Accumulation of electrical energy. What energy transformations occur during the operation of a galvanic cell? And what kind of energy transformations occur when charging and discharging the battery

On the oxidizing properties of tetravalent lead and its transition to a more stable divalent state, the design and operation of lead batteries that are widely used in practice are based.

Electric batteries are devices that allow you to accumulate electrical energy in order to then spend it at the right time. This accumulation of energy is carried out by passing an electric current through the battery, due to which a chemical process takes place in it, accompanied by the conversion of electrical energy into chemical energy; the battery is said to be charging. A charged battery can be used as a galvanic cell, and the same reaction that occurred when the battery was charging proceeds in the opposite direction and the chemical energy stored in the battery is converted into electrical energy; as it is used up, the battery is discharged.

In the simplest case, a lead battery is made up of two lattice lead plates, the cells of which are filled with a doughy mixture of lead oxide and water. The plates are immersed in a rectangular glass jar filled with dilute sulfuric acid b.p. weight 1.15-1.20 (22-28% H 2 SO 4).

Due to the reaction

PbO + H 2 SO 4 \u003d PbSO 4 + H 2 O

lead oxide turns after some time into sulfate. If we now pass a direct current through the device, connecting one plate to the negative and the other to the positive pole of the current source, the battery will be charged, and the following processes will occur at the electrodes:

Adding these equations, we get the general equation for the reaction that occurs when the battery is charged:

2PbSO 4 + 2H 2 O \u003d Pb + PbO 2 + 4H + 2SO 4 "

Thus, as current is passed, sulfuric acid is converted at the cathode into a loose mass of metallic lead, and at the anode into dark brown lead dioxide.

When this process is completed, the battery is charged. The end of charging is indicated by the beginning of vigorous decomposition of water: it is released at the cathode, at the anode - (the battery “boils”).

When the plates of a charged battery are connected by a conductor, a current appears in the latter, and the electrons move from the plate coated with lead to the plate coated with lead dioxide. The occurrence of current is explained as follows. From the lead-coated plate, part of the Pb ++ ions goes into solution, as a result of which the plate is charged negatively. The electrons released from the lead plate pass to PbO 2 and restore the tetravalent to bivalent. As a result, Pb ions are formed at both plates, which combine with SO 4 ions in solution into insoluble lead sulfate, and the battery is discharged.

The processes that occur when the battery is discharged are conveyed by the following scheme:

Having added the written equations, it is easy to make sure that the reaction that occurs when the battery is discharged is the opposite of the one that took place when it was charged. Therefore, both processes can be expressed by one equation:

charger

2PbSO 4 + 2H 2 O ⇄ Pb + Pb0 2 + 4H + 2SO 4 "

discharge

When the battery is discharged, the concentration of sulfuric acid decreases, since H and SO 4 ions are consumed and formed. Therefore, the degree of discharge of the battery can be judged by the specific gravity of the acid, measuring it with a hydrometer.

The lead battery voltage is 2 volts andnormal load remains almost unchanged during its operation. If the voltage starts to drop, the battery needs to be charged again.

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With the widespread introduction of maintenance-free batteries, many motorists have already forgotten what it means to charge their battery. And when they still have to do this procedure, to their surprise they find a boiling battery. Why this happens and how to avoid it, we will analyze in this article.

The modern battery was invented in the 19th century, and during this time it has not undergone significant changes.

Still, the principle of operation of the battery is based on the oxidation of lead in an aqueous solution of sulfuric acid. At the same time, at the moment of discharging the battery, the metal lead of the electrodes turns into lead sulfate.

When charging, the reverse process occurs. These are the main reactions on the basis of which the accumulation and return of electrical energy occurs. However, in addition to them, 60 different reactions occur in the battery banks.

The general arrangement of the battery is shown in the figure above. In explanation to it, it should be noted that the lead plates are made in the form of a grid, the cells of which are filled in the positive electrodes with lead dioxide (PbO2) in the form of a powder, in the negative electrodes - with lead, also in powder form.

In the gap between the main plates there are other plates of porous plastic that do not interact with the acid, which separate the electrodes and prevent them from shorting.

So, when charging the battery, lead sulfate passes into the category of pure metal, while water is consumed and sulfuric acid is formed. As a result, the density of the electrolyte increases.

What is considered battery boiling?

This process follows directly from the charging process. As described above, lead sulfate is consumed during charging, and when the amount of sulfate becomes less, a certain critical level, the process of water electrolysis begins.

This process releases hydrogen and oxygen, which are known to be gases. And the whole process, outwardly, resembles boiling.

How to properly charge the battery to avoid this unpleasant process? Further on this in more detail.

How to properly charge the battery

Today, there are two main ways to charge a battery, and we will describe both of them.

It is worth remembering that a special charger with the ability to change the charging current is used for charging.

Low current charging

With this method, you must select a charging current with a voltage equal to 0.1 of the battery capacity.

That is, if you have the most common battery with a capacity of 60 amperes / hour, then the charging current should be a voltage of 6 amperes.

Charging the battery in this way takes about a day. The fact that charging is completed, you will know by the beginning of the battery boil.

High current charging

Charging should be started with a voltage of 14.5 volts, after the battery stops taking charge, it will be charged somewhere around 80%. To bring charging to 90% capacity, the charging voltage must be raised to 15 volts.

Well, the last stage is bringing the charge to 100%. It is carried out by adding voltage up to 16.5 V.

It is worth noting that with this method, you need to not only constantly monitor the battery, but also have a professional charger.

In what cases will the battery start to boil

As already mentioned above, the boiling of the electrolyte is not quite boiling, in the usual sense, it is just a figure of speech.

This expression is called the process of gas evolution from the electrolyte, which occurs when the battery is charged. There is nothing terrible in this process, however, by the way it happens, you can assess the condition of the battery.

If this process began immediately after the start of charging, then this is a very bad signal. With a higher probability, we can say that the battery has already worked out its resource.

Boiling at the end of the battery life. In this case, boiling starts immediately when the charger is connected. In this case, the process usually does not begin in all, but only in some banks. This may indicate that there are short-circuited plates in these banks. In this case, you cannot save the battery, and it's time to change it.
Boiling when the battery is fully charged. If boiling starts after a long time, after 8 hours or more, then this is normal. This indicates that the density of the electrolyte has already risen to the standard value and the battery is charged. In this case, you just need to stop charging the battery.

Why does a car battery boil?

If the battery boiling during charging is most often a normal process and does not indicate anything bad, then boiling on a running engine is definitely bad.

Such a moment indicates a malfunction in the electrical equipment of the car.

Below we will consider in what cases the battery boils on a running engine.

Methods for determining a boiling battery

If your battery is serviced, then this process is easiest to determine visually. For example, as shown in the video below:

If you have the most common today, maintenance-free battery, then the boiling process can be determined by indirect signs.

The first most common sign of boiling is the appearance of a greenish coating and abundant oxides on the battery terminals, such as those shown in the figure below;

Another sign of boiling is the smell of electrolyte that has appeared in the engine compartment. It is sharp enough that even people without an acute sense of smell can hear it;
Another sign may be the appearance of rust on the hood in the area of \u200b\u200bthe battery and severe corrosion of the under-battery shelf;
There are also exotic ways to determine the boiling process. Some drivers, when a boiling battery is suspected, connect a balloon or condom to its vent tube. If the battery is boiling, it will begin to inflate;
Another exotic way is to use a medical stethoscope. If it is applied to a boiling jar, then a characteristic gurgling can be heard;

Causes of battery boiling on a car

The most common cause of a battery boiling on a running engine is a short circuit in one of the cans.

Unfortunately, this is a sign that the battery in the car has failed. It is worth noting that recently this has begun to happen not only on old batteries, but also on relatively fresh ones.

Very often, the banks close from the vibration of the power unit. Or because of, banal, the marriage of the device. So if you bought a new battery, then take care of the warranty for it.

Well, when the warranty period comes to an end, conduct its comprehensive testing. Perhaps this will help you save money that you spend on buying a new battery.

The second most common problem is when overcharging occurs.

Recharging is the process of charging from the generator with currents whose voltage is higher than the standard ones.

This is usually due to a faulty car alternator. Usually, the nominal charging voltage from the generator should not exceed 14.5 volts.

It can be more in cases where the voltage regulator on the generator is faulty. This malfunction is eliminated by repairing the generator.

On old batteries, the recharging process can occur not only when the plates in the bank are shorted, but also when the plates are sulphated.

Sulfation is a chemical process that forms lead sulfate on the surface of the plates.

In older batteries, lead sulfate accumulates so much that the charging current decreases. In this case, if the generator continues to produce a voltage of 14.5 V, the battery begins to boil.

Another common cause, especially if the battery is no longer new, is a heavy load on the battery.

That is, if you have a lot of electrical consumers and all of them are turned on, for example, high beams, air conditioning, wipers and others, and the battery is not the first freshness, then it will not cope with the load and will heat up and boil.

Well, the least common cause, but not so rare, is insufficient battery ventilation. This happens if the battery vent is clogged or due to the use of a non-standard battery, there is not enough space near it for ventilation.

Actually, these are all the main reasons for battery boiling.

Prevention of electrolyte boiling on a running engine

In order for your battery to last as long as possible, you need to follow simple and simple rules for preventing electrolyte boiling:

First of all, in the summer, check the electrolyte level in serviced batteries.
It must be remembered that the plates must always be covered with electrolyte. And if the level drops, then you just need to add distilled water. You need to know that ordinary water cannot be added to the battery.
In addition, regularly visually check the condition of the device. It should be clean, and there should be no plaque on the terminals.
And finally, when visiting service stations, do not be too lazy to ask to check the charging current that the car's generator produces.

That's all, good luck on the roads and never break down.

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

Primary chemical current sources or galvanic cells;

Secondary sources or electric accumulators.

Primary sources allow only a single use, since the substances formed during their discharge cannot be converted into the original active materials. A completely discharged galvanic cell, as a rule, is unsuitable for further work - it is an irreversible source of energy.

Secondary chemical current sources are reversible sources of energy - after an arbitrarily deep discharge, their performance can be fully restored by charging. To do this, it is enough to pass an electric current through the secondary source in the opposite direction to that in which it flowed during the discharge. During the charging process, the substances formed during the discharge will turn into the original active materials. This is how the free energy of a chemical current source is repeatedly converted into electrical energy (battery discharge) and the reverse conversion of electrical energy into free energy of a chemical current source (battery charge).

The passage of current through electrochemical systems is associated with the chemical reactions (transformations) occurring in this case. Therefore, between the amount of a substance that entered into an electrochemical reaction and underwent transformations, and the amount of electricity spent or released in this case, there is a relationship that was established by Michael Faraday.

The appearance of a potential difference is explained by the fact that the electrode substance dissolves in the electrolyte under the action of chemical forces (for example, zinc in a solution of sulfuric acid) and its positive ions pass into the electrolyte. By placing two electrodes of equal metals in the electrolyte, we obtain between them the difference in electrode potentials - the external EMF E = φ1-φ2- Therefore, a device consisting of two dissimilar electrodes placed in an electrolyte is a power source - a galvanic or primary cell in which the process of converting (irreversible) chemical energy into electrical energy takes place.

Dry and bulk manganese-zinc elements are widely used. By design, they are divided into glass and biscuit. In the element of the glass design, the zinc electrode has the shape of a glass, inside of which there is a positive electrode - a carbon rod. The carbon electrode is surrounded by a depolarizer of manganese dioxide, graphite and carbon black. The zinc glass is filled with an electrolyte - an aqueous solution of ammonium chloride (ammonia) with the addition of starch as a thickener. The electromotive force of the element is E=1.5 V. The rated discharge current of the element is the highest continuous current allowed during its operation. The capacity of the cell is the amount of electricity, expressed in ampere-hours (A h), that can be obtained from the cell for the entire period of its operation. Both individual elements and batteries assembled from them are widely used in radio engineering, wired communication equipment, for flashlights, hearing aids, etc.

Batteries(secondary elements). Galvanic cells, in which, after their discharge, a reverse charging process is possible with the conversion of electrical energy into chemical energy, are called batteries or secondary cells.

The alkaline battery got its name from the electrolyte - alkali, namely, a 21% aqueous solution of caustic potassium KOH or sodium hydroxide NaOH. The battery consists of two blocks - plates, located in a steel vessel with electrolyte. Plates are steel frames with steel boxes inserted into them filled with active mass. The active mass of the negative plates of cadmium-nickel elements consists of sponge cadmium, and those of iron-nickel elements consist of sponge iron. The active mass of the positive plates in both batteries consists of nickel oxide hydrate Ni(OH)3.

When discharging, nickel oxide hydrate passes into nickel oxide hydrate, and spongy cadmium (iron) - into nickel oxide hydrate. The chemical reaction during discharge is expressed by the equation:

2Ni(OH)3 + 2KOH + Cd ->- 3Ni(OH)2 + 2KOН + Cd(OH)2.

When charging, the reaction goes in the opposite direction and, therefore, the active mass of the electrodes is restored. The electrolyte concentration during discharging and charging remains unchanged. When discharging, the voltage from 1.4 V first rapidly decreases to 1.3 V, and then slowly to 1.15 V; at this voltage, the discharge must be stopped. When charging, the voltage quickly increases from 1.15 V to 1.75 V, and then, after a slight decrease, slowly increases to 1.85 V. In addition to alkaline, acid / lead) batteries are also widely used.

1. Copper, iron, and nickel wires of the same length and cross-sectional area were soldered (in series) and included in the circuit. Which

Will the wire give off more heat? Why? (copper resistivity 0.017 ohm x mm2/m, iron 0.10 ohm x mm2/m, nickeline 0.40 ohm x mm2/m.)

2. A nichrome spiral 5 m long and with a cross-sectional area of 0.5 mm2 is connected to a 110 V voltage network. Find the current power in the spiral. (Resistivity of nichrome 1.1 Ohm x mm2/m.)

3. An 800 W hotplate is switched on for 5 hours. Determine the energy consumption (in watt-hours and kilowatt-hours).

4. What kind of energy conversion occurs during the operation of an electric current generator?

1. On which method of heat transfer is the heating of solids based? A. Thermal conductivity.B. Convection.B.Radiation.2. What kind of heat transfer

accompanied by the transfer of matter? A. Thermal conductivity. B. Radiation.B.Convection.3. Which of the following substances has the highest thermal conductivity? A. Fur. B. Tree. B. Steel. 4. Which of the following substances has the lowest thermal conductivity? A. Sawdust. B. Lead. B. Copper.5. Name a possible method of heat transfer between bodies separated by airless space. A. Thermal conductivity. B. Convection. B. Radiation. 6. A metal handle and a wooden door will feel the same heat to the touch at a temperature... below body temperature. B. equal to body temperature. 7. What happens to the temperature of a body if it absorbs as much energy as it emits? The body cools down.B. Body temperature does not change.8. Which of the ways heat transfer occurs in liquids? A. Thermal conductivity. B. Convection.B.Radiation.9. Which of the following substances has the least A. Air. B. Cast iron. B. Aluminum10. The specific heat capacity of water is 4200 (J / kg * 0С). This means that ... A. to heat water of mass 4200 kg by 1 ° C, an amount of heat equal to 1 J.B. is required. heating water weighing 1 kg by 4200 ° C requires an amount of heat equal to 1 J.B. heating water weighing 1 kg by 1 ° C requires if11. complete combustion of the fuel.B. with complete combustion of fuel weighing 1 kg.12. Evaporation occurs... A. at any temperature. B. at the boiling point.B.at a specific temperature for each liquid.13. In the presence of wind, evaporation occurs...A.faster.B. slower.B. with the same speed as in its absence.14. Can the efficiency of a heat engine become 100% if the friction between the moving parts of this machine is reduced to zero? A. Yes. B. No.15. From which pole of the magnet do the magnetic field lines come out? A. From the north. B. From the south. B. From both poles.16. To the ball of an uncharged electroscope bring, without touching it, body-charged with a negative charge. What charge will the leaves of the electroscope acquire? A. Negative. B. Positive. B. None.17. Can an atom of hydrogen or any other substance change its charge by 1.5 electron charges? A. Yes. B. No.18. What image is obtained on the human retina? A. Enlarged, real, inverted. B. Reduced, real, inverted. Enlarged, imaginary, direct.G. Reduced, imaginary, direct.19. What does the ammeter measure? A) The electrical resistance of conductors B) The voltage at the poles of the current source or in some part of the circuit Diffusion is: A) The process of increasing the temperature B) The phenomenon in which the molecules of one substance interpenetrate between the molecules of another C) The phenomenon in which the body passes from the state of a solid to the state of a liquid D) The process of increasing the density of a body21. Efficiency formula:A) ŋ= An* 100%AɜB) ŋ= Aɜ * 100%AnB) ŋ= An * Aɜ100%D) ŋ= An * Aɜ * 100%22. What does the law of Archimedes say? A) The buoyant force acting on a body immersed in a liquid is equal to the weight of the liquid displaced by this body B) The buoyant force acting on a body immersed in a liquid is equal to the speed of this body immersed in a liquid C) The buoyant force acting on a body immersed in a liquid , is equal to the density of this body D) The buoyant force acting on a body immersed in a liquid is equal to the weight of this body23. What a day) warm24. Inside A) only B) only C) only G) from those 25. Which of the following substances are conductors? a) rubber; b) copper, c) plastic; d) glass.26. The body is electrified only when it ...... charge. a) acquires; b) loses; c) acquires or loses.27. Which of the following substances are dielectrics? a) rubber; b) copper; c) sulfuric acid solution; d) steel.28. Likely charged bodies ......., and oppositely charged - .........a) ... repel, ... attract, b) ... attract, ... repel.29. Electric current is called ... A. Movement of electrons along a conductor.B. Ordered motion of electrons along a conductor.V. Ordered motion of protons along a conductor.G. Ordered motion of charged particles.D. The movement of electric charges along the conductor.30. What kind of energy transformation occurs during the operation of an electric coffee grinder? Electric energy is converted ... A. In the chemical B. In mechanical. B. Into the light. D. Into the inner

What transformation of energy occurs during the operation of electric current, when an advertising neon lamp is lit? Electrical energy is converted into...

A. Chemical
B. Mechanical
V. Light
G. Internal

1) Under what conditions is only a penumbra obtained from an object? 2) What is the difference

between radiation, created radiator central heating, and radiation burning candle?

3) what kind of energy transformations occur when a flashlight lamp is lit?

4) In what material medium does light travel at the highest speed?

5) Why are shadows never completely dark even with one light source?

6) Why is it bright in the room even when direct sunlight does not enter its windows?

7) why are beams of car headlights visible in fog, in dusty air?

8) Why do we not see the faces of the athlete-fencer looking through the fine mesh, but the fencer sees all the objects through the mesh well?

10) Why is mirror glass ground and polished with special care?

11) beam incidence angle=60. What is the angle of reflection of the beam?

12) Beam incidence angle-25. What is the angle between the incident and reflected rays?

13) The angle between the incident and reflected rays is 50. At what angle does the light fall on the mirror?

Guys, please help)

Batteries are otherwise called secondary cells, or secondary sources of electrical energy. They differ from galvanic cells in that they cannot give off energy immediately after manufacture, they must first be charged.

When the battery is charged, electrolysis occurs (the breakdown of electrolyte molecules into positive and negative ions, called cations and anions), accompanied by the conversion of electrical energy into chemical energy. As a result of this process, an emf is created at the battery terminals. After charging, the battery can serve as a power source. During battery discharge, stored chemical energy is converted into electrical energy. Thus, the battery stores (accumulates) electrical energy when charging and gives it away when discharging.

Acid batteries

Acid batteries are widely used both for powering radio and telephone equipment, and for powering electrical equipment of vehicles.

An acid battery element consists of a vessel filled with electrolyte, in which there are positive and negative electrodes (in the form of plates) separated from one another. Separate cells, called banks, are combined into rechargeable batteries, which are called batteries for short. The acid battery device is shown in fig. 28. The case of an acid battery is made of electrically insulating and acid-resistant material (glass, ebonite and special grades of plastic).

The positive plates of acid batteries are made from red lead pressed into a lead grid (lead oxide with a slightly higher oxygen content). Negative plates are made from lead litharge (lead oxide) pressed into a lead grid.

The plates are separated from one another by a porous insulating gasket to avoid short circuits - a separator. For the manufacture of separators, wood (alder, pine, cedar), hard rubber with microscopic pores (called mipore), microporous plastic (miplast), etc. are used.

The electrolyte is a solution of sulfuric acid in distilled water. Depending on the ambient temperature during battery operation, the density of the electrolyte should be different.

The density of the electrolyte is measured with a hydrometer, which is a small tube expanding downwards. In the lower part of the hydrometer there is a strictly defined amount of weight, and the upper part has a scale, the divisions of which show the density. When the hydrometer is lowered into the electrolyte, it is immersed to the division that corresponds to the density of the electrolyte.

New factory batteries are sold uncharged, and the duration of their operation depends on the correctness of their first charge. A new battery should be filled with electrolyte with a density of 1.12 at a temperature of +20 ° C and left for five to six hours so that the active mass of the plates is saturated with electrolyte. Filling is done through a funnel into a special filling hole. The electrolyte level should be 10-15 mm above the top edge of the plates.

To prepare the electrolyte, industrial sulfuric acid with a density of 1.83-1.84 is used, which is diluted with distilled water. Concentrated sulfuric acid is highly toxic and must be handled with care. The electrolyte is made in the following sequence. The required amount of distilled water is poured into a glass vessel, and then sulfuric acid is poured into the water in a thin stream and in small portions from the bottle, stirring the solution with a glass rod.

It is strictly forbidden to pour water into sulfuric acid, as this begins a violent boil and splashing of the acid in all directions. Drops of acid on hands and face can cause severe burns.

The battery is charged by direct current from a direct current network or a special rectifier.

The rectifier must be equipped with a rheostat or an autotransformer that allows you to change the amount of charging current. The battery is included in the charging circuit as follows: the positive terminal of the battery (+) is connected to the plus of the rectifier (network), and the negative terminal (-) to the minus of the rectifier (network). Charging the battery is shown in fig. 29.

An ammeter is included in the charge circuit to control the amount of current.

The batteries are charged with a current, the value of which is indicated by the manufacturer in the technical data sheet (for stationary batteries, the value of the charging current is equal to one fifteenth of the battery capacity).

The first charge usually lasts continuously for 36 hours. After that, they take a break for 3 hours and continue charging with the same current for another 12 hours. By the end of charging, the electrolyte "boils" (there is an abundant release of gas bubbles - hydrogen and oxygen), and the electrolyte level can rise significantly. Excess electrolyte should be sucked off with a rubber bulb.

When the voltage at the terminals of one bank rises to 2.3-2.5 V, the density of the electrolyte should be measured and brought to a value of 1.285.

After charging is completed, the new battery should be discharged with a current equal to one twentieth of the battery capacity until the voltage on each bank becomes 1.8 e. Then the battery is charged for 10-12 hours and after that it can be put into operation. The voltage on each bank of a freshly charged battery is 2.6-2.86 V. The voltage on the bank should be measured with a special voltmeter equipped with a load resistance, called a battery probe. In order to prevent the explosion of explosive gas generated during charging as a result of electrolysis of water, you can use the probe no earlier than two to three hours after charging.

The battery voltage can be measured with a conventional DC voltmeter when the battery is loaded with a current equal to Vio of its capacity.

Depending on the purpose, there are several types of acid (lead) batteries. To power stationary devices, stationary batteries are used, the body of which is usually made of glass or wood lined with a layer of lead.