Autonomous sources of electricity are one of the most useful inventions of mankind. What is a telephone or radio that does not have batteries installed ? The device of many devices, as well as the conditions for their use, do not always provide for a constant network power supply, therefore, such sources of electricity allow you to comfortably carry out your activity almost anywhere in the world. After a short introduction, let's get down to the article.
What is a rechargeable battery?
In a broad sense, this concept means a device that, under certain conditions of use, can accumulate some kind of energy, and under others, it can be consumed in order to satisfy human needs.
Batteries accumulate electricity from an external power source, and then give it to connected consumers so that they can do their job. So, when the devices are working, chemical reactions constantly occur between the electrolyte and the electrode plates. By the way, a similar design is placed in banks, from which the batteries are formed. The device of these structures provides for the creation of voltage, as a rule, 1.2-2 V, which is very small. Therefore, to increase the performance of power sources, different types of compounds are used.
How do batteries work when discharged?
The device of these power sources provides for connection to plus and minus. They function as follows: when a load is connected to the electrodes (as an example, you can consider a light bulb), then a closed electrical circuit occurs. A discharge current begins to flow through it. It is formed due to the motion of electrons, anions and cations. More detailed information about what and how is proceeding can be described only with a specific example.
Suppose we have a battery where the positive electrode is nickel oxide, in which graphite has been added to increase conductivity. Sponge cadmium was used for the negative plate. So, when there is a discharge, particles of active oxygen are released and enter the electrolyte. At the same time, parts that go like electricity (the same electrons) are separated from them. Then the particles of active oxygen are directed towards the negative plates, where they oxidize cadmium.
Battery Performance
It is necessary to disconnect the load on the terminals of the plates. As a rule, a constant voltage is applied to them (but it can also be pulsating, depending on the case), which is greater than the size of the battery that is being charged. Moreover, the polarity should be the same. That is, the minus and plus terminals of the consumer and the source must match. Note that the
charger must necessarily have more power than there is in the battery in order to suppress the remaining energy in it and create an electric current, the direction of which will be opposite to the discharge. As a result, the chemical processes that occur in the battery change.
Let's look at an example from the previous subclause of the article. Here, the positive electrode will be enriched with oxygen, and pure cadmium will be restored on the negative. Summing up, we can say that during the charge and discharge only the chemical composition of the electrodes changes. This does not apply to electrolyte. But it can evaporate, which will negatively affect the battery life.
So, we examined the principle of operation of any battery. Now let's find out how during operation they can improve their performance.
Parallel connection
The magnitude of the current depends on a significant number of factors. First of all, this means the design, the materials used and their dimensions. The larger the area the electrodes have, the greater the current they can withstand. This principle is used for parallel connection of the same type of cans in batteries. This is done if it is necessary to increase the current value that goes to the load. But along with this, it is necessary to raise the power of the energy source.
Serial connection
If we consider the banks that make up the batteries, it must be said that they are, as a rule, in one housing. A similar type of connection is used to obtain large voltage readings with less loss.
You can see the application of this design by disassembling automotive batteries, which are lead-acid. It is worth saying that this type is used not only in the device of a car battery, it is simply the most likely way to understand how this type of connection works. In this case, it is necessary to ensure that there is no metal contact, and there is a reliable galvanic connection through the electrolyte. But this only needs to be understood in relation to this type. In other cases, the set connection task will be implemented differently.
Battery Types
They differ due to their purpose, capabilities, implementation and material. At the moment, modern production has mastered the production of more than three dozen types, which differ in their composition of the electrodes, as well as the electrolyte used. For example, li-ion batteries boast a family of 12 well-known models. Conventionally, the following types can be distinguished:
- Lead acid.
- Lithium
- Nickel cadmium.
These are the most popular representatives. But to understand the possibilities, we suggest that you familiarize yourself with the list of materials that can act as electrodes:
- iron;
- lead;
- titanium;
- lithium;
- cadmium;
- cobalt;
- nickel;
- zinc;
- vanadium;
- silver;
- aluminum;
- a number of other elements, which, however, are very rare.
The use of different materials affects the resulting output characteristics and, therefore, the scope of application. So, for example, li-ion batteries are used in computer and mobile devices. Whereas nickel cadmium is used as a replacement for standard galvanic cells. Theoretically, all types of batteries can handle any load. The only question is how justified this application is.
Main characteristics
We have already considered what batteries are, the device of these structures, what they are made of. Now let's focus on what affects their operation. Important characteristics for us are:
- Density is the characteristic of the ratio of the amount of energy to the volume or weight of the battery.
- Capacity is the value of the maximum battery charge that it can give off during the discharge process until the lowest voltage is reached. This indicator is expressed in ampere hours or pendants. The energy capacity may also be indicated. It is measured in watt hours or joules. The task of such a capacity is to report on the amount of energy that is given during the discharge until the minimum allowable voltage is reached.
- Temperature conditions affect the electrical properties of the battery. When there are serious deviations from the operating range recommended by the manufacturer, there is a high probability of a power supply failure. This is explained by the fact that cold and heat affect the intensity of chemical reactions, as well as internal pressure.
- Self-discharge refers to capacity losses that occur after a battery is charged when there is no load on the terminals. In many respects, this indicator depends on the design and may increase if the insulation is broken.
These are the characteristics of the batteries and provide us with the greatest interest. Of course, if you have to do something new and exclusive, previously unprecedented, you may need something else. But this is highly unlikely.
Electrode arrangement
We take lead plates as an example. Although they were before. Modern plates are made of lead-calcium alloy. Due to this, a low level of self-discharge of the battery is achieved (50% of the capacity is lost in 18 months). It also allows you to save water (only 1 gram per amp hour).
You can also find a hybrid design, where, in addition to lead, antimony is added to the positive electrode, and calcium to the negative electrode. True, in such cases there is an increased water consumption. To increase resistance to corrosion processes, add tin or silver.
The electrodes are made with a lattice structure, they are covered with a layer of active mass. The principle of operation of the battery to a large extent depends on what material is used for the plates. We consider lead ones that are easy to learn, but we always do not recommend focusing on them.
Electrolyte
We consider all the same lead-acid batteries. Sulfuric acid most often acts as the electrolyte in which they are placed. It has a certain density, which can vary depending on the battery level. In this case, the principle applies: the more, the higher. Over time, the electrolyte disappears, and the battery capacity drops. The service life is affected by the features of operation (compliance with safety regulations). There are two types of electrolyte in batteries:
- liquid;
- in the form of impregnated special material.
At the moment, the first type is the most common.
Battery Operation
Battery usage can be seen almost everywhere. Think of your mobile phones or
uninterruptible power supplies for computers. An example is a regular flashlight (modern designs are increasingly being made with a built-in battery and are not designed for galvanic cells). What about cars? The "stop-start" and regenerative braking systems operate on batteries, and they put forward high demands on the starting current, deep discharge and durability. As you can see, without these sources of nutrition is difficult to do in modern life to any person.
Battery design diagram
We reviewed the basic information about these devices. Let's pay attention to such a concept as a battery circuit. Indeed, in the framework of the article, it was only walked about in passing. The battery of a modern circuit, according to history, was first created by the French physicist Gaston Plant. The area of his creation exceeded 10 square meters! Modern batteries, in fact, are simply significantly reduced and slightly modified copies of its battery. Only the body is visible to humans. It provides a common and consistent design.