Is it possible to charge a charged car battery? Charging the battery at idle - truth and fiction

Despite its fairly simple device, a car battery still remains one of the most complex and incomprehensible parts of a car. Motorists have a lot of traditional questions related to its proper operation, and one of them is the question of whether it needs to be charged, how often to do it, and whether it is always necessary to remove it for this. Any battery needs periodic charging and, basically, this requires its removal - for example, during mandatory maintenance.

It will also require charging if it just sits down and is unable to provide adequate starting current. This often happens when some electrical device is running in the car all night - radio, headlights or dimensions, interior lighting. In other cases, the battery does not need to be charged. Subject to regular monitoring of battery voltage, which It is recommended to carry out 4-5 times a year. To do this, it is enough to use an ordinary ammeter. In cold weather, the frequency of monitoring can be increased.

Charging the battery - remove it from the car or not

In general, it is much more convenient to charge a battery that has been removed from the car. This way you can carefully inspect it for damage to the case, clean it, check the electrolyte level and its density - and all in comfortable conditions. But owners of cars with a huge amount of complex electronics try not to do this, citing possible problems with the electronics that arise after the charged battery is returned to its place. To be fair, it should be noted that such fears are well founded.

The fact is that most complex on-board electronics are extremely sensitive to power outages. There are many cases where a newly supplied battery damaged sensors, controllers or on-board computer. Owners of such cars try by hook or by crook to charge the battery without removing it from the car. Or they go to the other extreme - they don’t charge the installed battery at all, hoping that the on-board charging system will do it.

This is far from true. The fact is that while the engine is running, the battery is recharged by the generator. But at the same time it is necessary to ensure maximum safety of the process. In order to ensure that the gas emission process remains under control and does not exceed normal values, a special regulator is located near the generator, which is responsible for ensuring that the charging current does not exceed 14 V, while 14.5 V is required to fully charge the battery. Thus The car battery is never 100% charged

Correctly charging the battery without removing it

So, the answer to the question is it possible to charge a battery without removing the terminals - yes. Therefore, you need to understand how to do it correctly, quickly and safely. To begin with, it is worth keeping in mind the fact that even the ignition key removed from the lock does not block the supply of energy to some devices. Fine, The supply voltage for all auto electronics does not exceed 12 V, while the charging current for the battery is 1.5-16 V. Therefore, if you are not sure that all electronics are de-energized, it makes sense to remove the negative terminal from the battery - this will save the devices.

When charging the battery without removing it from the car, you must proceed as follows:

• remove the battery from the protective cover, remove the metal bolts, clean the top surface, including the terminals;
• check the electrolyte level; if there is a shortage, be sure to replenish the deficiency with distilled water - otherwise there will not be a 100% charge;
• prepare the charger - it must be disconnected from the network; when connecting, strictly ensure that the polarity is observed;
• plug in the charger.

Attention! With this method of charging the battery, it is unacceptable to use homemade or outdated models of chargers, since it is extremely important to ensure “high-quality” current and accurately maintain the required voltage. This is the only way to charge the battery without removing it from the car.

How long does it take to charge properly?

If you can definitely charge the battery without removing the terminals, then with the time it takes to fully charge, everything is not so clear. The time it takes to charge each battery varies. Thus, particularly powerful batteries take much longer to charge than low-capacity batteries. The time it takes to fully charge is also influenced by the degree of its discharge - if there is a complete absence of energy in the battery, it will take quite a lot of time to charge it. Of course, the strength of the charging current, the ambient temperature, and the charger itself also matter. You can watch the practical charging process and its time in the video:

The purpose of the charge also matters. For example, if you urgently need to charge the battery without removing it from the car, then in order to start the engine, you can do the following:

• disconnect the wires from it;
• connect the charger, then turn it on;
• set the current value to the limit;
• wait 15 minutes;
• disconnect the “charger”, connect the wires and start the car.

This measure is forced, and you should not resort to it too often. For a better and more complete charge, it is better to remove the battery. After completing all the necessary preliminary steps (cleaning, checking and adjusting the electrolyte), leave it connected to the charger for the whole night. Just don’t forget to leave the plugs unscrewed. The end of the charging cycle is best judged not by time, but by the charger.

Important! The arrow of its indicator should be located on the left side either at 0 or below.

New battery - should it be charged?

A newly purchased battery can also be charged without removing the terminals, but many car enthusiasts are concerned about the question of whether this is necessary. It’s worth starting with the fact that it will be new only for the buyer. Before the moment of purchase, it could “gather dust” in the store for many months, and if after purchase it is immediately installed in the car, its power very soon may not be enough to start the engine, especially in winter. That's why It would be more correct to charge it first, and only after that start using it.

Regardless of which battery is charged and how - by removing it from the car or not, all precautions must be taken, since improper charging can end very badly. The first thing it is important to pay close attention to is good ventilation. During the “recharging” process, the battery releases into the surrounding air a huge amount of chemical compounds that are extremely aggressive to humans. These include sulfur dioxide, arsenic hydrogen and many others, and in addition, a huge amount of hydrogen, which, when combined with oxygen, forms an explosive mixture.

In addition, it is necessary to work with the battery only with gloves, since sulfuric acid can cause deep chemical burns to the skin. Naturally, if you start the charging process with the lids of the cans closed, the battery is very likely to explode. In the event that the charge is carried out by home-made devices, it is necessary to remember the approximate time of completion of the charge, since overcharging is just as harmful to the battery as a complete discharge.

The winter period is perhaps the most difficult for a car, and in particular for its battery. During cold starts, the battery suffers greatly - it loses charge and cannot be recharged properly because it is cold (as you know, a cold battery charges much worse). And if you travel short distances, for example, 15 minutes by car to work, you end up with chronic “undercharges.” In general, once a month, and maybe more often, you need to recharge with a special charger. BUT here another question arises - how to do this correctly? Do I need to remove the battery or can it be done without removing it from the car? After all, there are so many electronics in cars now that can be burned. Let's find out...

It seems to me that the problem was “pulled out of thin air” out of the blue. All modern chargers can charge your car even if the terminals are not removed from your battery, that is, it is connected to the on-board system. If you are the happy owner of a garage, just come into it, open the hood without removing the battery and terminals (though if they are clean), connect the wires from the “charger” and charge to the required parameters! ALL! Nothing will burn out, nothing will short out, nothing will “fly”. Anyone who says this simply does not understand the structure of a car.

After such a statement, many can now tell me - JUSTIFY, which is what I want to do. However, before that, I want to note that now there are two main types of cars, this is conditionally the “old” carburetor type, they are becoming scarce every year, but they still exist. And the conditionally “new” injection type, the vast majority of cars. In this article we will analyze each option separately. BUT first, a few words about overvoltage.

Overcharge problems

There are a lot of reviews and discussions on this topic on the Internet. Some write that it is necessary to remove the terminals, and if you do not remove them, this can lead to complex breakdowns. Others write that nothing bad will happen and you can charge without removing it. BUT there is NO one opinion here!

I suggest you think logically. From an electrical equipment point of view.

What's wrong with an incorrect charger? YES, it’s simple - high voltage, at which electronic devices can hypothetically burn out, even if they are de-energized through the ignition switch.

So, many chargers produce a maximum voltage of 15V; it can do little for the on-board electronics, since the generator often produces approximately the same voltage.

However, there are specialized charging systems designed, say, for calcium batteries, where the voltage can be 16 - 17V, which can already be critical for many electronic systems.

Therefore, it is initially correct. We take into account that the on-board network can handle 15V MAXIMUM, otherwise we get overvoltage and the possibility of damaging the car’s electronics.

There can be no problems here at all - ZERO. There is simply nothing to burn here, because there is no computer here! Except, but even if it fails, it will most likely simply recharge your battery. BUT the charger has no effect on this relay! How does the charging system of this variant work? The diagram is a little exaggerated, but it is just needed to understand the process.

After starting the engine, the generator begins to produce energy; it is closely connected to the engine crankshaft through a belt drive. The energy is intermittent and is removed by special “brushes” from the rotor. Next, the energy is “rectified” through a special “relay-regulator rectifier”. It provides a constant voltage of, say, 13.8 - 14.2 V, sufficient to charge the battery.

It is clear that when the power unit is operating, the generator powers all the other equipment necessary for igniting fuel, lighting, etc., the battery is simply charged in this mode.

The generator cannot recharge the battery, everything is controlled by special “relays”; this is the mechanical principle of charging.

In a carburetor car, there are no specialized control units at all; here many operations are performed mechanically.

Actually, if you do not remove the battery from the car, connect the ends of the charger to the terminals, and the engine will not work at this time. Nothing bad can simply happen, the battery will be charged the same way as from a generator, and the “relay” will essentially be de-energized. Personally, I myself have done this many times, on my VAZ 2101 - 2105.

Injection type

These are modern units that contain a lot of electronics. In general, motors have now evolved very much; they are a bunch of electronics, sensors and other things. The main device that controls everything is, of course, the ECU (Electronic Control Unit). Not only charging, but also ignition and other vehicle functions are controlled. If you tear out this block now, the car will become just a “piece of metal.”

However, for the generator, the evolution is not so noticeable. Again, it spins off from the engine crankshaft (connected by a belt). It again has a “relay-rectifier”, and it again powers the system when the engine starts and recharges the battery.

BUT now power goes not just to consumers, but also to the “brain” of the car’s ECU. This is where the myths were born that - if you connect the charger without removing the terminals, and even the battery itself from the car. Then this “charging” will disable it.

However, this is not true! Let's think logically:

• If the ignition is turned off, then often there is no power going to the ECU. Nowadays, ignition switches are increasingly being installed that turn off all electrical appliances, in order to avoid
• Modern ECUs are fully protected from power surges
• The charger supplies exactly the same voltage as the alternator. I repeat once again from 13.8 to 14.5V (in modern cars), so in principle nothing can burn here
• Also, the “charger” will not burn out either the generator or the starter, because they are simply turned off
• Charger currents, not so large, often range from 2 to 8 Amps

I can assure you with confidence that the battery can be charged without removing the terminals from the car. Nothing bad will happen.

I will say even more - now many sophisticated cars (usually elite class) that have several ECUs, an additional one, can be used for secondary equipment. It is generally not recommended to remove the terminals from the battery. Because certain settings may go wrong, to restore which you will need to visit the stations of an official dealer.

Running engine

This is when you shouldn’t connect the contacts from the “charger” - this is when the engine is running. After all, here the power comes from a standard generator + you also supply power from the charger. First of all, either the generator can be damaged, or the “relay-rectifier” can burn out. Or you can burn the “charger” itself; it is not designed to work with the engine running.

And even in such conditions, the ECU is unlikely to burn out, I want to repeat it again - the charging itself is more likely to suffer.

Dirty terminals and oxides

However, if you want to charge the battery without removing it from the car, you should take care of the car terminals. Sometimes, due to oxides and other deposits, simply moisture, charging will not be possible, or incorrect data will be indicated!

5 minutes to read.

Probably every car enthusiast has at least once thought about charging the battery without removing it from the car. This means without disconnecting the battery terminals. Most continue to follow the classic recommendations, “no matter what happens.” But part of us is still trying to figure out whether it is possible to simplify our life? Unfortunately, no search leads to a clear and uncompromising answer. So you'll have to figure it out a little.

A battery is a device that performs a number of important functions in a car. It provides electricity to the car’s devices when the engine is turned off, maintains their condition, performance and settings, allows you to start the car, and also acts as a protective buffer between the generator and the car’s electrical circuit. The battery discharges periodically - this is a normal phenomenon characteristic of any type, type or instance. In addition, over time, during operation, the battery exhausts its resource, and its properties are lost, and the discharge period is reduced. So, you will have to recharge it more often.

Every car enthusiast should know and be able to charge the battery on time. Correct charge restoration can significantly extend the life of the device. The canonical rules state that proper charging should begin by disconnecting the dead battery from the car circuit. It is believed that this is less likely to overload the network and damage the expensive electrical equipment of the machine.

What is the problem?

Or why charge the battery without removing it from the car? Monitoring forums, autoblogs, stories from friends and acquaintances and, perhaps, even personal experience, allows us to identify the following pattern: when the battery is disconnected, all settings and settings of the on-board computer, multimedia system and other devices connected to the network are lost. Of course, you want to avoid lengthy reconfigurations of all electronics, which are abundant in a modern car.

In the opposite situation, there is a risk of equipment failure. On the one hand, the loss does not seem critical if we are talking about a radio or a clock; on the other hand, new cars can be equipped with rather expensive electronic devices, the performance of which, in addition, can be fundamental for the normal functioning of all car systems.

Consequences of battery disconnection

There is no strictly defined range of consequences of disconnecting the battery when it is necessary to charge it. Actually, even in car models that are very similar in functionality, when removing the terminals, you can find completely different results. The most common occurrences are:

• resetting the on-board climate control settings in the cabin;
• blocking the standard radio.

Of course, such problems do not pose great threats. To unlock the media, you just need to enter the code, and the electrical adaptation settings themselves will be restored after a couple of tens of kilometers. However, less common, but no less unpleasant consequences of briefly disconnecting the battery from the car circuit also occur:

• climate system settings failure;
• deleting RAM memory;
• failures in the system of modern speaker systems, which may lead to the need to reinstall the software.

Obviously, after a car owner encounters at least one of the described (or undescribed) problems, he has a desire to eliminate them in the future. Therefore, the question of whether a battery connected in a circuit can be charged becomes relevant and quite logical.

So, is it possible to charge without removing the terminals?

The simplest and shortest answer to this question may be “you can”! However, due to the complexity of the system, of course, there are many “BUTs”!

Having delved into the literature and notes of car enthusiasts, you can easily find both supporters and opponents of this approach. The pros and cons are distributed in the same way as the answers to the question whether it is possible to remove the battery terminals while the car engine is running. An analysis of forums and reviews from car enthusiasts on the topic can be briefly described as follows: against isolated evidence of unpleasant consequences, dozens of reviews that everything went well. So, there are few victims, however, their presence indicates a risk.

Charging the battery, which is carried out without removing the terminals, is fraught with high voltage entering the vehicle network. In principle, devices should normally tolerate surges up to 15.7 V. However, as practice shows, anything can happen. Therefore, to minimize the likelihood of electronics failure, it is recommended to use a charger that has safe current output parameters. Thus, if you are planning to charge a dead battery without disconnecting it from the network, you should carefully familiarize yourself with its characteristics. As a rule, in the documentation supplied with the car battery charger, the manufacturer notes whether it is safe (especially when used in automatic mode) for the car's electronics.

It is much less likely that problems will arise if a factory device is used. An attempt to charge a connected battery with a homemade device can lead to the described undesirable consequences with a much higher probability.

While charging is in progress, it is better to constantly monitor the operation of the charger. In addition, experts recommend adhering to certain rules when recharging:

• The terminals should be connected in this order: first “plus”, then “minus”. You need to turn off the device in the reverse order.
• Avoid contact between the charger wires and the surface of the battery, tubes and metal parts of the car.
• The charger should be connected to the 220 V electrical network after the battery is connected, and disconnected after disconnecting the terminals.
• Do not turn on any devices in the car during charging.
• Do not leave the charging device unattended.
• Ensure good ventilation of the room in which charging is carried out.

However, the procedure for recharging a car battery that has not been removed from the car does not differ from the standard one.

Summary

Thus, the answer to the question whether it is possible to charge the battery without removing it from the car is “you can”. But in some cases, if there are fluctuations in the car’s network caused by unstable operation of the charger, you can lose expensive devices connected to the car’s electrical circuit.

(battery) is a specially designed type of lead-acid battery for motorized vehicles and is used to start the engine and operate on-board electrical equipment when the engine is stopped.

The battery in the car is charged by an electric generator. To extend the battery life and protect the vehicle's electrical equipment from overvoltage, a relay regulator is installed after the generator, limiting the voltage to 14.1±0.2 V. In order for the battery to be charged 100%, it must receive a voltage of at least 14.5 V. Therefore, it is impossible to fully charge the battery with a car generator, even during long trips, and it becomes necessary to periodically charge the battery with a mains charger.

When it’s warm outside, you can start the engine from a battery charged only 20%. When frost sets in, the battery capacity is reduced by more than half, and the starting current due to thickened oil in the engine increases significantly. As a result, if you do not fully charge the car battery from an external charger before the onset of cold weather, you may not be able to start the engine without “lighting up.”

What current and how long should I charge?
car battery

With the standard charging mode recommended by battery manufacturers, the charge current should be 10% of the battery capacity, while a completely discharged battery needs to be charged in 15 hours. For example, with a battery capacity of 45 Ah, the charging current should be 4.5 A. It is better to charge with a lower current and for a longer time. For example, a battery with a capacity of 45 Ah should be charged with a current of 2.8 A for 24 hours.

If the battery is 50% discharged, then in the “Enter battery capacity” field you need to enter half of its factory capacity. For example, for a battery with a capacity of 60 Ah, you will need to enter the value 30 Ah.

As you can see, to correctly select the battery charging time, it is necessary to determine to what extent it is discharged. There are several methods available to the car enthusiast, which are given below.

How to know if the battery is fully charged

If it is not possible to determine the residual capacity of the battery, then you can determine the moment it is fully charged using a voltmeter. When, while charging the battery, the voltage at its terminals stops increasing with a constant charging current for more than an hour, it means the battery is 100% charged. The current consumed by the battery will begin to be spent only on its heating.

For modern maintenance-free batteries, the voltage should reach the value 16.2±0.1 V, which depends on the charge current, battery capacity, electrolyte density and other factors, and is for reference only. For these measurements, you can use a voltmeter with any error, since an accurate voltage measurement is not required, but its constancy.

How to determine the battery charge level

To determine the time and amount of charging current, you need to know the state of charge of the battery. Of the existing measurement methods, the following are available to the car enthusiast:

• by voltage at the battery terminals without load;
• by electrolyte density (for batteries with liquid acid);
• by voltage at the battery terminals with a plug load;
• by voltage at the battery terminals under load of the vehicle’s electrical equipment;
• according to the built-in hydrometric indicator.

It is impossible to accurately measure the battery charge level, since there is no method for practical use. You can only estimate it by measuring the voltage at the battery terminals or the density of the electrolyte (only for batteries with liquid electrolyte).

Measuring the voltage at the terminals without load

The table shows data for all types of acid batteries with a nominal voltage of 6, 12 and 24 V. The data corresponds to a temperature of 20-25°C.

It is recommended to measure the voltage at the battery terminals at rest, not earlier than after six o'clock after disconnecting the battery from the car circuit or charger.

Measuring electrolyte density

If the battery contains liquid electrolyte, then it is possible, if you have a hydrometer, to determine the degree of its charge by measuring the density of the electrolyte. The data in the table corresponds to a temperature of 20-25°C. The voltage for which the battery is designed does not affect the density of the electrolyte.

With load fork

Without waiting, you can check the state of charge of the battery by measuring the voltage at its terminals under load. For this purpose, load forks are used, which are a voltmeter with a resistance of 0.018-0.020 Ohms connected parallel to its terminals (for a battery with a capacity of 40-60 Ah). The plug is connected to the battery terminals and after 5-7 seconds the voltmeter readings are taken.

The photo shows checking the battery capacity using a VIN-10 load fork. Although the plug is the simplest, it allows you to estimate the battery charge level with sufficient accuracy. The voltmeter showed 9.5 V. Based on the data from the table below, we determine that the battery is 60% charged.

Voltage under load of vehicle electrical equipment

If there is no load plug and the battery is connected to the vehicle’s on-board power supply, then you can load the battery by turning on the side lights and high beam headlights. Since the power of the headlight bulbs is at least 50 W, the load current will be at least 10 A. The measured voltage with a sufficiently charged battery should be at least 11.2 V.

Another way to assess the state of charge of a battery is to measure the voltage at its terminals when starting the engine. If the starter is working properly, the voltage should not drop below 9.5 V. If the voltage drops below 9.5 V, the battery is very discharged and needs to be charged. By the way, This method can determine the serviceability of the starter. If a serviceable and fully charged battery is installed in the car, then a voltage drop at the battery terminals during engine starting below 9.5 V indicates a malfunction in the starter.

Since the voltage value, depending on the state of charge of the battery, changes in tenths of a volt, the voltmeter must be highly accurate. A voltmeter with a measurement error of only 1% will already give an error in the results of measuring the degree of charge of 10%. Therefore, to determine the degree of battery charge by voltage, a device with a measurement error of no worse than 0.1% is required.

According to the built-in hydrometric indicator

In some models of car batteries, to be able to assess the degree of their charge, a hydrometric indicator is built in, which is a transparent peephole, as in the photo.

The hydrometric indicator allows you to assess the condition of the battery without instruments. If the indicator eye glows green, this means that the battery is charged more than 60%. This level of battery charge is quite sufficient for reliable starting of the engine and operation of the vehicle’s electrical equipment.

If the eye is colorless and dark, as in the photo on the left, then the battery charge level is below 60%, and in order to start the engine without failure in any weather, the battery must be recharged from a charger. And if the indicator eye is colorless and light, photo on the right, then the electrolyte level in this jar is below normal and distilled water should be added to it.

The hydrometric indicator is designed in such a way that if the electrolyte level in the battery bank is insufficient, it cannot work, and here’s why.

The hydrometric indicator is a plug screwed into the body of one of the battery cans, in which a transparent tube (light guide) is installed. At the end of this tube, a V-shaped tube is attached using a plastic sleeve, in which a green ball is placed. The light guide tube is sealed, and electrolyte can flow freely into the V-shaped tube. The weight and volume of the ball are selected in such a way that at an electrolyte density of 1.226 g/cm 3 at 20°C it floats up (position 1 in the drawing), and at a lower density it rolls down to position 2. Thus, if the battery is charged more than 60% , the ball is visible through the indicator eye, and if the degree of charge is less, then only the electrolyte is visible. If the electrolyte level drops below the V-shaped tube, the incoming light through the indicator eye is reflected from the electrolyte surface and the reflected light is visible through the eye.

Unfortunately, the hydrometric indicator has a number of serious shortcomings, due to which the accuracy of its readings is low. The fact is that when the temperature of the electrolyte changes, its density changes greatly, and when the temperature decreases, it increases. Therefore, for example, at an air temperature of minus 30°C, the indicator will show that the battery is charged by 60%, but in reality it is only 40%. In addition, the indicator monitors the condition of only the battery bank in which it is installed, and the condition of the remaining batteries can only be judged indirectly.

Rules for charging a car battery

The battery is a source of direct current and when connecting it, polarity must be observed. The battery terminals are marked. A positive conclusion is indicated by the sign “ + ", and the negative sign " - " The terminals of the charger for connecting the battery also have the same markings. When connecting the battery for charging, you need the positive terminal " + "connect the battery to the positive terminal of the charger, and the negative " - " – with a negative. If the connection polarity is reversed, the battery will discharge instead of charging and even damage the charger.

The cross-section of the wires for connecting the battery to the charger must be at least 1 mm 2, which corresponds to a wire diameter excluding insulation of 1.3 mm.

Before charging, the battery removed from the car must be cleaned of dirt and its surface wiped to remove acidic residues with a cloth moistened with an aqueous solution of soda, prepared at the rate of a tablespoon of soda per glass of water. If there is acid on the surface, then the aqueous soda solution foams.

If the battery has plugs for filling acid, then all the plugs must be unscrewed so that the gases formed in the battery during charging can escape freely. It is imperative to check the electrolyte level, and if it is less than required, add distilled water.

According to the theory, the battery can be charged with a current that does not have enough capacity to fully charge it. That is, if the battery has a capacity of 50 Ah and is half charged, then at the first moment of charging you can set the current to 25 A and reduce it every minute, down to zero when fully charged. Some automatic chargers operate on this principle, allowing you to fully charge a car battery in just a few hours. But such chargers are very expensive. And there will be no need for them if you charge the battery in advance.

Although some chargers allow semi-automatic charging, I still prefer to charge the battery manually. As a rule, the battery is no more than half discharged, so knowing its capacity, it is not difficult to calculate the charging time. For example, for a 50 Ah battery, to fully charge it you need to supply a current of 30 Ah, taking into account losses. I set the charging current to 3 A, and after 10 hours the battery will be fully charged. To ensure that the battery is fully charged, if time permits, you can set the current to 0.5 A and continue charging the battery in this mode as long as time allows. For high-capacity car batteries, this charge current is safe.

If time is pressing, you can first charge the battery with a current of, say, 8 A for three hours, and then reduce the current to 6 A and charge for another hour. The battery will be charged in just 4 hours. But, nevertheless, the optimal mode for charging is a small current, 2-3 A. With this current, overcharging and overheating of the battery, which greatly reduce its service life, are eliminated. All ingenious charging methods to reduce sulfation of battery plates, as practice shows, are nothing more than theory. If the operating conditions of the battery are observed (full discharge is not allowed), a high-quality acid battery will last from 3 to 5 years, at best seven.

Is it permissible to charge a car battery?
at negative temperatures

Yes, it is acceptable, but not in all cases. During charging, the battery heats up, and after a while the electrolyte temperature will rise above zero. You drive a car in winter at sub-zero air temperatures, and the generator regularly recharges the battery even at a temperature of minus 30˚C.

It is unacceptable to charge a battery if it is in a highly discharged state in the cold and the electrolyte has turned into ice, which can form already at a temperature of minus 10˚C. A frozen battery should be moved to a warm room and charging should begin only after the ice has melted.

phone charger

I am often asked the question about the possibility of charging a car battery using chargers designed for charging mobile phones, cameras and similar devices.

These chargers are not suitable for charging a car battery. the following reasons.

A necessary condition for current from the charger to flow into the battery is the presence at the output of the charger of a voltage exceeding the voltage at the battery terminals. For a 12 V battery, the voltage at the charger output must be at least 14 V. And the output voltage of most mobile phone chargers is 1.5-6 V.

Is it possible to charge a car battery?
laptop power supply

The laptop charger has an output voltage of 18 V, but if you connect it directly to the terminals of the car battery, it will be equivalent to short circuiting the terminals of the unit, the protection will work and the current will not flow. This is due to the fact that the internal resistance of a car battery is a few ohms and direct connection of the charger is equivalent to short circuiting its terminals.

But if you plug a light bulb from a car headlight into the gap of one of the wires, it will act as a current limiter and in this case the car battery can be charged. True, the charging current will not exceed 2 A and will be needed to charge a completely discharged battery with a capacity of 50 Ah by 50% in about 20 hours.

Can the battery be charged?
without disconnecting from the vehicle's on-board network

When charging the battery, the voltage at its terminals can reach, depending on the type of charger, 16 V. Even when the ignition key is removed from the ignition switch, some devices still remain connected, for example, the security alarm system, interior light bulb, trunk light. Depending on the vehicle model, other devices may be connected. Thus, instead of the maximum permissible supply voltage according to the passport, more will be supplied to the devices, which can lead to their failure. Thus, if you are not sure that all devices are de-energized when the key is removed from the ignition switch, then it is better not to risk it and disconnect its negative terminal from the on-board network before charging the battery.

Why negative? Because the negative terminal of the battery is connected to the vehicle's on-board network by direct connection to the body using a threaded connection. If you disconnect the positive terminal of the battery first, you may accidentally touch the metal parts of the engine or car body with a wrench. There will be a short circuit.

How to start a car safely
from the battery of another car (light)

No one is immune from the case when you need a donor battery to start the engine of your own car, or, as people say, “light it.” Usually, the battery terminals of the same name are connected to each other with alligator clip wires, the gas is added, and the engine of the other car is started, leaving your own running. Such “lighting” can damage the electronics of a modern car’s electrical equipment and you should not be surprised if a malfunction occurs in your car immediately or after some time. How to “light a cigarette” correctly? The answer is very simple.

In winter, before you let it light up, you need to start your car and warm up the engine for at least five minutes. Turn off the engine. In a car whose battery has died, you must first disconnect the terminal from the negative terminal of the battery, and then connect the cigarette lighter wires to the positive terminal and to the removed terminal from the negative terminal of the battery.

Since the current consumed by the starter when starting the engine is about 100 A, the cross-section of the cigarette lighter wires must be at least 10 mm 2, which corresponds to a wire diameter excluding insulation of 3.6 mm.

Connect the other ends of the wires to the terminals of the donor battery. Start the engine, let it run for a couple of minutes, and, without stopping, disconnect the cigarette lighter wires.

The generated electricity from a car generator is quite enough to power all the included electrical equipment of the car. Connect the negative terminal of the on-board network to the standard battery.

To recharge the battery faster, you should try to drive in low gears to ensure at least 3000 rpm of the engine shaft. At these speeds, the car's generator will generate sufficient current to power electrical equipment and charge the battery.

To guarantee the next start of the engine after it has cooled down, you must immediately fully charge the battery from the charger.

How does a completely discharged battery affect its service life?

Negative. Full discharge is especially dangerous for modern maintenance-free batteries. As the manufacturers of such batteries warn, even a one-time full discharge can damage the battery. From personal experience, I will say that it happened to me twice that a maintenance-free battery was discharged to zero (I forgot to turn off the side lights in the summer), but there were no serious consequences. True, I didn’t allow it a third time; I installed an alarm that would emit a signal when the driver’s door was opened with the engine off but the lights and headlights on.

How long does the battery last?
can remain operational without recharging

The storage time of a fully charged battery disconnected from the vehicle's on-board power supply depends on its capacity. Internal leakage currents are about 10 mAh. Knowing this, it is easy to calculate the time. Taking into account the permissible discharge of the battery to 30% of the original capacity, for a 50 Ah battery we get 50/3.3 = 16 Ah - this is the permissible degree of discharge. This means that the battery can self-discharge with a capacity of 50 A h - 16 A h = 34 A h. Now we divide 34 A h by 0.01 A h and it turns out 3400 hours or 141 days, about 5 months. It should be taken into account that storing a discharged battery at a temperature below minus 10°C is unacceptable, since the density of the electrolyte will decrease and it will turn into ice, which will deform the battery and render it inoperable.

If the battery is connected to the vehicle’s on-board network, then due to leakage currents in the electrical equipment, the period will be halved and will be 2.5 months.

If the alarm is connected, it also consumes current, which, depending on the model of the security system, ranges from 0.02 Ah to 0.05 Ah. The current consumption of the alarm can be found out from its passport. In this case, the time, with a current consumption of the alarm system of 0.02 A h, the time will be 1.2 months, and with a current of 0.05 A h only 20 days. At negative air temperatures, the time will be halved and will be only 10 days.

How to check leakage current in car electrical equipment

Sometimes motorists complain that a fully charged battery, even when the car is not in use, quickly discharges and after a week of inactivity the engine cannot be started. One of the reasons for this behavior of the car may be a large leakage current in electrical equipment.

To measure the leakage current of electrical equipment, it is necessary to remove the terminal from the negative terminal of the battery and connect a DC ammeter into the gap between the battery terminal and the removed terminal, observing the polarity, as shown in the photograph. In order not to hold the multimeter probe in your hand, it is advisable to use a piece of copper wire with a bare wire twisted at the end into a ring around the diameter of the battery terminal.

During measurements, all electrical appliances must be turned off (the key should not be in the ignition switch), including the security alarm disconnected from the car's circuitry. If the current exceeds 10 mA, there is a fault in the wiring or equipment.

If it is difficult to turn off the alarm, then measurements can be carried out without turning it off. Then the ammeter will show the total current - the leakage current in electrical equipment and consumed by the alarm, the value of which should be in the range of 50-100 mA. If the current is greater, then there is a malfunction in the electrical wiring or electrical equipment of the machine.

As you can see in the photo, the total current consumption in this car is 50 mA. When measuring, the readings will increase by several milliamps at approximately one-second intervals. This is normal and is related to the operation of the security alarm system. In this case, the amount of current consumption from the battery will be the same, both when the alarm system is turned on using the key fob, and when it is turned off. When turning the security alarm on and off, due to current consumption by the central locking system, a current surge of up to 3-5 A will be observed for a couple of seconds. And if a current of this magnitude continues to flow for a longer time, it means that one of the door activators is faulty.

How to choose a car battery when purchasing

Sooner or later, every car enthusiast is faced with the need to replace the battery in their car. When purchasing a new battery, you need to consider the following issues:

– dimensions battery and the possibility of fixing it in your car;

– The order of the positive and negative terminals on the battery;

– Date of issue, if you do not find the release date on the label or more than 3 months have passed since the release date, then it is better not to buy such a battery;

– Battery voltage and capacity in Ah. The capacity should be equal to, or better yet greater than, that of a standard battery.
All statements that with a larger capacity there will be greater wear on the starter brush-commutator assembly have nothing to do with reality. According to Ohm's law, the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance. The starter resistance did not change as the battery capacity increased, and neither did the voltage. Consequently, the magnitude of the starting current will remain the same and, by definition, there can be no additional wear on the starter brush-commutator assembly when installing a battery with a larger capacity;

– Cold cranking inrush current at −18°C in Amps (A), the more the better. For reference, the minimum and identical starting current for different standards is marked with different values: DIN (Europe, Russia) – 170 A, EN (Europe, Russia) – 280 A, SEA (USA) – 300 A;

– Battery type it doesn’t matter if you like to do chemistry (add distilled water to battery jars, measure the density of electrolyte with a hydrometer), take an ordinary battery. Otherwise, buy a maintenance-free battery;

– You need to buy the battery in specialized auto stores., the more expensive it is, the better it is usually. Make sure to include the date of sale of the battery stamped on the warranty card.

And it’s easier, in order not to ask numerous questions, you need to copy (photograph) its type from the label of the old battery and purchase the same one.

How to check if your car is working properly
battery charge regulator relay

To do this, you need to start the car engine and, without turning on electrical appliances, change the engine speed (manipulating the gas pedal) and measure the voltage at the battery terminals. The voltage value must be within 13.9V-14.3V. If the voltage at high engine speeds is less than the specified value, then the generator or relay regulator is faulty, or the tension of the belt transmitting torque from the engine shaft to the generator may have weakened. If the voltage is higher, then the relay regulator is faulty and requires repair or replacement. At low engine speeds, the voltage may be less than 13.9 V and this is normal.

How to check the operation of a car generator without instruments

To check the serviceability of the car generator, you need to remove the terminal from the negative terminal of the battery while the engine is warm. Next, without pressing the gas pedal, turn on the high beams, heater fan and rear window heater in sequence. The engine should continue to run stably, with only a slight reduction in speed. If the engine stalls when you turn on the next device, you need to restart it and perform the steps described above, first increasing the speed to 1500. If the generator is working properly, the engine should not stall.

Is it possible to install two batteries in a car?
and connect them in parallel

Yes. When the battery in your car is discharged and you “light” your car from the battery of another car to start the engine, you practically connect two batteries in parallel (it’s not correct to “light” this way). It is possible to install and connect two or more car batteries in parallel in a car, but their capacity and technical condition do not matter. The main thing is that they are designed for the same voltage and are in good condition. Before connecting in parallel, both batteries must be fully charged. In the future, during operation, if you need to charge the battery, you will need to charge both batteries. It will be possible to first remove and charge one battery, so as not to leave the car without a security device, and then the second.

Is it possible to drive a car with a loose battery?

Some car enthusiasts are too lazy to secure the battery after charging or replacing it. As a result, during sharp maneuvers of the car, the plastic battery case can be damaged by the sharp edges of the car body parts and become unusable. Constant movement of the battery while driving leads to friction between its walls and the body of the body, which can lead to the same consequences. In addition, due to the movement of the battery, the current-carrying wires are constantly bent, which can lead to their breakage. In the event of a serious accident, it is difficult to say where the loose battery will fly and the severity of the possible consequences. The conclusion is obvious, the battery must be securely fastened.

How not to leave your car while charging the battery
without burglar alarm

When charging a car battery, it is usually removed from the car while charging. In this case, the car remains without an electronic security alarm system. It’s rare that anyone has a spare car battery to swap out. But you don’t have to have one; you can get by with a small-capacity 12V battery, for example, from an uninterruptible power supply for computer equipment. After all, when electrical appliances are turned off, the current consumption of the car circuit does not exceed 0.01 Ah, and if the alarm is turned on, it increases to a maximum of 0.05 Ah. So, for a full replacement for a day, any battery with a capacity of even 1.2 Ah is suitable. even an unsuitable battery for UPS operation due to loss of capacity. Before use, the replacement battery must be charged and its performance checked. To check, just connect a light bulb from a car headlight to the battery terminals. If the light shines at full strength, then the battery is suitable for replacement.

To connect the battery, you first need to prepare the wires for connection to the vehicle's on-board electrical wiring, equip the ends of the wires with terminals, and remove the insulation by 8-10 cm.

Next, you need to remove the standard battery and place the prepared battery from UPS in its place. Observing polarity, wrap the stripped ends of the wires around the standard lugs for connecting the battery. Place the terminals on the contacts of the temporary battery. Make sure that the positive tip does not accidentally touch any metal parts of the vehicle.

All that remains is to close the hood and doors and set the car alarm using the key fob. The central locking will also work. While the battery is charging, the security system will successfully perform its assigned task.

Many car owners worry about the battery in cold weather, because it is discharged. They are interested in: does the battery charge at idle? The Internet is filled with various answers. After all, when starting a car, a lot of charge is consumed. Does the alternator charge the battery when not driving? At what speed will there be no charging? We will answer these and some other questions in our article.

The principle of operation of the generator and why does it produce energy whenever the engine is spinning?

The units are connected using a drive belt, which transmits engine speed from the crankshaft to the generator pulley. The generating device converts the mechanical energy generated when the engine is idling and when driving into electrical energy. Magnets attached to the shaft, together with the copper windings of the generating equipment, create an electric field. When this charge is transferred to the generating plant, the battery is recharged.

It is fundamentally wrong to think that the process of replenishing the battery capacity occurs constantly. This is wrong. The power source will take as much electricity as it consumed, and then simply will not consume any further. Constantly charging the battery from the generator will cause it to boil over. The current transmission is stopped using a voltage relay located in the generating unit.

While the engine is running, the generator takes on the maximum consumer load - it is the generator that supplies electricity to the entire vehicle system. The use of battery energy begins when the load on the equipment generating electricity increases. Therefore, the operation of this unit and the power source must be smooth and uninterrupted.

Is the energy generated by the generator always sufficient?

The maximum performance of the generating system is set by the manufacturer and indicated on the device housing. Fully operational and meeting the requirements, generating equipment will generate as much energy as necessary if all conditions are met: the health of the car’s electrical system and the battery capacity corresponding to the make of the car.

On the dashboard of any vehicle with an internal combustion engine there is a battery charging light. When the ignition key is in the pre-start position, all indicators should light for a while, then they go out. If the battery light is on, this indicates its low charge - it is worth checking the equipment.

Interesting! Idle speed is an individual indicator for each car model, which is set by the manufacturer and indicated by him in the operating book or under the hood. You can find cars with an idle of about 500 rpm, and others with an idle speed of 1500 rpm.

The number of crankshaft rotations depends on many parameters:

• engine volume;
• injection type;
• type of gearbox;
• air temperature;
• machine condition, etc.

Accordingly, depending on the number of crankshaft revolutions at idle, the generator produces different amounts of energy, which on two brands of cars with different idle speeds can vary almost twice.

Charging the battery from idle in winter (features)

Idling is usually understood as the operation of a car engine without load, during which the voltage in the system ensures the maintenance of processes only in the internal combustion engine. This mode is necessary for the car to warm up all fluids to operating temperatures. Each car has its own idle speed. If their value is lower than those specified by the manufacturer, then this indicates an imbalance in the operation of the internal combustion engine.

Does the battery charge while idling in winter? The principle of operation of the generator does not depend on the time of year and temperature conditions - when the engine is running, it generates a certain amount of electricity. Therefore, the car battery is recharged even in winter. However, it is worth remembering that in conditions of low temperature the battery takes on an electrical charge very poorly. The activity of this process will increase as soon as the engine warms up and the engine compartment becomes warmer.

Problems with starting a car in the winter months are caused by short trips during which the battery does not have time to replenish its capacity, or a malfunction in the electrical system. To avoid one day facing the problem of a non-cranking engine, we recommend periodically diagnosing the battery.

Table of energy consumption by different equipment.

Charging the battery is necessary in cases where it takes on part of the load of the energy supply system. How much energy does the equipment in the car need?

Table 1. Electricity consumption in the car by additional equipment.

By simple calculations we get a total consumption of 1070 watts, which when converted to amperes will be approximately 90A. For many car generators, such a load, and they are the first to take it upon themselves, is at the limit of the equipment’s capabilities. When a certain threshold is reached, the system will transfer part of the load to the battery. Therefore, it is necessary to carefully calculate the characteristics of the generator and battery.

Briefly about the power of generators in different cars.

The ratio of the work of generating equipment and the time during which it performs it is called generator power. To charge a car battery, the generating equipment must provide it with the necessary voltage and current for a certain amount of time. Traditionally, passenger cars use equipment with a power of about 1 kW.

But it is worth remembering that each car has personal energy consumption needs, which depend not only on the parameters of the engine system, but also on additional sources of consumption. Therefore, we recommend choosing a generator following the manufacturer’s instructions and taking into account additional costs.

Will the battery recharge while idling?

Very often on the Internet you can find discussions in which participants are trying to figure out whether the battery is charging at idle or not? Some people believe that the battery is charged only while the wheels are rotating; others defend a different position, arguing that there is no connection between travel and battery charging. Let's figure it out.

As we said above, the operation of the generator is correlated with the movement of the crankshaft. It works together with the engine. It doesn’t matter whether it’s idling or actively driving - there is physical energy in the car, regardless of the mobility of the wheels. It is the generator that converts it into electrical energy and transmits it to the power source if necessary to recharge it.

Therefore, we can safely say that the battery is charging at idle. Another question is how long it will take to replenish the battery capacity of a car.

How long does it take to charge the battery at idle?

Remember that the generator produces different amounts of current and voltage depending on its characteristics and battery discharge? Therefore, it is impossible to unequivocally answer the question: how long will it take to charge the battery at idle engine speed.

If the battery is not very discharged and other consumers are turned off, then the battery can be charged relatively quickly. If the power supply is severely discharged, it will take a little longer.

How to calculate charging time

The time required to recharge a car battery from a generator is not easy to know. If we take an ideal situation, then to carry out such calculations we need a formula: the amount of energy required to restore the full charge of the battery (Ah) must be divided by the amount of free current that the generating equipment produces (A).

By free current we mean that energy that is not spent on additional sources of consumption (headlights, stoves, heating, wipers, etc.)

However, it is worth understanding that in these calculations we do not take into account the ambient temperature and engine speed.

In conclusion, I would like to note that a large amount of unknown data does not make it possible to clearly answer the question: how long and does the battery charge at idle? Calculations require information about electricity consumers in the vehicle system, battery charge, generator production capabilities, and the idle speed of an individual engine. Of course, the easiest way would be to use a universal formula, but, unfortunately, there is none. Therefore, the most important thing is to understand the essence of the issue and the ability to apply knowledge in practice.

We hope that this article helped you understand the equipment that provides energy to the car and the principles of its operation. We strongly recommend monitoring the battery capacity and selecting power supply devices that meet the requirements. Then operating your car at any time of the year will not cause you any trouble. Remember that you should not overcharge the battery - this will shorten its service life.

How did you charge the car battery from a generator? How long did it take to recharge? Share your experience with readers in the comments. We'd love to read your stories and answer your questions.