Low generator voltage due to bad battery. The battery is supplying low voltage: why? Maximum battery charging voltage

Constant undercharging of the battery or its absolute discharge at the most inopportune moment is a headache for many car owners. One source of these problems may be the generator. But how to check it? Perhaps it's not his fault at all? Let's figure out together how much the generator must produce for the normal functioning of all car systems and maintaining the battery in a charged state.

The battery in a car is an important element of the system, which is responsible for providing the car’s on-board network with electricity. The generator is used to charge the battery while it is active. Unstable operation of a device generating electricity causes a voltage drop in the network and failure to restore the capacity of the power source.

Normal generator performance means timely and complete replenishment of the battery charge level, which decreases under load. Checking the battery charge level from the generator is simple and can be done by the car owner himself.

Diagnostics of an automotive energy-generating device includes a visual inspection of the unit, its elements and related parts, as well as voltage and current measurements. At least twice a year, you should check the tension of the drive belt, excessive weakening of which leads to a decrease in the performance of the generator, and sometimes can lead to breakdown of the device. Once a year, you can check equipment elements - fasteners, diode bridge, voltage regulator and others. Timely maintenance of the battery will also guarantee the absence of problems - cleaning the terminals, adding distilled water.

Diagnostics of indicators such as voltage, current, resistance are also necessary twice a year. To carry it out, you will need special devices - a voltmeter, multimeter or load fork.

What kind of charging should go to the battery from the generator?

It is traditionally believed that 13.5-14.5V should be supplied by the generator to the battery and this is absolutely enough to replenish the battery costs.

It is worth considering that using a battery with a higher power in a car than the manufacturer recommends also requires the installation of a more efficient generating device.

It is necessary to take into account the load that the generator must withstand - it is calculated based on the maximum indicators of all electrical appliances and car systems.

Do not forget that the charging current from the energy-generating device will allow you to start the car in the cold season. In order to avoid problems with starting the car, we recommend purchasing generating equipment, the charge current of which will be approximately 10% of the capacity of the power source. That is, a battery of 100 A/h requires a generator that can produce 10A. Please note that for many cars, 100 amp equipment will operate at its maximum capacity, because the power consumption of the automotive system is in the region of 80 amps. Therefore, the choice of a source generating energy must take into account both the battery capacity and network consumption.

How to check the alternator voltage on the battery

The potential difference can be diagnosed in two ways - directly at the generating equipment and through the battery. The generator is directly connected to the power source with a thick wire, therefore, to check the level of potential difference, you can measure the voltage at the power source. To do this, you will need special devices - a voltmeter, multimeter or load plug.

The wires of the first measuring instruments are connected to the battery in any sequence. The plug must be connected to the battery terminals with strict observance of polarity. It is generally accepted that the normal voltage in the network should not be lower than 12 volts. At idle speed without turning on all electrical devices of the car, this indicator should be at the level of 13.5-14V. A drop in voltage values to 13.3-13.8 volts is considered acceptable.

At the same time, using conventional testing equipment, you can check the resistance of the generator elements - rotor, stator and diode bridge. Diagnostics of rotary equipment is carried out by its winding. It is necessary to connect the probes of the device with slip rings. If the multimeter gives readings from 2, 3 to 5.1 ohms, then this element is working. The current consumption of the winding should be within 3-4.5 amperes.

Its normal resistance is 0.2 Ohm. The diode bridge is checked by the presence or absence of resistance, the indicators do not matter. The only thing worth considering is that there should not be a zero dimension. Measurements are carried out in pairs - positive output and all plates on this side or minus and all elements.

We remind you that for normal charging of a car battery, the voltage supplied by the generator must be from 13.5 to 14 volts.

How many amperes does a car alternator produce per battery?

The current strength required by the electrical system of each car is individual and depends on the number of electricity consumers and their values. And also the charge current must be sufficient to charge the power source.

It is worth noting that ampere readings appear only when there is a load in the vehicle’s electrical system and, accordingly, the battery is discharged. After starting the car engine, the charging current is about 6-10 amperes and drops over time, because the battery is charging, taking on the main energy consumption. If you turn on additional equipment - headlights, radio or heated mirrors, you can see an increase in the charging current values.

When purchasing a generator, pay attention to its technical characteristics, which the manufacturer indicates on the case - that is where you will find information about the maximum current that will flow to the battery.

In the table below you can see the approximate current values that the generator shows at different loads.

Table 1. How many amperes the generator produces under load.

Signs of a generator malfunction

In modern cars, breakdowns of the electrical system are one of the most common. A large number of electronics requires particularly careful monitoring of the operation and condition of the generator and battery, because their failure can immobilize the car. The most common signs of a generator malfunction are:

battery indicator light on the instrument panel;
unstable operation of the battery (its boiling over or undercharging);
different intensity of headlights;
extraneous sounds from the generator.

If you notice incorrect operation of the car, then perhaps the battery charging current from the generator is insufficient.

All malfunctions of electrical equipment, which includes the energy-generating device of a car, are mechanical (deformation or breakage of fasteners, housing, malfunction of bearings, pressure springs, drive belt, etc.) or electrical (winding breaks, diode bridge malfunctions, burnout or wear of brushes , short circuits between turns, breakdowns, etc.).

Don’t write off a non-working generator: find out if there are repair kits and spare parts. Replace them if possible. If you cannot carry out repair work yourself, then take the generator to a workshop. Many craftsmen will be able to restore the unit at no extra cost and in the shortest possible time.

However, some breakdowns require the purchase of a new device that generates electricity. For example, a failing bearing that is soldered into the generator housing cannot be restored or replaced in most cases.

Remember that failure of this unit can be caused not only by wear and corrosion, but also by poor quality of elements and components; excessive load; external influence of salts, liquids, temperatures.

Other causes of low voltage

A small potential difference in the system is not always associated with a breakdown of the generator or a bad battery. If the diagnosis of these elements does not reveal any problems, then you should pay attention to the following:

condition of the battery terminals - connection density and oxidation;
electrical wiring problems - oxidation, violation of its integrity;
output contacts to electrical appliances;
correctly selected energy consumers.

Each contact must be tightly adjacent and intact, that is, there must be no formations (for example, sulfation) that will disrupt the flow of current. Incorrect connection of contacts leads to accelerated battery discharge even when the car is not running.

To improve the connection of the elements of the car's electrical system, it is necessary to clean all contacts and restore the integrity of the wires by replacing them or connecting them and wrapping them with insulating tape.

In conclusion, I would like to repeat that stable operation of the car requires constant monitoring of all elements, and the generator should attract special attention. The battery is charged from it and provides electricity to the entire car system. Pay attention to all elements: generator brushes, slip rings, voltage regulator, equipment winding.

The most correct measurements should be carried out when the battery is fully charged and in various modes. Remember that the manufacturer links the characteristics of the generator to the number of engine revolutions - they are the ones that help generate a certain current.

Detailed video on how to check the generator:

Do you have experience diagnosing an alternator and solving problems in a vehicle's electrical system? Please share your experience and opinion with our readers in the comments. If you have questions about the topics covered, we will be happy to answer them.

If the battery is discharged in the morning, the headlights dim while driving, and the windshield wipers begin to work with difficulty, you need to pay attention to the serviceability of the generator and the entire electrical network. If you have free time and desire, you can deal with many problems on your own. If possible, it is better to contact a specialized workshop, since fixing serious damage requires experience and special equipment.

Reasons for battery discharge, why the car does not produce full voltage

Having turned the ignition key, the car enthusiast expects to hear the cheerful sound of the starter. If the battery is discharged, the starter does not have enough energy - the car will not start. Reasons for discharge:

The battery itself. Low electrolyte level, sulfation of plates, short circuit, long standing without recharging. The battery needs to be charged and tested with a load plug.
Constant passive discharge. There is a consumer in the car that consumes energy even when the ignition is turned off. This is most often an incorrectly installed radio, alarm system, or poorly repaired factory parts - fans, lights. Wiring that is frayed at bends can also drain the battery.
The battery is undercharged when driving. This happens during frequent short trips or when faulty generator.

Basic faults

To determine the malfunction, you need to carry out general diagnostics of the vehicle's electrical system.

It is carried out in order of eliminating possible causes from easily corrected and cheap to complex and expensive. Here is an approximate algorithm on how to check the electrical system of a car.

Frequent short trips

The battery must be replenished every time the engine is started. In city mode with short trips, more energy is consumed than is replenished. The battery should be periodically recharged with a charger. Just keep track of your travel times, especially in winter, and check the condition of your battery more often.

Leakage current

If the car uses more electricity than it replaces, the battery will be discharged. Faulty wiring, breakdowns in electric motor windings, shorted circuit paths are a source of constant energy consumption. A short circuit “drinks” the energy of the battery, which can be completely discharged in a couple of hours.

Current leakage is checked in two ways:

At ignition off remove the terminal from the battery and slowly put it back on. If when connecting the terminal "sparks", there is a reason to check further.

Important! Do not use this method to test cars with an electronic control unit - voltage surges may burn out the ECU capacitors.

Checking with an ammeter. An ammeter with a measurement amplitude of up to 20 amperes is installed in the gap between the negative terminal of the battery and the ground terminal. The ignition is turned on if the leak is higher 0.1 - 0.3 ampere, you need to find unauthorized current consumption.

Finding the cause of current leakage

Disable in order cooling fan circuits, generator and starter. They usually operate without fuses.
In order turn off with the ignition on circuit breakers. If the needle on the ammeter drops, we are looking for a short circuit or a damaged consumer in the circuit of this fuse.
Chain "rings up" for the presence of a short circuit in order - from fuse to consumer.

Generator faults

If there is no current leakage, and the trips are quite long, then the battery is not being charged. It is important to know what kind of charging should a working generator provide? With the engine running, you need to check the voltage at the battery terminals.

Without turning on additional electrical appliances, the voltmeter should show values of 13.5 - 14 volts, this is exactly the charge that a working generator should produce. If on the voltmeter low voltage(less than 13 volts), then you should begin to identify the reasons Why doesn't the system give a full charge?

The scheme for charging a battery from a generator is simple; it is often directly connected to the main output of the generator, using a thick cable, and sometimes even two.

A modern generator is a durable device; all “childhood diseases” have long been resolved. However, without timely maintenance and replacement of consumable parts, it may break.

If you have the proper knowledge, it is not difficult to identify generator malfunctions; this will require a minimum of tools. It is better to carry out the check according to the same principle of eliminating possible causes. from simple and cheap to complex and expensive.

Belt tension

If the drive belt breaks or stretches over time, the generator will “slip” under load. The need for tightening is indicated by a whistle that disappears when the gas is applied.
The solution is to tighten the belt; depending on the design of the generator mounting, this procedure may differ. There are three types of tensioner: self-tightening spring tensioner, worm tensioner, and lever tensioner. Without proper belt tension, the situation will increasingly repeat when the car works but does not charge the battery.

Bearings

The generator rotor rotates on bearings. If they jam or fall apart, the generator will not work. When replacing or tightening the belt, you should unscrew and shake the pulley; there should be no backlash, jamming, or extraneous knocks or hums.

To replace the bearings, the generator will have to be completely disassembled; you will need bench tools, a vice and pullers.

If the bearing falls apart, the armature touches the stator windings, resulting in a short circuit. As a rule, such a generator must be replaced.

Excitation check

In most cars, a separate live wire comes to the alternator to begin producing electrical current.

This is called "excitement." To prevent the device from burning out and consuming electricity when the ignition is turned off, current is supplied through a resistance - a light bulb on the dashboard. If the light does not light up when you turn on the ignition, then no current is supplied to the battery.

Diagnostic procedure:

When the ignition is turned on, the indicator light check if there is voltage at terminal “30” generator. As a rule, it fits blue wire small section.
If there is no voltage, check the fuses.
The fuses are ok check the light on the dashboard.
If the light bulb is ok, checking the electrical circuit: fuses - ignition switch - dashboard - generator. We eliminate broken or frayed wire insulation.

Generator brushes

Carbon current collectors wear out over time.

We remove the voltage regulator (in the everyday life of car enthusiasts it is called “chocolate”), check the length of the carbon brushes. Brushes that are short or stuck in the body may not fit tightly. They are soldered or replaced along with the regulator.

When replacing brushes, it is worth assessing the condition of the rotor's current collector copper tracks. If the brushes have gnawed deep grooves, the tracks will need to be disassembled and replaced. This operation is only possible in a specialized workshop - the tracks are welded or soldered, pressed onto the shaft “hot”.

Diode bridge

At night, the following effect may be observed: the headlights burn brighter as the engine speed increases. This indicates damage to the regulator or diode bridge. What could be the reason why the generator does not charge.

The regulator can be replaced with a known good one, and if the defect is not corrected, you need to check the diodes. They serve to straighten current fluctuations. There are three windings on the generator stator; they alternately produce electric current. Each winding produces a current “burst”, the voltage rises and falls. The diode is needed to regulate the voltage, resulting in a constant current without voltage surges.

Diodes are checked using a multimeter or oscilloscope. A diode passes electric current in one direction, but not in the other.

It is better to replace diodes with melting or mechanical damage. It’s easier and more efficient to order a whole diode bridge; it looks like a horseshoe.

Breakdown of the windings.

If a short circuit occurs between the housing and the stator or rotor windings, the generator will not work. In some cases, the defect is not externally noticeable, but smoking or sparking may occur.

A breakdown can be diagnosed using a 3-volt test light or a multimeter.

To contacts generator removed from the car voltage is applied, on the body connects weight.
One wire indicator light join the mass battery, the second - to the body.
Slowly rotate the pulley.
If the light bulb lights up - there is a short circuit.
The stator or rotor windings will have to be rewound or replace the entire device.

Useful video

Brief video instructions for checking a car alternator:

How to choose a replacement generator

When purchasing a new generator with a warranty, this item will be unnecessary. But most often it will be cheaper and more practical to purchase a used part from disassembly. When purchasing a generator secondhand, there is a risk of receiving a faulty part.

When purchasing, you need to check the generator using the following algorithm:

Visual inspection. Dents, cracks on the body, broken seats and broken fasteners are a reason to bargain or refuse to purchase.
Pulley rotation. The shaft should not jam and rotate silently; radial and axial play is unacceptable.
Inspection of the plate. It is better to choose a generator that is completely identical to the standard one in voltage and speed.
Inspection of slip rings and brushes. If there are deep grooves from brushes on the copper tracks of the rotor, then the generator has served for a long time.
Checking the functionality of the generator. You will need a battery and a 3-volt control lamp. We connect the minus of the battery to the body of the part, the plus to the excitation terminal, marked with the number “30”. We connect one wire of the light bulb to ground, the second to the “+” terminal of the generator. We sharply turn the generator pulley by hand. If it is working properly, the three-volt light bulb will flash brightly.
Checking the generator for breakdown of the windings. The technology is described above.

How to avoid serious damage

To minimize the risk of generator and wiring failure, scheduled maintenance should be carried out on time.

Replacing generator brushes.
Timely tension of the belt.
Bearing inspection and replacement.
Be careful when carrying out repair work.
High-quality insulation of contacts and twists.
The use of crimp terminals and terminal contacts when repairing wiring.

To carry out routine maintenance, it is advisable to contact a specialized service that can check the condition of the electrical wiring and promptly carry out maintenance.

Malfunctions of the generator or electrical wiring can cause many unpleasant moments for the car owner. Difficulties with starting, dim headlights, slow wiper blades... Gasoline engines cannot go very far without a generator - it takes a lot of energy to form a spark on the spark plugs. At the first signs of malfunctions, it is better to carry out a full diagnosis and maintenance of the vehicle’s electrical systems.

Good evening friends. Please help me with my problem. I have a VAZ 21114 2008, and the problem is that my battery is supplied with a voltage of 13.2 V. And it started because the bearings on my generator fell apart and, in order not to kill the generator, I removed the belt and I drove about 50 km on the battery. Then I replaced the bearings, brushes, diode bridge, threw the generator on the stand and it produced a voltage of 13.9 V, under load it dropped to 13.5 V. Then I installed the generator on the car, took the tester and decided to measure the charging, threw the tester on the battery and it gave me showed 13.2 V when the car was warm. I threw the tester on the generator, the output from the generator showed 13.7 V. I began to think that the bank had shorted in the battery. I found a new battery, installed it, and the charging is the same - 13.2 V. Help, I don’t know what to do, maybe there’s a problem with the computer.
Thank you in advance. Sasha

Hello, Alexander. We have analyzed your problem and will try to help you. If you have already tried to operate your car with a new battery, then you might understand that low voltage in the network is not related to its performance. What could be the reasons?

[Hide]

Possible malfunctions in the generator

The main malfunctions in the operation of this device may be:

lack of charge;
low voltage (as in your case) or overcharge;
the device supplies charge, but the indicator on the dashboard is on;
The device is very noisy during operation.

DIY repair

If the battery does not supply voltage, this is the result of:

the fuse fails, or the fuse comes off;
complete wear of the generator brushes, their breakage or jamming;
failure of the regulator relay;
a short circuit in the circuit winding or an open circuit in the rotor or stator circuit of the generator.

Replacing the fuse

If you have not yet tried to replace the fuse on the unit responsible for the operation of the generator, now is the time to do it:

Open the hood and disconnect the battery.
Open the fuse box. On the back of the cover there is a diagram of the location of the elements and their purpose.
Remove the fuse and replace it with a new one. There may be no visual signs of its failure, but you should try to change the element and install a known good one in its place.
Check the voltage.

Replacing brushes

To change the brushes of the device, you must dismantle the voltage regulator assembled with them. Purchase the brushes that need to be replaced in advance from the auto store:

Replacing the regulator relay

To replace the regulator relay, you will need to remove the unit. To do this, you will need a soldering iron, since the relay will need to be desoldered and then soldered in place. It will be easier to turn to an electrician for help, but if you decide to do it yourself, then prepare a soldering iron, as well as a new relay.

Remove the device and disassemble it.
Find the regulator relay.
Using a soldering iron, you need to desolder it from the installation location.
Having done this, install a new relay in place of the old one and solder it.

Rotor or stator repair

Replacing or repairing the stator is more labor-intensive, but you can choose one of the options. In particular, you can replace the stator winding yourself, or buy a new one in the store and install it. It would be best to replace the winding, since today repairs are sometimes more expensive than replacements. Therefore, first you need to understand how much the repair will cost and compare it with the prices for a new part.

As for rotor repair, it is quite possible to do it yourself. There can be many reasons for the failure of this element, but we will consider the most common option. That is, we will talk about a break near the contact elements or unsoldering of the end of the winding.

In this case, you will need a soldering iron:

Take the rotor winding and, in the place where the break occurred, rewind one turn back. This must be done in such a way that the wire that you unwinded is enough to solder it to the slip ring without any problems.
The end of the winding that broke off must be desoldered.
Then take the end of the winding that you unwound and solder it in place of the soldered section.
Also, if necessary, you need to clean the slip rings.

In addition, burnt out diodes can be the cause of low voltage. They can be replaced with new ones, but to do this you need to have sufficient knowledge and equipment. To replace the diodes, we recommend that you contact a qualified specialist.

In addition, it is also a good idea to check the tension of the alternator belt. If the belt is worn out or needs to be tightened, this may be the cause of insufficient voltage in the network.

Video from Vyacheslav Lyakhov “ Diagnostics and repair of generators»

Now you can find out how the process of diagnosing and repairing generators occurs in practice.

The voltage of a vehicle battery, as well as its capacity, are the most important indicators of this automotive unit, on which its functionality and quality of work directly depend. Batteries are used to start the power unit, so every car owner should know what the normal voltage of a car battery is, constantly maintaining it in working condition. Of course, I have already touched on this topic in previous ones, but today I want to clarify this information...

To begin with, I would like to say that modern cars no longer have devices that measure “Volts,” although they used to exist. Therefore, to determine the voltage, you first need to get a multimeter. I would like to note that it is advisable to check the battery voltage at least once a month or two in order to take timely measures.

Standard for basic battery properties

What minimum value should this value be in order to start the engine? There is no exact indicator here. In the standard state, this property for a fully charged battery should average 12.6-12.7 volts.

Depending on specific conditions, this indicator may vary slightly, and there is nothing wrong with that. For example, some manufacturers assure that their products have a voltage of about 13 - 13.2 V, this is acceptable, but I want to warn you right away.

You should not measure the voltage immediately after charging the battery, as many experts write, you need to wait at least an hour, then it should drop from 13 to 12.7 Volts.

But it can go the other way when it drops below 12 volts - this indicates that the battery is 50% discharged.

In this case, the device will need urgent charging, since its operation in this state is guaranteed to lead to sulfation of the lead plates. This reduces both the performance of the battery and its service life.

But even in the case of such a low voltage, it is quite possible to start the engine of a passenger vehicle. If the battery is in working condition, it does not require repairs and the generator charges the battery while the engine is running, the device can be safely used even in this condition.

In the same case, when this electrical parameter of the battery drops below 11.6 V, the battery is almost completely discharged; its further use in this state without recharging and testing for functionality is impossible.

Thus, the normal voltage level is in the range of 12.6 - 12.7 Volts (rare, but possible up to 13.2 V maximum.)

However, in practice this is very rare. Most often for passenger cars it is 12.2-12.49 volts, which indicates an incomplete charge.

But there is nothing wrong with this: a decrease in the performance and quality of the device begins if there is a decrease to 11.9 volts or lower.

Under load

Voltage can be divided into three main indicators:

Nominal;
Actual;
Under load.

If speak about rated voltage , by the way, it is customary to indicate it in literature and other materials, it is equal to 12V, but this figure is actually far from the actual parameter, I am silent about the load.

As we already said, normal battery operating voltage a passenger car is 12.6 - 12.7 volts. But in fact, the actual indicator is more reliable, which can range from 12.4 volts to approximately 12.8 V. I want to emphasize that this parameter is taken without load, which is said at rest.

But if we apply a load to our battery, the parameters will be completely different. The load is mandatory, this test shows the battery’s performance, because often all batteries can withstand normal voltage, but “dead” ones cannot withstand the load.

The essence of the test is simple - a fully functional battery is placed under a load (using a special device - a “load fork”) that is twice its capacity.

That is, if you have a battery with a capacity of 60 Am/h, then the load should be 120 Amperes. The duration of the load is approximately 3 - 5 seconds, and the voltage should not drop below 9 Volts; if the indicator is 5 - 6, then your battery is either discharged or almost dead. I would also like to note that after the load, the voltage should recover in about 5 seconds to the normal value, at least 12.4.

When there is a “sag”, the first thing you need to do is charge the battery, and then repeat the experiment with the “load fork”; if a large sag is not noticed, then the battery needs recharging. Watch a video about testing under load.

A few words about electrolyte

The main parameter that determines the voltage level in the battery is the density of the electrolyte that is inside this device.

When the battery is discharged, acid is consumed, the share of which in this composition is 35 - 36%. As a result, the density level of this liquid decreases. During the charging process, the reverse process occurs: water consumption leads to the formation of acid, which results in an increase in the density of the electrolytic composition.

In the standard state at 12.7 V, the density of this liquid in the battery is 1.27 g/cm3. If any of these parameters decreases, the other also decreases.

Reduce voltage in winter

Car owners often complain that in winter, when there is severe frost, the main parameters of the battery drop, as a result of which the car does not start. Therefore, some drivers take the battery into a warm place at night.

But in reality, things are not quite like that. At negative temperatures, the density of the electrolyte changes, which, as already noted, affects the voltage level. But if the battery is sufficiently charged, the density of the electrolyte increases in cold weather, and as a result, the second of the most important properties also increases. Therefore, a sufficiently charged battery is not in danger even in severe frost. If you leave it discharged in cold weather, the density of the electrolyte will decrease, as a result of which problems will arise with starting the car engine.

Problems with using and starting a vehicle’s power unit in winter are not associated with a decrease in the basic parameters of its battery, but with the fact that the main chemical processes inside it at negative temperatures are slower than in normal times.

A car battery consists of 6 cells connected in series. Each bank has a full charge of 2.10-2.15 V, so the total voltage is summed up and is 12.6 - 12.8 V. What is the voltage of the battery after the charger is turned off? When installing the battery in a car, the voltage after charging should be 12.4 V. This is normal. The car's starter battery is discharged during engine startup and, while driving, it recovers energy from the car's generator. If the battery voltage drops to 12 V, the device requires charging from the network. A large loss of charge in banks is characterized as a deep discharge that destroys the battery.

A car operated with the advantage of long runs has time to be fully charged from the generator for the next start. But its charge will not be full. The state of charge of the battery can be determined by the voltage at the terminals. The lower the value, the weaker the electrolyte concentration in the jars.

You can check the battery charge using a multimeter. You should set the “alternating current” calibration and measure the indicator at the terminals. You can determine the charge level by the density of the electrolyte.

The degree of charge of a car battery is determined by voltage, as in the table.

To increase the battery capacity, you need to charge it with a special charger. This is a voltage converter, rectifier. Batteries are serviced, maintenance-free, gel, AGM, lithium. Their charging voltage and current differ in voltage, time, and cycle duration. There are universal chargers designed to switch modes for different battery models and regulate parameters.

Voltage at battery terminals when charging

To charge the battery from a charger, select a mode with constant current or voltage. Both are equally effective, but apply to different batteries. During charging and operating the battery, it is necessary to measure the voltage at the terminals of the acid battery.

To charge a 12 V battery, you will need to set the constant voltage mode to 16 -16.5 V. Using a current of 14.4 V, you can charge the battery by 75-85%. At a constant voltage, the charging current is variable and is limited only by the charger.

What charging voltage should I set? They proceed from the achievement of a critical voltage, accompanied by “boiling” - the release of gas from the car battery cans. A battery is considered to be normally charged, with a voltage at the terminals from 12.6 to 14.5 V. Readings should be taken with the device, without relying on the on-board computer. The measurements with the engine running and with the battery disconnected are different.

The permissible charging voltage at the battery terminals when the engine is running varies from 13.5 -14 V. The indicator shows the battery is undercharged if the voltage is higher. You need to repeat the measurement after 2 minutes, the battery may have been discharged during startup. If the charging voltage is low, the battery is losing its life or the problems are coming from the car alternator. Measurements must be taken by turning off the on-board systems.

By measuring the battery charging voltage with the car not running, it is impossible to identify problems with the generator, but the degree of battery charge is well determined. A voltage of 12.5 - 14 V indicates no problems. If the indicator is low, you need to check:

electrolyte condition - the substance should be transparent, the level should be normal;
a lot depends on the battery charge level;
determining the possibility of recharging to the optimal voltage.

Testing will reveal problems with the battery and its performance.

Charging a battery with constant resistance

Is it possible to charge a battery with a constant resistance? From the formula I =U*R, it is clear that if you set the resistance to a constant value, then the current or voltage will become variable. But inside the battery, resistance is a variable value that affects energy absorption. The total resistance consists of the polarization resistance, which changes, and the ohmic resistance, which remains stable under the same conditions and for a particular battery.

The resistance is affected by temperature, degree of discharge, and electrolyte concentration, which are taken into account in the characteristics of the battery discharge curves. But if in the formula resistance is a variable value over time and the state of the car battery, then current, voltage, or a combination of current and voltage can be constant during charging. To smooth out the charging current, a resistor is used - ballast resistance.

What voltage should I set when charging the battery?

Voltage is a potential difference, and the current will flow in the direction where this value is smaller. Therefore, the charger voltage is always selected higher than the charging level of the car battery. The greater the voltage difference, the faster and more fully the car battery will gain capacity after charging.

During charging at a constant voltage, the limit of the parameter set on the charger is lower than the characteristic at which the release of gases from the battery being serviced begins. What potential difference is needed to charge a car battery? The maximum voltage used when charging the battery is 16.5 V. Which parameter should be depends on the type of battery. The time and completeness of battery charging depends on the voltage. The ratio of charge voltage and capacity recovery for a 12 V battery in 24 hours is as follows:

With a voltage of 14.4 V you can charge the battery by 75-80%;
Using a voltage of 15 V, the charge level is 85 - 90%;
With a voltage of 16 V, the battery is charged by 95 - 97%;
With a maximum voltage of 16.3 -16.5 V, the batteries are fully charged.

When the battery voltage reaches 14.4 - 14.5, the charging end signal lights up on the charger.

It has been established that it is this voltage of the car battery that does not create gas emissions after and during charging. Therefore, during actual vehicle operation, the generator, through a voltage regulator, limits the maximum voltage level to this value. In summer this figure is close to 100% capacity, in winter it corresponds to 13.9-14.3 V, with the engine running, which corresponds to 70-75% capacity.

Maximum battery charging voltage

We know that modern high-class cars have an on-board system that runs on 16 V. What batteries are used in these batteries? To avoid gas emissions, the system must be closed.

This means that maintenance-free Ca/Ca batteries can withstand harsh operating conditions. They use a special charging mode. Using calcium instead of antimony allows the battery to be charged at higher voltage, which causes the electrolyte to boil. A maintenance-free battery does not tolerate sudden changes in voltage in the on-board network. It is designed for vehicles with a good electronic voltage control system. Hybrid batteries made from low-antimony and calcium plates are more tolerant of operating conditions.

Battery voltage at the end of charging

After the battery is fully charged, the charge will change slightly. The electrolyte dissociates and the pores of the current-carrying plates are filled. A car battery installed in the engine compartment takes in the ambient temperature, and the capacity will increase in the heat or decrease at sub-zero temperatures. Therefore, after charging, you can find out exactly what the voltage of the car’s battery is by installing it in place. Even while in the workshop, the voltage at the terminals changes. This is especially noticeable if the cycle is not completed and the charging current has not dropped to 200 mA. In this case, charge redistribution occurs, and additional energy replenishment of the device is possible.

But if, after charging the battery, the voltage drops while the car is running, this is a reason to inspect the generator or replace the battery.

Dependence of battery charging on voltage

Each type of battery is charged based on the characteristics of the types of designs used. Serviced, gel and lithium batteries have the lowest charging voltage. Causes: boiling over, destruction of the composition, fire hazard. If the battery being serviced can be charged with a simple charger, lithium and gel systems require compliance with a 2-stage combined energy storage mode.

All systems are designed to prevent overcharging and are equipped with automatic power off when the voltage required for a car battery is reached. When charging, the current gradually decreases due to an increase in resistance, but the voltage remains stable. After charging, the electrochemical reaction process continues in the form of a slight self-discharge.

It is important that the charging voltage always exceeds the parameters required for operating the device. For current to flow, you need a slope, which is the voltage difference between the charger and the battery.

Video

We suggest you look at expert advice on how to properly charge and maintain a car battery, what voltage should be on the battery after charging.