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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING On the restoration and operation of nickel-cadmium disk batteries. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells Small-sized disk batteries (YES) are good only in situations where they are not operated in modes close to the limit. In small-sized hand-held flashlights (RF), the modes are actually prohibitive, since the discharge current far exceeds the nominal value for DA types D-0,26D and D-0,55D. In other words, the discharge occurs almost by extra currents when these DAs are used in conjunction with regular miniature RF incandescent bulbs (ML). Recharging YES is very slow (on milliamps, depending on the circuit of the standard charger (charger) and the capacitance value of its ballast capacitor). Practice has shown that recharging DA specimens that are regularly operated at high discharge currents with a low current does not contribute to full recharging and often reduces the life of the DA itself. Batteries of the D-0,26D type, which are installed everywhere in the Russian Federation, are designed for a very specific value of the discharge current - 26 mA. This is also evidenced by the letter D after the designation of the capacity (0,26 Ah), i.e. YES is designed for long-term (10-hour) discharge. Indeed, with this discharge mode, YES, the standard memory is quite suitable, but the discharge mode is violated by 10 times. A light bulb installed by the RF manufacturer for a current of 0,26 A violates the YES discharge mode. In such a situation, there is nothing to be surprised that YES very often fail. At the same time, they do not work out even half of the guaranteed resource. Instead of 100-200 cycles, even 50 does not come out, and often the last figure is completely unattainable. A large discharge current is not the only reason for the rapid defects of YES. The careless attitude of the owner of the RF or YES is the second reason that leads the YES to premature disrepair. This includes both a deep discharge of the YES, and long-term operation of the YES in this state. Great harm is done to DA during their storage, when they are heavily discharged. Widespread chargers designed for simultaneous recharging of several instances of DA are not able to equally well charge the DA that make up the storage battery (AB). The vast majority of such memory. The fact is that the mentioned memory devices are designed for series-connected YES. However, DAs of the same type have a very significant scatter in parameters. Here, the value of the internal resistance of the DA plays a special role. It does not allow to charge normally all the DA instances that make up the AB, if the latter has a DA with a significantly increased internal resistance. It often happens that the battery becomes impossible to communicate even half of its nominal capacity. If the AB contains not one, but several instances of such DA, then charging the AB becomes practically impossible. In the best case, it is possible to charge such a battery by 10 ... 30%, and operation with high discharge currents becomes impossible. AB discharges catastrophically quickly. At low discharge currents, long-term operation is quite possible. For example, such batteries may still be suitable for powering many digital measuring instruments. However, the "disease" associated with an increase in internal resistance only progresses over time. Such DAs are likened to equivalent resistors connected in series with the AB. It comes to the point that the internal resistance of such a "resistor" already many times exceeds the total internal resistance of all YES of one battery. In such a situation, with frequent recharging of the battery, the "memory effect" of the YES only intensifies, and other copies of the YES are already becoming unusable. Given the fact that the vast majority of chargers, both industrial and home-made, are designed for serial connection of several YES when recharging, it is not necessary to count on a real increase in the service life of YES. That is why it is so important to know at least approximately the value of the internal resistance of each individual instance of YES in the battery. Moreover, it will be possible to select YES to work in the battery pack. Since, over time, DAs change their internal resistance, when several ABs are operated, a very attractive prospect appears in changing the places of DAs in sections of different ABs. In fact, already "new" ABs are formed from DA, using specimens from other ABs, having selected DA that are closest in terms of the specified resistance. This allows you to sort YES, avoiding the above problems. It becomes possible to evaluate the real abilities (in terms of application) of newly compiled ABs in terms of the magnitude of the discharge current. AB formed by DA with the highest resistance values are operated at low currents, and the best specimens (with a minimum internal resistance), on the contrary, are suitable for working with high currents. Perhaps the most important is the fact of a uniform distribution of energy between the DA, both in the process of charging and during the discharge. There is a real possibility (after the selection of YES) for the normal charging of all YES with a serial connection in the existing memory. At the initial stage of operation of any battery composed of DA, the internal resistance of each DA should be measured. It is even better from the very beginning to make AB from YES, selected with approximately the same resistance. When it was necessary to deal with sealed batteries (for example, 7D-0,1), it was necessary to disassemble them. To do this, a cut was carefully made in the upper part of the AB plastic case (near the AB connection terminals). This is the only way to get close to the electrodes of each individual AB battery and carry out its diagnostics and recovery. First of all, each YES is discharged to a voltage of 0,9 ... 1,0 V, then the required charge is reported to YES. The easiest way in this situation is to use a fixed current value and charge using a switchable timer. After that, YES is discharged in accordance with its rated discharge current. For D-0,1, the discharge mode is 20 mA for five hours. In this situation, it is necessary to control the voltage on the YES with an indication (sound or light, or combined). The most reliable option if YES will automatically turn off after the end of the discharge. In this case, YES will not be damaged. Radio amateurs in such situations use time relays that disconnect YES from the discharge circuit. Everything would be fine, but used YES lose part of their capacity, and the timer is late with the shutdown, while YES deteriorate. Therefore, it is necessary to use such a discharge method for DA or AB, when the discharge automatically stops when the voltage on the AB (DA) drops to 0,9 ... 1 V. If DA is "planted" very quickly without turning off its load, for example, ML, then the charge-discharge procedure was repeated at least once more. Very often it was possible to restore YES, especially recently discharged copies. The restored capacity of YES already depends on many of the factors listed above (but most of all on the operating conditions). Reducing the total number of series-connected YES to two or three does not solve the problems discussed earlier. Evidence of this is, for example, the frequent failures of DA in the Russian Federation, where the number of DA is three. The charge of YES with a regular memory only exacerbates the process of destruction of YES. However, if you charge each YES separately, then the difference in the service life of the YES that make up the AB is erased, as it were. No need to be lazy to remove YES from the RF case and recharge them normally (at least periodically). In addition, over time, the DA needs to be cleaned of secretions that accumulate between the positive and negative electrodes of the DA. It must be cleaned thoroughly, leaving nothing behind. Of course, metal objects cannot be used here, although they are very convenient in this case. To measure the internal dynamic resistance (VDR), the author used the technique described in [1]. This method is well suited for assessing the quality of any galvanic cells and batteries, both single and various batteries. The special value of this method lies precisely in the "dynamics" of diagnostics, i.e. in the greatest objectivity of the results obtained. The real "scourge" of AB on the basis of the DAs under consideration lies precisely in the large scatter in the GVA of the specimens that form the AB. It can be impossible to charge them normally, and discharge occurs at the most inopportune moment. Owners of wearable equipment, such as most metal detectors, are well aware of this. Another disadvantage is that DA-based ABs are more difficult to get rid of the "memory effect" than single instances of DA. This problem depends on the scatter in the DA parameters that make up the AB. The main place here is occupied by the GVA. It is noteworthy that both the discharge-charge procedure and the personal charge of each DA (individually) are able to reduce the GVA value. However, this can only be verified by measuring the GVA before and after DA restoration operations. Recently, cases of the appearance of defective YES on sale have become more frequent. During the acquisition of YES, special attention must be paid to the accuracy of the YES seller and the conditions under which he stores the YES. Several times the author has seen how sellers put YES in one pile (in plastic bags and similar "packages"). Dozens of DA type D-0,26D found themselves in such storage conditions after the end of each trading day. The saddest thing, perhaps, is that the sellers didn't care about it at all. They don’t even want to realize that they are not selling nuts or nuts, but products that require elementary and mandatory packaging, excluding the short circuit of the “plus” and “minus” terminals (electrodes). It is known from practice that DA, often subjected to extra discharges (electrode shorting), serve much less. They are more difficult to recover, especially in terms of maximum capacity. Such DAs not only lose part of their capacity, but also acquire an increased GVA value. But now we are not talking about used copies of YES, but about new YES, which are widely represented everywhere in our markets. All issues related directly to DA are important not only in relation to the Russian Federation, but are also very relevant in general, since DA with superiority replace 9-volt batteries that are too expensive in our time (such as "Krona", i.e. its numerous foreign analogues). However, not only 9-volt batteries can be composed of DA and successfully replace galvanic cells with them. Hundreds of operating cycles of YES will easily block the resource of dozens of Toshiba 9-volt cells and similar batteries. The prices for the latter are clearly too high and do not correspond to their energy intensity. For the price of one such "Toshiba" you can buy two or three copies of D-0,26D. From the cheapest 9-volt batteries there will be even less good (in terms of capacity), and for the price of such a power source we get at least one D-0,26D battery. An objective assessment of the situation allows us to draw the following conclusions. The economic benefits of using DA are obvious. Quite often, complaints about DA are associated with unsuccessful acquisitions of DA ("storage-destruction" in bags and similar packages or defective DA copies), but most of all - with improper operation. But it is possible to ensure the maximum number of DA work cycles only by appropriate (careful) operation. And nothing else. Disastrous for DA is not only the operation of DA in the transcendental zone at high discharge currents, when the voltage on DA is less than 0,9 V, but also long-term storage of DA in a deeply discharged state. It must be remembered that at a voltage of 0,9 ... 1 V, YES is most susceptible to energy accumulation. However, the situation is quite different when the voltage has dropped to 0,6 ... 0,7 V. You should not get carried away with large values of charging currents. It is hardly advisable to choose the value of this current more than 0,25 A for D-0,26 and 0,55 A for D-0,55 or 0,1 A for D-0,1. However, such advice is often found. The above figures are the limiting values of the charging currents. And second-hand copies of YES, which have been actively used for years, should be recharged with even lower currents. So, for example, the long-term operation of a large number of D-0,26 type DAs showed that it is expedient to replace the existing DA park, which are used at the highest discharge currents, with new DAs. And the older YES were transferred to a sparing mode, i.e. used where the discharge currents YES are much less than the previous ones. This approach is very beneficial in extending the life of a used YES. For example, for a long time, DAs were used in the Russian Federation. These YES began to annoy by the fact that they began to "sit down" in the Russian Federation at an accelerated pace. In their place, they installed brand new YES. The old DAs began to be used to power digital multimeters of the 8300 and 8900 series. Usually, in a battery, one of the DAs fails during a deep discharge. Do not rush to throw away these instances of YES. You should try to revive YES. The less YES was in a discharged state, the more chances for resuscitation. The essence of the resuscitation method is to charge with a high current (for DA type D-0,26 from 0,2 to 0,5 A) from a voltage generator. As the latter, a stabilized voltage source (power supply) was used with the ability to adjust the output voltage and current limited by the protection. If the YES starts to charge only at high voltage, then a mechanical operation to restore the YES is necessary, but not by using a vise, as many people advise. Clamping in a vise (with insulating gaskets) can destroy the DA housing. In this case, the desired recovery result may not occur, since the force should not be applied to the entire surface of the negative electrode YES, but only to its central part. With traditional restoration of DA (in a vice), it is often impossible to achieve the required depth of deformation of the material of the negative electrode, when a satisfactory result of restoration of DA is achieved. Local impact, on the contrary, makes it quite easy to restore those instances of DA that could not be restored by the traditional method (in a vice). Of course, not all batteries are recyclable. However, the proposed method managed to revive YES, which went through the old recovery method, but to no avail. Another advantage of this variant of DA resuscitation is that it does not compress the DA body, i.e. there are no problems when installing DA in the AB, when the negative electrode of one DA is connected to the positive electrode of the adjacent DA and is located above it. A deformed housing of the DA can lead to problems of this kind (short circuits of the DA electrodes). However, the diameter of the object acting on the negative electrode YES should not be less than 6 mm. The force must be applied in the center of the YES body. Otherwise, you can only harm, even to no avail. The author made special cassettes, which housed 7 pcs. YES, which allows serving all instances of YES from one AB. Each YES in this cassette has its own personal place and its own individual "press". The latter is represented by a MB or M8 screw. Thus, it is possible to carry out and recharge each YES separately very quickly. Easy to restore YES. It is very convenient to diagnose YES. The probability of an internal defect associated with the destruction of the spring inside the DA (between the negative electrode and the DA itself) was immediately determined. The main disadvantage of all considered and similar YES lies precisely in these springs. Made up of 7 pcs. YES AB must periodically undergo a kind of maintenance at the specified "bench". Fully serviceable YES behave quite decently. An increase in pressure from the side of the negative electrode should not lead to a decrease in the GVA value. If YES already during the charging process "requests" an increase in mechanical force, then it is necessary to check such an "appetite", i.e. it is required to check how "rotten" the internal spring YES. Often YES serve for years after a slight deformation of the case. If this is not done, then the contact formed by the spring will only degrade, and when operating the YES with high currents, it will very quickly. That is why YES in the Russian Federation almost never last their hundreds of duty cycles. These cycles are shallow; defective (in terms of energy intensity YES). YES themselves are covered with "moss" (excretions), which in no way contribute to increasing the service life of YES. For some time, DA was withdrawn from the GF and operated in other equipment, where energy consumption is an order of magnitude less than in the Russian Federation. For six months or a year, many YES came to life and were installed again in the Russian Federation. Naturally, with these DA, the above-described restoration or resuscitation measures were carried out, if such a need arose. The value of the GVA was also checked. So, when YES does not perceive a charge, i.e. when the magnitude of the charge current is negligible (a few milliamps or less), YES is subjected to the method of mechanical deformation of the negative electrode. At the same time, the readings of the ammeter are closely monitored. An increase in pressure should be accompanied by an increase in the charging current. It is very important not to overdo it here, so as not to damage the body of the YES. As soon as the increase in the charging current has stopped, the increase in the force acting on the body of the YES should also stop. However, a small margin for electrode deformation should be created. There are no complications here. The fruits of resuscitation YES are perfectly observed by the ammeter. It should be noted that the use of a screw mechanism is very convenient, not to mention the transience of the entire process. Due to the loss of time required for the maintenance of YES, many refuse them. But in vain. If everything is well thought out and organized, then the operation of DA becomes cost-effective and cost-effective, especially if there are tens or hundreds of DA copies in operation. This approach actually neutralizes the main drawback of AB based on DA - AB failure due to problems with single DA. Many YES can be quickly put back into operation, thereby restoring the entire AB. At an early stage of DA operation, it is possible to detect degradation of DA or AB parameters, which makes it possible to replace DA in a timely manner if necessary. After all, do not hide the fact that YES are very reliable. However, careless operation (left on its own) can quickly destroy YES. The selection of YES by GVA makes it possible to select the most "powerful" specimens. When DAs are selected in ABs by GVA, ABs behave very decently both during discharge and during recharging. Selected YES according to the GVA evenly redistribute the energy of the charge. They are also discharged more evenly. Not at all like in AB, where random instances of YES are used. In the latter case, one or two YES are very often discharged to the limit (before failure), preventing the normal charge of the entire battery. References:
Author: A.G. Zyzyuk
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