In operation, the car battery, regardless of the type, is recharged from the vehicle alternator. To control the battery charge, a device called a relay regulator is installed on the alternator.

We also recommend reading the article about what an alternator regulator relay is and what signs you can determine its malfunction. From this article, you will learn about the device, purpose and common failures of the regulator and how to diagnose and repair the relay regulator with your own hands.
The specified relay relay-regulator allows you to supply the battery with a necessary voltage to recharge the battery. This voltage is 14.1V. At the same time, a full charge of the battery assumes a voltage of 14.5 V. It is quite obvious that the charge from the alternator can maintain the battery’s performance. Still, this solution is not able to provide the maximum full charge of the battery. For this reason, it is necessary to charge the battery from time to time using a charger (external charger).

It is also possible to charge the battery using a special starter charger. Still, such solutions often provide only additional charging of a dead battery without fully charging the car battery.

How often to charge the car battery?

Usually, there are no problems with a working battery when the outside temperature is positive. Starting the engine in such conditions can provide the battery, which is only half charged. When the air temperature drops below zero, the battery capacity immediately decreases from 1.5 to 2 times. Also, in the cold season, a higher starting current is required to start the engine since the engine oil in the crankcase thickens, and it is more difficult for the starter to crank the crankshaft.

The very operation of a car in winter often involves short trips, including a large number of energy-intensive equipment (heated mirrors, glass, seats, etc.) The load on the battery increases significantly. At the same time, the battery does not have time to charge from the alternator and compensate for the losses spent on starts. Considering the above, it is optimal to fully charge the battery with a charger to 100% at least once a year before the onset of cold weather.

We add that in case of problems with starting the engine due to engine malfunctions (problems with fuel equipment, compression, etc.), the owner has to turn the starter much longer and more intensively. In such cases, you will need to charge the battery with an external charger much more often.

Charging the battery with a charger

To know how to charge a maintenance-free car battery with a charger and charge a service-type battery, You must follow certain rules. The charger (charger, external charger OVC, starting charger) is actually a capacitor charger.

The car battery is a constant current source. When connecting the battery, be sure to observe the polarity. For this purpose, the positive and negative terminals are marked with a plus and minus sign (“+” and “-“) on the battery. The terminals on the charger have a similar marking, which allows you to connect the battery to the charger correctly. In other words, the “plus” of the battery is connected to the “+” terminal of the charger, the “minus” on the battery is connected to the “-” output of the charger.

Note that accidental polarity reversal will result in the battery being discharged instead of being charged. You should also bear in mind that a deep discharge (the battery is completely seated) can, in some cases, damage the battery, as a result of which it may not be possible to charge such a battery with a charger.
You should also bear in mind that before connecting to the charger, the battery must be removed from the car and thoroughly cleaned of possible contamination. Acid streaks are well removed with a damp cloth, which is moistened in a solution with soda. 15-20 grams of soda is enough for 150-200 grams of water to prepare the solution. The presence of acid will be indicated by the foaming of the specified solution when applied to the battery case.

As for the serviced batteries, You should unscrew the plugs on the “cans” for filling acid. The fact is that during charging, gases are formed in the battery, which you must provide with a free exit. You should also check the electrolyte level. When the level drops below the norm, distilled water is topped up.

What voltage to charge the car battery

Battery charging voltage

Car Battery Measurement. Professional Car Mechanic Testing Vehicle Battery

To begin with, charging a battery involves supplying it with a current that is not enough for a battery to charge fully. Based on this statement, you can answer the questions with what current to charge the car battery and how much you need to charge the car battery with the charger.

If a battery with a capacity of 50 Ampere-hours is 50% charged, then at the initial stage, a charging current of 25 A should be set, after which you must dynamically reduce this current. By the time the battery is fully charged, the current supply should stop. This principle of operation is the basis of automatic chargers, with the help of which a car battery is charged on average in 4-6 hours. The only drawback of such chargers is their high cost.

It is also worth highlighting semi-automatic chargers and solutions that involve completely manual configuration. The latter are the most affordable and widely available for sale. Considering that the battery is usually 50% discharged, you can calculate how much to charge a maintenance-free car battery and understand how much to charge a car battery of a serviced type.

The basis for calculating the battery charging time is the battery capacity. Knowing this parameter, the charging time is calculated quite simply. If the battery has a capacity of 50 A • h, then for a full charge, it must supply such a battery with a current of no more than 30 A • h. The charger reads 3A, which will take ten hours to charge the battery with the charger fully.

To be 100% sure that the battery is fully charged, after 10 hours, you can set the current to 0.5 A on the charger and then continue charging the battery for another 5-10 hours. This charging method is not dangerous for car batteries, which have a large capacity. The downside is the need to charge the battery for about a day.

To save time and quickly charge the battery, you can set it to 8 A and charge for about 3 hours. After this period, the charge current is reduced to 6 A, and the battery is charged with this current for another 1 hour. As a result, it will take 4 hours to charge. Note that this charging mode is not optimal since charging the battery with a small current of up to 3 A is advisable.

Charging with high currents can overcharge and overheat the battery, resulting in a significant reduction in battery life. We also note that the use of battery charging methods that are aimed at minimizing the negative process of sulfation of plates, in practice, do not have noticed positive results.

Correct operation of the battery, depending on its type (serviced and unattended), the elimination of deep discharge and timely charging with the help of a charger, allow an acid battery to work properly for 3-7 years.

How to assess the condition and charge of a car battery

auto service, repair and maintenance concept – digital multimeter or voltmeter testing car battery

Proper charging and several conditions that you must observe during the operation of a car battery can ensure a normal engine start even in shallow temperatures. The main indicator of the state of the battery is the degree of its charge. Next, we will answer how to find out if the car battery is charged.

To begin with, some battery models have a special colour indicator on the battery itself, which indicates whether the battery is charged or discharged. It is worth noting that the indicated indicator is a very rough indicator by which it is possible, with a certain degree of probability, to determine only the need for recharging. In other words, the charge indicator can indicate that the battery is charged, but at the same time, the starting current at negative temperatures is insufficient.

Another way to determine the degree of battery charge is to measure the voltage at the battery terminals. This method also allows a very rough estimate of the state and degree of charge. To measure the battery, you need to remove it from the car or disconnect it from the charger, after which you need to wait an additional 7 hours. The outside temperature is not critical.

Next, you can assess the condition of the battery by the voltage at the battery terminals:

  • 12.8V-100% charge;
  • 12.6V-75% charge;
  • 12.2V-50% charge;
  • 12.0V-25% charge;

A voltage drop of less than 11.8 V indicates a complete discharge of the battery.
It is also possible to check the state of charge of the battery without waiting. The voltage at the battery terminals must be measured by the load using the so-called load plugs. This method is more accurate and reliable. The specified plug is a voltmeter; a resistance is connected in parallel to the terminals of the voltmeter. The resistance value is 0.018-0.020 Ohm for a battery with a 40-60 Ampere-hours capacity indicator.

You must connect the plug to the corresponding outputs on the battery, then after 6-8 seconds. Fix the readings that the voltmeter displays. Next, you can estimate the state of charge of the battery by voltage using a load plug:

  • 10.5 V – 100% charge;
  • 9.9 V – 75% charge;
  • 9.3 V – 50% charge;
  • 8.7 V – 25% charge;
  • Indicator less than 8.18 V – full battery discharge;

You can also take measurements without a load plug without removing the battery from the car. You must connect the battery to the vehicle electrical system. Then you will need to load the battery by turning on the dimensions and high beam of the head optics (for cars with standard halogen lamps). The headlight bulbs have a power of 50 W; the load is about 10 A. The voltage of a normally charged battery, in this case, should be about 11.2 V.

The next method that allows you to check the battery charge is to measure the voltage at the battery terminals when the internal combustion engine is started. These measurements can only be considered reliable if the starter is working properly.

At the time of start-up, the voltage indicator should not be below the 9.5 V mark. A voltage drop below the indicated mark means that the battery is severely discharged. In this case, it needs to be charged with a charger. This test method also allows you to identify problems with the starter. A known serviceable and 100% charged battery is installed on the car, after which the measurement is taken. If the voltage at the battery terminals at the time of starting drops below 9.5 V, then problems with the starter are obvious.

Finally, we add that measurements in different ways involve fixing fluctuations in fractions of a volt. For this reason, increased requirements are imposed on the voltmeter. The device’s accuracy is essential since the slightest error of even one or two per cent will lead to an error in measuring the degree of battery charge by 10 -20%. For measurements, it is recommended to use devices with a minimum error.

How to charge a fully discharged car battery

battery cables

A car mechanic uses battery jumper cables to charge a dead battery.

A common cause of deep battery discharge is banal inattention. It is often enough to leave the car with the included dimensions or headlights, interior lighting or radio tape recorder for 6-12 hours, after which the battery is completely discharged. For this reason, many car owners are interested in the question of whether it is possible to restore a completely discharged battery.

As you know, a complete discharge of a battery has a strong effect on battery life, especially when it comes to a maintenance-free battery. Manufacturers of car batteries indicate that even one full discharge is enough to damage the battery. In practice, You can restore relatively new batteries at least 1 or 2 times after their complete discharge without significant performance loss.

First, you need to determine how much the battery is discharged using one of the above methods. You can also put the battery on charge right away. Further, You must charge a completely discharged battery in the mode recommended by the battery manufacturer. The standard is to supply a charge current at 0.1 of the total battery capacity.
A fully planted battery is charged with this current for at least 14-16 hours. For example, consider charging a 60 Amp-hour battery. In this case, the charge current should be, on average, from 3 A (slower) to 6 A (faster). You should properly charge a fully discharged car battery with the smallest current and as long as possible (about a day).

When the voltage at the battery terminals no longer increases for 60 minutes. (assuming the same charging current is supplied), then the battery is fully charged. When fully charged, maintenance-free batteries assume a voltage value of 16.2 ± 0.1 V. One should bear in mind that this voltage value is a standard. Still, at the same time, there is a dependence on the battery capacity indicator, charge current, electrolyte density in the battery, etc. Any voltmeter is suitable for measurement, regardless of the error of the device, since it is necessary to measure a constant, not an exact voltage.

How to charge a car battery if there is no charger

The easiest way to charge the battery is to start the car using the “lighting” method from another car, after which you need to drive the car for about 20-30 minutes. For the efficiency of charging from the alternator, either dynamic driving in higher gears or driving on “low” is assumed.

The main condition is to maintain the crankshaft speed at around 2900-3200 rpm. At the specified speed, the alternator will provide the required current to recharge the battery. Note that this method is suitable only if the battery is partially and not deeply discharged. Also, after the trip, you will still need to charge the battery fully.

Quite often, motorists are interested in what else you can charge a car battery beside the charger. As a replacement, it is often supposed to use chargers that charge mobile phones, tablets, laptops, and other gadgets. Immediately, we note that these solutions do not allow charging a car battery without several manipulations.

The fact is that the main condition for supplying current from the charger to the battery is that a voltage must be present at the output of the charger, which will be higher than the voltage at the outputs of the battery. In other words, when the voltage of the battery outputs is 12 V, the output voltage of the charger should be 14 V. As for various devices, the voltage of their batteries often does not exceed 7.0 V. Now, imagine that you have at hand a charger from a gadget that has the required voltage 12 Q. The problem will still be present since the resistance of the car’s battery is measured in whole ohms.

It turns out that connecting charging from a mobile device to the battery outputs will actually be a short circuit of the terminals of the charging power supply. The protection will operate in the unit, as a result of which such a charger will not supply current to the battery. In the absence of protection, there is a high probability of failure of the power supply from a significant load.

You should add that the car battery should also not be charged from various power supplies with a suitable output voltage. Still, they structurally lack the ability to adjust the amount of the supplied current. Only a special charger for a car battery is a device that has the required voltage and current for charging the battery at its output. In parallel with this, it is possible to control a constant current value.

Homemade charger for car battery

Now let’s move from theory to practice. Let’s start with the fact that you can make a charger for a battery from a power supply from a third-party device with your own hands.

Please note that these actions pose a certain danger and are performed solely at your own peril and risk. The resource administration does not bear any responsibility, and the information is presented for informational purposes only!

There are several ways to make a charger. Let’s take a quick look at the most common ones:

  1. Making a charger from a source with a voltage of about 13-14 V at its output and capable of providing a current of more than 1 Ampere. For such a task, a laptop power supply is suitable.
  2. Charging from a regular household electrical outlet 220 volts. To do this, you will need a semiconductor diode and an incandescent lamp, which are connected in series in a circuit.

You should bear in mind that the use of such solutions means charging the battery through a current source. As a result, constant monitoring of the time and moment of the end of the battery charge is required. This control is carried out using regular measurements of the voltage at the battery terminals or counting the time the battery is charged.

Remember, overcharging the battery leads to an increase in the temperature inside the battery and the active release of hydrogen and oxygen. Boiling the electrolyte in the “banks” of the battery causes an explosive mixture. The battery may explode if an electrical spark is generated or other sources of ignition occur. An explosion like this can lead to fires, burns and injuries!
Now let’s focus on the most common method of self-manufacturing a charger for a car battery. We are talking about charging from a laptop PSU. To accomplish the task, certain knowledge, skills and experience in assembling simple electrical circuits are required. Otherwise, the best solution would be to contact a specialist, purchase a ready-made charger or replace the battery with a new one.

The scheme for manufacturing the memory itself is quite simple. A ballast lamp is connected to the PSU, and the outputs of a homemade charger are connected to the outputs of the battery. A lamp with a small rating is required as a “ballast”.

If you try to connect the power supply unit to the battery without using a ballast lamp in the electrical circuit, you can quickly disable both the power supply unit itself and the battery.

You should select the right lamp step by step, starting with the minimum ratings. To begin with, you can connect a low-power turn signal lamp, then a more powerful turn signal lamp, etc. Each lamp should be tested separately by connecting it to a circuit. If the light is on, then you can proceed to connect an analogue of greater power. This method will help not to damage the power supply. Finally, we add that the burning of the ballast lamp will indicate the battery charge from such a homemade device. In other words, if the battery is charging, then the lamp will burn, even if it is very dim.

Do I need to charge a new battery for the car

Auto mechanic replacing car battery

A car mechanic replaces a battery.

The new battery must be fully charged and functional; that is, you must immediately install it on the car to start further operation. Before purchasing, it is necessary to check the battery for several parameters:

  • the integrity of the case;
  • measuring the voltage at the outputs;
  • checking the density of the electrolyte;
  • date of manufacture of the battery;

At the initial stage, it is necessary to remove the protective film and inspect the case for cracks, streaks and other defects. If the slightest deviation from the norm is found, it is recommended to replace the battery.

Then the voltage is measured at the terminals of the new battery. You can measure the voltage with a voltmeter, while the accuracy of the device does not matter. The voltage should not be below the 12-volt mark. A voltage reading of 10.8 volts indicates that the battery is completely discharged. This indicator is unacceptable for a new battery.

The density of the electrolyte is measured using a special plug. Also, the density parameter indirectly indicates the battery charge level. The final stage of the check is to determine the date of release of the battery. Batteries that you released 6 months. Back or you should not purchase more from the day of the planned purchase. The fact is that a battery ready for use tends to self-discharge. For this reason, you must prepare the battery in advance for long-term storage, but in this case, the battery can no longer be considered a new finished product.

Other questions about car battery charging

Very often, during operation, owners try to charge the battery without removing the battery from the car. In other words, the battery is charged without removing the terminals directly on the car; that is, the battery while charging remains connected to the vehicle’s network.

We draw your attention to the fact that when the battery is charging, the voltage at the battery terminals may be around 16 V. This voltage indicator strongly depends on what type of charger is used for charging. We add that even turning off the ignition and removing the key from the lock does not mean that all devices in the car are de-energized. The security complex or alarm system, multimedia head unit, interior lighting and other solutions can remain on or in standby mode.

Charging the battery without removing and disconnecting the terminals can result in too high a supply voltage applied to powered devices. The result is usually the breakdown of such devices. If your car has devices that cannot be completely de-energized after turning off the ignition, it is prohibited to charge the battery without disconnecting the terminals. Before charging, in this case, it is necessary to make a mandatory disconnection of the “minus” terminal.
Also, do not start disconnecting the battery from the positive terminal. The negative terminal on the battery is connected to the vehicle’s electrical system through a direct connection to the body. An attempt to turn off the “plus” first can have dire consequences. Unintentional contact of a wrench or other tool with metal parts of the car body / engine will cause a short circuit. This situation is quite common when the positive terminal is unscrewed from the battery output with the help of keys while the minus is not removed.

As for charging the battery in the cold or indoors in winter without heating, you can safely recharge the battery in such conditions. During charging, the battery heats, the temperature of the electrolyte in the “banks” will be positive. In parallel with this, bringing the battery into heat for charging is required if the electrolyte has frozen inside the battery and the battery has been completely seated. It is necessary to charge such a battery strictly after the frozen electrolyte thaws.