleasant and untimely surprise in the form of a suddenly dead battery.

Source: https://volt-index.ru/podelki-dlya-avto/radiotehnika-zaryadnyie-ustr-va/chto-delat-esli-akkumulyator-ne-zaryazhaetsya-ot-zaryadnogo-ustroystva.html

Poor battery charging: looking for reasons and solutions

Home page » Electronics » Battery » Poor battery charging: looking for reasons and solutions

Charging and checking battery density

How can a motorist know whether the battery charge level is low or the battery does not hold a charge? If the battery does not charge, this will affect the functionality of all electrical equipment.

During normal operation of the car, the battery is always slightly charged from the generator.

Therefore, if the battery is completely discharged, you can try to jump start the car (this does not apply to vehicles with automatic transmissions).

But the car battery may not be charged even despite the generator. How can the driver be sure of this? To carry out diagnostics, a tester is used that allows you to measure voltage.

If the battery is operating in normal mode, during diagnostics the voltage level will be 14 volts, and if the battery is not charging, this parameter will be only 12 volts.

The diagnostic procedure is performed with the engine running, otherwise the results will be incorrect.

If the engine cannot be started, a tester is used to measure the parameter at the battery terminals. With a zero charge of the device, the resulting indicator will be 11.8 volts, and if the battery is fully charged, this parameter will be equal to 12.8 volts. In addition, if you use a battery charger, the voltage reading will always change at the device terminals during the process.

The main reasons why the battery does not charge

Oxidized battery terminals are one of the most common problems.

For what reasons does the battery not charge? Why may the device become warm and not charge?

Terminal oxidation. When charging, the battery often does not charge for this reason. Perform a visual diagnosis of the battery - if a white coating is visible on the terminals, charging will be impossible, since such oxidation will cause high resistance. You can get rid of such plaque, but it must be done as carefully as possible. Plaque is removed using fine-grain sandpaper. It is only necessary to remove the plaque; the lead must retain its layer, otherwise the terminals may fall off the battery when driving on a rough road.
If there are no results when charging, this may be due to a broken alternator strap. In some cases, this problem occurs as a result of the belt weakening or slipping on the shaft. In the event that the belt breaks, it will be visible. Such a malfunction can only be eliminated by replacing the belt. As for slippage, there can be many reasons. For example, sometimes this occurs as a result of wear or stretching. Quite often, the belt slips as a result of moisture getting on it or the pulley itself, as a result of which the adhesion force between these elements is reduced. Accordingly, the battery charge will be insufficient. If the strap is simply worn out, it will be enough to tighten it; if there are traces of moisture on the pulley, it must be dried before further use of the car.
If the battery is heating up, but the battery is not being recharged enough, the cause may be oxidation of the wires on the generator. This kind of malfunction can be solved by stripping the terminals and wires, for which fine-grained sandpaper is also used. However, the wiring does not always oxidize; sometimes the wires can burn out or break due to voltage surges. It's not that difficult to identify. Typically, if wires burn out, the driver will be able to smell the smell of burnt insulation. Before replacing a burnt-out wiring with a new one, it is necessary to identify the cause, otherwise even new wiring will burn out over time. Moreover, the consequences in the latter case can be even more serious.
There may be poor charging, or rather undercharging of the battery from the generator. If you have short runs between engine starts, the generator simply does not have time to recharge.

Cross-section of a car battery

The battery does not charge from the charger: external factors causing a malfunction

When charging the battery, the charger should heat up, since current will flow through it. If the charging battery does not hold a charge, it is necessary to promptly identify the cause. The diagnostic procedure in this case includes the use of a tester to measure the voltage parameter at the terminals of the device. The process itself is carried out with the engine turned off.

Source: https://labavto.com/elektronika/akb/ne-idet-zaryadka-na-akkumulyator/

The car battery is not charging, reasons

The car battery may either not charge at all, or it may charge, but weakly and insufficiently. The reasons why the car battery does not take a charge can be a malfunction of the battery itself, a malfunction of the car's power supply system, or a malfunction of the charger (when charging the battery in a stationary manner).

A sign of malfunction may be the need to constantly charge the battery, although it should be recharged while the engine is running. Or the inability to charge the battery using a charger (charging takes more than two days).

Car battery lost charging, reasons

— The battery terminals and (or) the terminals of their wires have oxidized

A gradually growing layer of oxidation on the battery terminals makes it impossible to fully contact the wire terminals and battery terminals. It is necessary to periodically clean the terminals and terminals with sandpaper.

— The wire from the positive terminal of the battery to terminal “30” of the generator is damaged

Perhaps it has become frayed or broken, its tip to terminal “30” of the generator has oxidized, or the terminal to the battery terminal has oxidized.

— The wire to the negative terminal of the battery is damaged

Its terminal on the battery terminal has oxidized, the wire is broken, there is poor contact with the ground on the body and (or) gearbox. Most often in such a situation it is impossible to start the engine.

— The battery itself is faulty

It does not accept a charge, since the plates inside it have crumbled due to old age, mechanical damage, or too high a charging current (the voltage regulator in the generator or the charger during stationary charging is faulty). “Sulfation” of the plates inside the battery is also the reason for the inability to fully charge the battery.

— The generator drive belt is loose

The generator stops producing the required voltage current due to the drive belt slipping. It is necessary to check the belt tension and adjust it.

— The generator voltage regulator is faulty

The voltage regulator produces too little charging current or does not provide it at all. It is necessary to check the voltage at the battery terminals with the engine running. It should be between 13.5 - 14.5 V, depending on the installed generator. The regulator must be removed, cleaned, replaced brushes if necessary, checked for functionality, or replaced with a known good one.

— The diode bridge of the generator is faulty

Why the battery does not charge and how to find the problem to revive the battery

Many owners of used cars have encountered a problem when the battery does not charge and the corresponding indicator lights up on the dashboard.

In some cases, the battery will not charge even with a separate device, but no matter what, you should not rush to throw away the device.

You should first try to find the reason why the new battery does not charge at all, charges too quickly or does not hold a charge for long. We will tell you in detail how to do this below.

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How to identify the problem?

Checking with a tester

If your car's battery has stopped charging, you will feel it through the operation of the electrical equipment. In normal mode, it constantly receives recharge from the generator, and you do not experience discomfort. When the battery is completely drained, a car with a manual transmission can be started by pushing or towing, but you cannot start a car with an automatic transmission so easily.

There are situations when the battery charger works normally, but the battery still does not charge. You need to make certain checks using a multimeter.

With a regular tester, you should measure the electrical voltage at the terminals. If the generator does not charge the battery, the tester will show 12 volts, but normally this value should be 14-14.4 volts.

The check must be done with the engine running.

When it is not possible to start the engine, using a tester you need to find out the voltage at the battery terminals. A value below 11.8 volts indicates a zero battery charge. If the figure is 12.8 volts or something close, the charge is almost full.

When connecting the battery to a charger, the tester should show a constant change in voltage at the terminals if fully charged. If the voltage first increases and then stops at a certain value, the battery is discharged. If it does not change since connection, then the battery is not charging at all.

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Common Causes

Sulfitation

Having accurately determined that the car battery is not charging, you can begin to troubleshoot the problem that caused the problem. It is important to note that sometimes the battery can be fully charged, but runs out very quickly after that.

In this case, the reason is related to a leakage of electrical energy due to the dimensions not being turned off, lighting in the cabin, or other consumers. On some car models, the cause may be switched on consumers, the DVR, or the charger.

This is due to the fact that the on-board socket does not turn off even in a closed car, and during long-term parking it can drain the battery.

When it comes to the battery, the reason may be sulfation of the plates, which are sometimes covered with a white coating, which is lead sulfate in the form of large crystals. If there is minor sulfitation, it can be eliminated without any problems by correcting the damage.

In some cases, the battery is not charged either from the generator in the car or from the charger. In this case, the cause may be significant oxidation of the terminals , a break in the generator belt, or oxidation of the wires. Check all these elements and components.

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Oxidized terminals

When the battery charge indicator on the dashboard lights up, this is sometimes due to such a banal reason as oxidation of the terminals. The formation of a whitish coating significantly increases the resistance, so normal charging becomes impossible.

Getting rid of plaque is not difficult, but you need to do it carefully. Take fine-grained sandpaper and carefully sand the surface of the terminals. Please note that lead is very soft, so do not press too hard. You also need to understand that the terminals will become a little thinner after sanding.

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Belt break

Another reason why the car battery does not charge from the generator may be a broken belt or a loose belt that leads to slippage. If the belt really breaks, you can notice it by opening the hood. Fixing the problem involves replacing it.

If the belt has stretched over time and started to slip, you can slightly tighten the special roller. Be sure to pay attention to the condition of the belt, and if there are signs of wear, be sure to replace it.

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Oxidation of generator wires

Broken generator wires

Sometimes the battery takes a long time to charge due to oxidation of the wires coming from the generator. In this case, their contacts need to be cleaned with sandpaper. In rare cases, wires break or burn out due to severe voltage drops.

You can identify the problem by the smell of burnt insulation. In this case, you will have to become an electrician for a while and replace the burnt wires. It is imperative to identify the root cause and eliminate it to avoid re-burnout.

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Generator relay diodes

The charging system of a car battery consists of many external devices that affect the normal charging of the battery. To check them, you will need a multimeter with which you will measure the voltage at the terminals. This must be done with the engine turned off and after disconnecting the wires from the terminals.

Normally, the voltage at the terminals should be in the range of 12.5-12.7 volts, and with the engine running - 13.5-14.3 volts. If you see a lower value, try increasing the engine speed and see if the voltage on the tester display changes. If so, the cause may be due to a faulty regulator relay diode in the alternator.

In this case, you can replace the diodes or completely change the regulator relay. Please note that in normal condition, diodes pass current flows in one direction. Otherwise, at least one diode is broken. To replace diodes you will need a soldering iron and some experience.

After soldering in new diodes, check their operation. When starting the engine, they should not get very hot, and the battery should receive normal current. If they are very hot, the diodes will not be able to work for a long time, so in this case they should be immediately replaced with more suitable ones.

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Battery problem

If the generator is functioning normally, but the battery is not charging, the problem may be related to the battery. Malfunctions can be different, but the most common is sulfation.

If a new battery does not charge and shows zero charge, the reason is that it is sulfated. We talked about this above, but we’ll try to figure out how to deal with the problem further.

Density measuring device

First, you need to rinse the battery with distilled water to remove all debris and dirt. Leave it to dry completely and then try charging it if possible.

The electrolyte density must be brought to 1.285 g/cm3 using a liquid with a density of 1.4 g/cm3. Do not allow the electrolyte to boil or overheat. Continue charging until each section reaches 1.3-1.4 volts.

Reduce the current by half, but continue to charge the battery. If the voltage on the sections and the density of the electrolytic liquid do not change within two hours, stop the charging process. Add more electrolyte with distilled water. Using the light bulb on, reduce the voltage on each section to 1.7 volts.

After the completed operations, the battery should work. In addition to sulfation, the battery may not charge due to destruction of the plates. In this case, you will notice a blackening of the electrolyte. You can't fix anything and the battery will have to be replaced.

If all else fails, you should know how to choose a new battery in the store?

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Generator malfunction

When the battery does not charge from the generator, the reason may be a breakdown of the charger. The most common reasons include:

Wear of the rotor, as a result of which it stops rotating in the stator and constantly gets stuck. This can happen with different frequencies and frequency, but in any case, a complete replacement of the generator will be required.
Circuit break. Sometimes the battery charger in a car stops working due to an open circuit that powers the generator. It is not easy to determine the damaged area, so it is better to immediately contact specialists at a service station.

Now you know all the reasons why the car battery does not charge. You can diagnose and fix some of them yourself using our instructions.

The battery is not charging: we’ll figure out the reasons and fix the problem

Home » Battery » The battery is not charging: we’ll figure out the reasons and fix the problem

Sulfated plates

How can a car enthusiast understand that the battery is not charging? If it happens that the battery does not charge, then this will, one way or another, affect the operation of the electrical equipment in the car. In normal operation, the battery charge is replenished using a generator device. However, even the operation of the generator does not always allow the battery to function again.

What symptoms can you use to determine the lack of charge:

The battery light on the dashboard is on. When the car's battery charge level is too low and the battery is heating up, an indicator light will appear on the dashboard. But the appearance of a light bulb can also be caused by incorrect operation of the generator with a loose drive belt.
If the battery does not hold a charge, then the voltage at the battery terminals will be about 12 volts. With proper charging, this parameter will be 14 volts. To check this parameter, you will need a multimeter, and the diagnosis should be carried out with the power unit running.
The inability to start a car engine is one of the main symptoms. If the battery drains completely, the device will not be able to power the electrical equipment installed in the car. Also, the device will not be able to perform the primary function assigned to it, namely, turning the starter and crankshaft and starting the engine (video filmed by the AutoHandMade channel).

The main reasons for poor battery charging

We suggest that you familiarize yourself with the main reasons for the malfunction why the battery is not charging:

Voltage is not supplied to the device as a result of terminal oxidation.
Over time, the terminals oxidize and a coating forms on them, which prevents the passage of voltage. To determine the cause, you should visually inspect the device, in particular, we are talking about the terminals. If you see that there is a coating on them, then this indicates the presence of oxidation, which contributes to the formation of resistance. The problem can be solved by removing the oxidation using fine-grit sandpaper or a wire brush. Moreover, it is the coating that needs to be removed, and not the layer of lead on the terminals, otherwise the latter may randomly fall off when vibrations occur.
As stated above, the cause of poor charging may be due to stretching or breakage of the generator set drive belt. If the strap is too loose, it may slip on the shaft. You can try to tighten the belt, but as a rule, when it wears out, the belt must be replaced. A slippage problem can occur when moisture gets on the strap or the pulley on which it spins, and this can cause a weakening of the grip force. If there are traces of moisture, the belt and pulley should be dried.
If you are faced with the problem of battery overheating, then there is a possibility that such a malfunction is associated with oxidation of the wires of the generator device. In this case, you can try to clean the wires, as well as the connectors and connection terminals, but the reason is not always oxidation. The problem of broken or burnt contacts cannot be ruled out, with the latter cause occurring as a result of overvoltage in the system. When a burnout occurs, there is usually a pronounced symptom - a burning smell in the cabin or in the engine compartment. Before changing a burnt-out contact or wire, you need to accurately determine the cause of the malfunction, otherwise the replaced contacts may also quickly burn out.
If the battery was purchased several years ago, then it probably may not have time to replenish its charge from the generator. This problem is especially relevant if the mileage between engine starts is short. In too short a time, the generator unit simply will not have time to optimally recharge the battery.
Sulfation of plates. Sulfation occurs as a result of natural or increased wear and tear on the battery. When sulfated, the plates gradually begin to deteriorate and crumble; they cannot be restored.

The battery does not charge from the charger: external factors causing the malfunction

When a battery is charged from a charger, it will heat up anyway as current flows through it.

If you notice that when charging the device still cannot hold a charge, the following factors will help you make sure of this:

First of all, you need to check the condition of the terminals. As we have already said, due to oxidation, the charger will not be able to transmit current to the battery.

Source: https://avtoklema.com/akkymylyator/ne-idet-zaryadka-na-akb-4137/

How to properly charge a car battery with a charger

Recommendations for charging a car battery in the garage, on the street or at home using a manual or automatic charger.

Preparing to charge

Remove the battery from the car or at least disconnect it from the on-board network by disconnecting the negative wire
Clean the terminals from grease and oxide
It is advisable to wipe the surface of the battery with a cloth (dry or soaked in a 10% solution of ammonia or soda ash)
Unscrew the plugs on each of the battery cans or remove the plug to allow electrolyte vapors to escape freely and prevent excess pressure
If the electrolyte level is insufficient, add distilled water to the battery so that it completely covers the lead plates.

Selecting a charging method

Constant current charging is more efficient, but requires control, and constant voltage charging only charges the battery to 80%. Ideally, the methods are combined using an automatic charger.

DC charging

The charging current should not exceed 10% of the battery's rated capacity. This means that a battery with a capacity of 72 Ampere-hour will require a current of 7.2 amperes.
First charging stage: bring the battery voltage to 14.4 V.
Second stage: reduce the current by half and continue charging to a voltage of 15V.
Third stage: reduce the current by half again and charge until the watt and ampere indicators on the charger stop changing.
A gradual reduction in current eliminates the risk that the car battery will “boil.”

Constant voltage charging

Everything is much simpler here. You just need to set the voltage within 14.4–14.5 V and wait. Unlike the first method, with which you can fully charge the battery in a few hours (about 10), constant voltage charging lasts about a day and allows you to replenish the battery capacity only up to 80%.

Safety precautions

The negative terminal is disconnected before charging the battery, since it is connected to the on-board network and the car body. If you disconnect the positive terminal first and accidentally touch the body or metal on the engine, you can cause a short circuit.

In winter, the electrolyte may freeze to ice. Therefore, in cold weather, the battery is moved to a warm room, allowed to warm up, and then charged.

The lower the charging current, the more fully the battery will be charged, but it will take longer.

It is not recommended to charge the battery at home. It is better to do this in a garage or in a well-ventilated non-residential area. Smoking, open fire, sparking near the battery are not allowed.

The charger is first connected to the battery, and only then connected to the network. The red wire is attached to the positive, and the black to the negative. It is best to remove the battery from the car.

The charger is first connected to the device, and only after that it is connected to the network.

The plugs of each can of the battery being serviced are unscrewed. What to do with a maintenance-free battery is indicated in the instructions.

Acid stains are removed with a damp cloth soaked in a soda solution (20 grams of soda per 200 milliliters of water)

Before and after charging, check the electrolyte level. If the level is below normal, add distilled water.

How is electrolyte density and freezing temperature related?

The normal density of electrolyte in a battery is 1.27. With a further increase in density, the electrolyte breaks down into water and acid. The water, in turn, boils when current passes and can rupture the battery, splashing acid all around.

The correct name for the process of "boiling" the electrolyte is bubble sparging, which occurs when lead sulfate is reduced from the electrolyte. On the negative electrode, lead itself is formed from sulfate, and on the positive electrode it is oxidized to lead dioxide. The electrolyte density increases.

When the battery is discharged, the processes proceed in reverse: lead dissolves in the electrolyte, and the dioxide turns into peroxide. The electrolyte density decreases.

Intense bubbling indicates a “sick” battery. It is better to replace such a battery.

A 100% charged battery has an electrolyte density of 1.27 to 1.29 g/cm3 and a terminal voltage of 12.3 to 12.9 V. A completely discharged battery has a density of 1.11 to 1.13 g/cm3, and the voltage will drop below 11 V. A battery with a voltage below 11 V is practically dead!

Sulfation of battery plates

The formation of large crystals of lead sulfate on the surface and walls of the battery is called sulfation. The process is harmful and leads to a decrease in battery capacity. Modern chargers provide a battery desulfation mode, which allows you to return the capacity to normal.

Causes of sulfation: