Batteries for cars. Akb. © Borisov Mikhail. Electrical characteristics of batteries What is the EDF battery

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1.3. The main electrical characteristics of batteries

Electrical power and voltage . Electrical power (EMF) is the difference of potentials of positive and negative battery electrodes with an open external circuit.
The value of the EDC depends mainly on the electrode potentials, i.e., from the physical and chemical properties of substances from which the plates and electrolyte are made, but does not depend on the size of the battery plates.
EMF acid battery depends on electrolyte density. Theoretically, it is practically established that the EMF of the battery with sufficient accuracy to practice can be determined by the formula
E \u003d 0.85 + g,
where G is the density of the electrolyte at 15 ° C, g / cm 3 .
For acid starter batteries, in which the electrolyte density ranges from 1.12 to 1.29 g / cm 3 , EMF varies respectively from 1.97 to 2.14 V .
It is almost impossible to measure the EMF with absolute accuracy. However, for the practical purposes of EDC, approximately and sufficiently definitely can be measured with a voltmeter having a high internal resistance (at least 1000 ohms per 1 B). At the same time, a slight amount will pass through the voltmeter.
The battery voltage is the difference of potentials of positive and negative plates with a closed outer chain, which includes any consumer of the current, i.e., when the current is passed through the battery. At the same time, the testimony of the voltmeter when measuring the voltage will always be less than when measuring the EMF, and this difference will be the greater that the larger current passes through the battery.
EMF and tension depend on a number of factors. EMF varies from the density and temperature of the electrolyte. The voltage in turn depends on the EMF, the size of the discharge current (load) and the internal resistance of the battery.
The dependence of the EMF of the battery from the electrolyte density (concentration of the H2SO4 solution) is shown below:

Electrolyte density at 25 ° C,
g / cm 3 .................................... 1.05 1,10 1,15 1 , 20 1.25 1.28 1.30
H2SO4,% ............................. 7.44 14,72 21,68 27.68 33.8 37,4 39,7
EMF battery, in .......... 1.906 1,960 2,005 2,048 2,095 2,125 2,144
From this dependence, it can be seen that with an increase in the concentration of sulfuric acid, the EMF also increases. Hence, however, it does not follow that in order to obtain a greater EDF, it is possible to excessively increase the density of the electrolyte. It has been established that the starter batteries work quite well when the electrolyte density in them is 1.27 - 1.29 g / cm 3. In addition, the electrolyte is a density of 1.29 g / cm 3 has the lowest freezing point.
When changing the electrolyte temperature, the EMF battery is also changing. Thus, with a change in the electrolyte temperature from + 20 ° C to -40 ° C, the battery is reduced from 2.12 to 2.096 V. In a significantly greater degree with a change in the electrolyte temperature, voltage changes, as it depends not only on EMF, but also from the internal resistance of the battery, which decreases significantly with a decrease in temperature.
Between EDC, voltage, internal resistance and size of the discharge current exists the following dependence:
U \u003d E-IR,
Where U - voltage;
E.- e. d. s. battery;
I. - the magnitude of the discharge current;
r.- Internal battery resistance.
From this formula, it can be seen that with a constant value of the EMF, measured with an open circuit, the battery voltage drops as an increase in the current discharge.
Internal resistance. The internal resistance of the battery is relatively small, but in cases where the battery is discharged by the current strength of a large value, for example, when starting the engine starter, the internal resistance of each battery has a very essential value.
Internal resistance is made up of electrolyte resistance, separators and plates. The main component is the electrolyte resistance, which varies with the change in temperature and the concentration of sulfuric acid.
The dependence of the electrolyte resistance with a density of 1.30 g / cm 3 on temperature is shown below:

Temperature, ° С Oh electrolyte resistance · cm
+ 40 0,89
+ 25 1,28
+ 18 1,46
0 1,92
– 18 2,39
As can be seen from the given data, with a decrease in the electrolyte temperature from + 40 ° C to -18 ° C, the resistivity increases by 2.7 times. The smallest value of the resistivity has an electrolyte with a density of 1.223 g / cm 3 at 15 ° C (30% solution H2SO4 by weight).
The second component of the resistance in the battery is the resistance of separators. It depends mainly on their porosity. Separators are made from an electrically insulating material, the pores of which are filled with electrolyte, which causes the electronics of the separator.
In this regard, it would be possible to assume that with a change in temperature, the resistance of the separator will change in the same proportion as the electrolyte resistance, but this is not quite so. Some types of separators, for example, microporous ebonite separators (Mijor) are not sensitive to temperature change.
The third factor containing in the total amount of the internal resistance of the element is the active mass and lattice of positive and negative plates.
The resistance of the spongy lead of the negative plate is slightly different from the resistance of the lattice material, while the resistance of the pitch peroxide of the positive plate exceeds the lattice resistance of 10,000 times. In contrast to the electrolyte resistance, the lattice resistance decreases with a decrease in temperature. But in view of the fact that the resistance of the electrolyte is many times more than the resistance of the plates, then the decrease in their resistance with a decrease in temperature very slightly compensates for the overall decrease in electrolyte resistance.
The resistance of the plates affects the degree of charge batteries. In the process of discharge, the resistance of the plates increases, as the sulfate lead, formed on positive and negative plates, almost does not conduct an electric current.
Compared with other types of batteries, acidic batteries have relatively small internal resistance, which determines their wide use as starter batteries in road transport.
Capacity. The battery capacity is the amount of electricity that can give a fully charged battery at a given discharge mode, temperature and final voltage. Capacitance is measured in amps clocks and are determined by the formula
C \u003d IPTP,
Where FROM- Capacity, and · h ;
IP- the power of the discharge current, and ;
tP.- discharge time, h .
The magnitude of the battery capacity is mainly determined by the following factors: the discharge mode (discharge current), electrolyte concentration and temperature. Batteries with forced discharge modes give a capacity less than when discharged longer modes (small current).
Reducing the capacity for the forced discharge modes occurs for the following reasons.
In the process of discharge, the transformation of the active mass of the plates sulphate lead occurs not only on the surface of the plates, but also inside them. If the discharge is carried out by a current of a small force and slowly, the electrolyte has time to penetrate into the deep layers of the active mass, and the water formed as a result of the reaction in the pores has time to mix with the bulk of the electrolyte. With the forced discharge modes, the concentration of sulfuric acid in the electrolyte inside the plates is significantly reduced, the fresh electrolyte does not have time to penetrate into the depth of the active mass, the reaction is mainly on the surface of the plates, since the pores are blocked and intra-sensitive layers of active mass almost do not participate in the reaction. At the same time, as a result of a significant increase in the internal resistance of the battery, the voltage on its clips drops sharply.
However, after the battery is discharged with a forced mode, after a small break, it can be discharged again. This serves as acknowledged confirmation that the decrease in the battery capacity in the discharge of the large amount of current flow occurs as a result of the incomplete use of the active mass of the plates.
In addition to the size of the discharge current, the electrolyte concentration is significantly affected by the capacity of the battery, which determines the potential of the plates, the electrical resistance of the electrolyte and its viscosity affecting the ability to penetrate the electrolyte in the deep layers of the active mass of the plates.
In the process of discharge, the electrolyte density decreases at the end of the discharge to the active mass of the plates, an insufficient acid is received, as a result of which the battery voltage drops and its further discharge becomes impossible. The greater the difference between the electrolyte concentrations, which is outside the plates, and the electrolyte, which is in the pores of the active mass, the intensively the process of penetration of the acid in the pores of the plates occurs. In this regard, the use of electrolyte with greater density, it would seem, should increase the container. But in reality excessively big density It does not lead to an increase in the capacity, since an increase in the density of the electrolyte inevitably leads to an increase in the viscosity of the electrolyte, as a result of which the process of penetration of the electrolyte in the depth of the active mass of the plates deteriorates, and the voltage on the clips of the battery drops.
Determined that the greatest container It has a battery with an electrolyte density of 1.27 - 1.29 g / cm 3.
The battery capacity also depends on temperature. With a decrease in temperature, the container decreases, and increases with the increase. This is due to the fact that with a decrease in temperature, the viscosity of the electrolyte increases, as a result of which it enters the plates in insufficient quantity.
The values \u200b\u200bof the electrolyte viscosity with a density of 1.223 g / cm 3, depending on the temperature, are shown below:
Temperature, ° С ............ +30 +25 +20 +10 0 - 10 - 20 - 30
Absolute viscosity
PZ (Poise) ....................... 1.596 1,784 2,006 2,600 3,520 4,950 7,490 12,200
The capacity of positive and negative plates with a change in temperatures changes not to the same extent. If at normal temperature the element capacity is limited by positive plates, then at low temperatures - negative, since when the temperature decreases, the tank of the negative plate decreases to a much greater extent than positive.
Recently, the capacity of batteries at low temperatures was significantly increased due to the use of more subtle synthetic separators with high porosity (up to 80%) and additives, so-called expansion, to the active mass of negative plates that give it a large porosity.
In addition to the category of discharge, the concentration of electrolyte and temperature, the battery capacity depends on the service life of its service, during the storage period during which the battery was inactive, from the presence of harmful impurities, etc. The capacity of the new rechargeable battery coming into operation, first time (for The warranty service life) increases, since the formation of plates occurs, after which it remains constant for a certain period and then begins to fall gradually. The loss of the capacity of the battery at the end of the service life is due to a decrease in the porosity of the negative plates and the loss of the active mass of positive plates.
If the charged battery has prolonged for a long time, then with its discharge, the given capacity will be significantly less. This is due to the natural phenomenon of a self-discharge during battery idle.

Purpose of starter batteries
Theoretical foundations of transformation of chemical energy into electric
Battery discharge
Battery charge
Consumption of the main tok-forming reagents
Electromotive force
Interior resistance
Tension during charge and discharge
Battery capacity
Energy and battery power
Battery self-discharge

Purpose of starter batteries

The main function of the battery is a reliable engine start. Another function is an energy buffer when the engine running. After all, along with traditional consumer visits, there have been many additional service devices that improve the driver's comfort and traffic safety. The battery compensates for energy deficit when moving through the urban cycle with frequent and long stops, when the generator cannot always ensure the power return required to fully provide all the included consumers. The third operating function is an energy supply when the engine is turned off. However, the long-term use of electrical appliances during a parking lot with a non-working engine (or an engine running idling) leads to a deep discharge of the battery and a sharp decrease in its starter characteristics.

The battery is also designed for emergency power supply. If the generator fails, the straightener, voltage regulator or when the generator belt breaks, it should ensure the operation of all consumers needed to safely move to the nearest one hundred.

So, starter batteries must meet the following basic requirements:

Provide the discharge current for the starter work, that is, possess a small internal resistance for the minimum internal loss of voltage inside the battery;

Provide the required number of attempts to start the engine with a duration set, that is, to have a necessary reserve of energy of the starter discharge;

Have quite greater power and energy with minimally possible sizes and mass;

Have a reserve of energy to power consumers when disabled Engine or in an emergency (reserve capacity);

Save the stress required for the starter operation when the temperature is reduced in the specified limits (cold scrolling current);

Save for a long time performance at elevated (up to 70 "c) ambient temperature;

Take a charge to restore the capacity spent on the start of the engine and the nutrition of other consumers, from the generator with the engine running (charge reception);

Do not require special preparation of users, maintenance during operation;

Have a high mechanical strength corresponding to the operating conditions;

Maintain the specified operating characteristics for a long time during operation (service life);

Have a slight self-discharge;

Have a low cost.

Theoretical foundations of transformation of chemical energy into electric

The chemical source of current is called a device in which, due to the flow of spatially separated redox chemical reactions, their free energy is converted into electrical. By the nature of the work, these sources are divided into two groups:

Primary chemical current sources or galvanic elements;

Secondary sources or electrical batteries.

Primary sources allow only one-time use, since substances formed by their discharge cannot be turned into source active materials. Fully discharged galvanic element, as a rule, is not suitable for further work - it is an irreversible source of energy.

Secondary chemical current sources are reversible energy sources - after any deepest discharge, their performance can be fully restored by charge. To do this, through a secondary source, it is enough to skip the electric current in the direction conversely in which it proceeded by discharge. In the process of charge formed by the discharge of the substance, turn into initial active materials. So there is a repeated transformation of free energy chemical source Current in electrical energy (battery discharge) and the inverse transformation of electrical energy into the free energy of the chemical current source (battery charge).

The passage of current through electrochemical systems is associated with occurring chemical reactions (transformations). Therefore, between the amount of substance that has entered into an electrochemical reaction and subjected to transformations, and the amount of electricity spent or released, there is a dependence that was installed by Michael Faraday.

According to the first law of the Faraday, the mass of the substance that has entered into an electrode reaction or the resulting flow is proportional to the number of electricity passed through the system.

According to the second law of Faraday, with an equal amount of the mass of reversing substances over the system of electricity, as their chemical equivalents.

In practice, a smaller amount of substance is subjected to electrochemical change than according to the laws of Faraday - during current passage, in addition to the main electrochemical reactions, there are also parallel or secondary (side), changing the mass of products, reactions. To account for the influence of such reactions, the concept of current yield has been introduced.

The current output is the part of the amount of electricity passed through the system, which falls on the share of the main electrochemical reaction

Battery discharge

Active substances of a charged lead battery involving participation in the current-forming process are:

On a positive electrode - lead dioxide (dark brown);

On a negative electrode - sponge lead (gray);

Electrolite - aqueous solution of sulfuric acid.

Part of the acid molecules in the aqueous solution is always dissociated by positively charged hydrogen ions and negatively charged sulfate ions.

Lead, which is the active mass of the negative electrode, is partially dissolved in the electrolyte and is oxidized in the solution with the formation of positive ions. Released excess electrons communicate the electrode negative charge and start moving along a closed section of the outer chain to a positive electrode.

Positively charged lead ions react with negatively charged sulfate ions, with the formation of lead sulfate, which has insignificant solubility and is therefore deposited on the surface of the negative electrode. In the process of discharge of the battery, the active mass of the negative electrode is converted from spongy lead to a sulfate lead with a change in gray to light gray.

The lead dioxide of the positive electrode is dissolved in the electrolyte in a much smaller quantity than the lead of the negative electrode. When the water interacts with water, dissociates (disintegrates in the solution on charged particles - ions), forming the ions of tetravalent lead and hydroxyl ions.

The ions report the electrode positive potential and, connecting electrons that came along the outer chain from the negative electrode are restored to the ions of bivalent lead

Ions interact with ions, forming a sulfate lead, which, according to the above reason, is also deposited on the surface of the positive electrode, as it took place on the negative. The active mass of the positive electrode as the result is converted from lead dioxide into lead sulfate with a change in its color from dark brown in light brown.

As a result of the discharge of the battery, active materials and positive, and negative electrodes turn into lead sulfate. At the same time, sulfuric acid is consumed on the formation of lead sulfate and water is formed from the released ions, which leads to a decrease in the electrolyte density during discharge.

Battery charge

In the electrolyte, both electrodes are present in small quantities of sulfate ions of lead and water sulfate. Under the influence of the voltage of the source direct currentThe chain of which includes a charged battery, in the external circuit, the directional movement of the electrons to the negative output of the battery is installed.

Bivalent lead ions in the negative electrode are neutralized (restored) by two electrons by two electrons, turning the active mass of the negative electrode into the metal sponge lead. The remaining free ions form sulfuric acid

At the positive electrode under the action of the charging current, bivalent lead ions give two electrons, oxidizing in tetravalent. The latter, connecting through intermediate reactions with two oxygen ions, form lead dioxide, which is released on the electrode. The ions and the same as in the negative electrode form sulfuric acid, with the result that the electrolyte density increases when charging.

When the transformation processes of substances in the active masses of the positive and negative electrodes are over, the electrolyte density ceases to change, which is a sign of the end of the battery charge. With a further continuation of the charge, the so-called secondary process occurs - electrolytic decomposition of water for oxygen and hydrogen. Holding out of the electrolyte in the form of gas bubbles, they create the effect of its intensive boiling, which also serves as a sign of the end of the charge process.

Consumption of the main tok-forming reagents

To obtain a capacity in one ampere hour, when the battery is discharged, in order to participate in the reaction:

4,463 g of lead dioxide

3,886 g of spongy lead

3,660 g of sulfuric acid

The total theoretical consumption of materials for obtaining 1 A-h (specific consumption of materials) of electricity will be 11.989 g / A-h, and the theoretical specific capacity - 83.41 A-h / kg.

With the value of the nominal battery voltage 2, the theoretical specific consumption of materials per unit of energy is 5.995 g / VTC, and the specific energy of the battery will be 166.82 W / kg.

However, in practice it is impossible to achieve the full use of active materials involved in the current-forming process. Approximately half of the surface of the active mass is not available for electrolyte, as it serves as the basis for constructing a volume porous frame that provides mechanical strength of the material. Therefore, the real coefficient of use of the active masses of the positive electrode is 45-55%, and a negative 50-65%. In addition, a 35-38% sulfuric acid solution is used as an electrolyte. Therefore, the value of the actual specific consumption of materials is significantly higher, and the real values \u200b\u200bof the specific capacity and specific energy are significantly lower than theoretical.

Electromotive force

The electromotive force (EMF) of the battery e is called the difference in its electrode potentials, measured with an open external chain.

EMF Battery consisting of n series connected batteries.

EMF is measured by a high-resistance voltmeter (internal resistance of at least 300 ohms / c). For this, the voltmeter is attached to the outputs of the battery or battery. At the same time, a charging or discharge current should not flow through the battery (battery).

The equilibrium EMF of a lead battery, as well as any chemical source of current depends on the chemical and physical properties of substances involved in the current-forming process, and absolutely independent of the size and shape of the electrodes, as well as on the number of active mass and electrolyte. At the same time, in the lead battery, the electrolyte takes directly involved in the current-forming process on the battery electrodes and changes its density depending on the degree of charge of batteries. Therefore, the equilibrium EMF, which in turn is the function of density

The change in the EMF of the battery from temperature is very little and can be neglected during operation.

Interior resistance

The resistance reserved by the battery flowing within it (charger or discharge) is called the internal battery resistance.

The resistance of the active materials of the positive and negative electrodes, as well as the resistance of the electrolyte vary depending on the degree of charge of the battery. In addition, the electrolyte resistance is very significantly dependent on temperature.

Therefore, ohmic resistance also depends on the degree of charge of the battery and the electrolyte temperature.

The resistance of polarization depends on the strength of the discharge (charging) current and temperature and does not obey the law of Oma.

The internal resistance of one battery and even a battery consisting of several successively connected batteries is slightly and is in the charged state of only a few thousandths of Ohm. However, during the discharge, it changes significantly.

The electrical conductivity of the active masses decreases for a positive electrode by about 20 times, and for negative - 10 times. Electrolyte electrical conductivity also varies depending on its density. With an increase in the electrolyte density of 1.00 to 1.70 g / cm3, its electrical conductivity is first grows to its maximum value, and then decreases again.

As the battery discharge, the electrolyte density decreases from 1.28 g / cm3 to 1.09 g / cm3, which leads to a decrease in its electrical conductivity by almost 2.5 times. As a result, the ohmic resistance of the battery as it increases. In the discharged, the resistance reaches the value, more than 2 times higher than its magnitude in the charged state.

In addition to the state of charge, the temperature has a significant effect on the resistance of the batteries. With a decrease in temperature, the specific electrolyte resistance increases at a temperature of -40 ° C becomes approximately 8 times more than at +30 ° C. The resistance of separators also increases sharply with a decrease in temperature and in the same temperature range increases almost 4 times. This is a determining factor in increasing the internal resistance of batteries at low temperatures.

Tension during charge and discharge

The potential difference on the poles of the battery (battery) in the process of charge or discharge in the presence of current in the external circuit is called the battery voltage (battery). The presence of internal resistance of the battery leads to the fact that its voltage at the discharge is always less than EDC, and when charging is always more EDC.

When charging the battery, the voltage at its conclusions should be more of its EDC in the amount of internal losses.

At the beginning of the charge, the voltage jump occurs on the size of ohmic losses inside the battery, and then a sharp increase in voltage due to the polarization potential caused mainly by a rapid increase in the electrolyte density in the pores of the active mass. Next, there is a slow voltage growth, due to the mainly increasing EMF of the battery due to an increase in electrolyte density.

After the main amount of lead sulfate is converted to ppco and ply, energy costs are increasingly caused by water decomposition (electrolysis) excess number of hydrogen and oxygen ions appearing in the electrolyte, further increases the difference in the potentials of variance electrodes. This leads to a rapid growth of the charging voltage, causing the acceleration of the water decomposition process. The hydrogen and oxygen ions formed at the same time do not interoperade with active materials. They are recombined into neutral molecules and are excreted from electrolyte in the form of gas bubbles (oxygen is released on a positive electrode, on a negative - hydrogen), causing the "boiling" of the electrolyte.

If you continue the charge process, it can be seen that the growth of the density of the electrolyte and charging voltage is practically terminated, since almost all of the lead sulfate reacted, and the entire energy supplied to the battery is now spent only on the effect of the side process - electrolytic water decomposition. This explains the constancy of the charging voltage, which serves as one of the signs of the end of the charging process.

After stopping the charge, that is, turning off the external source, the voltage at the battery outputs is sharply reduced to the value of its nonequilibrium EMF, or by the value of ohmic internal losses. Then there is a gradual decrease in EMF (due to the decrease in the electrolyte density in the pores of the active mass), which continues until complete alignment of the electrolyte concentration in the volume of the battery and the pores of the active mass, which corresponds to the establishment of the equilibrium EMF.

When the battery discharge, the voltage at its leads is less than the EDC by the value of the internal drop in the voltage.

At the beginning of the discharge, the battery voltage drops sharply by the magnitude of ohmic losses and polarization caused by a decrease in the concentration of electrolyte in the pores of the active mass, that is, the concentration polarization. Next, with a steady (stationary) discharge process, a decrease in the electrolyte density in the amount of battery, which causes a gradual decrease in the discharge voltage. At the same time, a change in the ratio of lead sulphate in the active mass is occurring, which also causes an increase in ohmic losses. In this case, particles of lead sulfate (having an approximately three times large volume in comparison with lead particles and its dioxide, of which they were formed) closed the pores of the active mass, which prevent the passage of electrolyte into the depth of the electrodes.

This causes an increase in concentration polarization, leading to a faster reduction in discharge voltage.

When the discharge stops, the voltage at the outputs of the battery is rapidly rising by the amount of ohmic losses, reaching the value of the nonequilibrium EMF. Further change in EMF due to the leveling of the electrolyte concentration in the pores of the active masses and in the amount of the battery leads to a gradual setting of the equilibrium EMF.

The battery voltage during its discharge is determined mainly by the temperature of the electrolyte and the power of the discharge current. As mentioned above, the resistance of the lead accumulator (batteries) is slightly and in chargeable state is only a few. However, at currents of the starter discharge, the strength of which is 4-7 times the value rated tankThe internal drop of voltage has a significant effect on the discharge voltage. An increase in ohmic losses with a decrease in temperature is associated with increasing electrolyte resistance. In addition, the electrolyte viscosity increases sharply, which makes it difficult to diffuse it in the pores of the active mass and increases the concentration polarization (that is, it increases the loss of the voltage inside the battery due to the decrease in the electrolyte concentration in the pores of the electrodes).

At a current of more than 60 and the dependence of the discharge voltage from the current strength is almost linear at all temperatures.

The average value of the battery voltage during charge and discharge is defined as the mean arithmetic voltage values \u200b\u200bmeasured at equal intervals.

Battery capacity

Battery capacity is the amount of electricity obtained from the battery when it discharges to the installed final voltage. In practical calculations, the battery capacity is made to express in amps-hours (Ah). The discharge capacity can be calculated, multiplied by the power of the discharge current on the duration of the discharge.

The discharge container on which the battery is calculated and which is indicated by the manufacturer, is called a nominal capacity.

In addition to it, an important indicator also contains a battery capacity when charging.

The discharge capacity depends on the whole range of the structural and technological parameters of the battery, as well as the conditions for its operation. The most essential structural parameters are the amount of active mass and electrolyte, thickness and geometric dimensions of the battery electrodes. The main technological parameters affecting the battery capacity are the formulation of active materials and their porosity. Operational parameters - the temperature of the electrolyte and the power of the discharge current - also have a significant effect on the discharge container. A generalized indicator characterizing the efficiency of the battery is the utilization of active materials.

To obtain a capacity of 1 A-h, as mentioned above, 4.463 g of lead dioxide, 3,886 g of spongy lead and 3.66 g of sulfuric acid are theoretically necessary. Theoretical specific consumption of the active mass of the electrodes is 8.32 g / Ah. In real batteries, the specific consumption of active materials at 20-hour discharge mode and electrolyte temperature of 25 ° C ranges from 15.0 to 18.5 g / A-h, which corresponds to the coefficient of use of the active masses of 45-55%. Consequently, the practical consumption of active mass exceeds theoretical values \u200b\u200bof 2 or more times.

On the degree of use of the active mass, and therefore, the following major factors affect the amount of discharge capacity.

Porosity of active mass. With increasing porosity, the diffusion conditions of the electrolyte are improved into the depth of the active mass of the electrode and the true surface increases, on which the current-forming reaction occurs. With increasing porosity, the discharge capacity increases. The magnitude of porosity depends on the size of the particles of lead powder and the formulation of the preparation of active masses, as well as from the supplements used. Moreover, the increase in porosity leads to a decrease in durability due to the acceleration of the process of destruction of high-resistant active masses. Therefore, the magnitude of porosity is chosen by manufacturers, taking into account not only high capacitive characteristics, but also to ensure the necessary durability of the battery in operation. Currently, porosity is considered optimal within 46-60%, depending on the purpose of the battery.

The thickness of the electrodes. With a decrease in thickness, the non-uniformity of the loading of the outer and inner layers of the active mass of the electrode is reduced, which contributes to an increase in the discharge capacity. In thicker electrodes, the inner layers of the active mass are used very slightly, especially when the discharge of large currents. Therefore, with an increase in the discharge current, the differences in the capacity of batteries having electrodes of various thicknesses decrease sharply.

Porosity and rationality of the design of the separator material. With the increasing porosity of the separator and the height of his ribs, the supply of electrolyte in the interelectrode gap increases and the conditions of its diffusion are improved.

Electrolyte density. Affects the battery capacity, and its service life. With an increase in the density of the electrolyte, the capacity of positive electrodes increases, and the tank of negative, especially at a negative temperature, decreases due to the acceleration of the passivation of the surface of the electrode. Increased density also adversely affects the battery life due to the acceleration of corrosion processes on the positive electrode. Therefore, the optimal density of the electrolyte is established on the basis of the set of requirements and conditions in which the battery is operated. For example, the working density of the electrolyte 1.26-1.28 g / cm3 is recommended for starter batteries operating in a moderate climate, and for districts with a hot (tropical) climate of 1.22-1.24 g / cm3.

The power of the discharge current to which the battery should be continuously discharged for a specified time (characterizes the discharge mode). The discharge modes are conditionally divided into long-term and short. With long modes, the discharge occurs with small currents for several hours. For example, 5-, 10- and 20-hour discharge. With short or starter discharges, the current is several times the nominal battery capacity, and the discharge lasts a few minutes or seconds. With an increase in the discharge current, the discharge rate of the surface layers of the active mass increases to a greater extent than deep. As a result, the growth of sulfate lead in the mouth of pores is faster than in depth, and it is time to be purchased with sulfate earlier than to react its inner surface. Due to the termination of the diffusion of electrolyte inside the pore, the reaction is stopped in it. Thus, the greater the discharge current, the smaller the battery capacity, and therefore, the coefficient of use of the active mass.

To evaluate the launchers of the batteries, their capacity is also characterized by the number of intermittent starter discharges (for example, a duration of 10-15 s with interruptions between them in 60 seconds). The capacitance that the battery gives intermittent discharges exceeds the container with the continuous discharge of the same current, especially when the discharge mode is started.

Currently, the concept of "backup" capacity is used in the international practice of assessing the capacitive characteristics of starter batteries. It characterizes the discharge time of the battery (in minutes) at the power of the discharge current 25 A, regardless of the nominal battery capacity. At the discretion of the manufacturer, it is allowed to set the value of the nominal capacity at a 20-hour mode of discharge in amps-hours or backup capacity in minutes.

Electrolyte temperature. With its decrease, the discharge capacity of batteries is reduced. The reason for this is to increase the viscosity of the electrolyte and its electrical resistance, which slows the diffusion rate of the electrolyte in the pores of the active mass. In addition, the process of passivating the negative electrode is accelerated with a decrease in temperature.

The temperature coefficient of tank A shows the change in the capacity as a percentage when the temperature changes by 1 ° C.

When testing, the discharge capacity obtained during long-term discharge mode from the value of the nominal containable at the electrolyte temperature is +25 ° C.

The temperature of the electrolyte when determining the container on a long discharge mode in accordance with the requirements of standards should be in the range from +18 ° C to +27 ° C.

The parameters of the starter discharge are assessed by the duration of the discharge in minutes and the voltage at the beginning of the discharge. These parameters are determined on the first cycle at +25 ° C (verification for dried batteries) and on subsequent cycles at temperatures -18 ° C or -30 ° C.

Degree of charge. With an increase in the degree of charge, with other things being equal, the container increases and reaches its maximum value with full battery charge. This is due to the fact that with an incomplete charge, the number of active materials on both electrodes, as well as the electrolyte density, do not reach their maximum values.

Energy and battery power

The battery power w is expressed in watt-hours and is determined by the product of its discharge (charging) capacity to the average bit (charging) voltage.

Since with a change in temperature and discharge mode, the battery capacity and its discharge voltage are changed, then with a decrease in temperature and increasing the discharge current, the battery energy decreases even more significantly than its capacity.

When compared with the chemical sources of current differing in tanks, structures, and even by the electrochemical system, as well as in determining the directions of their improvement, they use the specific energy indicator, the energy covered to the unit mass of the battery or its volume. For modern lead starter non-listed batteries, specific energy at 20-hour discharge mode is 40-47 W.

The amount of energy given by the battery per unit of time is called its power. It can be determined as a product of the size of the discharge current on the average discharge voltage.

Battery self-discharge

Self-discharge is called the decrease in the capacity of batteries with an open external circuit, that is, with inaction. This phenomenon is caused by redox processes, spontaneously flowing both on negative and positive electrodes.

The self-discharge is particularly susceptible to a negative electrode due to spontaneous dissolution of lead (negative active mass) in a solution of sulfuric acid.

The self-discharge of the negative electrode is accompanied by the release of gaseous hydrogen. The speed of spontaneous dissolution of lead increases significantly with an increase in electrolyte concentration. The increase in electrolyte density from 1.27 to 1.32 g / cm3 leads to an increase in the rate of self-discharge of a negative electrode by 40%.

The presence of impurities of various metals on the surface of the negative electrode has a very significant effect (catalytic) to increase the rate of lead self-reliance (due to reduction in the overvoltage of hydrogen release). Almost all metals encountered in the form of impurities in battery raw materials, electrolyte and separators, or in the form of special additives, contribute to the increase in the self-discharge. Finding on the surface of the negative electrode, they facilitate the conditions for the release of hydrogen.

Part of the impurities (salts of metals with variable valence) act as charge carriers from one electrode to another. In this case, metal ions are restored on a negative electrode and are oxidized on a positive (such a self-discharge mechanism is attributed to iron ions).

The self-discharge of a positive active material is due to the reaction.

2 RO2 + 2H2SO4 -\u003e PBSCU + 2H2O + O2 T.

The rate of this reaction also increases with increasing electrolyte concentration.

Since the reaction proceeds with the release of oxygen, its speed is largely determined by oxygen overvoligation. Therefore, additives that reduce the potential for oxygen isolation (for example, antimony, cobalt, silver) will contribute to the growth rate of the reaction of the self-reliance of lead dioxide. The rate of self-discharge of the positive active material is several times lower than the rate of self-discharge of the negative active material.

Another reason for the self-discharge of a positive electrode is the difference in the potentials of the material of the current and the active mass of this electrode. The electroplated microelement resulting as a result of this potential difference transforms the lead of the lead of the current flow and the lead dioxide of the positive active mass into lead sulfate.

The self-discharge may also arise when the battery is dirty or flooded with electrolyte, water or other liquids, which create the possibility of discharge through the electrically conductive film between the poles of the battery or its jumpers. This kind of self-discharge does not differ from the usual discharge very small currents at a closed external chain and easily eliminate. To do this, it is necessary to contain the surface of the batteries clean.

The self-discharge of the batteries largely depends on the temperature of the electrolyte. With a decrease in temperature, the self-disclosure decreases. At temperatures below 0 ° C, the new batteries it almost stops. Therefore, the storage of batteries is recommended in the charged state at low temperatures (up to -30 ° C).

During operation, self-discharge does not remain constant and sharply increases by the end of the service life.

The decrease in the self-discharge is possible by increasing the overvoltage of oxygen and hydrogen sections on the battery electrodes.

For this, it is necessary, firstly, to use more clean materials for the production of batteries, reduce the quantitative content of alloying elements in battery alloys, use only

pure sulfuric acid and distilled (or close to it clean with other purification methods) water for the preparation of all electrolytes, both in production and operation. For example, due to a decrease in the content of antimony in the alloy of current taps from 5% to 2% and the use of distilled water for all technological electrolytes, the average daily self-discharge is reduced by 4 times. Replacing antimony on calcium allows you to further reduce the rate of self-discharge.

Reducing the self-discharge can also contribute to the additives of organic substances - self-discharge inhibitors.

The use of a common lid and hidden inter-element compounds largely reduces the rate of self-discharge from leakage currents, as the likelihood of galvanic communication between far-distilled pole conclusions is significantly reduced.

Sometimes it is self-discord called a quick loss of tank due to a short circuit inside the battery. Such a phenomenon is explained by a direct discharge through conductive bridges formed between the variepete electrodes.

Application of envelope separators in non-servant batteries

eliminates the possibility of forming short circuits between the variemene electrodes during operation. However, this probability remains due to possible failures in the equipment mass production. Usually such a defect is detected in the first months of operation and the battery is subject to a replacement for warranty.

Usually, the degree of self-discharge is expressed as a percentage of loss of tank for the set period of time.

The presents currently, the standards are characterized by the voltage of the starter discharge at -18 ° C after the test: inaction for 21 days at a temperature of +40 ° C.

Battery(element) - consists of positive and negative electrodes (lead plates) and separators separating these plates mounted in the housing and immersed in the electrolyte (sulfuric acid solution). The accumulation of energy in the battery occurs when the chemical oxidation reaction is restored by electrodes.

Accumulator battery It consists of 2 or more sequentially or (s) parallel to interconnected sections (batteries, elements) to provide the desired voltage and current.It is able to accumulate, store and give electricity, to ensure the start of the engine, as well as feed the electrical appliances when the engine is not working.

Lead-acid rechargeable battery - Battery, in which electrodes are manufactured mainly from lead, and the electrolyte is a solution of sulfuric acid.

Active mass- This is the component of the electrodes, which undergoes chemical changes during the passage of electric current during the discharge charge.

Electrode - conductive material capable of producing electrical current when reaction with electrolyte.

Positive electrode (anode) -the electrode (plate) The active mass of which the charged battery consists of lead dioxide (PBO2).

Negative electrode (cathode) -the electrode, the active mass of which the charged battery consists of spongy lead.

Electrode grilleit serves to hold the active mass, as well as for supplying and removing the current to it.

Separator - The material used to isolate the electrodes from each other.

Pole conclusionsserve for charging current supply and for its return under the general battery voltage.

Lead - (РБ) - chemical element of the fourth group of the periodic system D. I. Mendeleev, sequence number 82, atomic weight 207.21, valence 2 and 4. Lead - blue metal, the proportion of it, in a solid form of 11.3 g / cm 3, decreases when melting, depending on temperature. The most plastic among the metals, it is well rolled to the finest sheet and easily goes. Lead is easily machined, refers to the number of low-melting metals.

Lead oxide (IV) (lead dioxide) PBO 2 is a dark brown heavy powder having a subtle characteristic odor of ozone.

Antimonyit is a metal silver-white metal with a strong glitter, crystalline structure. In contrast, the lead is a solid metal, but very fragile and easily crushing into pieces. The antimony is much lighter than lead, its share is 6.7 g / cm 3. Water and weak acids do not act on antimony. It is slowly dissolved in strong hydrochloric and sulfuric acids.

Tubes of cells Close the holes of the cells in the battery lid.

Tube of central ventilationserves for overlapping a gas-linguized hole in the battery lid.

Monoblock- This is a polypropylene battery case separated by partitions into separate cells.

Distilled waterit fills in the battery to reimburse its losses as a result of decomposition of water or evaporation. Only distilled water should be used to eliminate batteries!

Electrolyte It is a solution of sulfuric acid in distilled water, which fills free volumes of cells and penetrates the active mass of electrodes and separators.

It is able to carry out an electric current between the electrodes immersed in it. (For the middle strip of Russia, a density of 1.27-1.28 g / cm3 at T \u003d + 20 ° C).

Low-moving electrolyte:To reduce the danger from the electrolyte spacing from the battery, use means that reduce its fluidity. The electrolyte can be added substances that turn it into the gel. Another way to reduce electrolyte mobility is the use of glassmates as separators.

Open battery - A battery having a tube with a hole through which distilled water fills, and gaseous products are removed. The hole can be equipped with a ventilation system.
Closed battery - Battery, which is closed under normal conditions, but has a device that allows gas to be released when the internal pressure exceeds the set value. Usually an additional fill of the electrolyte in such a battery is not possible.
Dry-grooved battery - Battery stored without electrolyte, plates (electrodes) of which are in a dry charged state.

Tubular (Pacir) Plate - Positive plate (electrode), which consists of a set of porous tubes filled with active mass.

Safety valve - Detail of the ventilation plug, which allows to exit gas in the case of excess internal pressure, but does not allow air flow into the battery.

Ampere-hour (A · h)- This is a measure of electrical energy equal to the product of current force in amperes for time in hours (tank).

Battery voltage - Potential differences between battery outputs when discharge.
Battery capacity - The amount of electrical energy given by a fully charged battery when it discharges until the final voltage is reached.

Interior resistance - Current resistance through an element measured in Omah. It consists of electrolyte resistance, separators and plates. The main component is the electrolyte resistance, which varies with the change in temperature and the concentration of sulfuric acid.

Electrolyte density - ethe characteristics of the physical body equal to the ratio of its mass to the occupied volume. It is measured, for example, in kg / l or in g / cm3.

Battery life - Period useful work Batteries in specified conditions.
Gas emplation - gas formation in the electrolysis process of electrolyte.

Self-discharge - spontaneous loss of tank capacity by the battery alone. The rate of self-discharge depends on the material of the plates, chemical impurities in the electrolyte, its density, from the purity of the battery and the duration of its operation.

EMF battery(Electrical force) is a voltage at the pole conclusions of a fully charged battery with an open circuit, i.e., with the complete absence of charge or discharge currents.

Cycle - One charge and discharge element sequence.

Gas formation on lead batteries. Especially abundantly stands out in the final phase of the charge of a lead battery.

Gel batteries - These are sealed lead-acid batteries (Not sealed, because a small separation of gases when opening valves still occurs), closed, fully maintenanceable (non-replaced) with gel-shaped acid electrolyte (Dryfit and Gelled ElectroLite-GEL).

AGM technology (ABSORBED Glass Mat) - absorbing gaskets from fiberglass.

Return in energy - The ratio of the amount of energy given during the discharge of the battery, to the amount of energy necessary for charge to the initial state under certain conditions. The return on energy for acid batteries under normal operating conditions is 65%, and for alkaline 55 - 60%.
Specific energy - Energy that is given to the battery when discharged per unit of its volume V or mass M, i.e. w \u003d W / V or W \u003d w / m. The specific energy of acid batteries is 7-25, nickel-cadmium 11-27, nickel-iron 20-36, silver-zinc 120-130 W * h / kg.

Short circuit in batteries It occurs with the electrical connection of plates of different polarity.

The batteries are filled with sulfuric acid and in the process of a normal charge-discharge cycle in them, explosive gases (hydrogen and oxygen) are distinguished. In order to avoid injury to personnel or damage to the car, strictly follow the following safety regulations:

Before you start working with any electrical components of the car, disconnect the power cable from the minus battery terminal. With a minus power cable, all electrical circuits in the car will be open, which will prevent accidental closure of any electrical component for mass. Electric spark creates a potential danger of injury and fire.
Any work related to the battery must be performed in protective glasses.
To protect against sulfuric acid, which is filled with a battery, use protective clothing on the skin.
Do not violate the safety regulations specified in the maintenance procedures when accessing the equipment used for maintenance and testing batteries.
It is strictly forbidden to smoke or use open fire in close proximity to the battery.

Current battery maintenance

The current maintenance of the battery is to check the cleanliness of the battery case and, if necessary, add clean water to it. All battery manufacturers recommend using distilled water for this purpose, but in the case of its absence, it is possible to use pure drinking water with low salts. Since water is the only battery consumable component, to foster the acid to the battery is not allowed. Part of the water from the electrolyte is destroyed in the process of charge and discharge of the battery, but the acid contained in the electrolyte remains in the rechargeable battery. Do not overflow the battery with an electrolyte, because in this case the normal bubbage (gas formation) arising in the electrolyte during the battery process will lead to an electrolyte leakage that causes corrosion of the battery terminals, its attachment brackets and pallet. Rechargeable batteries should be filled with an electrolyte to an approximately one and a half inches (3.8 cm) below the top of the filling neck.

Contacts of power cables connected to the battery, and the terminals of the battery itself must be examined and cleaned to avoid dropping voltage on them. One of the common reasons that the engine does not start, is the weakening or corrosion of the contacts of the power cables connected to the battery terminals.

Fig. Strongly corrected battery terminal

Fig. It was found that this power cable connected to the battery was very corroded under insulation. Although corrosion through the wasolation was insulated, but remained unnoticed until the cable was carefully examined. This cable is replaced.

Fig. Carefully check all the battery terminals for signs of corrosion. In this car, two power cables are attached to the positive battery terminal with a long bolt. This is a common cause of corrosion, which causes a disruption of an electric start-up engine

Measurement of the EMF of the Battery

Electromotive force (EMF) is the difference of potentials of positive and negative battery electrodes with an open external circuit.

The value of the EDC depends mainly on electrode potentials, i.e. From the physical and chemical properties of substances from which plates and electrolyte are made, but does not depend on the size of the battery plates. EMF acid battery depends on electrolyte density.

Measurement of electromotive power (EMF) battery with a voltmeter is a simple way to determine its degree of charge. EMF of the battery is not an indicator that guarantees the performance of the battery, but this parameter fully characterizes the state of the battery, which is simply an inspection. Rechargeable battery that appearance It is quite efficient, it may actually be not as good as it seems.

This check is called voltage measurement idle move (EMF Verification) Battery Because the measurement is performed on the terminals of the battery without a load connected to it, with a zero consumption current.

If the check is performed immediately at the end of charging the battery or in the car at the end of the trip, it is necessary to release the rechargeable battery from the emission of polarization before measurement. EMF polarization is an increased, compared to normal, voltage that occurs only on the surface of the battery plate. EMF polarization quickly disappears when the battery operates under load, so it does not give an accurate assessment of the degree of charge of the battery.
To release the battery from EMF polarization, turn on the headlights into mode far Light For one minute, and then, turn them off and wait a couple of minutes.
When the engine is turned off and the rest of the electrical equipment, with the door closed (so that the light in the cabin is turned off), connect the voltmeter to the battery terminals. Red, plus, voltmeter wire Connect to the plus terminal of the battery, and black, minus, wire to its minus terminal.
Fix the voltmeter reading and compare it with the battery charges table. The table below is suitable for evaluating the degree of charge rate of the battery in the value of the EDC at room temperature - from 70 ° F to 80 ° F (from 21 ° C to 27 ° C).

Table

EMF rechargeable battery (B)	Degree of charge
12.6 V and above	Charged 100%
12,4	Charged by 75%
12,2	Charged by 50%
12	Charged by 25%
11.9 and lower	Descessable

Fig. The voltmeter shows the battery voltage after one minute after the headlight on (A). After turning off the headlights, the voltage measured on the battery quickly recovered to 12.6 V (b)

NOTE

If the voltmeter gives a negative reading, then, or the battery is charged in reverse polarity (and then to be replaced), or the voltmeter is connected to the battery in reverse polarity.

Rechargeable battery voltage measurement under load

One of the most accurate ways to determine the performance of the battery is the measurement of the battery voltage under load. In most testers of the launchers and charging characteristics of automotive batteries, a coal rheostat is used as a load of the battery. Load parameters are determined by the nominal capacity of the rechargeable battery. The rated capacity of the battery is characterized by the value of the start current, which is capable of providing a battery at 0 ° F (-18 ° C) for 30 seconds. Previously, the characteristic of the nominal capacity of batteries in amps clock was used. Measurement of the battery voltage under load is performed at the value of the discharge current equal to half the nominal CSA of the current battery or the tripled nominal capacity of the battery in amps-hours, but not less than 250 amps. Measuring the battery voltage under load is performed after checking the degree of its charges by the built-in range or by measuring the EMF of the battery. The battery must be charged at least 75%. The corresponding load is connected to the battery and after 15 seconds of the battery operation, the voltmeter readings are recorded under the load when the load is connected. If the rechargeable battery is good, then the testimony of the voltmeter should remain above 9.6 V. Many battery manufacturers recommend measuring twice:

the first 15 seconds of the battery operation under load are used to exemplate from EMF polarization.
the second 15 seconds - to obtain a more reliable estimate of the rechargeable battery state

Between the first and second cycle of work under load, it is necessary to make an excerpt of 30 seconds to give the battery to restore.

Fig. Tester of the starting and charging characteristics of automotive batteries, released by Bear Automotive, automatically enables the currently checked battery into operation mode for 15 seconds - to remove the polarization EMF, then turns off the load for 30 seconds to restore the battery and connects the load on 15 seconds. The tester display displays the state of the battery.

Fig. VAT 40 Tester (voltarmeter, model 40) of Sun Electric, connected to the battery for testing under load. The operator using the load current regulator sets the amount of the discharge current to the ammeter, equal to half the battery value of the current CSA. The battery operates under load for 15 seconds and at the end of this time interval, the battery voltage measured when the load is connected must be no less than 9.6 V

NOTE

Some testers for determining the degree of charge and efficiency of the battery measure the battery capacity. Observe the verification procedure set by the test equipment manufacturer.

If the battery has not passed the test under load, recharge it and repeat it. In case the second check ended unsuccessfully, the battery is subject to replacement.

Battery charging

If the battery is strongly discharged, it must be recharged. Charging the battery, in order to avoid its damage due to overheating, it is best to produce in standard charging mode. Explanations regarding the standard battery charging mode are shown in the figure.

Fig. This battery charging device is adjusted for charging the battery with a nominal charging current of 10 A. Charging the battery in standard mode, as on the photo above, it does not act so much on the battery, as an accelerated charging mode, in which the battery overheating is not eliminated Battering of battery plates

It must be remembered that for charging a fully discharged battery may take hours eight, or even more. Initially, it is necessary to maintain a charging current at about 35 A for 30 minutes - in order to facilitate the beginning of the battery charging process. In the accelerated battery charging mode, it is heated and the risk of battery packs increases. In accelerated charging mode, enhanced gas formation (hydrogen and oxygen isolation) occurs, which creates a hazard for health and risk of fire. The accumulatory battery temperature should not go beyond 125 ° F (52 ° C, the battery is hot to the touch). Charging batteries is recommended, as a rule, to produce a charging current equal to 1% of the SSO current passport.

Accelerated charging mode - a maximum of 15 A
Standard charging mode - maximum 5 A

It can happen with each!

Owner toyota car Disconnected battery. After connecting a new battery, the owner noticed that dashboard The yellow light bulb "Airbag" lights up, and the radio was blocked. The owner acquired a used car from the dealer and did not know the secret four-digit code necessary to unlock the radio. Forced to look for a way to solve this problem, he has tried to introduce three different four-digit numbers in the hope that one of them is suitable. However, after three unsuccessful attempts, the radio was completely disconnected.

Upset owner appealed to the dealer. The elimination of the problem has cost more than three hundred dollars. To reset the signaling "Airbag" required a special device. The radio has had to be removed from the car and send to another state to an authorized service center, and on returning to re-install in the car.

Therefore, before turning off the battery, be sure to agree with the owner of the car - you must make sure that the owner is known for the secret code for the inclusion of the coded radio receiving, which is simultaneously used in the car's protection system. It may be necessary to use the radio receiver's backup memory device when the battery is disabled.

Fig. Here is a good thought. The technician made a backup power source from an old battery lantern and cable with an adapter to the cigarette lighter socket. It just connected the wires to the battery conclusions that had a battery lantern. The flashlight battery is more convenient than the usual 9-volt battery - in case someone comes to open the car door at a time when the memory backup source is turned on in the chain. The 9-volt battery having a small container in this case would quickly discharged, while the battery capacity of the flashlight is large enough and it is enough to ensure that even when the interior lighting is turned on

Electromotive force

The electromotive force (EMF) of the battery e is called the difference in its electrode potentials, measured with an open external chain.

EMF Battery consisting of n series connected batteries.

It is necessary to distinguish the equilibrium EMF of the battery and the non-equilibrium efficiency of the battery during the time from the opening of the chain before establishing the equilibrium state (the period of the transition process). EMF is measured by a high-resistance voltmeter (internal resistance of at least 300 ohms / c). For this, the voltmeter is attached to the outputs of the battery or battery. At the same time, a charging or discharge current should not flow through the battery (battery).

The change in the EMF of the battery from temperature is very little and can be neglected during operation.

Tension during charge and discharge

When charging the battery, the voltage at its conclusions should be more of its EDC in the amount of internal losses. At the beginning of the charge, the voltage jump occurs on the size of ohmic losses inside the battery, and then a sharp increase in voltage due to the polarization potential caused mainly by a rapid increase in the electrolyte density in the pores of the active mass. Next, there is a slow voltage growth, due to the mainly increasing EMF of the battery due to an increase in electrolyte density.

When the battery discharge, the voltage at its leads is less than the EDC by the value of the internal drop in the voltage.

The battery voltage during its discharge is determined mainly by the temperature of the electrolyte and the power of the discharge current. As mentioned above, the resistance of the lead accumulator (batteries) is slightly and in chargeable state is only a few. However, with the currents of the starter discharge, the strength of which is 4-7 times the value of the nominal container, the internal drop in the voltage has a significant effect on the discharge voltage. An increase in ohmic losses with a decrease in temperature is associated with increasing electrolyte resistance. In addition, the electrolyte viscosity increases sharply, which makes it difficult to diffuse it in the pores of the active mass and increases the concentration polarization (that is, it increases the loss of the voltage inside the battery due to the decrease in the electrolyte concentration in the pores of the electrodes). At a current of more than 60 and the dependence of the discharge voltage from the current strength is almost linear at all temperatures.

The average value of the battery voltage during charge and discharge is defined as the mean arithmetic voltage values \u200b\u200bmeasured at equal intervals

Current battery maintenance

Measurement of the EMF of the Battery

Rechargeable battery voltage measurement under load

Battery charging

Electromotive force

Tension during charge and discharge

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