Nickel-cadmium and nickel-metal hydride batteries are the two main types of alkaline chemical current sources for autonomous power supply of various equipment. They are similar in their structure. An alkali is used as an electrolyte, and nickel oxide is used as a cathode.

Ni-cd was the first to be invented. This technology is over a hundred years old. NI-MH is widely used in consumer devices, it began only in the 90s of the twentieth century. The mass appearance on the market of more capacious (NI-MH) batteries initially caused a real sensation. But then the shortcomings emerged.

Features and Applications of Ni-cd Batteries

Compared to metal hydride batteries, Ni-cd batteries have two main disadvantages. This is a smaller capacity and memory effect. The memory effect is called “remembering” the lower limit of discharge by the battery. That is, if such a battery is not completely discharged, the duration of work in the next cycle will be less by this very amount from full discharge to the limit that the battery “remembers”. To “reset” the memory, you need to fully charge-discharge such a battery two or three times.

It would seem that with such properties, this type of battery should go into oblivion. But that doesn't happen. Due to two other properties of this type of battery - high current output and the ability to work well at low temperatures.

Approximately 90% Ni-cd today, these are battery packs for power tools, children's toys, electric shavers, self-contained vacuum cleaners, medical equipment, etc. Application in the household segment (instead of conventional primary batteries) is practically reduced to zero.

Some countries have laws restricting the use of Ni-cd cells due to the toxicity of cadmium. In new devices, their place is taken by lithium-ion batteries with a high current output.

Charging ni cd batteries

One element has a nominal voltage of 1.2V. During operation, this value can vary from 1.35V (fully charged) to 1V (full discharge). These elements have one interesting feature, which is tied to the shutdown mode in the charger (if it is automatic). After a set of capacitance, the voltage at the terminals is slightly reduced by 50-70 mV. Such a jump is called ΔV(delta V). The charger reacts to such a decrease and cuts off the charge current.

In practice, only intermediate and advanced chargers can operate on ΔV. And often you have to manually calculate how to charge ni cd batteries.

The charge voltage of any charge will give out at the rate of 1.5-1.6v per element. But the charge current can be different. It can always be viewed on the charger itself (usually from the back).

The battery capacity must be divided by the charge current and multiplied by a loss factor of 1.4. For example, 1000mAh/200mA=5 hours*1.4=7 hours. What current to charge? The nominal charge current is 0.1C, where C is the battery capacity. For 1000mAh, the nominal current is 100mA. The charge time in this case will be 14 hours. Not very comfortable. Almost always used accelerated mode 0.2-0.5C. This shortens battery life somewhat, but improves usability.

Important! The average service life of nickel-cadmium batteries is 500 charge-discharge cycles. The manufacturer claims, as a rule, UP TO 1000. Such indicators can only be achieved under ideal conditions and clearly maintaining the nominal operating modes.

Basic rules for charging nickel-cadmium batteries

• be sure to discharge the batteries before charging;
• connect the charger (or install batteries in it for home use) and wait for it to turn off when fully charged;
• if the charger does not provide auto-shutdown, calculate the required charge time and, after its expiration, turn off;
• store ni cd batteries in a discharged state.

Features and Applications of NI MH Batteries

The scope of metal hydride batteries is directly related to their properties. The maximum capacity with a minimum volume allowed them to take place in those electronics where disposable batteries have to be changed very often. These are cameras, wireless mice and keyboards, radio remote controls, children's toys.

Basically, two sizes of such elements are used - these are AA and AAA. You can use these cells anywhere where disposable batteries are used. But often this does not make economic sense (in the event that a disposable battery has been in the device for years)

Rated voltage ni mh battery 1.2v. With a slight deviation under load, this voltage is maintained throughout the entire cycle of the battery. The voltage of a disposable battery in operation drops smoothly from 1.5 to 1 volt. Toi is 1.2-mean. This allows the battery to perfectly replace a disposable battery in 99% of cases. Cases when exactly 1.5v is needed for the operation of the device are rare and are often “treated” by changing the mode in the “battery / accumulator” device menu.

Attention! The maximum capacity (physical limit) for an AA battery is 2700mAh, for AAA 1000mAh. If the label has a larger value and the “mysterious” name of the manufacturer, you are guaranteed a fraud.

The memory effect when charging nickel-metal hydride batteries is less noticeable than that of Ni-cd cells. For the first few years of mass sales, manufacturers placed the inscription “no memory effect”. Subsequently, this inscription was removed. The recommendation “charge after discharge” is also relevant for metal hydride batteries.

Charging Nickel Metal Hydride Batteries

The charging voltage ni mh is the same as that of nickel-cadmium batteries. The charger will supply 1.5-1.6v to one element. The charge current of ni mh batteries can vary from 0.1 to 1C. But any manufacturer of household batteries must indicate their recommendation for this parameter on them. The manufacturer's recommendation is 0.1C. For example, for 2500mAh, the nominal charge current of ni mh batteries is 250mA. Charging time with rated current 14 hours. By the same formula. Capacity / charge current, multiply the result by 1.4. In this mode, you can count on the number of cycles declared by the manufacturer. In accelerated mode, the service life is reduced.

Metal hydride batteries do not tolerate overheating, deep discharge, strong overcharging. Overheating can occur with a large charge current, increased internal resistance. With strong heating, the charge should be stopped. Deep discharge occurs when the element is not used for a long time. If left idle for a year or more, the battery will most likely need to be replaced. Overcharging occurs when using a charger without a shutdown function or incorrectly calculated charge time.

Chargers and charge methods

There are a lot of chargers on the market. They implement different shutdown schemes or no shutdown is implemented at all. You can easily divide them into subspecies in appearance.

1. Protozoa. Plugged into the outlet - the charge went, turned off - the charge is finished. The charge time is controlled by the user. Such devices have the right to exist in order to save money. You just need to choose one of them that will charge each element separately. If the charge channels are paired, skew occurs. This mode shortens battery life. It's easy to distinguish. The number of LED indicators must match the number of charge channels.
2. With the inscription AUTO. Such an inscription indicates that a timer shutdown is implemented here. Usually 6 to 12 hours. Not the worst option. There won't be a reload. But most likely there will not be a full charge. In this case, you can choose the batteries specifically for this charger. But the correct operation of the charger will be the first 100-200 cycles.
3. ΔV control. If the manufacturer has implemented this function, he will definitely write it on the package. If there is no inscription, the charger belongs to point 2. With the presence of ΔV control, the charger is already fully automatic. Do not forget about the separate charging of each channel (popular 10-12 years ago, chargers with an index of 508 have ΔV control, but they perceive the batteries installed in it as one battery).
4. With liquid crystal display. As a rule, its presence indicates that everything listed above is implemented, plus temperature control. Chargers with an entry-level display do not require programming the charge mode and current, but they do an excellent job with their function - to properly charge ni mh batteries.
5. Charging - combine. Larger than in paragraph 4. Assume user programming of charge modes and current. If nothing is programmed in the “default” mode, charge the batteries with a minimum current and turn off the charge by ΔV control.

The more functional the charger, the more expensive it is. But even in an expensive version, the cost is about 50 alkaline batteries. Payback comes fairly quickly. A charger of this class is usually universal. And it allows you to charge, in addition to nickel batteries, also lithium-ion batteries. It also has the functions of measuring the capacity, internal resistance of batteries, the mode of resetting the memory effect for nickel batteries.

NI-MH batteries with low self-discharge

This is enough new technology. The abbreviation LSD is sometimes used. What is translated from English as “low self-discharge” - low self-discharge.

Such batteries appeared on sale a little more than 10 years ago and have proven themselves very well. Compared to conventional batteries, they have lower internal resistance and, as a result, higher discharge currents. Their capacity is somewhat lower than that of conventional NI-MH batteries. But due to the fact that a conventional battery has a self-discharge on the first day of about 10%, they show themselves no less effectively.

It is quite easy to distinguish such a battery from a regular one. There will be an inscription “ready to use” on the packaging and on the element itself. “ready to use”. Such elements are sold already charged. This is the best choice for amateur photography, when the task is not to take several thousand shots in one day.

NI MH Charge Rules

The answer to the question - how to charge ni mh batteries depends, first of all, on what kind of charger the user has. In order to charge correctly, it is enough to adhere to simple rules.

• Before charging, it is advisable to discharge the batteries. This is not a strict norm, unlike Ni-cd batteries, but desirable.
• The ambient temperature must be at least 5 o C. The upper temperature limit is 50 o C. This temperature can occur in summer when exposed to direct sunlight.
• Learn the features of the charger. If it does not provide automatic shutdown, calculate the charging time.
• Install the batteries in the charger and connect it to the mains. After a while, check the degree of heating of the batteries. In case of strong heating, stop charging.
• Disconnect the charger either after the estimated time has elapsed or after the corresponding indication has turned on (depending on the type of charger).
• Store Ni-MH cells charged at 10-20% capacity. The voltage should not drop lower than 0.9v.

When properly charged, nickel-metal hydride batteries last a long time. From 500 to 1000 charge-discharge cycles. The main reason for premature failure is long-term disuse and, as a result, deep discharge. Often, the desire of users to abandon Ni-MH or Ni-cd technology and transfer all their equipment to lithium-ion batteries is completely unjustified. These batteries firmly occupy their place, both in the domestic segment and in the industry.

After purchasing a certain type of charger, many are faced with the problem of how to properly recharge it? One of the main types are nickel-metal hydride (NiMh) batteries. They have their own characteristics of how to charge them.

How to properly charge a NiMh battery?

A feature of NiMh batteries is their sensitivity to heat and overload. This can lead to negative consequences that affect the ability of the device to hold and deliver a charge.

Almost all batteries of this type use the "delta peak" method (determining the peak of the charging voltage). It allows you to indicate the moment of the end of the charge. The property of nickel chargers is that the voltage of a charged NiMh battery begins to decrease by some insignificant amount.

How much current to charge a NiMh battery?

The "delta peak" method is able to work well at charge currents of 0.3C and above. The C value is used to indicate the nominal capacity of a rechargeable aa ni NiMh battery.

So, for a charger with a capacity of 1500 mAh, the “delta peak” method will work confidently with a minimum charge current equal to 0.3x1500 = 450 mA (0.5 A). If the current is with a lower value, there is a great danger that at the end of the charge the voltage on the battery will not begin to decrease, but will freeze at a certain level. This will result in the charger not detecting the end of the charge. As a result, it will not turn off and recharging will continue. The capacity of the battery will decrease, which will adversely affect its performance.

Currently, almost everyone can be charged with current up to 1C. Under this condition, which must be respected is normal air cooling. Room temperature (about 20⁰С) is considered optimal. Charging at temperatures less than 5⁰C and more than 50⁰C will greatly reduce battery life.

To prolong the life of the NiMH charger, it is recommended to store it with a small amount of charge (30-50%).

Thus, proper charging of a nickel-metal hydride battery will favorably affect its operation and help it function normally.

This article about Nickel-metal hydride (Ni-MH) batteries has long been a classic on the Russian Internet. I recommend checking out…

Nickel-metal hydride (Ni-MH) batteries are similar in design to nickel-cadmium (Ni-Cd) batteries, and electrochemically similar to nickel-hydrogen batteries. The specific energy of a Ni-MH battery is significantly higher than the specific energy of Ni-Cd and hydrogen batteries (Ni-H2)

VIDEO: Nickel Metal Hydride Batteries (NiMH)

Comparative characteristics of batteries

Options	Ni-Cd	Ni-H2	Ni-MH
Rated voltage, V	1.2	1.2	1.2
Specific energy: Wh/kg | Wh/l	20-40 60-120	40-55 60-80	50-80 100-270
Service life: years | cycles	1-5 500-1000	2-7 2000-3000	1-5 500-2000
Self-discharge, %	20-30 (for 28 days)	20-30 (for 1 day)	20-40 (for 28 days)
Working temperature, °С	-50 — +60	-20 — +30	-40 — +60

*** A large spread of some parameters in the table is caused by different purpose (designs) of batteries. In addition, the table does not take into account data on modern batteries with low self-discharge.

History of the Ni-MH battery

The development of nickel-metal hydride (Ni-MH) batteries began in the 50-70s of the last century. As a result, it was created new way storage of hydrogen in nickel-hydrogen batteries, which were used in spacecraft. In the new element, hydrogen accumulated in alloys of certain metals. Alloys absorbing 1,000 times their own volume of hydrogen were discovered in the 1960s. These alloys are composed of two or more metals, one of which absorbs hydrogen and the other is a catalyst that promotes the diffusion of hydrogen atoms into the metal lattice. The number of possible combinations of metals used is practically unlimited, which makes it possible to optimize the properties of the alloy. To create Ni-MH batteries, it was necessary to create alloys that can work at low hydrogen pressure and room temperature. Currently, work on the creation of new alloys and technologies for their processing continues throughout the world. Alloys of nickel with metals of the rare earth group can provide up to 2000 charge-discharge cycles of the battery with a decrease in the capacity of the negative electrode by no more than 30%. The first Ni-MH battery, using LaNi5 alloy as the main active material of the metal hydride electrode, was patented by Bill in 1975. In early experiments with metal hydride alloys, nickel-metal hydride batteries were unstable, and the required battery capacity could not be achieved. Therefore, the industrial use of Ni-MH batteries began only in the mid-80s after the creation of the La-Ni-Co alloy, which allows electrochemically reversible absorption of hydrogen for more than 100 cycles. Since then, the design of Ni-MH batteries has been continuously improved in the direction of increasing their energy density. The replacement of the negative electrode made it possible to increase the load of active masses of the positive electrode by 1.3-2 times, which determines the capacity of the battery. Therefore, Ni-MH batteries have significantly higher specific energy characteristics compared to Ni-Cd batteries. The success of the distribution of nickel-metal hydride batteries was ensured by the high energy density and non-toxicity of the materials used in their production.

Basic processes of Ni-MH batteries

Ni-MH batteries use a nickel-oxide electrode as the positive electrode, like a nickel-cadmium battery, and a hydrogen-absorbing nickel-rare-earth alloy electrode instead of the negative cadmium electrode. On the positive nickel oxide electrode of the Ni-MH battery, the reaction proceeds:

Ni(OH) 2 + OH- → NiOOH + H 2 O + e - (charge) NiOOH + H 2 O + e - → Ni(OH) 2 + OH - (discharge)

At the negative electrode, the metal with absorbed hydrogen is converted into a metal hydride:

M + H 2 O + e - → MH + OH- (charge) MH + OH - → M + H 2 O + e - (discharge)

The overall reaction in a Ni-MH battery is written as follows:

Ni(OH) 2 + M → NiOOH + MH (charge) NiOOH + MH → Ni(OH) 2 + M (discharge)

The electrolyte does not participate in the main current-forming reaction. After reporting 70-80% of the capacity and during recharging, oxygen begins to be released on the oxide-nickel electrode,

2OH- → 1/2O 2 + H2O + 2e - (recharge)

which is restored at the negative electrode:

1/2O 2 + H 2 O + 2e - → 2OH - (recharge)

The last two reactions provide a closed oxygen cycle. When oxygen is reduced, an additional increase in the capacitance of the metal hydride electrode is also provided due to the formation of the OH - group.

Construction of Ni-MH battery electrodes

Metal hydrogen electrode

The main material that determines the performance of a Ni-MH battery is a hydrogen-absorbing alloy that can absorb up to 1000 times its own volume of hydrogen. The most widely used alloys are LaNi5, in which part of the nickel is replaced by manganese, cobalt and aluminum to increase the stability and activity of the alloy. To reduce the cost, some manufacturers use misch metal instead of lanthanum (Mm, which is a mixture of rare earth elements, their ratio in the mixture is close to the ratio in natural ores), which, in addition to lanthanum, also includes cerium, praseodymium and neodymium. During charge-discharge cycling, there is an expansion and contraction of 15-25% of the crystal lattice of hydrogen-absorbing alloys due to the absorption and desorption of hydrogen. Such changes lead to the formation of cracks in the alloy due to an increase in internal stress. The formation of cracks causes an increase in the surface area, which is corroded when interacting with an alkaline electrolyte. For these reasons, the discharge capacity of the negative electrode gradually decreases. In a battery with a limited amount of electrolyte, this causes electrolyte redistribution problems. Corrosion of the alloy leads to chemical passivity of the surface due to the formation of corrosion-resistant oxides and hydroxides, which increase the overvoltage of the main current-generating reaction of the metal hydride electrode. The formation of corrosion products occurs with the consumption of oxygen and hydrogen from the electrolyte solution, which, in turn, causes a decrease in the amount of electrolyte in the battery and an increase in its internal resistance. To slow down the undesirable processes of dispersion and corrosion of alloys, which determine the service life of Ni-MH batteries, two main methods are used (in addition to optimizing the composition and production mode of the alloy). The first method is microencapsulation of alloy particles, i.e. in covering their surface with a thin porous layer (5-10%) - by weight of nickel or copper. The second method, which has found the widest application at present, consists in treating the surface of alloy particles in alkaline solutions with the formation of protective films permeable to hydrogen.

Nickel oxide electrode

Nickel oxide electrodes in mass production are manufactured in the following constructive modifications: lamella, lamellaless sintered (metal-ceramic) and pressed, including tablet. In recent years, lamellaless felt and polymer foam electrodes have begun to be used.

Lamellar electrodes

Lamellar electrodes are a set of interconnected perforated boxes (lamellae) made of thin (0.1 mm thick) nickel-plated steel tape.

Sintered (cermet) electrodes

electrodes of this type consist of a porous (with a porosity of at least 70%) cermet base, in the pores of which the active mass is located. The base is made from carbonyl nickel fine powder, which, mixed with ammonium carbonate or carbamide (60-65% nickel, the rest is filler), is pressed, rolled or sprayed onto a steel or nickel mesh. Then the grid with the powder is subjected to heat treatment in a reducing atmosphere (usually in a hydrogen atmosphere) at a temperature of 800-960 ° C, while the ammonium carbonate or carbamide decomposes and volatilizes, and the nickel is sintered. The substrates thus obtained have a thickness of 1-2.3 mm, a porosity of 80-85% and a pore radius of 5-20 µm. The base is alternately impregnated with a concentrated solution of nickel nitrate or nickel sulfate and an alkali solution heated to 60-90 ° C, which induces the precipitation of nickel oxides and hydroxides. Currently, the electrochemical impregnation method is also used, in which the electrode is subjected to cathodic treatment in a nickel nitrate solution. Due to the formation of hydrogen, the solution in the pores of the plate is alkalized, which leads to the deposition of oxides and hydroxides of nickel in the pores of the plate. Foil electrodes are classified as varieties of sintered electrodes. The electrodes are produced by applying on a thin (0.05 mm) perforated nickel tape on both sides, by spraying, an alcohol emulsion of nickel carbonyl powder containing binders, sintering and further chemical or electrochemical impregnation with reagents. The thickness of the electrode is 0.4-0.6 mm.

Pressed electrodes

Pressed electrodes are made by pressing under a pressure of 35-60 MPa of the active mass onto a mesh or a steel perforated tape. The active mass consists of nickel hydroxide, cobalt hydroxide, graphite and a binder.

Metal felt electrodes

Metal felt electrodes have a highly porous base made of nickel or carbon fibers. The porosity of these foundations is 95% or more. The felt electrode is made on the basis of nickel-plated polymer or graphite felt. The thickness of the electrode, depending on its purpose, is in the range of 0.8-10 mm. The active mass is introduced into the felt by different methods, depending on its density. Can be used instead of felt nickel foam obtained by nickel-plating polyurethane foam followed by annealing in a reducing environment. A paste containing nickel hydroxide and a binder are usually introduced into a highly porous medium by spreading. After that, the base with the paste is dried and rolled. Felt and foam polymer electrodes are characterized by high specific capacity and long service life.

Construction of Ni-MH batteries

Cylindrical Ni-MH batteries

The positive and negative electrodes, separated by a separator, are rolled up in the form of a roll, which is inserted into the housing and closed with a sealing cap with a gasket (Figure 1). The cover has a safety valve that operates at a pressure of 2-4 MPa in the event of a failure in the operation of the battery.

Fig.1. The design of the nickel-metal hydride (Ni-MH) battery: 1-body, 2-cap, 3-valve cap, 4-valve, 5-positive electrode collector, 6-insulating ring, 7-negative electrode, 8-separator, 9- positive electrode, 10-insulator.

Ni-MH Prismatic Batteries

In prismatic Ni-MH batteries, positive and negative electrodes are placed alternately, and a separator is placed between them. The block of electrodes is inserted into a metal or plastic case and closed with a sealing cover. A valve or pressure sensor is usually installed on the cover (Figure 2).

Fig.2. Ni-MH battery structure: 1-body, 2-cap, 3-valve cap, 4-valve, 5-insulating gasket, 6-insulator, 7-negative electrode, 8-separator, 9-positive electrode.

Ni-MH batteries use an alkaline electrolyte consisting of KOH with the addition of LiOH. As a separator in Ni-MH batteries, non-woven polypropylene and polyamide 0.12-0.25 mm thick, treated with a wetting agent, are used.

positive electrode

Ni-MH batteries use positive nickel oxide electrodes, similar to those used in Ni-Cd batteries. In Ni-MH batteries, ceramic-metal electrodes are mainly used, and in recent years, felt and polymer foam electrodes (see above).

Negative electrode

Five designs of a negative metal hydride electrode (see above) have found practical application in Ni-MH batteries: - lamellar, when the powder of a hydrogen-absorbing alloy with or without a binder is pressed into a nickel mesh; - nickel foam, when a paste with an alloy and a binder is introduced into the pores of the nickel foam base, and then dried and pressed (rolled); - foil, when a paste with an alloy and a binder is applied to perforated nickel or nickel-plated steel foil, and then dried and pressed; - rolled, when the powder of the active mass, consisting of an alloy and a binder, is applied by rolling (rolling) on ​​an tensile nickel grate or copper mesh; - sintered, when the alloy powder is pressed onto a nickel grid and then sintered in a hydrogen atmosphere. The specific capacitances of metal hydride electrodes of different designs are close in value and are determined mainly by the capacitance of the alloy used.

Characteristics of Ni-MH batteries. Electrical characteristics

Open circuit voltage

Open circuit voltage value Ur.c. Ni-MH systems are difficult to accurately determine due to the dependence of the equilibrium potential of the nickel oxide electrode on the degree of nickel oxidation, as well as the dependence of the equilibrium potential of the metal hydride electrode on the degree of hydrogen saturation. 24 hours after the battery is charged, the open circuit voltage of the charged Ni-MH battery is in the range of 1.30-1.35V.

Rated discharge voltage

Ur at a normalized discharge current Ir = 0.1-0.2C (C is the nominal capacity of the battery) at 25 ° C is 1.2-1.25V, the usual final voltage is 1V. Voltage decreases with increasing load (see figure 3)

Fig.3. Discharge characteristics of a Ni-MH battery at a temperature of 20°C and different normalized load currents: 1-0.2C; 2-1C; 3-2C; 4-3C

Battery capacity

With an increase in load (decrease in the discharge time) and with a decrease in temperature, the capacity of a Ni-MH battery decreases (Figure 4). The effect of temperature reduction on the capacitance is especially noticeable at high discharge rates and at temperatures below 0°C.

Fig.4. The dependence of the discharge capacity of Ni-MH battery on temperature at different discharge currents: 1-0.2C; 2-1C; 3-3C

Safety and service life of Ni-MH batteries

During storage, the Ni-MH battery self-discharges. After a month at room temperature, the loss of capacity is 20-30%, and with further storage, the loss decreases to 3-7% per month. The self-discharge rate increases with increasing temperature (see figure 5).

Fig.5. The dependence of the discharge capacity of the Ni-MH battery on the storage time at different temperatures: 1-0°С; 2-20°C; 3-40°С

Charging a Ni-MH battery

The operating time (number of discharge-charge cycles) and service life of a Ni-MH battery are largely determined by operating conditions. The operating time decreases with an increase in the depth and speed of the discharge. The operating time depends on the speed of the charge and the method of controlling its completion. Depending on the Ni-MH type batteries, operating mode and operating conditions, batteries provide from 500 to 1800 discharge-charge cycles at a depth of discharge of 80% and have a service life (on average) from 3 to 5 years.

To ensure reliable operation of the Ni-MH battery during the guaranteed period, you must follow the manufacturer's recommendations and instructions. The greatest attention should be paid to the temperature regime. It is desirable to avoid overdischarges (below 1V) and short circuits. It is recommended to use Ni-MH batteries for their intended purpose, avoid mixing used and unused batteries, and do not solder wires or other parts directly to the battery. Ni-MH batteries are more sensitive to overcharging than Ni-Cd. Overcharging can lead to thermal runaway. Charging is usually carried out with a current of Iz \u003d 0.1C for 15 hours. Compensation charging is carried out with a current Iz = 0.01-0.03C for 30 hours or more. Accelerated (in 4 - 5 hours) and fast (in 1 hour) charges are possible for Ni-MH batteries with highly active electrodes. With such charges, the process is controlled by changes in temperature ΔТ and voltage ΔU and other parameters. Fast charge is used, for example, for Ni-MH batteries that power laptops, cell phones, electric tools, although laptops and cell phones now mainly use lithium-ion and lithium polymer batteries. A three-stage charge method is also recommended: the first stage of a fast charge (1C and above), a charge at a rate of 0.1C for 0.5-1 h for the final recharge, and a charge at a rate of 0.05-0.02C as a compensation charge. Information on how to charge Ni-MH batteries is usually contained in the manufacturer's instructions, and the recommended charging current is indicated on the battery case. The charging voltage Uz at Iz=0.3-1C lies in the range of 1.4-1.5V. Due to the release of oxygen at the positive electrode, the amount of electricity delivered during charging (Qz) is greater than the discharge capacity (Cp). At the same time, the return on capacity (100 Ср/Qз) is 75-80% and 85-90%, respectively, for disk and cylindrical Ni-MH batteries.

Charge and discharge control

To prevent overcharging of Ni-MH batteries, the following charge control methods can be used with appropriate sensors installed in batteries or chargers:

• charge termination method by absolute temperature Tmax. The battery temperature is constantly monitored during the charging process, and when the maximum value is reached, the fast charge is interrupted;
• charge termination method by temperature change rate ΔT/Δt. With this method, the slope of the battery temperature curve is constantly monitored during the charging process, and when this parameter rises above a certain set value, the charge is interrupted;
• charge termination method by negative voltage delta -ΔU. At the end of the battery charge, during the oxygen cycle, its temperature begins to rise, leading to a decrease in voltage;
• charge termination method according to the maximum charge time t;
• method of termination of the charge by the maximum pressure Pmax. Commonly used in prismatic accumulators large sizes and containers. The level of allowable pressure in a prismatic accumulator depends on its design and lies in the range of 0.05-0.8 MPa;
• method of termination of the charge by the maximum voltage Umax. It is used to disconnect the charge of batteries with high internal resistance, which appears at the end of the service life due to lack of electrolyte or at low temperature.

When using the Tmax method, the battery may be overcharged if the ambient temperature drops, or the battery may not be sufficiently charged if the ambient temperature rises significantly. The ΔT/Δt method can be used very effectively to terminate the charge at low temperatures environment. But if only this method is used at higher temperatures, the batteries inside the batteries will be exposed to undesirably high temperatures before the ΔT/Δt value for shutdown can be reached. For a certain value of ΔT/Δt, a larger input capacitance can be obtained at a lower ambient temperature than at a higher temperature. At the beginning of a battery charge (as well as at the end of a charge), there is a rapid rise in temperature, which can lead to premature charge shutdown when using the ΔT/Δt method. To eliminate this, charger developers use timers for the initial sensor response delay with the ΔT / Δt method. The -ΔU method is effective for terminating the charge at low ambient temperatures rather than at elevated temperatures. In this sense, the method is similar to the ΔT/Δt method. In order to ensure that the charge is terminated in cases where unforeseen circumstances prevent the normal interruption of the charge, it is also recommended to use a timer control that regulates the duration of the charge operation (method t). Thus, to quickly charge batteries with rated currents of 0.5-1C at temperatures of 0-50 °C, it is advisable to simultaneously apply the Tmax methods (with a shutdown temperature of 50-60 °C, depending on the design of the batteries and batteries), -ΔU (5- 15 mV per battery), t (usually to obtain 120% of the rated capacity) and Umax (1.6-1.8 V per battery). Instead of the -ΔU method, the ΔT/Δt method (1-2 °C/min) with an initial delay timer (5-10 min) can be used. For charge control, also see the corresponding article. After a quick charge of the battery, the chargers provide for switching them to recharge with a rated current of 0.1C - 0.2C for a certain time. Constant voltage charging is not recommended for Ni-MH batteries as "thermal failure" of the batteries can occur. This is because at the end of the charge there is an increase in current, which is proportional to the difference between the power supply voltage and the battery voltage, and the battery voltage at the end of the charge decreases due to the increase in temperature. At low temperatures, the charge rate should be reduced. Otherwise, oxygen will not have time to recombine, which will lead to an increase in pressure in the accumulator. For operation in such conditions, Ni-MH batteries with highly porous electrodes are recommended.

Advantages and disadvantages of Ni-MH batteries

A significant increase in specific energy parameters is not the only advantage of Ni-MH batteries over Ni-Cd batteries. Moving away from cadmium also means moving towards cleaner production. The problem of recycling failed batteries is also easier to solve. These advantages of Ni-MH batteries determined the faster growth of their production volumes in all the world's leading battery companies compared to Ni-Cd batteries.

Ni-MH batteries don't have the "memory effect" that Ni-Cd batteries have due to the formation of nickelate in the negative cadmium electrode. However, the effects associated with the overcharging of the nickel oxide electrode remain. The decrease in the discharge voltage, observed with frequent and long recharges in the same way as with Ni-Cd batteries, can be eliminated by periodically performing several discharges up to 1V - 0.9V. It is enough to carry out such discharges once a month. However, nickel-metal hydride batteries are inferior to nickel-cadmium batteries, which they are designed to replace, in some performance characteristics:

• Ni-MH batteries operate effectively in a narrower range of operating currents, which is associated with limited desorption of hydrogen from the metal hydride electrode at very high discharge rates;
• Ni-MH batteries have a narrower operating temperature range: most of them are inoperable at temperatures below -10 °C and above +40 °C, although in some battery series the adjustment of the recipes has provided an expansion of temperature limits;
• during the charge of Ni-MH batteries, more heat is released than when charging Ni-Cd batteries, therefore, in order to prevent overheating of the battery from Ni-MH batteries during fast charging and / or significant overcharging, thermal fuses or thermal relays are installed in them, which are located on the wall of one of the batteries in the central part of the battery (this applies to industrial battery assemblies);
• Ni-MH batteries have an increased self-discharge, which is determined by the inevitability of the reaction of hydrogen dissolved in the electrolyte with a positive oxide-nickel electrode (but, thanks to the use of special negative electrode alloys, it was possible to achieve a decrease in the self-discharge rate to values ​​close to those for Ni-Cd batteries );
• the risk of overheating when charging one of the Ni-MH batteries of the battery, as well as reversal of the battery with a lower capacity when the battery is discharged, increases with the mismatch of the battery parameters as a result of long cycling, so the creation of batteries from more than 10 batteries is not recommended by all manufacturers;
• the loss of capacity of the negative electrode that occurs in a Ni-MH battery when discharging below 0 V is irreversible, which puts forward more stringent requirements for the selection of batteries in the battery and the control of the discharge process than in the case of using Ni-Cd batteries, as a rule, discharge to 1 V/ac in low voltage batteries and up to 1.1 V/ac in a battery of 7-10 batteries.

As noted earlier, the degradation of Ni-MH batteries is determined primarily by a decrease in the sorption capacity of the negative electrode during cycling. In the charge-discharge cycle, the volume of the crystal lattice of the alloy changes, which leads to the formation of cracks and subsequent corrosion upon reaction with the electrolyte. The formation of corrosion products occurs with the absorption of oxygen and hydrogen, as a result of which the total amount of electrolyte decreases and the internal resistance of the battery increases. It should be noted that the characteristics of Ni-MH batteries significantly depend on the alloy of the negative electrode and the processing technology of the alloy to improve the stability of its composition and structure. This forces battery manufacturers to be careful in choosing alloy suppliers, and battery consumers to be careful in choosing a manufacturer.

Based on the materials of the sites powerinfo.ru, "Chip and Dip"

It's no secret that at any time you can find yourself in such conditions when it becomes necessary to recharge "dead" batteries. For example, Ni-MH batteries widely used in everyday life and in production - how to charge them correctly? Of course, you can use the simplest charger that comes with any household appliance. However, their strength is very low, so such a charge will “hold” for a very short time. The use of more complex chargers helps to ensure that the battery not only works “at full capacity”, but also uses all its possible resources. Also, batteries are different. Their names directly depend on what composition they are made of.

Common types of nickel batteries, their similarities and differences

There are many, which include various chemical compounds. In domestic consumption, it is optimal to use nickel-metal hydride, cadmium and nickel-zinc elements. Of course, any battery needs some care, so it is always important to follow the rules of operation and charging.

Ni-MH

Nickel-metal hydride batteries are secondary chemical current sources with a much higher capacity than their predecessors - but their service life is shorter. One of the popular applications for nickel cells is model building (except for aviation, due to the fact that the battery is quite heavy in weight).

The first development of these cells began in the 70s of the twentieth century with the aim of improving Cd batteries. After 10 years, in the late 80s, it was possible to ensure that the chemical compounds used to create Ni-MH batteries became more stable. In addition, they are much less susceptible to the “memory effect” than Ni-Cd: they do not immediately “remember” the charge current remaining inside if the element was not completely discharged before use. Therefore, they do not need a full discharge so often.

Ni-Cd

Although Ni-MH have a number obvious benefits before Ni-Cd, it is worth noting that the latter do not lose their popularity. Mainly because they do not heat up so much when charging due to the greater conservation of energy inside the cell. As you know, there are various types of chemical processes occurring between substances.

If you charge Ni-MH, the reactions will be exothermic, and if the cadmium batteries - endothermic, which provides a higher efficiency. Thus, Cd can be charged with a higher current without fear of overheating.

Ni-Zn

Recently, much attention has been paid to discussion on the Internet of batteries, which include zinc. They are not as well known to consumers as the previous ones, but are ideal for use as batteries for digital cameras.

Their main feature is high voltage and resistance, so that even by the end of the charge-discharge cycle, there is no sharp drop in voltage, like a Ni charge. If there are metal hydride batteries in the camera, it will turn off even if the battery is not completely discharged, and Ni-Zn does not have this even at the end of the discharge.

Due to the nature of these batteries, they may require an individual charger, or they can be charged on any universal smart charger, such as the ImaxB6. Ni-Zn batteries are also great for use in electric children's toys and blood pressure monitors.

Rapid charging of NiMH batteries and other power sources

It is better to charge the battery using more complex models of the corresponding devices. Their current algorithms have a more complex sequence. Of course, doing this is a bit more complicated than simply inserting the battery into the basic charger included in the package. But the quality of charging when using a "smart" device will be an order of magnitude higher. So how do you charge Ni-MH batteries?

First, the current is turned on and the voltage at the battery terminals is checked (the current parameters are 0.1 of the battery capacity, or C). If the voltage exceeds 1.8 V, this means either the battery is missing or the battery is damaged. In this case, the process cannot be started. You need to either replace the damaged element with a whole one, or insert a new one into the device.

After checking the voltage, the initial discharge of the battery is evaluated. If U is less than 0.8 V, then you can not immediately proceed to fast charging, and if U = 0.8 V or more, then you can. This is the so-called "pre-charge phase", used to prepare cells that are very heavily discharged. The current value here is 0.1-0.3 C, and the duration in time is half an hour, no less. It should immediately be noted that at all stages it is important to constantly control the temperature . Especially when it comes to what current and how to properly charge a Ni-MH battery. Such batteries heat up much faster, especially towards the end of the process. Their temperature should not exceed 50°C.

Fast charging is only carried out if the previous checks have been carried out correctly. How to charge the battery correctly? So, the initial voltage is 0.8 V or a little more. The power supply starts. It is carried out smoothly and carefully for 2-4 minutes - until the desired level is reached. Optimal current level for Ni-MH and Ni-Cd batteries - 0.5-1.0 C, but sometimes it is recommended not to exceed 0.75.

It is important to determine the moment when the fast phase ends in time to avoid damaging the battery. The most reliable, in this case, is the dv method, which is used differently when charging nickel-cadmium and Ni-MH batteries. For Ni-Cd, the voltage becomes larger and drops towards the end of charging, so the signal for its completion is the moment when U drops to 30 mV.

Since the drop in U of the charged cells is much less pronounced for Ni-MH, in this case, the dv=0 method is used. A period of 10 minutes is recorded during which U of the battery remains stable - that is, with a voltage fluctuation threshold set to zero.

In conclusion, a small recharging phase follows. Current - within 0.1-0.3 C, duration - up to half an hour. This is necessary to ensure that the battery is fully charged, as well as to equalize the charge potential in it.

An important point (this also applies to charging Ni-Cd batteries): if it is carried out immediately after a fast one, you should definitely cool the battery for several minutes: the heated element is unable to take charge properly.

In addition to fast charging, there is also drip charging, which is produced by small currents. Some believe that it "prolongs the life" of the batteries, but this is not so. In fact, drip charging is no different from the effect of a standard charger without “serious” adjustment of current indicators. Any battery, if it is not used, sooner or later loses the accumulated energy, and it will still need a full-fledged charging process, regardless of its duration and "labor intensity". Such a charging process is also attractive for many because the current indicators here can not be fixed due to their smallness. However, only a serious approach to the use of "smart" chargers can "extend the life" of batteries. As well as their proper storage, taking into account the characteristics of a particular type of battery.

Temperature factor and storage conditions

Modern chargers are equipped with a special system for "evaluating" environmental conditions, including temperature factors. Such a “charger” can determine for itself whether to charge under certain conditions or not. It has already been mentioned that the level of efficiency inside the battery is the highest precisely at the beginning of the process, when the hydride plan batteries do not heat up so much. At the end of the charging process or closer to it, the efficiency drops sharply, and all the energy, turning into heat due to exothermic chemical reactions, is released outside. It is important to stop charging the Ni-MH battery in time. And, if possible, get the latest charger that will accurately control this process.

Currently, all chargers, including Cd batteries, can be charged with current up to 1C with the establishment of standards air cooling. The optimum temperature of the room in which charging is carried out is 20 ° C. It is not recommended to start the process at temperatures below +5 and above 50°C.

Ni-Cd is unique in that it is the only type of cell that will not be damaged if stored completely discharged, unlike Ni-MH. For better current output, it is recommended to charge nickel-cadmium batteries immediately before use. Also, after long-term storage, they need a "buildup": you should fully charge and discharge the Ni-Cd battery in a day for optimal performance.

Nickel-metal hydride cells, unlike their predecessors, can easily fail when deeply discharged. Therefore, you need to store them only charged. At the same time, the voltage should be checked regularly every two months. Its minimum level should always remain 1 V, and if it drops, recharging is necessary.

A new Ni-MH battery must be fully charged and discharged three times before use, then immediately put on the "base" for 8-12 hours. Later, there will be no need to keep it on charge for a long time - remove it immediately after indicating a special indicator on the charger.

Although all these batteries have long been replaced by more capacious ones, based on lithium, they are actively used now. It's more familiar and much cheaper. In addition, lithium batteries perform much worse at low temperatures.

I bought a bunch of holders for AA batteries (or just batteries) on Ali ... A thing is sometimes needed in the household, especially if you assemble or repair any electronic devices or gadgets. Actually, there would be nothing more to write about them (well, just evaluate the resistance of the contacts, measure the length of the wires and evaluate the plastic by eye and tooth - what will be in the review), but I came across one article on the Internet and the idea was born to check whether it is possible to restore the capacity exhausted NiCd and NiMh batteries that have accumulated on the farm, and throwing them simply into a landfill does not raise a hand, because such elements need to be recycled ... What came of it, and did it work at all ... You can find out by reading the review ...
Attention- a lot of photos, traffic!!!

Here, in fact, the article itself, which I mentioned in the table of contents of the review ...


I started looking for more information about the recovery of NiCd and NiMh batteries that have lost their capacity and the search led me to an entertaining article in English, which you can read by clicking on the link: Those who do not know English can take advantage of the automatic translation into Russian by Google. From the article, I took out the main thing that NiCd and NiMh elements have memory (for NiCd this is very pronounced, for NiMh it is less pronounced, but still the effect takes place), and in order to prolong their life, they must be discharged to a certain voltage before charging.


Probably many people know about this, that the manufacturer recommends discharging the batteries to a residual voltage of 0.9-1V, and only then put them on charge. But often this is ignored and over time the elements lose their capacity, crystals of cadmium and nickel salts form in them. And in order to break them, at least partially, you need to discharge the batteries with a small current to a residual voltage of 0.4-0.5V ...

By the way, a little about how the battery works: The basis of any battery is positive and negative electrodes. Let's take a look at the NiCd battery. The positive electrode (cathode) contains nickel hydroxide NiOOH with graphite powder (5-8%), and the negative electrode (anode) contains metallic cadmium Cd in powder form.


Batteries of this type are often called roll batteries, since the electrodes are rolled into a cylinder (roll) together with a separating layer, placed in a metal case and filled with electrolyte. The separator (separator), moistened with electrolyte, isolates the plates from each other. It is made of non-woven material, which must be resistant to alkali. The most common electrolyte is potassium hydroxide KOH with the addition of lithium hydroxide LiOH, which promotes the formation of lithium nickelates and increases the capacity by 20%.

Nickel-metal hydride batteries in their design are analogous to nickel-cadmium batteries, and in electrochemical processes - nickel-hydrogen batteries. The specific energy of a Ni-MH battery is significantly higher than the specific energy of Ni-Cd and Ni-H2 batteries
The NiMh (Nickel Metal Hydride) battery is designed in much the same way as NiCd:


The positive and negative electrodes, separated by a separator, are folded into a roll, which is inserted into the housing and closed with a sealing cap with a gasket. The cover has a safety valve that operates at a pressure of 2-4 MPa in the event of a failure in the operation of the battery.

Armed with knowledge, I decided to try to assemble something similar as in the article “Automatic discharger”, and in practice it will help to check whether it will help or not, to restore, at least partially, batteries that have lost their capacity ... I assembled such a test device according to the scheme given in the article. In the article, a 1V 75mA light bulb was used as an indication, I don’t know where the author found one. It was also suggested in the article to use an LED, but this idea will not work, since all LEDs do not shine at 1-1.5V ... Therefore, an ammeter was used as an indicator ...

The initial discharge current of a freshly charged battery is 250mA, and gradually decreases. With a residual voltage of 1V, the discharge current drops to 30-40mA, just about the same current is needed to try to break the "slag" crystals in the battery ...
Conducted a small test of the "killed" radiotelephone Ni-Mh battery AAA format, a total of 4 charge-discharge cycles were carried out. Testing was carried out in this way: The battery was discharged to the manufacturer's recommended voltage of 1V and was fully charged using the Soshine Automatic Charger (thanks to the Chinese)

The charger counts the amount of charge “pumped” into the battery, of course this is the wrong way to assess the capacity, because you need to measure the battery capacity during discharge, not charge (we will measure the capacity correctly in the future), but indirectly you can judge whether the capacity changes or not " dead battery...

Lyrical digression

By the way, on Muska, many authors "sin" with this, measuring the capacity of batteries with the help of everyone's favorite, "white doctor" ... By measuring the charge "blown" into the battery, with important view they talk about the battery capacity, not taking into account that not everything “inflated” can be “blown out” back, as well as numerous energy losses for self-discharge, battery heating, etc. Any review of a device with a USB port is considered incomplete if it does not include a photo of a “white doctor”. The Chinese probably got rich on sales of these super-devices for testing ...))))

A fully charged battery took 480 mAh of “charge” and was put into discharge in a manufactured discharge device… Discharge cutoff occurred at a residual battery voltage of 0.5V… This value depends on the parameters of the transistors used in the discharge device… The Charge-Discharge cycle was repeated 4 times ... The results of preliminary testing are given below:

1 charge - 680mAh

2- charge - 726mAh

3- charge - 737mAh

4- charge - 814mAh

Well, we see a positive trend ... At least, more and more “charge” enters the battery, but unfortunately this is only an indirect estimate of the capacity, and in order to assess it accurately, you need to discharge the battery by measuring the capacity ...
What are we going to do next?
For a correct assessment of the battery capacity, a new VM200 Charger and Discharger was ordered from the Chinese ... It is capable of discharging the battery and measuring the capacity, it will be much more accurate ...

Since you can immediately test 4 batteries, it was decided to remake the discharger, and make it also 4-channel. The VM200 charger-discharge device is, of course, capable of discharging the battery on its own, but it does this to a residual voltage of 0.9V, which is not enough, I need to discharge each element to 0.4V, so a diagram of another discharge device was found on the Internet

I translated this scheme into modern elements and multiplied it to 4 channels ...
It turned out such a discharge device:




Since in all 4 channels, I set the same cutoff voltage of the comparators, I managed with one zener diode and one construction resistor for all four channels ...
For those who want to repeat, I give a link to the printed circuit board, all the elements are signed on it

This is where we got to our holders for batteries or batteries ... I needed 4 pieces, the rest will go “in reserve” ... As usual, the link already goes to “nowhere”, so I put a similar product from another seller in the title. I'm attaching a screenshot of the order under the spoiler, otherwise they won't believe that I order spare parts from the Chinese ...))))

Screenshot of the order

While the Chinese, in full swing, on rickshaws, in the sweat of their brows, are bringing my 2 parcels to me, I will allow myself a short lyrical digression ... There will definitely be a couple of “muska” readers who will say that I am doing garbage, especially making printed circuit boards, and in general you don’t have to take a steam bath, but just throw away used batteries ... Perhaps this is right, but everyone has their own way, someone drinks vodka, someone goes to the bathhouse, but I like to create something, even if it seems to someone it’s meaningless ... The main thing is that I like it, but I wish you just a good rest, reading my review, maybe learn something new and discuss it in the comments, just don’t bring disputes to “holivar” ...)))
While I was waiting for the parcel, I made an indication module, instead of a voltmeter for the first version of the board, which is on two transistors ...

having fun under the spoiler

This is all done on the LM3914 chip, almost according to the typical scheme from the datasheet. 5V power supply from some kind of cell phone charging ... There is a jumper on the board that can switch the microcircuit from the "Point" mode to the "Column" mode and vice versa ...

back side


When one red LED is on, the battery voltage is 0.2V, when the entire bar is on, it means 1.2V on the battery. Each extinguished LED indicates that the voltage on the battery has dropped by another 0.1V ... It is convenient to use this board in the form of an indicator voltmeter with a fairly high accuracy ...

Finally, both parcels arrived, I will not describe unpacking, weighing, measuring dimensions, because it is clear that AA battery holders are slightly larger than the batteries themselves ... Here is a general view of the holder.


The plastic is elastic, holds the battery well, moreover, it is quite difficult to pull the battery out with your fingers, you have to pry it with some thin object, a screwdriver, for example.
Check the resistance of the spring contact. 2 milliohm...


The length of the wires (red and black) is about 15 cm.

Now let's set the cutoff voltage of the comparators, this can be done on any of the four channels. And let's check the current with which our batteries will be discharged ... We supply 5V to the discharge device from some kind of power source from a cell phone. We see that all the LEDs are on. Green indicates that power is connected, and red 4 LEDs tell us that all comparators are in the closed state and no discharge occurs.

Description of the setup process and photos under the spoiler

We connect a laboratory power supply to the first channel and give 1.2V - this is the voltage of a fully charged battery ... We see that the discharge with a current of 70mA has begun (on the right is an accurate ammeter with 4 digits after the decimal point)


Please note that the LED of the first channel has gone out, signaling that the discharge in this channel has begun ...


With a battery voltage of 0.5V, the discharge current is 40mA, in principle, just about this current is what we need to successfully break the formed crystals ...


At a voltage of 0.4V, the comparator closes and the discharge is over. Note that the current on the ammeter has become zero

Using a crimper (not cheap, professional, bought on Ali), we crimp the wires into special lugs for connectors


It turns out such a crimped tip ... It's nice to work with a professional tool, although it is not cheap, but the convenience and result are worth it.

Well ... everything is ready, we select candidates for the restoration of capacity. Numbers 1 and 2 are NiMh batteries from the Panasonic electric shaver, the initial capacity is not known. After 3 years in an electric razor, fully charged batteries were no longer enough for one shave. Numbers 3 and 4 NiCd batteries, the initial capacity of 600mA, worked out their own in an electrocardiograph ...
Since the batteries have been lying without use for a long time, you first need to “cheer them up”, this can be done on the BM200 Charger by selecting the Gharge-Refresh mode - the charger will carry out 3 discharge cycles to 0.9V, and then fully charge and so on 3 times. In this case, the capacity increases slightly. Thus, we will eliminate the error, a slight increase in capacity, which will be added after several cycles of "training" for a long time lying without work batteries. The training was carried out, it took approximately 36 hours in time

Now you can start the recovery process...


We insert all the batteries into the charger, select the “Charging-Test” mode ... and wait ... After fully charging with a current of 200mA, the charger will discharge the batteries to 0.9V with a current of 100mA and calculate the given capacity. We will operate with it as the initial capacity before recovery.


In the morning, the charger gave out the calculated capacity of the batteries, we will use it as the initial values, Nickel-Cadmium batteries have lost half of their initial capacity, Nickel-metal hydride batteries, it is not known how many capacities they had initially, I suspect, somewhere around 1200mAh, but it doesn’t matter, the main thing for us is the dynamics and restoration of capacity.


We put all the batteries in the discharge device, we see that all the red LEDs have gone out, in all four channels the batteries have begun to discharge. When a residual voltage of 0.4V is reached on each battery, the comparators will close and the red LEDs will light up, signaling the end of discharging. This may take a long time...


I came home from work, all 4 red LEDs are lit on the discharge device. Just in case, I measured the residual voltage on all batteries with a voltmeter. Approximately 0.4V on each ...

Well, we begin to repeat the discharge-charge cycle. Long and tedious, day and night. All testing took 4 days. On the display of the VM200 memory, positive dynamics are visible, more and more charge “enters” the batteries ... It can be seen that the method works ...)))))


But dots over i will arrange the final test of battery capacity during discharge.
5 charge-discharge cycles have passed ... We put the batteries to determine the capacity, this is the “Gharge-Test” mode ... Well, here is the final result - the verdict ...


As we can see, the capacity has remained the same... The miracle did not happen, although everything said that the batteries were being restored, because. the “injected” capacity is growing ... But alas ...
At this point, the Muskovites, who have a humanitarian education, sadly closed the review and gave me a fat minus ... The Muskovites, who have an engineering education, giggled and thought that no one had yet deceived the laws of physics, chemistry, old age and an old woman with a scythe ... And they knew about it in advance … But… There is one small BUT…
As you remember, I wrote earlier about restoring AAA batteries from a radio phone, at the beginning of the article ... The batteries worked for 2 years and stopped holding a charge. If you remove the phone from charging, after 10-15 minutes the low battery icon flashed on the screen, and demanded to put the phone on charge. If his request was ignored, then the phone simply turned off. This was about a year ago. After 4 discharge-charge cycles, I again put the batteries in the phone, and they have been working in it for a year now, even if you have to put the phone on charge a little more often than with new batteries, BUT !!! The phone normally works for a year with refurbished batteries !!! Why and how, I don't know... But the fact remains...
Now let's return the charged batteries to the Panasonic razor ... Before restoring the batteries, it lasted about 4-5 minutes after a full charge ... Then the razor inevitably "died" ... Well, let's check, I put the batteries back in place ... I shaved ... then I kept it for another 25 minutes the razor turned on ... It buzzes, as if it has new batteries ... I didn’t torment the engine further ... turned it off ... I feel that these batteries will still be enough for me for a while ...
I will not draw conclusions, everyone can draw them on their own ... Thanks to everyone who read my review to the end ...
At the end of the review, according to tradition, the animal ... The animal liked the plastic and the resistance of the spring contact, but really did not like the length of the wires ... It needs to be longer ... and the rustler should be at the end of the wires ...