For a long time I could not upload the results of my experiments to LiveJournal ... there is no Internet at home now, there is a lot of workload at work.

Nevertheless, the work has not stood up, but is moving, and soon a report on the work done will appear here.

at this stage, I came across the fact that all the batteries I have in stock have gradually become unusable ... as a result, tests of an already autonomous device are being postponed ...

I rummaged through the Internet on this topic and honestly copy-paste a piece of the article here, directly the Ni-Mh recovery algorithm

Ni-MH battery recovery algorithm

As mentioned above, the loss of battery capacity is associated with the deposition of reaction products on the electrodes. To restore the battery, you must return these products to their original condition.

To do this, you must have the following:

• power supply with continuously adjustable voltage, current and voltage indicators (you can also use a separate voltmeter and ammeter);
• batteries prepared for charging;
• load - a rheostat or a light bulb, the resistance of which must be selected based on the formula:

R = U / I [Ohm], where U is the nominal voltage of the battery [V], I is the required current [A], which is taken from the calculation of I = 0.4 C (bat).

It is also desirable to have a temperature sensor or thermal relay available so that you can turn off the current in time in case of overheating.

Before charging, we discharge the battery to a voltage of about 1 V - we connect a voltmeter and a load in parallel with the element. We periodically control the voltage (it should not fall below 0.9 V - irreversible processes may begin). We periodically control the temperature - it should not rise above 50 degrees Celsius. Otherwise, it is necessary to disconnect the load until the element cools down to room temperature. After discharge, it is necessary to wait for the normalization of the processes inside the element (15-20 minutes). During this time, the element is “regenerated”, the voltage will increase, and it can be recharged to a voltage of 0.9 V. Then, after waiting 10-15 minutes, you can start charging.

Charger

For charging, we connect the ammeter in series to the element being charged, the power source and the voltmeter - in parallel, with one contact to the free pole of the battery, the other - to the free contact of the ammeter. A temperature sensor or a sensitive element, a thermal relay, it is desirable to fix it on the battery using thermal paste for more accurate measurements. We set the voltage regulator of the power supply to the minimum voltage (the rheostat - to the maximum resistance). Next, we gradually raise the voltage so that the current on the ammeter reaches the value:

I(zar) = 0.1C(bat)

For example, for a 1500 mAh battery, the maximum current will be 150 mA. The current will gradually decrease, and accordingly, it is necessary to increase the voltage. First - every 3-5 minutes during the first hour, then - every hour. As soon as the voltage reaches 1.3 nominal (1.4-1.5 volts), you need to leave the battery on charge as it is - you can’t increase the voltage further. When the current drops to a value close to zero (after 4-6 hours), you need to turn off the charging, wait 15-20 minutes for the processes to normalize, and charge for 8 hours. Throughout the charging, it is necessary to ensure that the temperature does not rise above 50 degrees Celsius. If the temperature exceeds this value, it is necessary to lower the charging current (by 1.5-2 times) until the battery cools down to 30 degrees. Then you can smoothly increase the current to the nominal value. It will take 3-4 such cycles to restore the original capacity.

Rechargeable batteries have become the main source of power for modern electronic devices. Ni-MH batteries are considered the most popular, as they are practical, durable and can have an increased capacity. But for safety specifications during the entire service life, you should learn some features of the operation of drives of this class, as well as the correct charging conditions.

Standard Ni-MH batteries

How to properly charge Ni-MH batteries

When you start charging any autonomous drive, be it a simple smartphone battery or a high-capacity truck battery, a series of chemical processes begin in it, due to which accumulation occurs. electrical energy. The energy received by the drive does not disappear, part of it goes to charge, and a certain percentage goes to heat.

The parameter by which the efficiency of battery charging is determined is called the efficiency of an autonomous drive. Efficiency allows you to determine how the ratio of useful work and its unnecessary losses that go to heating. And in this parameter, nickel-metal hydride batteries and batteries are much inferior to Ni-Cd drives, since too much of the energy spent on charging them is also spent on heating.

Nickel-metal hydride drive can be repaired by yourself

In order to quickly and correctly charge a NiMH battery, the correct current must be set. This value is determined based on such a parameter as the capacity of an autonomous power source. You can increase the current, but this should be done at certain stages of charging.

Specifically for nickel-metal hydride batteries, 3 types of charging are defined:

• Drip. It flows to the detriment of battery longevity, does not stop even after reaching 100% charge. But with drip charging, a minimal amount of heat is released.
• Fast. Following the name, we can say that this type of charging proceeds a little faster, due to this input voltage within 0.8 Volts. At the same time, the efficiency level rises to 90%, which is considered a very good indicator.
• recharge mode. Required to charge the drive to its full capacity. This mode is carried out using a small current for 30-40 minutes.

This is where the charge features end, now we should consider each mode in more detail.

Features of drip charging

The main feature of drip charging of NiZn, as well as Ni-MH batteries, is the reduction of its heating during the entire process, which can last until the full capacity of the drive is restored.

Standard charger for Ni-MH batteries

What is remarkable about this type of charging:

• A small current, respectively - the absence of a clear framework for the potential difference. The charge voltage can reach its maximum without any negative impact on the lifetime of the drive.
• Efficiency within 70%. Of course, this indicator is lower than the others, and the time required for full recovery of capacity increases. But this reduces the heating of the battery.

The above indicators can be classified as positive. Now you should pay attention to the negative qualities of drip charging.

• The drip recovery process does not stop even after the restoration of full capacity. Constant exposure to even a small current, when the battery is fully charged, quickly renders it unusable.
• It is necessary to calculate the charge time based on factors such as current, voltage and. Not very convenient and may take too long for some users.

Modern nickel-metal hydride power supplies don't take drip charge as negatively as older models. But manufacturers chargers are gradually abandoning the use of such a restoration of battery capacity.

Fast charge mode for Ni-MH batteries

The nominal charge rates for nickel-metal hydride batteries are:

• Current strength within 1 A.
• Voltage from 0.8 V.

Those data from which it is necessary to build on are given. For a fast charge mode, it is best to set the current to 0.75 A. This is quite enough to restore the drive in a short period of time without reducing its service life. If you raise the current more than 1 A, then the consequence may be an emergency release of pressure, at which the release valve opens.

Memory with accurate current readings

In order for the fast charging mode not to harm the battery, it is necessary to monitor the end of the process itself. The efficiency of fast recovery of capacity is about 90%, which is considered a very good indicator. But at the end of the charging process, the efficiency drops sharply, and the consequence of such a drop is not only the release of a large amount of heat, but also a sharp increase in pressure. Of course, such indicators negatively affect the durability of the drive.

The fast charge process consists of several steps, which should be considered in more detail.

Confirming the availability of charge indicators

Process sequence:

1. A preliminary current is supplied to the storage poles, which is no more than 0.1 A.
2. The charge voltage is within 1.8 V. At higher rates, fast charging of the battery will not start.

Nickel-Metal Hydride Medium Capacity Cell

The logic circuit in the chargers is programmed for no battery. This means that if the output voltage is more than 1.8 V, then the charger will perceive such an indicator as the absence of a power source. A high potential difference also occurs when the battery.

Power supply capacity diagnostics

Before starting the recovery of capacity, the memory must determine the level of charge of the power supply, so the fast recovery process cannot begin if it is completely discharged and the potential difference is less than 0.8 V.

To restore the partial capacity of the nickel-metal hydride drive, an additional mode is provided - pre-charge. This is a gentle mode that allows the battery to “wake up”. It is used not only after full recovery of capacity, but also during long-term storage of the battery.

It should be remembered that in order to preserve the operational life of nickel-metal hydride power supplies, they must not be completely discharged. Or, if there is no other way out, then do it as little as possible.

What is pre-charge? Process features

To know how to properly charge a battery, you need to understand the pre-charge process.

The main feature of the pre-capacity recovery mode is that a certain period of time is allotted for it, no more than 30 minutes. The current strength is set in the range from 0.1 A to 0.3 A. With these parameters, there is no unwanted heating, and the battery can calmly “wake up”. If the potential difference exceeds more than 0.8 V, the pre-charge is automatically turned off and the next stage of capacity recovery begins.

Variety of Nickel Metal Hydride Products

If after 30 minutes the power supply voltage has not reached 0.8 V, this mode is terminated, as the charger detects the power supply as faulty.

Quick battery charge

This stage is the very fast charging of the power source. It proceeds with the obligatory observance of several basic parameters:

• Control over the current strength, which should be in the range of 0.5-1 A.
• Time control.
• Continuous comparison of potential differences. Disable the recovery process if this indicator drops by 30 mV.

It is very important to monitor the change in voltage parameters, since at the end of fast charging, the battery begins to heat up quickly. Therefore, the memory includes separate nodes responsible for controlling the voltage of the power source. For this, the voltage delta control method is specially used. But some memory manufacturers use modern developments that turn off the device if there is no change in the potential difference for a long time.

A more expensive option is to install a temperature controller. For example, when the temperature of the Ni-MH drive rises, the fast capacity recovery mode is automatically disabled. This requires expensive temperature sensors or electronic circuits, respectively, the price of the charger itself also increases.

Recharging

This stage is very similar to the pre-charge of the battery, in which the current is set within 0.1-0.3 A, and the whole process takes no more than 30 minutes. Recharging is necessary, since it is it that allows you to equalize the electronic charges in the power source, and increase its operational life. But with a longer recovery, on the contrary, there is an accelerated destruction of the battery.

Super Fast Charging Features

There is another important concept of restoring the capacity of Ni-MH batteries - ultra-fast charging. Which not only quickly restores the power source, but also extends its service life. It is connected with one interesting feature NiMH batteries.

Metal hydride power supplies can be charged with increased currents, but only after reaching 70% capacity. If you skip this moment, then an overestimated current strength parameter will only lead to the rapid destruction of the battery. Unfortunately, charger manufacturers consider it too costly to install such control nodes on their products, and use simpler fast charging.

Convenient finger-type power supplies

Ultra-fast charging should only be carried out on new batteries. Increased currents lead to rapid heating, the next stage of which is the opening of the pressure shut-off valve. Once the shut-off valve is opened, the nickel battery cannot be recovered.

Choosing a charger for Ni-MH batteries

Some charger manufacturers are leaning towards products made specifically for charging Ni-MH batteries. And this is understandable, since these power sources are the largest in many electronic devices.

It is necessary to consider in more detail the functionality of chargers designed specifically to restore the capacity of nickel-metal hydride batteries.

• Mandatory presence of several protective functions, which are formed by a certain combination of some radio elements.
• The presence of a manual or automatic mode current adjustment. Only in this way it will be possible to set the various stages of charging. The potential difference is usually taken constant.
• Automatic recharge of the battery, even after reaching 100% capacity. This allows you to constantly maintain the main parameters of the power source, without compromising the service life.
• Recognition of current sources operating in a different way. A very important parameter, since some types of batteries, with too much charge current, can explode.

The last function also belongs to the category of special ones and requires the installation of a special algorithm. Therefore, many manufacturers prefer to abandon it.

Ni-MH power supplies are widely popular due to their durability, ease of use, and affordable price. Many users have appreciated positive traits these products.

In modern devices - flashes, cameras, etc., AA batteries are widely used. They are most often nickel-metal hydride (Ni-MH), less often nickel-cadmium (Ni-Cd, Ni-Cad).
Each of these types has its pros and cons:

• Ni-MH - quite capacious and stable, best suited for cameras, but suitable for flashes when fast charging is not required
• Ni-Cd - the least capacitive of all, but capable of delivering more current, even with a strong discharge - are best suited for flashes, as they provide a quick charge. Extremely toxic - cadmium from one battery can poison a huge amount of water, so now such batteries produce very little

Batteries of even the same type, for example, Ni-MH, even those produced by the same company, are very different. For example, more capacitance almost always means less current.
Charging nickel-metal hydride and nickel-cadmium (the most common AA batteries) is not so easy:

• For example, the charging current can be large or small. Small charging current means a very long charge, but the battery will be better charged.

  High charging current means very fast charging (with a lot of battery heat, which is why fast chargers are necessarily equipped with fans), but incomplete charging and faster battery wear. An ancient rule says "a good charge is provided by charging with a current equal to 0.1 of the battery capacity." Fast charging breaks this rule.

• There is also such a bad phenomenon as the "battery memory effect": incomplete discharge of the battery with subsequent charge means that the next time the battery will work to the state when it was not completely discharged last time - that is, it loses capacity.

  Nickel-cadmium are more susceptible to this effect than nickel-metal hydride. That is why it is so important to completely discharge the battery before its next charge (but even here it is important not to overdo it - because a battery discharge of up to 1 volt can permanently ruin the battery).

  The problem with the loss of capacity also occurs during normal battery operation - when batteries are used for a long time. However, the "memory effect" can be overcome by "training" batteries, that is, multiple full discharges and subsequent charges.

Personally, I had 2 chargers - a fast half-hour charger (by the way, there are even faster chargers, for example, fifteen-minute ones, and they are inexpensive and trademark, like, not bad - Duracell) and a slow eight-hour charger. Both chargers are from good manufacturers (Duracell and Annsman).

Batteries charged with these different chargers behaved differently - the clear advantage of an 8-hour charge is clearly noticeable, because after charging an eight-hour charge, the batteries lasted noticeably longer. Therefore, most of the time I used an eight-hour charge, leaving a half-hour charge as a last resort.

Although advertising says that modern batteries good models they don’t have this problem with “capacity loss due to the battery memory effect”, but my experience (about 15 sets of 4 batteries in each set, all sets of the most different brands- specially bought different ones, both cheap and very expensive) suggests the opposite. That is, at different models Indeed, during operation, there is a different loss of capacity - some have more, some have less, but advertising is lying - modern batteries are not completely free from problems with the "memory effect".

The most unpleasant thing is that bad batteries fail precisely in photography. It manifests itself like this - fully charged batteries die after several tens of frames (and sometimes after several frames, even dozens are not discussed). Sometimes the "law of meanness" works - the less time you have for shooting - the more worthless sets of batteries you find.

When this happened to me on a reportage shoot - the moments of which cannot be repeated - after the shooting, I bought several new sets of batteries. But when, after three months of operation at moderate loads (discharges-charges about once every 2 weeks for each set), several sets, including new ones, failed in a row on a leisurely object shooting after several flashes - I spent some time searching for information about normal chargers.

I found out another interesting thing - the ideal charging current, at which the batteries are charged to the maximum and the ideal charging time, depends on the capacity of the battery. And, therefore, there can be no better charging fully automatic charger. After all, AA batteries are not equipped with a feedback mechanism that could transmit any information (for example, at least information about the nominal capacity) to the charger. Of the most common batteries, only lithium-ion and lithium-polymer batteries are equipped with such a device, but not the AA size.

It turns out that it is not at all easy to properly charge batteries without a feedback mechanism. Moreover, even new batteries should be "trained" before use. With batteries that have been lying for more than 3 months, you should also do a "training". Light "training" should also be done with batteries that have lain for a short time (more than 2 weeks and less than 3 months).

Since manually "training" batteries is very tedious, smart chargers are also being produced. And since the charging current and time and additionally necessary operations for "training" the battery depend on the battery itself - on its nominal capacity, actual capacity, idle time (storage time), features of the internal chemistry of the battery - that is, very, very smart chargers.

The use of very smart chargers allows you not to end up on a responsible shoot with a full bag of fully charged, but very quickly depleting batteries, as happened to me several times. Well, in general, working with batteries will become more convenient - they will last much longer, less often you will need to buy new ones.
The following very smart chargers are currently known to me:

• Maha Energy PowerEx MH-C9000 WizardOne Charger-Analyzer for 4 AA / AAA
• La Crosse Technology BC-900 AlphaPower Battery Charger (also known as Techno Line BC900, Techno Line iCharger)
• La Crosse Technology BC-700 (differs from the BC-900 in a reduced charge current, but this is enough for the eyes)

Some more information about batteries for photographers (AA Ni-MH, Ni-Cd) and how to properly charge them.

Grand battery test

Every time I buy batteries, I have a lot of questions:

Are expensive batteries better than cheap ones?
Which of the batteries that cost the same is better to buy?
How much larger are lithium batteries than regular batteries?
How much capacity of saline batteries is less than that of alkaline?
Are batteries for digital devices different from ordinary ones?

To get answers to these questions, I decided to test all the "finger" (AA) and "little finger" (AAA) batteries that can be found in Moscow. I collected 58 types of AA batteries and 35 types of AAA. A total of 255 batteries were tested - 170 AA and 85 AAA.

To improve the accuracy of measurements, the battery analyzer does not use PWM - it creates a constant resistive load on the battery. The device can operate in different modes. Three main modes were used to test AA batteries:

Discharge direct current 200mA. Such a load is typical for electronic toys;
. Discharge with 1000 mA pulses (10 seconds load, 10 seconds pause). This load is typical for digital devices;
. Discharge with 2500 mA pulses (10 seconds load, 20 seconds pause). Such a load is typical for powerful digital devices - cameras, flashes.

In addition, four batteries were discharged with small currents of 50 and 100 mA.

Measurements were made when the batteries were discharged to a voltage of 0.7 V.

All test data are summarized in a table.
The discharge graph clearly shows how different types of batteries behave.

Discharging AA batteries with a current of 200 mA

The first five lines are salt batteries. It is clearly seen how much smaller their capacity is.
The last three lines are lithium batteries. They not only have a large capacity, but they also discharge differently: the voltage on them does not decrease almost to the very end, and then drops sharply. This is especially pronounced in the GP Lithium battery. In addition, lithium batteries can work in the cold.
Among the many similar alkaline batteries, two outsiders are clearly visible - Sony Platinum and Panasonic Alkaline and two leaders - Duracell Turbo Max and Ansmann X-Power. The remaining batteries differ in capacity by only 15%.

In the first diagram, AA batteries are sorted by capacity at a discharge current of 200 mA.

Duracell Turbo Max batteries do have a slightly higher capacity than all other alkaline batteries, but I came across one package of Duracell Turbo Max that was significantly worse than others. In terms of capacity, they corresponded to ordinary cheap batteries. They are labeled "Duracell Turbo Max BAD" in the table and graphs.

The diagram clearly shows that different batteries behave differently when discharged with large and small currents. For example Camelion Plus Alkaline gives more energy than Camelion Digi Alkaline at low current. But on the big one it's the other way around. As a rule, batteries designed for high currents indicate that they are designed for digital devices. At the same time, there are many universal batteries that work perfectly with any currents.

I averaged the amount of power that batteries put out at high and low currents and based on the results and the price of batteries (which in some cases is only an approximation) I made a chart of the cost per watt-hour for all AA batteries.

All types of AAA batteries were discharged with a constant current of 200 mA. Some types of AAA batteries were subjected to a second test - a discharge with a current of 1000 mA in the "constant resistance" mode (the current decreased as the discharge progressed). This mode emulates the operation of batteries in a flashlight.

In AAA format, Duracell Turbo Max turned out to be far from the best alkaline battery. Many cheap batteries (eg Ikea, Navigator, aro, FlexPower) had a larger capacity.

Technical conclusions:

Most alkaline batteries differ in capacity by only 15%;
. Lithium batteries have 1.5-3 times (depending on the load current) greater capacity than alkaline ones;
. Unlike alkaline batteries, the voltage on lithium batteries almost does not decrease during the discharge process;
. Salt batteries are 3.5 times worse than alkaline batteries at low currents and cannot work at all at high ones;
. There are three types of alkaline batteries: universal, designed for low load currents and designed for high load currents. At the same time, universal ones are better than the other two at all currents.

Consumer Conclusions:

Salt batteries are not worth buying. Even in devices with the smallest consumption, alkaline (Alkaline) will last much longer due to their long shelf life;
. It is most profitable to buy batteries sold under the brands of Auchan and Ikea stores;
. In other stores, you can safely buy the cheapest alkaline batteries;
. From what is sold in grocery stores, the best choice- GP Super;
. Lithium batteries are expensive, but they are light, capacious and can work in the cold.

Grand testing of AA/AAA batteries

Many have asked for the same thorough testing of NiMh batteries. In four months, I tested 198 batteries (44 AA models and 35 AAA models).

Usually, on the Lamptest.ru blog, I talk about testing LED lamps, which consume 6-10 times less than traditional ones and can significantly save on electricity bills. Today I want to touch on another aspect of savings - the use of rechargeable batteries instead of batteries.

Batteries were charged using La Crosse BC-700 and Japcell BC-4001 chargers. Batteries with a capacity of more than 1500 mAh were charged with a current of 700-800 mA, batteries of a smaller capacity with a current of 500-600 mA.

To determine the capacity, the batteries were discharged by Oleg Artamonov's analyzer. Batteries with a capacity of more than 1500 mAh were discharged with currents of 500 mA and 2500 mA, batteries with a smaller capacity - with currents of 200 mA and 1000 mA.

Basically, two copies of the batteries of each model were tested. For comparison, I used the results of the worst battery of the pair, but if four batteries were tested, for comparison, I took the penultimate one in terms of capacity.

Let's start with the simplest - battery capacity at average currents of 500/200 mA. Of course, it is more correct to take into account the capacity in watt-hours, but all batteries have a capacity in milliamp-hours, so I will use them.

As can be seen from the test results, the maximum capacity of AA batteries is 2550 mAh. All batteries with beautiful numbers 2600, 2700, 2800 and 2850 mAh are just the fruit of marketers. Their real capacity is sometimes even less than that of batteries from the same manufacturers with more modest numbers. On some batteries with large capacity values ​​indicated, the minimum capacity is indicated in small print (for example, Ansmann 2700, Panasonic 2700, Maha Powerex 2700 have a minimum capacity value of 2500 mAh and their actual capacity is close to this value).
But at AAA everything is honest. The maximum indicated capacity is 1100 mAh and the actual capacity is close to this value.

Duracell 1300 batteries showed very poor results after the first charge-discharge cycle, but after several charge-discharge cycles they showed the results that I take into account.
One of the four Turnigy 2400 LSD batteries had a capacity 30% less than the rest. I'm guessing it's a marriage. Its result is not taken into account.
The two Camelion 2800 batteries had a capacity of 2270 mAh and 2610 mAh (13% difference). Although the best of the pair turned out to be the most capacious of all AA batteries, I am forced to use the data of the worst copy, because no one knows what copies may still be caught when buying.
Chinese batteries BTY AA 3000 and BTY AAA 1350 have such a low capacity that they only belong in the trash and I will not mention them in further tests.

Unlike batteries, batteries cannot be categorized as good/bad simply by their capacity, because there are batteries of different nominal capacities on the market. Let's see how the capacity of the tested batteries corresponds to the declared one. If the battery is indicated not only nominal, but also the minimum capacity, I will proceed from it. For comparison, data obtained during discharge with an average current of 500/200 mA are used.

The quality of the batteries can be judged by how the instances differ from each other.

For most batteries, instances differ by no more than 5%.

Unlike batteries, accumulators almost do not lose capacity at high discharge currents. I compared the capacity at discharge currents of 2500 mA and 500 ma for AA batteries with a capacity of 1500 mAh and 1000/200 mA for AAA batteries and AA batteries with a capacity of less than 1500 mAh.

Some batteries at high currents are capable of delivering even more energy than at small ones (for such batteries, the difference between the capacity at high and low current is more than 100%).

Half of all tested batteries are made using LSD (Low Self-Discharge) technology. These batteries are sold already charged. I measured their capacity immediately after unpacking without pre-charging.

On average, LSD batteries were 70% charged. Of course, the level of their charge depended not only on the quality of the batteries, but also on the time and conditions of their storage, and the date of manufacture is only on some batteries.

I tested all batteries a week and a month after charging. The results in a week can be seen in the general table, but the results in a month.

Surprisingly, the Navigator 2100 AA and GP 1000 AAA non-LSD batteries were among the best in terms of charge retention during the month. Most batteries (both LSD and non-LSD) retain 90% of their charge after a month.

I will give prices for batteries as of 11/1/2015. Wholesale is the wholesale price at Istochnik Battery, RRP is the recommended retail price, Mag is the minimum prices in stores and online stores (mostly leftovers purchased at a lower exchange rate), $ and € are prices in dollars and euros in foreign online stores, RUB — prices in terms of the current exchange rate ($1=64 RUB, 1€=70.5 RUB). In shops hobbyking.com and ru.nkon.nl delivery is paid, the cost of the cheapest delivery when buying 12 batteries is included in the price in the table.

The first comparison is at the cost of 1000 mAh based on the RRP and prices in online stores, if the batteries are not sold in regular stores.

IKEA batteries are in the lead, followed by batteries from foreign online stores PKCELL and Turnigy. The most expensive based on recommended prices were Panasonic Eneloop.

Many people buy batteries in foreign online stores, so I made the second comparison at the prices of foreign online stores and the minimum prices that I managed to find in Russian stores.

IKEA is ahead of everyone here, Panasonic Eneloop are not at all so expensive if you buy them online, and Fujitsu, produced in the same factory using the same technology, is even cheaper.

For most batteries, manufacturers indicate 1000 charge-discharge cycles, some manufacturers do not indicate the number of cycles at all (Camelion, Turnigy, GP, Varta). Some batteries only have 500 guaranteed cycles (IKEA LADDA 2000 LSD, Energizer PreCharged 2400, Panasonic Eneloop Pro 2450 LSD, Fujitsu 2550 LSD, IKEA LADDA 750 LSD, Energizer PreCharged 800, Panasonic 750 LSD, Fujitsu 900 LSD, Panasonic Eneloop Pro 900 LSD) .
For AA Panasonic Eneloop 1900 LSD, AAA Panasonic Eneloop 750 LSD, AA Fujitsu 1900 LSD, AAA Fujitsu 800 LSD manufacturers guarantee 2100 cycles.
The maximum number of cycles of 3000 is guaranteed for low capacity batteries AA Panasonic Eneloop Lite 950 LSD and AAA Panasonic Eneloop Lite 550 LSD.

1. The maximum achievable capacity for NiMh AA batteries is 2550 mAh, for AAA - 1060 mAh. All batteries that say 2600, 2700, 2800 mAh and more actually have a lower capacity.
2. All AA batteries of famous manufacturers from 950 mAh to 2450 mAh have a real capacity of at least 97% of the indicated one, all AAA batteries of famous manufacturers from 550 mAh to 1100 mAh have a real capacity of at least 94% of the indicated one.
3. NiMh batteries, unlike batteries, almost do not reduce the amount of energy output at high discharge currents.
4. For a month of storage, both conventional and LSD batteries lose 4-20% of their charge.
5. New LSD batteries are usually 70% charged.

I spent four months testing and three days writing this article. Hope you find it useful.

2015, Alexey Nadezhin

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

Despite the fact that Ni-MH has a number of obvious advantages over 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

Lately great attention discussion on the Internet is given to 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, due to which 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.

From operating experience

NiMH cells are widely advertised as high energy, cold and memory free. Having bought a Canon PowerShot A 610 digital camera, I naturally supplied it with a capacious memory for 500 shots highest quality, and to increase the duration of filming, I bought 4 NiMH cells with a capacity of 2500 mA * hour from Duracell.

Let's compare the characteristics of the elements produced by the industry:

Parameters		Lithium ion Li-ion	Nickel Cadmium NiCd	Nickel- metal hydride NiMH	Lead acid Pb
service duration, charge/discharge cycles		1-1.5 years	500-1000		3 00-5000
Energy capacity, W*h/kg
Discharge current, mA * battery capacity
Voltage of one element, V
Self-discharge rate		2-5% per month	10% for the first day, 10% for each subsequent month	2 times higher NiCd	40% in year
Permissible temperature range, degrees Celsius	charging
	detente		-20... +65
Permissible voltage range, V		2,5-4,3 (coke), 3,0-4,3 (graphite)			5,25-6,85 (for batteries 6 V), 10,5-13,7 (for batteries 12V)

Table 1.

From the table we see NiMH elements have a high energy capacity, which makes them preferable when choosing.

To charge them, an intelligent DESAY Full-Power Harger charger was purchased, which provides charging of NiMH cells with their training. The elements of it were charged with high quality, but ... However, on the sixth charge, it ordered a long life. Burnt out electronics.

After replacing the charger and several charge-discharge cycles, the batteries began to run out in the second or third ten shots.

It turned out that despite the assurances, NiMH elements also have memory.

And most modern portable devices using them have built-in protection that turns off the power when a certain minimum voltage is reached. This prevents the battery from being fully discharged. Here the memory of elements begins to play its role. Cells that are not fully discharged are not fully charged and their capacity drops with each recharge.

High-quality chargers allow you to charge without losing capacity. But I could not find something like this for sale for elements with a capacity of 2500mah. It remains to periodically conduct their training.

Training NiMH elements

Everything written below does not apply to battery cells with a strong self-discharge . They can only be thrown away, experience shows that they cannot be trained.

Training of NiMH elements consists of several (1-3) discharge-charge cycles.

Discharging is performed until the voltage on the battery cell drops to 1V. It is advisable to discharge the elements individually. The reason is that the ability to receive a charge can be different. And it intensifies when charging without training. Therefore, there is a premature operation of the voltage protection of your device (player, camera, ...) and subsequent charging of an undischarged element. The result of this is a progressive loss of capacity.

Discharging must be carried out in a special device (Fig. 3), which allows it to be performed individually for each element. If there is no voltage control, then the discharge was carried out until a noticeable decrease in the brightness of the light bulb.

And if you detect the burning time of the light bulb, you can determine the battery capacity, it is calculated by the formula:

Capacity = Discharge current x Discharge time = I x t (A * hour)

A battery with a capacity of 2500 mAh is capable of delivering a current of 0.75 A to the load for 3.3 hours, if the time obtained as a result of discharging is less, and accordingly the residual capacity is less. And with a decrease in capacity, you need to continue training the battery.

Now, to discharge the battery cells, I use a device made according to the scheme shown in Fig. 3.

It is made from an old charger and looks like this:

Only now there are 4 bulbs, as in Fig. 3. Light bulbs should be mentioned separately. If the light bulb has a discharge current equal to the nominal for a given battery or slightly less, it can be used as a load and an indicator, otherwise the light bulb is only an indicator. Then the resistor must have such a value that the total resistance of El 1-4 and the resistor R 1-4 parallel to it is of the order of 1.6 ohms. Replacing a light bulb with an LED is unacceptable.

An example of a light bulb that can be used as a load is a 2.4 V krypton flashlight bulb.

A special case.

Attention! Manufacturers do not guarantee the normal operation of batteries at charging currents exceeding the accelerated charging current. I charge should be less than the battery capacity. So for batteries with a capacity of 2500 ma * h, it should be below 2.5A.

It happens that NiMH cells after discharging have a voltage of less than 1.1 V. In this case, it is necessary to apply the technique described in the above article in the PC MIR magazine. An element or a series of elements is connected to a power source through a 21 W car light bulb.

Once again, I draw your attention! Such elements must be checked for self-discharge! In most cases, it is elements with low voltage that have an increased self-discharge. These elements are easier to throw out.

Charging is preferably individual for each element.

For two cells with a voltage of 1.2V, the charging voltage should not exceed 5-6V. With forced charging, the light is also an indicator. By reducing the brightness of the light bulb, you can check the voltage on the NiMH element. It will be greater than 1.1 V. Typically, this initial boost charge takes 1 to 10 minutes.

If the NiMH element, during forced charging, does not increase the voltage for several minutes, heats up, this is a reason to remove it from charging and reject it.

I recommend using chargers only with the ability to train (regenerate) elements when recharging. If there are none, then after 5-6 operating cycles in the equipment, without waiting for a complete loss of capacity, train them and reject elements with a strong self-discharge.

And they won't let you down.

In one of the forums commented on this article "badly written but nothing else". So, this is not "stupid", but simple and accessible for everyone who needs help in the kitchen. That is, as simple as possible. Advanced can put a controller, connect a computer, ......, but this is already another history.

To not seem stupid

There are "smart" chargers for NiMH cells.

This charger works with each battery separately.

He can:

1. work individually with each battery in different modes,
2. charge batteries in fast and slow mode,
3. individual LCD display for each battery compartment,
4. charge each battery independently,
5. charge from one to four batteries of different capacities and sizes (AA or AAA),
6. protect the battery from overheating,
7. protect each battery from overcharging,
8. determination of the end of charging by voltage drop,
9. identify faulty batteries
10. pre-discharge the battery to the residual voltage,
11. restore old batteries (charge-discharge training),
12. check battery capacity
13. display on the LCD: - charge current, voltage, reflect the current capacity.

Most importantly, I emphasize of this type devices allow you to work individually with each battery.

According to user reviews, such a charger allows you to restore most of the running batteries, and serviceable ones can be used for the entire guaranteed service life.

Unfortunately, I did not use such a charger, since it is simply impossible to buy it in the provinces, but you can find a lot of reviews in the forums.

The main thing is not to charge at high currents, despite the declared mode with currents of 0.7 - 1A, this is still a small-sized device and can dissipate 2-5 watts of power.

Conclusion

Any recovery of NiMh batteries is strictly individual (with each individual element) work. With constant monitoring and rejection of elements that do not accept charging.

And the best way to deal with their recovery is with smart chargers that allow you to individually reject and charge-discharge cycle with each cell. And since there are no such devices automatically working with batteries of any capacity, they are designed for elements of a strictly defined capacity or must have controlled charging and discharging currents!