In the fifth issue of our magazine, we told you how to make a gas battery yourself, and in the sixth, a lead-potash one. We offer readers another type of current source - a zinc-air element. This element does not require charging during operation, which is a very important advantage over batteries.

The zinc-air element is now the most advanced current source, since it has a relatively high specific energy (110-180 Wh/kg), is easy to manufacture and operate, and is the most promising in terms of increasing its specific characteristics. The theoretically calculated specific power of a zinc air cell can reach 880 Wh/kg. If even half of this power is achieved, the element will become a very serious rival to the internal combustion engine.

A very important advantage of the zinc air element is

small change in voltage under load as it discharges. In addition, such an element has significant strength, since its vessel can be made of steel.

The operating principle of zinc air elements is based on the use of an electrochemical system: zinc - caustic potassium solution - activated carbon, which adsorbs air oxygen. By selecting the compositions of the electrolyte, the active mass of the electrodes and choosing the optimal design of the element, it is possible to significantly increase its specific power.

The release of compact zinc-air batteries into the mass market can significantly change the situation in the market segment of small-sized autonomous power supplies for laptop computers and digital devices.

Energy problem

and in recent years, the fleet of laptop computers and various digital devices has increased significantly, many of which have only recently appeared on the market. This process has accelerated noticeably due to the increase in popularity mobile phones. In turn, the rapid growth in the number of portable electronic devices caused a serious increase in demand for autonomous sources of electricity, in particular for various types of batteries and accumulators.

However, the need to provide a huge number of portable devices with batteries is only one side of the problem. Thus, as portable electronic devices develop, the density of the elements and the power of the microprocessors used in them increase; in just three years, the clock frequency of the PDA processors used has increased by an order of magnitude. Tiny monochrome screens are being replaced by high-resolution color displays with larger screen sizes. All this leads to an increase in energy consumption. In addition, there is a clear trend towards further miniaturization in the field of portable electronics. Taking into account these factors, it becomes quite obvious that increasing the energy intensity, power, durability and reliability of the batteries used is one of the most important conditions for ensuring the further development of portable electronic devices.

The problem of renewable autonomous power sources is very acute in the segment of portable PCs. Modern technologies make it possible to create laptops that are practically not inferior in their functionality and performance to full-fledged desktop systems. However, the lack of sufficiently efficient autonomous power sources deprives laptop users of one of the main advantages of this type of computer - mobility. A good indicator for a modern laptop equipped with a lithium-ion battery is a battery life of about 4 hours 1, but for full-fledged work in mobile conditions this is clearly not enough (for example, a flight from Moscow to Tokyo takes about 10 hours, and from Moscow to Los Angeles). Angeles almost 15).

One of the options for solving the problem of increasing time battery life portable PCs is a shift from the currently common nickel-metal hydride and lithium-ion batteries to chemical fuel cells 2 . The most promising fuel cells from the point of view of application in portable electronic devices and PCs are fuel cells with low operating temperatures such as PEM (Proton Exchange Membrane) and DMCF (Direct Methanol Fuel Cells). An aqueous solution of methyl alcohol (methanol) 3 is used as fuel for these elements.

However, at this stage, it would be too optimistic to describe the future of chemical fuel cells solely in rosy tones. The fact is that there are at least two obstacles to the mass distribution of fuel cells in portable electronic devices. Firstly, methanol is a rather toxic substance, which implies increased requirements for the tightness and reliability of fuel cartridges. Secondly, to ensure acceptable rates of chemical reactions in fuel cells with low operating temperatures, it is necessary to use catalysts. Currently, catalysts made of platinum and its alloys are used in PEM and DMCF cells, but natural reserves of this substance are small and its cost is high. It is theoretically possible to replace platinum with other catalysts, but so far none of the teams engaged in research in this direction have been able to find an acceptable alternative. Today, the so-called platinum problem is perhaps the most serious obstacle to the widespread adoption of fuel cells in portable PCs and electronic devices.

1 This refers to the operating time from a standard battery.

2 More information about fuel cells can be read in the article “Fuel cells: a year of hope”, published in No. 1’2005.

3 PEM cells operating on hydrogen gas are equipped with a built-in converter to produce hydrogen from methanol.

Zinc air elements

Although the authors of a number of publications consider zinc-air batteries and accumulators to be one of the subtypes of fuel cells, this is not entirely true. Having become familiar with the design and principle of operation of zinc-air elements, even in general terms, we can make a completely unambiguous conclusion that it is more correct to consider them as a separate class of autonomous power sources.

The zinc air cell cell design includes a cathode and anode separated by an alkaline electrolyte and mechanical separators. A gas diffusion electrode (GDE) is used as a cathode, the water-permeable membrane of which allows oxygen to be obtained from atmospheric air circulating through it. The “fuel” is the zinc anode, which is oxidized during the operation of the cell, and the oxidizing agent is oxygen obtained from atmospheric air entering through the “breathing holes”.

At the cathode, the electroreduction reaction of oxygen occurs, the products of which are negatively charged hydroxide ions:

O 2 + 2H 2 O +4e 4OH – .

Hydroxide ions move in the electrolyte to the zinc anode, where the zinc oxidation reaction occurs, releasing electrons that return to the cathode through an external circuit:

Zn + 4OH – Zn(OH) 4 2– + 2e.

Zn(OH) 4 2– ZnO + 2OH – + H 2 O.

It is quite obvious that zinc-air cells do not fall under the classification of chemical fuel cells: firstly, they use a consumable electrode (anode), and secondly, the fuel is initially placed inside the cell, and is not supplied from the outside during operation.

The voltage between the electrodes of one cell of a zinc-air cell is 1.45 V, which is very close to that of alkaline (alkaline) batteries. If necessary, to obtain a higher supply voltage, several cells connected in series can be combined into a battery.

Zinc is a fairly common and inexpensive material, so when deploying mass production of zinc-air cells, manufacturers will not experience problems with raw materials. In addition, even at the initial stage, the cost of such power supplies will be quite competitive.

It is also important that zinc air elements are very environmentally friendly products. The materials used for their production do not poison the environment and can be reused after recycling. The reaction products of zinc air elements (water and zinc oxide) are also absolutely safe for humans and the environment; zinc oxide is even used as the main component of baby powder.

Among the operational properties of zinc-air elements, it is worth noting such advantages as a low self-discharge rate in the non-activated state and a small change in the voltage value during discharge (flat discharge curve).

A certain disadvantage of zinc air elements is the influence of the relative humidity of the incoming air on the characteristics of the element. For example, for a zinc air element designed for operation in conditions of relative air humidity of 60%, when the humidity increases to 90%, the service life decreases by approximately 15%.

From batteries to batteries

The easiest option for zinc-air cells to implement are disposable batteries. When creating zinc air elements large size and power (for example, intended to power vehicle power plants), zinc anode cassettes can be made replaceable. In this case, to renew the energy reserve, it is enough to remove the cassette with the used electrodes and install a new one in its place. Used electrodes can be restored for reuse using the electrochemical method at specialized enterprises.

If we talk about compact elements power supplies suitable for use in laptop PCs and electronic devices, then here practical implementation The option with replaceable zinc anode cassettes is not possible due to the small size of the batteries. This is why most compact zinc air cells currently on the market are disposable. Disposable small-sized zinc-air batteries are produced by Duracell, Eveready, Varta, Matsushita, GP, as well as the domestic enterprise Energia. The main area of ​​application for such power sources is hearing aids, portable radios, photographic equipment, etc.

Currently, many companies produce disposable zinc air batteries

A few years ago, AER produced Power Slice zinc air batteries designed for laptop computers. These items were designed for Hewlett-Packard's Omnibook 600 and Omnibook 800 series laptops; their battery life ranged from 8 to 12 hours.

In principle, there is also the possibility of creating rechargeable zinc-air cells (batteries), in which, when an external current source is connected, a zinc reduction reaction will occur at the anode. However, the practical implementation of such projects for a long time were hampered by serious problems caused by the chemical properties of zinc. Zinc oxide dissolves well in an alkaline electrolyte and, in dissolved form, is distributed throughout the entire volume of the electrolyte, moving away from the anode. Because of this, when charging from an external current source, the geometry of the anode changes significantly: the zinc recovered from zinc oxide is deposited on the surface of the anode in the form of ribbon crystals (dendrites), shaped like long spikes. The dendrites pierce through the separators, causing a short circuit inside the battery.

This problem aggravated by the fact that to increase power, the anodes of zinc-air cells are made from crushed powdered zinc (this allows to significantly increase the surface area of ​​the electrode). Thus, as the number of charge-discharge cycles increases, the surface area of ​​the anode will gradually decrease, having a negative impact on the performance of the cell.

To date, the greatest success in the field of creating compact zinc-air batteries has been achieved by Zinc Matrix Power (ZMP). ZMP specialists have developed a unique Zinc Matrix technology, which has solved the main problems that arise during battery charging. The essence of this technology is the use of a polymer binder, which ensures unhindered penetration of hydroxide ions, but at the same time blocks the movement of zinc oxide dissolving in the electrolyte. Thanks to the use of this solution, it is possible to avoid noticeable changes in the shape and surface area of ​​the anode for at least 100 charge-discharge cycles.

The advantages of zinc-air batteries are a long operating time and high specific energy intensity, at least twice that of the best lithium-ion batteries. The specific energy intensity of zinc-air batteries reaches 240 Wh per 1 kg of weight, and the maximum power is 5000 W/kg.

According to ZMP developers, today it is possible to create zinc-air batteries for portable electronic devices (mobile phones, digital players, etc.) with an energy capacity of about 20 Wh. The minimum possible thickness of such power supplies is only 3 mm. Experimental prototypes of zinc-air batteries for laptops have an energy capacity of 100 to 200 Wh.

A prototype of a zinc-air battery created by Zinc Matrix Power specialists

Another important advantage of zinc-air batteries is the complete absence of the so-called memory effect. Unlike other types of batteries, zinc-air cells can be recharged at any charge level without compromising their energy capacity. In addition, unlike lithium batteries, zinc-air cells are much safer.

In conclusion, it is impossible not to mention one important event, which became a symbolic starting point on the path to the commercialization of zinc-air cells: on June 9 last year, Zinc Matrix Power officially announced the signing of a strategic agreement with Intel Corporation. In accordance with the terms of this agreement, ZMP and Intel will combine their development efforts new technology rechargeable batteries for laptop PCs. Among the main goals of this work is to increase the battery life of laptops to 10 hours. According to the current plan, the first models of laptops equipped with zinc-air batteries should appear on sale in 2006.

Battery technology has improved significantly over the past 10 years, increasing the value of hearing aids and improving their performance. Since the digital processor took over the CA market, the battery industry has exploded.

The number of people using zinc air batteries as a power source for their hearing aids is growing day by day. These batteries are environmentally friendly and, due to their increased capacity, last much longer than other types of batteries. However, it is difficult to determine the exact service life of the element used; it depends on many factors. At certain moments, users have questions and complaints.<Радуга Звуков>will try to give a comprehensive answer to a very important question: So what does the battery life depend on?

ADVANTAGES...

For many years, the main source of power for hearing aids was mercury oxide batteries. However, in the mid-90s. it became clear that they were completely outdated. Firstly, they contained mercury - an extremely harmful substance. Secondly, digital batteries arose and began to rapidly conquer the market, placing fundamentally different requirements on the characteristics of batteries.

The mercury-oxide technology has been replaced by zinc air technology. It is unique in that oxygen from the surrounding air is used as one of the components (cathode) of the chemical battery, which enters through special holes. By removing mercury or silver oxide from the battery case, which until now served as the cathode, more space has been made available for zinc powder. Therefore, a zinc-air battery is more energy-intensive when compared to each other different types batteries of the same size. Thanks to this ingenious solution, the zinc-air battery will remain unrivaled as long as its capacity is limited by the tiny volume of modern miniature batteries.

On the positive side of the battery there are one or more holes (depending on its size) into which air enters. The chemical reaction during which the current is generated proceeds quite quickly and is completely completed within two to three months, even without a load on the battery. Therefore, during the manufacturing process, these holes are covered with a protective film.

To prepare for work, you need to remove the sticker and give the active substance time to saturate with oxygen (3 to 5 minutes). If you start using the battery immediately after opening, activation will occur only in the surface layer of the substance, which will significantly affect its service life.

The size of the battery plays an important role. The larger it is, the more active substance reserves it contains, and, therefore, the more accumulated energy. Therefore, the largest capacity battery is size 675, and the smallest is size 5. The capacity of the batteries also depends on the manufacturer. For example, for size 675 batteries it can vary from 440 mAh to 460 mAh.

AND FEATURES

Firstly, the voltage supplied by the battery depends on its operating time, or more precisely, on the degree of its discharge. The new zinc air battery can supply up to 1.4V, but only for a short time. Then the voltage drops to 1.25 V and remains for a long time. And at the end of the battery’s life, the voltage drops sharply to less than 1 V.

Secondly, zinc air batteries function better the warmer it is around. In this case, of course, you should not exceed the maximum temperature set for this type of battery. This applies to all batteries. But the peculiarity of zinc air batteries is that their performance also depends on air humidity. The chemical processes occurring in it depend on the presence a certain amount moisture. To put it simply: the hotter and more humid, the better (this only applies to CA batteries!). But the fact that humidity has a negative effect on other components of the auditory system is another matter.

Thirdly, the internal resistance of the battery depends on a number of factors: temperature, humidity, operating time and technology used by the manufacturer. The higher the temperature and humidity, the lower the impedance, which has a beneficial effect on the functioning of the auditory system. The new 675 battery has an internal resistance of 1-2 ohms. However, at the end of its service life, this value can increase to 10 ohms, and for the 13th battery - up to 20 ohms. Depending on the manufacturer, this value can vary significantly, which creates problems when the maximum power recorded in the technical data sheet is required.

When a critical current consumption value is exceeded, the final stage or the entire hearing system is switched off to allow the battery to recover. If after<дыхательной паузы>the battery again begins to produce sufficient current for operation, and the SA turns on again. In many hearing systems, restarting is accompanied by an audible signal, the same one that notifies you when the battery voltage has dropped. That is, in a situation where the SA turns off due to high current consumption, when it is turned on again, an alert signal sounds, although the battery may be completely new. This situation usually occurs when the hearing aid is receiving a very high input SPL and the hearing aid is set to full power.

Factors affecting service life

One of the main challenges facing batteries is to ensure a constant supply of current throughout the life of the battery.

First of all, the battery life is determined by the type of CA used. As a rule, analog devices consume more current than digital devices, and high-power devices consume more current than low-power ones. Typical current consumption values ​​for medium-power devices range from 0.8 to 1.5 mA, and for high-power and ultra-power devices - from 2 to 8 mA.

Digital CAs are generally more economical than analog CAs of the same power. However, they have one drawback - when switching programs or automatically triggering complex signal processing functions (noise reduction, speech recognition, etc.), these devices consume significantly more current than in normal mode. The energy requirement can rise and fall depending on what signal processing function is performed in the at the moment digital circuit, and even whether correction of a patient's hearing loss requires different amplification at different input SPLs.

The ambient acoustic situation also affects the battery life. In a quiet environment, the acoustic signal level is usually low - about 30-40 dB. In this case, the signal entering the SA is also small. In a noisy environment, for example, in the subway, train, factory or noisy street, the level of the acoustic signal can reach 90 dB or more (a jackhammer is about 110 dB). This leads to an increase in the level of the output signal of the CA and, accordingly, to an increased current consumption. At the same time, the settings of the device begin to have an effect - with greater amplification, the current consumption is also greater. Typically, ambient noise is concentrated in the low-frequency range, so when the tone control suppresses the low-frequency range more, the current consumption also decreases.

The current consumption of medium-power devices does not depend too much on the level of the input signal, but for powerful and ultra-powerful CAs the difference is quite large. For example, with an incoming signal with an intensity of 60 dB (at which the current consumption of the SA is normalized), the current strength is 2-3 mA. With an input signal of 90 dB (and the same CA settings), the current increases to 15-20 mA.

Methodology for assessing battery life

Typically, the battery life is assessed taking into account its nominal capacity and the estimated current consumption of the device, specified in the technical data (passport) for the device. Let's take a typical case: a zinc-air battery of size 675 with a typical capacity of 460 mAh.

When used in a medium-power device with a current consumption of 1.4 mA, the theoretical service life will be 460/1.4 = 328 hours. When wearing the device for 10 hours a day, this means more than a month of operation of the device (328/10=32.8).

When powering a powerful device in a quiet environment (current consumption 2 mA), the service life will be 230 hours, that is, about three weeks with 10-hour wear. But, if the environment is noisy, then the current consumption can reach 15-20 mA (depending on the type of device). In this mode, the service life will be 460/20=23 hours, i.e. less than 3 days. Of course, no one walks in such an environment for 10 hours, and the real mode will be mixed in terms of current consumption. So this example simply illustrates the calculation methodology, giving extreme values ​​for service life. Typically, the battery life in a powerful device ranges from two to three weeks.

Use batteries designed specifically for hearing aids (labeled or labeled as such) from reputable power source manufacturers (GP, Renata, Energizer, Varta, Panasonic, Duracell Activair, Rayovac).

Do not break the protective film of the battery (do not open it) until it is installed in the hearing aid.

Store batteries in blisters at room temperature and normal humidity. Wish<сберечь>leaving the battery in the refrigerator longer can lead to the exact opposite result - the appliance with a new battery will not work at all.

Before installing the battery into the device, leave it without film for 3-5 minutes.

Turn off your CA when not in use. At night, remove power sources from the device and leave the battery compartment open.

These elements have the highest density of all modern technologies. The reason for this was the components used in these batteries. These cells use atmospheric oxygen as a cathode reagent, which is reflected in their name. In order for air to react with the zinc anode, small holes are made in the battery body. Potassium hydroxide, which has high conductivity, is used as an electrolyte in these cells.
Originally created as non-rechargeable power sources, zinc air cells have a long and stable shelf life, at least when stored airtight in an inactive state. In this case, over a year of storage, such elements lose about 2 percent of their capacity. Once air gets into the battery, these batteries won't last more than a month, whether you use them or not.
Some manufacturers have begun to use the same technology in rechargeable cells. Such elements have proven themselves best when long work in low-power devices. The main disadvantage of these elements is their high internal resistance, which means that to achieve high power, they must be of enormous size. This means the need to create additional battery compartments in laptops, comparable in size to the computer itself.
But it should be noted that they began to receive such use only recently. The first such product is a joint creation of Hewlett-Packard Co. and AER Energy Resources Inc. - PowerSlice XL - showed the imperfection of this technology when used in laptop computers. This battery, created for the HP OmniBook 600 laptop, weighed 3.3 kg - more than the computer itself. She provided only 12 hours of work. Energizer also began using this technology in its small button batteries used in hearing aids.
Recharging batteries is also not such an easy task. Chemical processes are very sensitive to the electrical current supplied to the battery. If the supplied voltage is too low, the battery will send current rather than receive it. If the voltage is too high, unwanted reactions may occur that can damage the element. For example, when the voltage increases, the current will necessarily increase, as a result the battery will overheat. And if you continue to charge the element after it is fully charged, explosive gases may begin to be released in it and even an explosion may occur.

Charging technologies
Modern devices for recharging - these are quite complex electronic devices with varying degrees of protection - both for you and your batteries. In most cases, each type of cell has its own charger. At misuse Using a charger can damage not only the batteries, but also the device itself, or even the systems powered by the batteries.
There are two operating modes chargers- with constant voltage and constant current.
The simplest are constant voltage devices. They always produce the same voltage, and supply a current that depends on the battery's charge level (and other environmental factors). As the battery charges, its voltage increases, so the difference between the potential of the charger and the battery decreases. As a result, less current flows through the circuit.
All that is needed for such a device is a transformer (to reduce the charging voltage to the level required by the battery) and a rectifier (to rectify the alternating current into direct current, used to charge the battery). Such simple devices rechargers are used to charge car and ship batteries.
As a rule, lead batteries for uninterruptible power supplies are charged with similar devices. In addition, constant voltage devices are also used to recharge lithium-ion cells. Only there circuits have been added to protect the batteries and their owners.
The second type of charger provides a constant current and varies the voltage to provide the required amount of current. Once the voltage reaches full charge, charging stops. (Remember, the voltage produced by the cell drops as it discharges). Typically, such devices charge nickel-cadmium and nickel-metal hydride cells.
In addition to the required voltage level, chargers must know how long to recharge the cell. The battery can be damaged if you charge it for too long. Depending on the type of battery and the “intelligence” of the charger, several technologies are used to determine the charging time.
In the simplest cases, the voltage generated by the battery is used for this. The charger monitors the battery voltage and turns off when the battery voltage reaches a threshold level. But this technology is not suitable for all elements. For example, for nickel-cadmium it is not acceptable. In these elements, the discharge curve is close to a straight line, and it can be very difficult to determine the threshold voltage level.
More “sophisticated” chargers determine the charging time based on temperature. That is, the device monitors the temperature of the cell, and turns off, or reduces the charge current, when the battery begins to heat up (which means it is overcharged). Typically, thermometers are built into such batteries, which monitor the temperature of the element and transmit the corresponding signal to the charger.
Smart devices use both of these methods. They can switch from a high charge current to a small one, or they can support D.C. using special voltage and temperature sensors.
Standard chargers provide a charge current that is lower than the cell's discharge current. And chargers with a higher current value provide more current than the rated discharge current of the battery. Devices for continuous charging with low current use such a small current that it only prevents the battery from self-discharging (by definition, such devices are used to compensate for self-discharge). Typically, the charging current in such devices is one twentieth or one thirtieth of the rated discharge current of the battery. Modern charging devices can often operate at several charge currents. They use higher currents at first and gradually switch to lower ones as they approach full charge. If you are using a battery that can withstand low-current charging (nickel-cadmium batteries, for example, cannot), then at the end of the charging cycle the device will switch to this mode. Most laptop chargers and cell phones designed so that they can be permanently connected to the elements without causing harm to them.

Miniature zinc air batteries (galvanic “pills”) with a nominal voltage of 1.4 V are used for reliable and uninterrupted operation of analog and digital hearing aids, sound amplifiers and cochlear implants. The high environmental friendliness of microbatteries and the inability to leak ensure complete safety for consumers. Our online store offers you to buy at affordable prices the widest range of high-quality batteries for in-canal, in-ear and behind-the-ear hearing aids.

Benefits of hearing aid batteries

The zinc-air battery body contains a zinc anode, an air electrode and an electrolyte. Catalyst for oxidation reactions and formation electric current atmospheric oxygen enters through a special membrane in the housing. This battery configuration provides a number of operational advantages:

• compactness and light weight;
• ease of storage and use;
• uniform charge release;
• low self-discharge (from 2% per year);
• long service life.

So that you can promptly replace worn-out batteries with new ones in devices of low, medium and high power, we sell batteries for hearing aids in St. Petersburg in convenient packages of 4, 6 or 8 pcs.

How to buy the right batteries for hearing aids

On our website you can always buy batteries for hearing amplification devices at retail and wholesale from well-known manufacturers Renata, GP, Energizer, Camelion. To correctly select the battery size, use our table, focusing on the color of the protective film and the type of device.

Attention! After removing the colored sealing sticker, you must wait a few minutes and only then insert the “pill” into the device. This time is necessary for a sufficient amount of oxygen to get inside the battery and for it to reach full power.

Our prices are lower than our competitors because we buy directly from the manufacturer.