Galvanic elements. Types and device. Work and features. Galvanic cells and batteries - device, principle of operation, types What applies to galvanic batteries - energy storage devices

Prerequisites for the emergence of galvanic cells. A little history. In 1786, the Italian professor of medicine, physiologist Luigi Aloisio Galvani discovered an interesting phenomenon: the muscles of the hind legs of a freshly opened frog corpse, suspended on copper hooks, contracted when the scientist touched them with a steel scalpel. Galvani immediately concluded that this was a manifestation of “animal electricity.”

After Galvani's death, his contemporary Alessandro Volta, being a chemist and physicist, would describe and publicly demonstrate a more realistic mechanism for the generation of electric current when different metals come into contact.

Volta, after a series of experiments, will come to the unequivocal conclusion that current appears in the circuit due to the presence in it of two conductors of different metals placed in a liquid, and this is not “animal electricity” at all, as Galvani thought. The twitching of the frog's legs was a consequence of the action of current generated by the contact of different metals (copper hooks and a steel scalpel).

Volta will show the same phenomena that Galvani demonstrated on a dead frog, but on a completely inanimate homemade electrometer, and will give in 1800 a precise explanation for the occurrence of current: “a conductor of the second class (liquid) is in the middle and is in contact with two conductors of the first class from two different metals... As a result, an electric current arises in one direction or another.”

In one of his first experiments, Volta dipped two plates - zinc and copper - into a jar of acid and connected them with wire. After this, the zinc plate began to dissolve, and gas bubbles appeared on the copper steel. Volta suggested and proved that an electric current flows through a wire.

This is how the “Volta element” was invented - the first galvanic cell. For convenience, Volta gave it the shape of a vertical cylinder (column), consisting of interconnected rings of zinc, copper and cloth, soaked in acid. A voltaic column half a meter high created a voltage that was sensitive to humans.

Since the research was started by Luigi Galvani, the name retained the memory of him in its name.

Galvanic cell is a chemical source of electric current based on the interaction of two metals and/or their oxides in an electrolyte, leading to the appearance of electric current in a closed circuit. Thus, in galvanic cells, chemical energy is converted into electrical energy.

Galvanic cells today

Galvanic cells today are called batteries. Three types of batteries are widely used: salt (dry), alkaline (they are also called alkaline, “alkaline” translated from English as “alkaline”) and lithium. The principle of their operation is the same as described by Volta in 1800: two metals, and an electric current arises in an external closed circuit.

The voltage of the battery depends both on the metals used and on the number of elements in the “battery”. Batteries, unlike accumulators, are not capable of restoring their properties, since they directly convert chemical energy, that is, the energy of the reagents that make up the battery (reducing agent and oxidizing agent), into electrical energy.

The reagents included in the battery are consumed during its operation, and the current gradually decreases, so the effect of the source ends after the reagents have reacted completely.

Alkaline and salt cells (batteries) are widely used to power a variety of electronic devices, radio equipment, toys, and lithium can most often be found in portable medical devices such as glucometers or in digital equipment such as cameras.

Manganese-zinc cells, which are called salt batteries, are “dry” galvanic cells that do not contain a liquid electrolyte solution.

The zinc electrode (+) is a glass-shaped cathode, and the anode is a powdered mixture of manganese dioxide and graphite. Current flows through the graphite rod. The electrolyte is a paste of ammonium chloride solution with the addition of starch or flour to thicken it so that nothing flows.

Typically, battery manufacturers do not indicate the exact composition of salt cells, however, salt batteries are the cheapest, they are usually used in devices where power consumption is extremely low: in watches, in remote controls remote control, in electronic thermometers, etc.

The concept of “nominal capacity” is rarely used to characterize zinc-manganese batteries, since their capacity greatly depends on operating modes and conditions. The main disadvantages of these elements are the significant rate of voltage decrease throughout the discharge and a significant decrease in the delivered capacity with increasing discharge current. The final discharge voltage is set depending on the load in the range of 0.7-1.0 V.

Not only the magnitude of the discharge current is important, but also the time schedule of the load. With intermittent discharge at high and medium currents, the performance of the batteries increases noticeably compared to continuous operation. However, at low discharge currents and months-long breaks in operation, their capacity may decrease as a result of self-discharge.

The graph above shows the discharge curves for an average salt battery for 4, 10, 20 and 40 hours for comparison with the alkaline battery, about which we'll talk Further.

An alkaline battery is a manganese-zinc voltaic battery that uses manganese dioxide as the cathode, powdered zinc as the anode, and an alkali solution, usually in the form of potassium hydroxide paste, as the electrolyte.

These batteries have a number of advantages (in particular, significantly higher capacity, best job at low temperatures and at high load currents).

Alkaline batteries, compared to salt batteries, can provide more current for a longer period of time. A higher current becomes possible because zinc is used here not in the form of a glass, but in the form of a powder that has a larger area of ​​​​contact with the electrolyte. Potassium hydroxide in the form of a paste is used as an electrolyte.

It is thanks to the ability of this type of galvanic cells to deliver significant current (up to 1 A) for a long time that alkaline batteries are most common today.

Electric toys, portable medical equipment, electronic devices, and cameras all use alkaline batteries. They last 1.5 times longer than salt ones if the discharge is low current. The graph shows the discharge curves at various currents for comparison with a salt battery (the graph was shown above) for 4, 10, 20 and 40 hours.

Lithium batteries

Another fairly common type of voltaic cell is lithium batteries - single non-rechargeable voltaic cells that use lithium or its compounds as the anode. Thanks to the use of alkali metal, they have a high potential difference.

The cathode and electrolyte of a lithium cell can be very different, so the term "lithium cell" combines a group of cells with the same anode material. For example, manganese dioxide, carbon monofluoride, pyrite, thionyl chloride, etc. can be used as a cathode.

Lithium batteries differ from other batteries in their long service life and high cost. Depending on the size chosen and the chemistries used, a lithium battery can produce voltages from 1.5 V (compatible with alkaline batteries) to 3.7 V.

These batteries have the highest capacity per unit weight and a long shelf life. Lithium cells are widely used in modern portable electronic equipment: to power watches motherboards computers, for powering portable medical devices, wristwatches, calculators, photographic equipment, etc.

The graph above shows the discharge curves for two lithium batteries from two popular manufacturers. The initial current was 120 mA (per resistor of about 24 Ohms).

Kyzyl, TSU

ABSTRACT

Topic: "Galvanic cells. Batteries."

Compiled by: Spiridonova V.A.

I year, IV gr., FMF

Checked by: Kendivan O.D.

2001

I. Introduction

II. Galvanic current sources

1. Types of galvanic cells

III. Batteries

1. Acidic

2. Alkaline

3. Sealed nickel-cadmium

4. Sealed

5. “DRYFIT” technology batteries

INTRODUCTION

Chemical current sources (CHS) for many years

firmly entered into our lives. In everyday life, the consumer rarely pays attention to

attention to the differences between the HIT used. For him these are batteries and

batteries. They are typically used in devices such as

flashlights, toys, radios or cars.

In the case where the power consumption is relatively

is large (10Ah), batteries are used, mainly acid ones,

as well as nickel-iron and nickel-cadmium. They are used in

portable computers (Laptop, Notebook, Palmtop), wearable devices

communications, emergency lighting, etc.

In recent years, such batteries have been widely used in

backup power supplies for computers and electromechanical

systems that store energy for possible peak loads

and emergency power supply of vital systems.

GALVANIC CURRENT SOURCES

Disposable galvanic current sources

are a unified container in which

contains an electrolyte absorbed by the active material

separator, and electrodes (anode and cathode), which is why they are called

dry elements. This term is used in relation to

all cells that do not contain liquid electrolyte. To ordinary

Dry elements include carbon-zinc elements.

Dry cells are used for low currents and intermittent

operating modes. Therefore, such elements are widely used in

telephones, toys, alarm systems, etc.

The action of any galvanic cell is based on the occurrence of a redox reaction in it. In its simplest form, a galvanic cell consists of two plates or rods made of different metals and immersed in an electrolyte solution. Such a system makes it possible to spatially separate the redox reaction: oxidation occurs on one metal, and reduction occurs on another. Thus, electrons are transferred from the reducing agent to the oxidizing agent through the external circuit.

Consider, as an example, a copper-zinc galvanic cell, powered by the energy of the above reaction between zinc and copper sulfate. This cell (Jacobi-Daniel cell) consists of a copper plate immersed in a copper sulfate solution (copper electrode) and a zinc plate immersed in a zinc sulfate solution (zinc electrode). Both solutions are in contact with each other, but to prevent mixing they are separated by a partition made of porous material.

When the element is operating, i.e. when the chain is closed, zinc is oxidized: on the surface of its contact with the solution, zinc atoms turn into ions and, when hydrated, pass into the solution. The electrons released in this case move along the external circuit to the copper electrode. The entire set of these processes is schematically represented by the half-reaction equation, or electrochemical equation:

Reduction of copper ions occurs at the copper electrode. The electrons coming here from the zinc electrode combine with the dehydrating copper ions coming out of the solution; copper atoms are formed and released as metal. The corresponding electrochemical equation is:

The total equation of the reaction occurring in the element is obtained by adding the equations of both half-reactions. Thus, during the operation of a galvanic cell, electrons from the reducing agent pass to the oxidizing agent through the external circuit, electrochemical processes take place at the electrodes, and directional movement of ions is observed in the solution.

The electrode at which oxidation occurs is called anode (zinc). The electrode at which reduction occurs is called the cathode (copper).

In principle, any redox reaction can produce electrical energy. However, the number of reactions

practically used in chemical sources of electrical energy is small. This is due to the fact that not every redox reaction makes it possible to create a galvanic cell with technically valuable properties. In addition, many redox reactions require the consumption of expensive substances.

Unlike the copper-zinc cell, all modern galvanic cells and batteries use not two, but one electrolyte; Such current sources are much more convenient to use.

TYPES OF GALVANIC CELLS

Carbon-zinc elements

Coal-zinc elements (manganese-zinc) are

the most common dry elements. In coal-zinc

elements use a passive (carbon) current collector in

contact with an anode made of manganese dioxide (MnO2), electrolyte made of

ammonium chloride and a zinc cathode. The electrolyte is in

paste form or impregnates a porous diaphragm.

Such an electrolyte is not very mobile and does not spread, so

the elements are called dry.

Coal-zinc elements are “restored” during

break from work. This phenomenon is due to the gradual

alignment of local inhomogeneities in the composition

electrolyte arising during the discharge process. As a result

periodic "rest" the service life of the element is extended.

The advantage of carbon-zinc elements is their

relatively low cost. To significant disadvantages

should include a significant decrease in voltage during discharge,

low specific power (5...10 W/kg) and short service life

storage

Low temperatures reduce efficiency of use

galvanic cells, and the internal heating of the battery

increases. An increase in temperature causes chemical corrosion of the zinc electrode by the water contained in the electrolyte and drying out of the electrolyte. These factors can be somewhat compensated for by keeping the battery at elevated temperatures and introducing a saline solution into the cell through a pre-made hole.

Alkaline elements

Like carbon-zinc cells, alkaline cells use a MnO2 anode and a zinc cathode with a separated electrolyte.

The difference between alkaline elements and carbon-zinc elements is

in the use of an alkaline electrolyte, as a result of which

There is virtually no gas evolution during discharge, and they can be

be sealed, which is very important for a number of them

applications.

Mercury elements

Mercury elements are very similar to alkaline elements. In them

Mercury oxide (HgO) is used. The cathode consists of a mixture of powder

zinc and mercury. The anode and cathode are separated by a separator and a diaphragm,

soaked in 40% alkali solution.

Since mercury is scarce and toxic, mercury elements are not

should be thrown away after they have been completely used. They have to

go for recycling.

Silver elements

They have "silver" cathodes made of Ag2O and AgO.

Lithium cells

They use lithium anodes, an organic electrolyte

and cathodes made of various materials. They have very large

shelf life, high energy densities and efficient

over a wide temperature range because they do not contain water.

Since lithium has the highest negative potential

in relation to all metals, lithium elements

characterized by the highest rated voltage at

minimum dimensions.

Ionic conductivity is ensured by introducing into

Solvents of salts having large anions.

The disadvantages of lithium cells include their

relatively high cost due to high price

lithium, special requirements for their production (the need

inert atmosphere, purification of non-aqueous solvents). Should

Also take into account that some lithium cells when they

are explosive if opened.

Lithium cells are widely used in backup power supplies for memory circuits, measuring instruments and other high-tech systems.

BATTERIES

Batteries are chemical sources

reusable electrical energy. They consist of

two electrodes (positive and negative), electrolyte

and hulls. The accumulation of energy in the battery occurs when

the occurrence of a chemical oxidation-reduction reaction

electrodes. When the battery is discharged, the reverse occurs

processes. Battery voltage is the potential difference

between the battery poles at a fixed load.

To obtain sufficiently large voltage values ​​or

charging, individual batteries are connected to each other

series or parallel to batteries. There are a number

generally accepted voltages for batteries: 2; 4; 6;

We will limit ourselves to considering the following batteries:

acid batteries made according to traditional

technologies;

stationary lead and drive (automotive and

tractor);

sealed maintenance-free batteries, sealed

nickel-cadmium and acid "dryfit" A400 and A500 (jelly-like

electrolyte).

ACID BATTERIES

As an example, consider a ready-to-use lead-acid battery. It consists of lattice lead plates, some of which are filled with lead dioxide and others with metal sponge lead. The plates are immersed in a 35-40% H2SO4 solution; at this concentration, the specific electrical conductivity of the sulfuric acid solution is maximum.

When the battery is operating - when it is discharged - an oxidation-reduction reaction occurs in it, during which the metal lead is oxidized:

Pb + SO4= PbSO4 + 2e-

And lead dioxide is reduced:

Pb + SO4 + 4H+ + 2e- = PbSO4 + 2H2O

Electrons given up by metallic lead atoms during oxidation are accepted by lead atoms PbO2 during reduction; electrons are transferred from one electrode to another through an external circuit.

Thus, lead metal serves as the anode in a lead battery and is negatively charged, and PbO2 serves as the cathode and is positively charged.

In the internal circuit (in the H2SO4 solution), ion transfer occurs during battery operation. SO42 ions move towards the anode, and H+ ions move towards the cathode. The direction of this movement is determined by the electric field resulting from the occurrence of electrode processes: anions are consumed at the anode, and cations are consumed at the cathode. As a result, the solution remains electrically neutral.

If we add up the equations corresponding to the oxidation of lead and the reduction of PbO2, we obtain the total reaction equation,

leaking in a lead-acid battery during its operation (discharge):

Pb + PbO2 + 4H+ + 2SO4 = 2PbSO4 + 2H2O

E.m.f. of a charged lead-acid battery is approximately 2V. As a battery discharges, its cathode (PbO2) and anode (Pb) materials are consumed. Sulfuric acid is also consumed. At the same time, the voltage at the battery terminals drops. When it becomes less than the value allowed by operating conditions, the battery is charged again.

To charge (or charge), the battery is connected to external source current (plus to plus and minus to minus). In this case, current flows through the battery in the direction opposite to that in which it passed when the battery was discharged. As a result of this, the electrochemical processes on the electrodes are “reversed”. The lead electrode now undergoes a reduction process

PbSO4 + 2e- = Pb + SO4

those. This electrode becomes the cathode. Oxidation process occurs on the PbO2 electrode

PbSO4 + 2H2O = PbO2 + 4H+ + 2e-

therefore this electrode is now the anode. The ions in the solution move in directions opposite to those in which they moved when the battery was operating.

Adding the last two equations, we obtain the equation for the reaction that occurs when charging the battery:

2PbSO4 + 2H2O = Pb + PbO2 + 4H+ + 2SO4

It is easy to see that this process is the opposite of the one that occurs when the battery is in operation: when the battery is charged, it again produces the substances necessary for its operation.

Lead-acid batteries are usually connected into a battery, which

placed in a monoblock made of ebonite, thermoplastic, polypropylene,

polystyrene, polyethylene, asphalt pitch composition, ceramics

or glass.

One of the most important characteristics of a battery is

service life or service life (number of cycles). Deterioration

battery parameters and failure are caused primarily

queue of lattice corrosion and sliding of the active mass

positive electrode. Battery life is determined

primarily by the type of positive plates and conditions

operation.

Improvements in lead-acid batteries are on track

researching new alloys for grilles (for example, lead-calcium), lightweight and durable housing materials

(for example, based on propylene-ethylene copolymer), improvements

quality of separators.

ALKALINE BATTERIES

Silver-zinc.

They have good electrical characteristics and are light in weight and volume. The electrodes in them are silver oxides Ag2O, AgO (cathode) and sponge zinc (anode); The electrolyte is a KOH solution.

During battery operation, zinc is oxidized, turning into ZnO and Zn(OH)2, and silver oxide is reduced to metal. The overall reaction that occurs when a battery is discharged can be approximately expressed by the equation:

AgO + Zn = Ag + ZnO

E.m.f. of a charged silver-zinc battery is approximately 1.85 V. When the voltage drops to 1.25 V, the battery is charged. In this case, the processes on the electrodes are “reversed”: zinc is reduced, silver is oxidized - the substances necessary for the operation of the battery are again obtained.

Cadmium-nickel and iron-nickel.

CN and ZHN are very similar to each other. Their main difference is the material of the negative electrode plates; in KN batteries they are cadmium, and in ZhN batteries they are iron. KN batteries are the most widely used.

Alkaline batteries are mainly produced with lamella electrodes. In them, the active masses are enclosed in lamellas - flat boxes with holes. The active mass of the positive plates of a charged battery mainly consists of hydrated nickel oxide (Ni) Ni2O3 x H2O or NiOOH. In addition, it contains graphite, which is added to increase electrical conductivity. The active mass of the negative plates of KN batteries consists of a mixture of sponge cadmium with iron powder, and of ZhN batteries - of reduced iron powder. The electrolyte is a solution of potassium hydroxide containing a small amount of LiOH.

Let us consider the processes occurring during the operation of a KN battery. When the battery is discharged, cadmium oxidizes.

Cd + 2OH- = Cd(OH)2 + 2e-

And NiOOH is restored:

2NiOOH + 2H2O + 2e- = 2Ni(OH)2 + 2OH-

In this case, electrons are transferred from the cadmium electrode to the nickel electrode along the external circuit. The cadmium electrode serves as the anode and is negatively charged, and the nickel electrode serves as the cathode and is positively charged.

The total reaction occurring in the KN battery during its operation can be expressed by the equation that is obtained by adding the last two electrochemical equations:

2NiOOH + 2H2O + Cd = 2NI(OH)2 + CD(OH)2

E.m.f. of a charged nickel-cadmium battery is approximately 1.4 V. As the battery operates (discharges), the voltage at its terminals drops. When it drops below 1V, the battery is charged.

When charging a battery, the electrochemical processes at its electrodes are “reversed.” Metal reduction occurs at the cadmium electrode

Cd(OH)2 + 2e- = CD + 2OH-

On nickel - oxidation of nickel hydroxide (P):

2Ni(OH)2 + 2OH- = 2NiOOH + 2H2O + 2e-

The total reaction during charging is the opposite of the reaction occurring during discharge:

2Ni(OH)2 + Cd(OH)2 = 2NiOOH + 2H2O + Cd

SEALED NICKEL-CADMIUM BATTERIES

A special group of nickel-cadmium batteries are sealed batteries. The oxygen released at the end of the charge oxidizes cadmium, so the pressure in the battery does not increase. The rate of oxygen formation should be low, so the battery is charged with a relatively low current.

Sealed batteries are divided into disk,

cylindrical and rectangular.

Sealed rectangular nickel-cadmium batteries

are produced with negative non-cermet cadmium oxide electrodes or with cermet cadmium electrodes.

SEALED BATTERIES

Widely used acid batteries,

made using classical technology, cause a lot of trouble

and have a harmful effect on people and equipment. They are the most

cheap, but require additional costs for their maintenance,

special premises and personnel.

"DRYFIT" TECHNOLOGY BATTERIES

The most convenient and safest of acid batteries

are completely maintenance-free sealed batteries

VRLA (Valve Regulated Lead Acid) produced using technology

"dryfit". The electrolyte in these batteries is in a jelly-like state. This guarantees the reliability of the batteries and the safety of their operation.

BIBLIOGRAPHY:

1. Deordiev S.S.

Batteries and their care.

K.: Technology, 1985. 136 p.

2. Electrical reference book.

In 3 volumes. T.2. Electrical products and devices/under

total ed. professors of Moscow Power Engineering Institute (editor-in-chief I.N. Orlov) and others. 7th ed. 6corr. and additional

M.: Energoatomizdat, 1986. 712 p.

3. N.L.Glinka.

General chemistry.

Publishing house "Chemistry" 1977.

4. Bagotsky V.S., Skundin A.M.

Chemical current sources.

M.: Energoizdat, 1981. 360 p.

Text provided by the Scientific Research Center "Science and Technology"
The rights to the electronic version of the publication belong to N&T (www.n-t.org)

The book contains information about the design, principles of operation and characteristic features of chemical power sources (batteries and accumulators). You will learn from this book how to choose the batteries and accumulators you need, how to charge and restore them correctly.

• The anode is the positive terminal of the battery.
• Battery - two or more cells connected in series and/or parallel to provide required voltage and current.
• Internal resistance is the resistance to current flow through an element, measured in ohms. Sometimes called internal impedance.
• Energy output is the capacity consumption multiplied by the average voltage during the discharge time of the batteries, expressed in Watt hours (Wh).
• Capacity is the amount of electrical energy that a battery releases under certain discharge conditions, expressed in ampere-hours (Ah) or coulombs (1 Ah = 3600 C).
• Charge is electrical energy transferred to an element to be converted into stored chemical energy.
• The cathode is the negative terminal of the battery.
• Compensatory charging is a method that uses direct current to bring the battery to a fully charged state and maintain it in this state.
• Cut-off voltage is the minimum voltage at which the battery is capable of delivering useful energy under certain discharge conditions.
• Open circuit voltage is the voltage at the external terminals of the battery in the absence of current draw.
• Rated voltage is the voltage across a fully charged battery when it is discharged at a very low rate.
• Float charge is a method of maintaining a rechargeable battery in a fully charged state by applying a selected constant voltage to compensate for various losses in it.
• Energy density is the ratio of the energy of an element to its mass or volume, expressed in Watt hours per unit mass or volume.
• Polarization is a voltage drop caused by changes in the chemical compositions of the components of the elements (the difference between the open circuit voltage and the voltage at any time during the discharge).
• Discharge is the consumption of electrical energy from an element into an external circuit. A deep discharge is a state in which almost the entire capacity of the element is used up. A shallow discharge is a discharge in which a small portion of the total capacity is consumed.
• Separator - a material used to isolate electrodes from each other. It sometimes retains electrolyte in dry cells.
• Shelf life is the period of time during which an element stored under normal conditions (20oC) retains 90% of its original capacity.
• Stability is the uniformity of voltage at which the battery releases energy during the full discharge mode.
• An element is a basic unit capable of converting chemical energy into electrical energy. It consists of positive and negative electrodes immersed in a common electrolyte.
• An electrode is a conductive material capable of producing current carriers when reacting with an electrolyte.
• Electrolyte is a material that conducts charge carriers in a cell.
• A cycle is one sequence of charging and discharging an element.

English terms

• A battery - incandescent battery
• acid storage battery - battery of acid (lead) batteries
• air battery - air-metal element
• alkaline battery - (primary) alkaline cell
• alkaline battery - alkaline manganese-zinc cell
• alkaline dry battery - dry mercury-zinc cell
• alkaline dry battery - dry alkaline cell
• alkaline manganese battery - alkaline manganese-zinc cell
• alkaline storage battery - alkaline battery
• alkaline storage battery - alkaline battery
• anode battery - anode battery
• B battery - anode battery
• Bansen battery - (nitric acid-zinc) Bunsen cell
• bag-type battery - cup (primary) element with a pupa
• balancing battery - buffer battery
• battery - battery
• bias battery - bias battery element, grid battery element
• biasing battery - bias battery, grid battery
• bichromate battery - (primary) cell with dichromate solution
• buffer battery - buffer battery
• bypass battery - buffer battery
• C battery - bias battery, grid battery
• Clark battery - (mercury-zinc) Clark cell
• cadmium normal battery - (mercury-cadmium) Weston normal cell
• cadmium-silver-oxide battery - cadmium oxide galvanic cell
• carbon battery - (primary) cell with a carbon electrode
• carbon-zinc battery - (dry) cell with a zinc anode and a carbon cathode
• cell - element, cell, galvanic cell (primary cell, battery or fuel cell)
• chemical battery - battery of chemical current sources
• chargeable battery - rechargeable element
• cooper-zinc battery - copper-zinc cell
• counter (electromotive) battery - counteracting element
• Daniel battery - (copper-zinc) Daniel cell
• decomposition battery - a cell with a (side) reaction of electrolytic decomposition
• dichromate battery - (primary) cell with dichromate solution
• displacement battery - a cell with a (side) electrolytic replacement reaction
• divalent silver oxide battery - a cell with oxidation of silver to the divalent state
• double-fluid battery - two-fluid element
• drum storage - nickel-zinc battery
• dry battery - dry cell
• dry battery - dry battery
• dry-charged battery - battery of dry-charged batteries
• dry-charged battery - dry-charged battery
• Edison battery - nickel-iron battery
• electric battery - galvanic battery (battery of primary cells, accumulators or fuel cells)
• electric battery - galvanic cell (primary cell), battery or fuel cell
• emergency batteries - emergency batteries
• emergency battery - emergency battery
• end batteries - spare batteries
• Faradey battery - Faraday cell
• Faure storage battery - battery with pasted plates
• filament battery - filament battery
• floating battery - spare battery (connected in parallel to the main battery)
• Grenet battery - (zinc dichromate) Grenet cell
• galvanic battery - electrochemical cell in galvanic cell mode
• grid battery - grid battery, displacement battery
• grid-bias battery - bias battery, grid battery
• Lalande battery - (alkaline copper zinc oxide) Lalande cell
• Leclanche battery - (manganese-zinc) Leclanche cell
• lead (-acid) battery - acid (lead) battery
• lead-acid (lead-storage) battery - battery of lead (acid) batteries
• lead-calcium battery - lead-calcium cell
• lead-dioxide primary battery - lead dioxide primary cell
• line battery - buffer battery
• lithium battery - a cell with a lithium anode
• lithium-iron sulfide secondary battery - iron-lithium chloride battery
• lithium-silver chromate battery - silver-lithium chromate cell
• lithium-water battery - lithium-water cell
• long wet-stand life battery - a battery of batteries with a long shelf life in a flooded state
• magnesium battery - primary cell with magnesium anode
• magnesium mercuric oxide battery - magnesium-oxide-mercury battery
• magnesium-cuprous chloride battery - copper-magnesium chloride cell
• magnesium-silver chloride battery - silver-magnesium chloride cell
• magnesium-water battery - magnesium-water battery
• mercury battery - (dry) mercury-zinc cell
• mercury battery - battery of (dry) mercury-zinc cells
• metal-air storage battery - metal air battery
• nicad (nickel-cadmium) battery - nickel-cadmium battery
• nickel-cadmium battery - nickel-cadmium battery
• nickel-iron battery - nickel-iron battery
• nickel-iron battery - nickel-iron battery
• Plante battery - lead (acid) battery with linen separator
• pilot battery - control battery battery
• plate battery - anode battery
• plug-in battery - replaceable battery
• portable battery - portable battery
• primary battery - (primary) element
• primary battery - battery of (primary) cells
• quiet battery - microphone battery
• Ruben battery - (dry) mercury-zinc cell
• rechargeable battery - battery of batteries
• rechargeable battery - battery of rechargeable elements
• reserve battery - galvanic element of a reserve battery
• ringing battery - ringing (telephone) battery
• sal-ammoniac battery - (primary) cell with solutions of ammonium salts
• saturated standard battery - saturated normal cell
• sealed battery - sealed battery
• sealed battery - sealed (primary) element
• secondary battery - battery of batteries
• signaling battery - calling (telephone) battery
• silver-cadmium storage battery - battery of silver-cadmium batteries
• silver-oxide battery - (primary) cell with a silver cathode
• silver-zinc primary battery - silver-zinc primary cell
• silver-zinc storage battery - battery of silver-zinc batteries
• solar battery - solar battery
• standard Daniel battery - (copper-zinc) normal Daniel cell
• standby battery - emergency battery
• stationary battery - stationary battery storage battery - battery of batteries
• talking battery - microphone battery
• Voltaic battery - Volta element; element with metal electrodes and liquid electrolyte
• Weston (standard) battery - (mercury-cadmium) normal Weston cell
• wet battery - cell with liquid electrolyte
• zinc-air battery - battery of zinc air cells
• zinc-chlorine battery - zinc chlorine battery
• zinc-coper-oxide battery - copper-zinc oxide cell
• zinc-iron battery - zinc iron cell
• zinc-manganese dioxide battery - battery of manganese-zinc cells
• zinc-mercury-oxide battery - zinc-mercury oxide cell
• zinc-nickel battery - nickel-zinc battery
• zinc-silver-chloride primary battery - silver-zinc chloride primary cell

Introduction

Chemical current sources (CHS) have become a part of our lives for many years. In everyday life, the consumer rarely pays attention to the differences between the HIT used. For him, these are batteries and accumulators. They are typically used in devices such as flashlights, toys, radios or cars.

Most often, batteries and accumulators are distinguished by their appearance. But there are batteries that are designed in the same way as batteries. For example appearance The KNG-1D battery differs little from the classic R6C AA batteries. And vice versa. Rechargeable batteries and disk-type batteries are also indistinguishable in appearance. For example, a D-0.55 battery and a push-button mercury cell (battery) RC-82.

In order to distinguish between them, the consumer must pay attention to the markings on the HIT body. The markings applied to the housings of batteries and accumulators are described in Chapters 1 and 2 in the figures and tables. This is necessary to correctly select the power supply for your device.

The emergence of portable audio, video and other more energy-intensive equipment required an increase in the energy intensity of HIT, their reliability and durability.

This book describes the technical characteristics and methods for selecting the optimal HIT, methods for charging, restoring, operating and extending the life of batteries and accumulators.

The reader is cautioned to note caution regarding the safety and disposal of chemical waste products.

In the case where the power consumption is relatively high (10Ah), batteries are used, mainly acid, as well as nickel-iron and nickel-cadmium. They are used in portable computers (Laptop, Notebook, Palmtop), wearable communications equipment, emergency lighting, etc.

Car batteries have a special place in the book. Diagrams of devices for charging and restoring batteries are provided, and new sealed batteries created using the “dryfit” technology that do not require maintenance for 5...8 years of operation are described. They do not have a harmful effect on people or equipment.

In recent years, such batteries have been widely used in backup power supplies for computers and electromechanical systems that accumulate energy for possible peak loads and emergency power supply of vital systems.

At the beginning of each chapter there is a glossary of special English terms that are used in the descriptions and labeling of batteries and accumulators. At the end of the book there is a consolidated dictionary of terms.

The main characteristics of CCIs for a wide range of applications that are of practical interest are given in Table B.1.

CHAPTER 1
GALVANIC CURRENT SOURCES, SINGLE ACTION

Disposable galvanic current sources are a unified container that contains an electrolyte, absorbed by the active material of the separator, and electrodes (anode and cathode), which is why they are called dry cells. This term is used to refer to all cells that do not contain a liquid electrolyte. Common dry cells include zinc-carbon or Leclanche cells.

Dry cells are used at low currents and intermittent operating modes. Therefore, such elements are widely used in telephones, toys, alarm systems, etc.

Since the range of devices that use dry elements is very wide and, in addition, they require periodic replacement, there are standards for their dimensions. It should be emphasized that the dimensions of the elements given in tables 1.1 and 1.2 produced by different manufacturers may differ slightly in terms of the location of the pins and other features specified in their specifications.

During the discharge process, the voltage of dry cells drops from the nominal voltage to the cut-off voltage (cut-off voltage is the minimum voltage at which the battery is capable of delivering minimum energy), i.e. typically 1.2V to 0.8V/cell depending on application. In case of discharge when connected to the element constant resistance after closing the circuit, the voltage at its terminals sharply decreases to a certain value, somewhat less than the original voltage. The current flowing in this case is called the initial discharge current.

The functionality of a dry cell depends on current consumption, cut-off voltage and discharge conditions. The efficiency of the element increases as the discharge current decreases. For dry cells, continuous discharge for less than 24 hours can be classified as high rate discharge.

The electrical capacity of a dry cell is specified for discharge through a fixed resistance at a given final voltage in hours depending on the initial discharge and is presented in a graph or table. It is advisable to use the manufacturer's chart or table for a specific battery. This is due not only to the need to take into account the features of the product, but also to the fact that each manufacturer gives its own recommendations on the best use of its products. Table 1.3 and Table 1.5 present the technical characteristics of galvanic cells that have recently been most common on the shelves of our stores.

The internal resistance of the battery may limit the current required, for example when used in a flash camera. The initial stable current that a battery can supply for a short time is called flash current. The designation of the element type contains letter designations that correspond to the flash currents and internal resistance of the element, measured at direct and alternating current (table 1.4). Flash current and internal resistance are very difficult to measure, and cells may have a long shelf life, but the flash current may decrease.

1.1. TYPES OF GALVANIC CELLS

Carbon-zinc elements

Carbon-zinc elements (manganese-zinc) are the most common dry elements. Carbon-zinc cells use a passive (carbon) current collector in contact with a manganese dioxide (MnO2) anode, an ammonium chloride electrolyte and a zinc cathode. The electrolyte is in a paste form or impregnates the porous diaphragm. Such an electrolyte is slightly mobile and does not spread, which is why the elements are called dry.

The rated voltage of the carbon-zinc cell is 1.5 V.

Dry elements can have a cylindrical shape, Fig. 1.1, a disk shape, Fig. 1.2, and a rectangular shape. The design of rectangular elements is similar to disk ones. The zinc anode is made in the form of a cylindrical glass, which is also a container. Disc elements consist of a zinc plate, a cardboard diaphragm impregnated with an electrolyte solution, and a compressed layer of the positive electrode. The disk elements are connected in series with each other, the resulting battery is insulated and packaged in a case.

Coal-zinc elements are “restored” during a break in operation. This phenomenon is due to the gradual alignment of local inhomogeneities in the electrolyte composition that arise during the discharge process. As a result of periodic “rest”, the service life of the element is extended.

In Fig. Figure 1.3 presents a three-dimensional diagram showing the increase in the operating time of a D-element when using an intermittent operating mode compared to a constant one. This should be taken into account when using the elements intensively (and use several sets for operation so that one set has a sufficient period of time to restore functionality. For example, when using a player, it is not recommended to use one set of batteries for more than two hours in a row. When changing two sets, the operating time elements increases threefold.

The advantage of carbon-zinc elements is their relatively low cost. Significant disadvantages include a significant decrease in voltage during discharge, low power density (5...10 W/kg) and short shelf life.

Low temperatures reduce the efficiency of using galvanic cells, and internal heating of the battery increases it. The effect of temperature on the capacitance of a galvanic cell is shown in Fig. 1.4. An increase in temperature causes chemical corrosion of the zinc electrode by the water contained in the electrolyte and drying out of the electrolyte. These factors can be somewhat compensated for by keeping the battery at elevated temperatures and introducing a saline solution into the cell through a previously made hole.

Alkaline elements

Like carbon-zinc cells, alkaline cells use a MnO2 anode and a zinc cathode with a separated electrolyte.

The difference between alkaline cells and carbon-zinc cells is the use of an alkaline electrolyte, as a result of which there is virtually no gas evolution during discharge, and they can be made hermetically sealed, which is very important for a number of their applications.

The voltage of alkaline cells is approximately 0.1 V less than that of carbon-zinc cells under the same conditions. Therefore, these elements are interchangeable.

The voltage of cells with an alkaline electrolyte changes significantly less than that of cells with a salt electrolyte. Cells with alkaline electrolyte also have higher specific energy (65...90 Wh/kg), specific power (100...150 kWh/m3) and a longer shelf life.

Charging of manganese-zinc cells and batteries is carried out by asymmetric alternating current. You can charge cells with a salt or alkaline electrolyte of any concentration, but not too discharged and without damaged zinc electrodes. Within the expiration date established for of this type cell or battery, you can restore functionality multiple times (6...8 times).

Charging of dry batteries and cells is carried out from a special device that allows you to obtain a charging current of the required form: with a ratio of charging and discharging components of 10:1 and a ratio of pulse durations of these components of 1:2. This device allows you to charge watch batteries and activate old small batteries. When charging watch batteries, the charging current should not exceed 2 mA. Charging time is no more than 5 hours. The diagram of such a device for charging batteries is shown in Fig. 1.5.

Here, the battery being charged is connected through two parallel-connected chains of diodes with resistors. The asymmetric charge current is obtained as a result of the difference in the resistances of the resistors. The end of the charge is determined by the cessation of voltage growth on the battery. Transformer secondary voltage charger is selected so that the output voltage exceeds the rated voltage of the element by 50...60%.

The battery charging time using the described device should be about 12...16 hours. The charging capacity should be approximately 50% greater than the rated battery capacity.

Mercury elements

Mercury elements are very similar to alkaline elements. They use mercury oxide (HgO). The cathode consists of a mixture of zinc powder and mercury. The anode and cathode are separated by a separator and a diaphragm impregnated with a 40% alkali solution.

These elements have long terms storage and higher capacities (with the same volume). The voltage of a mercury cell is approximately 0.15 V lower than that of an alkaline cell.

Mercury elements are characterized by high specific energy (90...120 Wh/kg, 300...400 kWh/m3), voltage stability and high mechanical strength.

For small-sized devices, modernized elements of the RC-31S, RC-33S and RC-55US types have been created. The specific energy of the RC-31S and RC-55US elements is 600 kWh/m3, the RC-33S elements are 700 kWh/m3. RC-31S and RC-33S elements are used to power watches and other equipment. RC-55US elements are intended for medical equipment, in particular for implantable medical devices.

The RC-31S and RC-33S elements operate for 1.5 years at currents of 10 and 18 µA, respectively, and the RC-55US element ensures the operation of implanted medical devices for 5 years. As follows from Table 1.6, the nominal capacity of these elements does not correspond to their designation.

Mercury elements are operational in the temperature range from 0 to +50oC; there are cold-resistant RC-83X and RC-85U and heat-resistant elements RC-82T and RC-84, which are capable of operating at temperatures up to +70oC. There are modifications of the elements in which indium and titanium alloys are used instead of zinc powder (negative electrode).

Because mercury is scarce and toxic, mercury cells should not be discarded after they are fully used. They must be recycled.

Silver elements

They have “silver” cathodes made of Ag2O and AgO. Their voltage is 0.2 V higher than that of carbon-zinc ones under comparable conditions.

Lithium cells

They use lithium anodes, an organic electrolyte and cathodes made of various materials. They have a very long shelf life, high energy densities and are operational in a wide temperature range, since they do not contain water.

Since lithium has the highest negative potential in relation to all metals, lithium cells are characterized by the highest rated voltage with minimal dimensions (Fig. 1.6). Specifications lithium galvanic cells are given in Table 1.7.

Organic compounds are usually used as solvents in such elements. Solvents can also be inorganic compounds, for example, SOCl2, which are also reactive substances.

Ionic conductivity is ensured by introducing salts with large anions into solvents, for example: LiAlCl4, LiClO4, LiBFO4. Specific electrical conductivity non-aqueous electrolyte solutions are 1...2 orders of magnitude lower than the conductivity of aqueous solutions. In addition, cathodic processes in them usually proceed slowly, therefore, in cells with non-aqueous electrolytes, current densities are low.

The disadvantages of lithium cells include their relatively high cost, due to the high price of lithium and special requirements for their production (the need for an inert atmosphere, purification of non-aqueous solvents). It should also be taken into account that some lithium cells are explosive if opened.

Such elements are usually made in a push-button design with a voltage of 1.5 V and 3 V. They successfully provide power to circuits with a consumption of about 30 μA in constant mode or 100 μA in intermittent modes. Lithium cells are widely used in backup power supplies for memory circuits, measuring instruments and other high-tech systems.

CHAPTER 1.2 BATTERIES FROM LEADING COMPANIES OF THE WORLD

In recent decades, the production volume of alkaline analogues of Leclanche elements, including zinc air, has increased (see Table B1).

For example, in Europe, the production of alkali manganese-zinc elements began to develop in 1980, and in 1983 it already reached 15% of total output.

The use of free electrolyte limits the possibilities of using autonomous ones and is mainly used in stationary HIT. Therefore, numerous studies are aimed at creating so-called dry cells, or cells with thickened electrolyte, free from elements such as mercury and cadmium, which pose serious dangers to human health and the environment.

This trend is a consequence of the advantages of alkaline chemicals in comparison with classical salt elements:

a significant increase in discharge current densities due to the use of a pasted anode;

increasing the capacity of chemical heating equipment due to the possibility of increasing the loading of active masses;

creation of zinc air compositions (elements of type 6F22) due to the greater activity of existing cathode materials in the electroreduction reaction of dioxygen in an alkaline electrolyte.

Batteries from Duracell (USA)

Duracell is a recognized leader in the world in the production of disposable alkaline galvanic sources. The history of the company goes back more than 40 years.

The company itself is located in the United States of America. In Europe, its factories are located in Belgium. According to consumers both here and abroad, Duracell batteries occupy a leading position in popularity, duration of use and price-quality ratio.

The appearance of Duracell on the Ukrainian market attracted the attention of our consumers.

The discharge current densities in lithium sources are not high (compared to other HITs), on the order of 1 mA/cm2 (see page 14). With a guaranteed shelf life of 10 years and low current discharge, it is rational to use Duracell lithium cells in high-tech systems.

US-patented EXRA-POWER technology using titanium dioxide (TiO2) and other technological features helps increase the power and efficiency of Duracell manganese-zinc chemical reactors.

Inside the steel body of Duracell alkaline cells is a cylindrical graphite collector that holds a paste-like electrolyte in contact with a needle cathode.

The guaranteed shelf life of the elements is 5 years, and at the same time, the capacity of the element indicated on the packaging is guaranteed at the end of the shelf life.

Technical characteristics of Duracell HIT are given in Table 1.8.

Batteries from Varta concern (Germany)

The Varta concern is one of the world leaders in the production of HIT. The concern's 25 factories are located in more than 100 countries around the world and produce more than 1,000 types of batteries and accumulators.

The main production facilities are occupied by the Department of Stationary Industrial Batteries. However, about 600 types of voltaic cells from watch batteries to sealed batteries are produced at the concern's factories by the Instrument Batteries Department in the USA, Italy, Japan, the Czech Republic, etc., with a guarantee of constant quality regardless of the geographical location of the plant. The photographic camera of the first man to set foot on the Moon was powered by Varta batteries.

They are quite well known to our consumers and are in steady demand.

Technical characteristics of HIT concern Varta with indication domestic analogues are given in table 1.9.

CHAPTER 2. BATTERIES

Batteries are reusable chemical sources of electrical energy. They consist of two electrodes (positive and negative), an electrolyte and a housing. Energy accumulation in the battery occurs during a chemical reaction of oxidation-reduction of the electrodes. When the battery is discharged, the reverse processes occur. Battery voltage is the potential difference between the poles of the battery at a fixed load.

Bibliography

1. Kaufman M., Sidman. A.G.
   A practical guide to circuit calculations in electronics. Directory. In 2 volumes: Transl. from English/Ed. F.N. Pokrovsky. M.: Energoatomizdat, 1991. 368 p.
2. Tereshchuk R.M. etc. Small-sized equipment. Amateur Radio Handbook. K.: Naukova Dumka, 1975. 557 p.
3. Sena L.A. Units of physical quantities and their dimensions. Educational and reference manual. 3rd ed., revised. and additional M.: Science. Ch. ed. physics and mathematics lit., 1988. 432 p.
4. Deordiev S.S. Batteries and their care. K.: Technology, 1985. 136 p.
5. Electrical reference book. In 3 volumes. T.2. Electrical products and devices/under general. ed. professors of Moscow Power Engineering Institute (editor-in-chief I.N. Orlov) and others. 7th ed. 6 rev. and additional M.: Energoatomizdat, 1986. 712 p.
6. Digital and analog integrated circuits. Directory. Ed. S.V. Yakubovsky. M.: Radio and communication, 1990. 496 p.
7. Semushkin S. Current sources and their application. "Radio", 1978. 2.3.
8. Veksler G.S. Calculation of power supply devices. K.: Technika, 1978. 208 p.
9. Lisovsky F.V., Kalugin I.K. English-Russian dictionary of radio electronics. 2nd ed., revised. and additional OK. 63000 terms. M.: Rus. lang., 1987.
10. Bagotsky V.S., Skundin A.M. Chemical current sources. M.: Energoizdat, 1981. 360 p.
11. Crompton T. Primary current sources. M.: Mir, 1986. 326 p.

Continue reading

Different types of galvanic cells convert their chemical energy into electrical current. They received their name in honor of the Italian scientist Galvani, who conducted the first such experiments and research. Electricity is generated by the chemical reaction of two metals (usually zinc and copper) in an electrolyte.

Operating principle

Scientists placed a copper and zinc plate in containers with acid. They were connected by a conductor, gas bubbles formed on the first, and the second began to dissolve. This proved that electric current flows through the conductor. After Galvani, Volt took up experiments. He created a cylindrical element, similar to a vertical column. It consisted of zinc, copper and cloth rings, pre-impregnated with acid. The first element had a height of 50 cm, and the voltage generated by it was felt by a person.

The principle of operation is that two types of metal in an electrolytic medium interact, as a result of which current begins to flow through the external circuit. Modern galvanic cells and batteries are called batteries. Their voltage depends on the metal used. The device is placed in a cylinder made of soft sheet metal. The electrodes are meshes with oxidative and reduction sputtering.

Converting chemical energy into electricity eliminates the possibility of restoring the properties of batteries. After all, when the element operates, reagents are consumed, which causes the current to decrease. The reducing agent is usually the negative lead from lithium or zinc. During operation, it loses electrons. The positive part is made of metal salts or magnesium oxide, it performs the work of an oxidizing agent.

Under normal conditions, the electrolyte does not allow current to pass through; it disintegrates into ions only when the circuit is closed. This is what causes conductivity to appear. An acid solution, sodium or potassium salts are used as an electrolyte.

Varieties of elements

Batteries are used to power devices, devices, equipment, and toys. According to the scheme, all galvanic elements are divided into several types:

• saline;
• alkaline;
• lithium

The most popular are salt batteries made of zinc and manganese. The element combines reliability, quality and reasonable price. But recently, manufacturers have been reducing or completely stopping their production, as companies producing household appliances are gradually increasing their requirements for them. The main advantages of galvanic batteries of this type:

• universal parameters allowing their use in different areas;
• easy operation;
• low cost;
• simple conditions production;
• accessible and inexpensive raw materials.

Among the disadvantages are a short service life (no more than two years), a decrease in properties due to low temperatures, a decrease in capacity with increasing current, and a decrease in voltage during operation. When salt batteries are discharged, they can leak as the positive volume of the electrode pushes out the electrolyte. Conductivity is increased by graphite and carbon black, the active mixture consists of manganese dioxide. The service life directly depends on the volume of electrolyte.

In the last century, the first alkaline elements appeared. The role of the oxidizing agent in them is played by manganese, and the reducing agent is zinc powder. The battery body is amalgamated to prevent corrosion. But the use of mercury was banned, so they were coated with mixtures of zinc powder and rust inhibitors.

The active substance in the device of a galvanic cell is these are zinc, indium, lead and aluminum. The active mass includes soot, manganese and graphite. The electrolyte is made from potassium and sodium. Dry powder significantly improves battery performance. With the same dimensions as salt types, alkaline ones have a larger capacity. They continue to work well even in severe frost.

Lithium cells are used to power modern technology. They are produced in the form of batteries and accumulators different sizes. The former contain a solid electrolyte, while other devices contain a liquid electrolyte. This option is suitable for devices that require stable voltage and average current charges. Lithium batteries can be charged several times, batteries are used only once, they are not opened.

Scope of application

There are a number of requirements for the production of galvanic cells. The battery case must be reliable and sealed. The electrolyte must not leak out, and foreign substances must not be allowed to enter the device. In some cases, when liquid leaks out, it will catch fire. A damaged item cannot be used. The dimensions of all batteries are almost the same, only the sizes of the batteries differ. The elements can have different shapes: cylindrical, prismatic or disk.

All types of devices have common advantages: they are compact and light in weight, adapted to different operating temperature ranges, have a large capacity and operate stably under different conditions. There are also some disadvantages, but they relate to certain types of elements. Salt ones do not last long, lithium ones are designed in such a way that they can ignite if depressurized.

The applications of batteries are numerous:

• digital technology;
• Kids toys;
• medical devices;
• defense and aviation industry;
• space production.

Galvanic cells are easy to use and affordable. But some types need to be handled carefully and not used if damaged. Before purchasing batteries, you should carefully study the instructions for the device that they will power.

Low-power sources of electrical energy

Galvanic cells and batteries are used to power portable electrical and radio equipment.

Galvanic cells- these are single action sources, batteries- reusable sources.

The simplest galvanic cell

The simplest element can be made from two strips: copper and zinc, immersed in water slightly acidified with sulfuric acid. If the zinc is pure enough to be free from local reactions, no noticeable change will occur until the copper and zinc are connected by wire.

However, the strips have different potentials relative to each other, and when they are connected by a wire, a will appear in it. As this action proceeds, the zinc strip will gradually dissolve, and gas bubbles will form near the copper electrode and collect on its surface. This gas is hydrogen, formed from the electrolyte. Electric current flows from the copper strip through the wire to the zinc strip, and from it through the electrolyte back to the copper.

Gradually, the sulfuric acid of the electrolyte is replaced by zinc sulfate, formed from the dissolved part of the zinc electrode. Due to this, the voltage of the element is reduced. However, an even greater voltage drop is caused by the formation of gas bubbles on the copper. Both of these actions produce "polarization." Such elements have almost no practical significance.

Important parameters of galvanic cells

The magnitude of the voltage provided by galvanic cells depends only on their type and design, i.e., on the material of the electrodes and the chemical composition of the electrolyte, but does not depend on the shape and size of the elements.

The amount of current that a galvanic cell can produce is limited by its internal resistance.

A very important characteristic of a galvanic cell is. Electrical capacity means the amount of electricity that a galvanic or battery cell is capable of delivering during the entire time of its operation, i.e., before the final discharge occurs.

The capacity given by the element is determined by multiplying the discharge current, expressed in amperes, by the time in hours during which the element was discharged until the onset of full discharge. Therefore, electrical capacity is always expressed in ampere-hours (A x h).

Based on the capacity of the element, you can also determine in advance how many hours it will work before it is completely discharged. To do this, you need to divide the capacity by the discharge current permissible for this element.

However, electrical capacitance is not a strictly constant value. It varies within fairly wide limits depending on the operating conditions (mode) of the element and the final discharge voltage.

If the element is discharged with maximum current and without interruption, then it will give off significantly less capacity. On the contrary, when the same element is discharged with a lower current and with frequent and relatively long breaks, the element will give up its full capacity.

As for the effect of the final discharge voltage on the capacitance of the element, it must be borne in mind that during the discharge of a galvanic cell, its operating voltage does not remain at the same level, but gradually decreases.

Common types of galvanic cells

The most common galvanic cells are manganese-zinc, manganese-air, zinc-air and mercury-zinc systems with salt and alkaline electrolytes. Dry manganese-zinc cells with a salt electrolyte have an initial voltage of 1.4 to 1.55 V, operating time at ambient temperatures from -20 to -60 o C from 7 hours to 340 hours.

Dry manganese-zinc and zinc-air cells with an alkaline electrolyte have a voltage from 0.75 to 0.9 V and an operating time from 6 hours to 45 hours.

Dry mercury-zinc cells have an initial voltage of 1.22 to 1.25 V and a run time of 24 hours to 55 hours.

Largest guarantee period dry mercury-zinc elements have a storage life of up to 30 months.

These are secondary galvanic cells.Unlike galvanic cells, no chemical processes occur in the battery immediately after assembly.

So that chemical reactions associated with movement begin in the battery electric charges, you need to change the chemical composition of its electrodes (and partly the electrolyte) accordingly. This change in the chemical composition of the electrodes occurs under the influence of electric current passed through the battery.

Therefore, in order for the battery to produce electric current, it must first be “charged” with a constant electric shock from some external current source.

Batteries also differ favorably from conventional galvanic cells in that after discharge they can be charged again. With good care and under normal operating conditions, batteries can withstand up to several thousand charges and discharges.
Battery device

Currently, lead and cadmium-nickel batteries are most often used in practice. For the former, the electrolyte is a solution of sulfuric acid, and for the latter, a solution of alkalis in water. Lead batteries are also called acid batteries, and nickel-cadmium batteries are called alkaline batteries.

The principle of operation of batteries is based on the polarization of electrodes. The simplest acid battery is designed as follows: these are two lead plates dipped into an electrolyte. As a result of the chemical substitution reaction, the plates are covered with a slight coating of lead sulfate PbSO4, as follows from the formula Pb + H 2 SO 4 = PbSO 4 + H 2.

Acid battery device

This state of the plates corresponds to a discharged battery. If the battery is now turned on for a charge, i.e., connected to a direct current generator, then due to electrolysis, polarization of the plates will begin in it. As a result of charging the battery, its plates are polarized, i.e., they change the substance of their surface, and from homogeneous (PbSO 4) turn into dissimilar (Pb and Pb O 2).

The battery becomes a source of current, and its positive electrode is a plate coated with lead dioxide, and the negative electrode is a clean lead plate.

Towards the end of the charge, the electrolyte concentration increases due to the appearance of additional sulfuric acid molecules in it.

This is one of the features of a lead-acid battery: its electrolyte does not remain neutral and itself participates in chemical reactions during battery operation.

Towards the end of the discharge, both battery plates are again covered with lead sulfate, as a result of which the battery ceases to be a source of current. The battery is never brought to this state. Due to the formation of lead sulfate on the plates, the electrolyte concentration at the end of the discharge decreases. If you put the battery on charge, you can again cause polarization in order to put it on discharge again, etc.

How to charge the battery

There are several ways to charge batteries. The simplest is normal battery charging, which occurs as follows. Initially, for 5 - 6 hours, the charge is carried out with double normal current until the voltage on each battery bank reaches 2.4 V.

Normal charging current is determined by the formula I charge = Q/16

Where Q - nominal battery capacity, Ah.

After this, the charging current is reduced to a normal value and the charge continues for 15 - 18 hours, until signs of the end of the charge appear.

Modern batteries

Cadmium-nickel, or alkaline batteries, appeared much later than lead batteries and, in comparison with them, are more advanced chemical current sources. The main advantage of alkaline batteries over lead batteries is the chemical neutrality of their electrolyte with respect to the active masses of the plates. Due to this, the self-discharge of alkaline batteries is much less than that of lead batteries. The operating principle of alkaline batteries is also based on the polarization of the electrodes during electrolysis.

To power radio equipment, sealed cadmium-nickel batteries are produced, which are operational at temperatures from -30 to +50 o C and can withstand 400 - 600 charge-discharge cycles. These batteries are made in the form of compact parallelepipeds and disks with a mass of several grams to kilograms.

They produce nickel-hydrogen batteries for power supply to autonomous facilities. The specific energy of a nickel-hydrogen battery is 50 - 60 Wh kg -1.