Is it possible to «revive» depleted battery ? Some craftsmen know how to do it: through a dry battery discharged special pulse current is passed. This operation sometimes doing a few times. However, she briefly restores the element.
Wait a minute, wait a minute! Whatever it was, it turns out that a galvanic cell - the same battery! Charging him electric shocks, restoring, we accumulate energy in it, which can then spend. Is this true?
It turns out, and did not. First of all, not every element can be recharged. It is impossible to do this, for example, an element in which there are two liquid electrolyte. Such, for example, the element of Daniel, where the two different liquids are separated by a porous cup. Gradually permeating through glass electrolytes are mixed to react with each other and produce a current. This element, if it already has fulfilled his term, did not recover.
The other elements with solid electrodes basically recharge, store energy, but the accumulation of so uneconomical and inefficient, that many consider him superfluous. It builds up only a tiny part of the feed to the power element and the element itself after several such chargings destroyed. To become a good drive, a galvanic cell should be good enough to carry the charging process. It finally succeeded in the middle of the XIX century.
In 1859, a French scientist and engineer Gaston Plante had a curious experience, looks very similar to the experience of the Volta. As Volta, Plante constructed electrochemical cell, but as he has taken two electrode lead plates normally coated film of lead oxide. The electrolyte was the same - diluted sulfuric acid. Plante connected to the electrodes of the constant current source and some time passes a current through your cell, just like when recharging dry cells. Then he turned off the current and connected to the electrodes of the galvanometer. The device showed that the element Plante was himself producing electric current, and thus singled out almost all the energy spent on charging. Charging can be repeated a large number of times - always an element worked fine, not destroyed, like the dry batteries.
This electrochemical cell called the element of the second kind, or accumulator. How does the accumulation of energy in the battery Plante? When a current is passed through the electrolyte of sulfuric acid at a lead plate connected to the negative pole of the power source - the cathode, hydrogen is released, which restores the lead oxide in pure lead. On the electrode connected to the positive pole - the anode, oxygen, which oxidize lead oxide to peroxide. The battery is charged when the cathode will be entirely pure lead, and the anode - peroxide lead. Then, the electrodes would be the greatest stress.
Connecting plate electrodes conductor with the consumer spending power, we discharge the battery. The direction of the current during discharge the opposite of what it was when charging. Positively charged plate will recover hydrogen and negative - oxidized by oxygen. Once the plate will be the same, the battery stops giving current. It is necessary to repeat the charge.
It is clear that the energy in the battery is stored in the form of a tangible substances - lead, rolling with the release of energy in the lead peroxide. The process of accumulation and release of energy going on here differently than in pure electric battery - capacitor. Therefore, this is called an electrochemical battery.
Fig. 1 Automotive lead-acid battery
The structures of lead-acid automotive batteries (Fig. 1), scientists have tried as much as possible to increase the electrode surface, while respecting their strength. After all, it depends on the size of the surface of the battery power. Now the battery plates are made in the form of lead grids coated with lead peroxide (positive electrode) and the spongy lead (negative electrode). The electrolyte is 25-35% aqueous sulfuric acid solution. Charged car battery has a voltage (more precisely - electromotive force) on the terminals 2 - 2.2 V. When battery voltage drops it, and when it reaches 1.8 V, discharge is usually stopped, otherwise the lattice of lead can too thinned during the reaction, and plates, losing strength, crumble.
You want to know what will happen to the battery, if you try to at least get away from it for a short high current power? Then activate the starter motor, powered by a rechargeable battery, but without the fuel supply to the engine. The engine, of course, will not start, and after 15-20 seconds, the starter will start to wind down. Some time later, he did stop. Will the overall impression that the battery is dead and more from it "squeeze" anything. But then, after a few minutes, the starter will work again! Where are the forces in the battery? He can not, as a living being, rest?
In fact, the behavior of the battery and the living organism are remarkably similar. When muscle fatigue from intensive work their strength is sharply reduced, and it takes time, so she recovered. Man will make a lot more if it will work equally, with constant but small power load. For example, if you try to run up on the 20th floor of the house, from once it is unlikely to succeed, it will require rest. And then fatigue will be felt considerable. And if you go quietly, the 20 floors can be overcome without much fatigue.
So the battery: When you turn it on high power sulfuric acid, which has been in the pores of the plates quickly consumed in the reaction, it turns into water, and the allocation of current stops. Only after some time, when sulfuric acid is gradually re-fill the pores, can discharge the battery again.
therefore discharged and the battery is charging (this applies to almost all types of electrochemical batteries) are generally sufficiently low load, small currents and for a long time - several hours. Here lies one of the main disadvantages of electrochemical batteries - their low power per 1 kg of battery, the so-called power density or power density.
Lead-acid batteries are quite economical, but they capricious, often corrupt, short-lived. Besides lead - relatively rare and expensive metal and the acid is dangerous to handle. Of course, that scientists began to look for new materials and new principles of battery life. So there was the second major type of electrochemical batteries - alkaline batteries. Making them is closely connected with the name of the famous American scientist and inventor Thomas Edison (1847-1931).
The battery electrolyte is not acid and alkali - 20% solution of potassium hydroxide. The plates are made of steel grates with pockets therein. Positive plates have pockets filled with a mixture containing nickel oxide and negative y - spongy cadmium. Housing alkaline battery steel, which gives the unit great strength.
Alkaline batteries are more acidic and less economical. But despite this positive quality prevail - they are unpretentious, strong, durable. Therefore, they are increasingly part of the technique. For example, on the trolley used just such drives. They can be seen in the transistor radio, the telephone and hearing aids, flashlights and other devices. In many radio devices present miniature batteries, too alkaline, push-called because they resemble button. Their value is that they are hermetically closed, absolutely insensitive to overcharge, require no maintenance. Conventional large batteries that can not boast.
Some communications satellites and space stations are used are very expensive, but beautiful in their characteristics silver-zinc alkaline batteries. They nipochem audio large currents or low (up to - 60 ° C) temperature. The density of the energy stored in them is 5 times higher than the acid batteries and a power density - twice.
But silver is expensive now, and will be even more expensive. A lot of silver is for technical needs, here it ends. So bet on these batteries do not worth it, especially when it comes to weight and powerful consumers, such as electric vehicles.