Charger for nickel-zinc batteries. NIZN batteries
Studies of the properties of coatings obtained using an acidic electrolyte. Zinc-nickel coating can be obtained using either an alkaline or an acidic electrolyte.
Alkaline processes for application zinc-nickel alloy They impart shine to the surface and are characterized by high scattering and covering power even when processing parts of complex configurations. These properties make alkaline galvanizing electrolytes cost-effective and convenient to use.
The cathodic current efficiency of alkaline processes usually varies between 40-60% for fresh solutions; as the electrolyte is used, this figure decreases due to the accumulation of organic decomposition products in the bath, as well as the formation of sodium carbonate. Typically, nickel is introduced into the solution through proprietary additives, which increases the cost of the coating process.
The cathodic current efficiency of acid processes for the deposition of zinc-nickel alloy is about 95%. The nickel contained in the treatment solution is contained in salts that are widely available on the industry market. Adjustment of the electrolyte (in order to increase the nickel concentration) is carried out using soluble nickel anodes or nickel salts. In this regard, the cost of the acid process is much lower than the cost of the alkaline process, taking into account the consumption of chemicals. In addition, the acid electrolyte provides greater performance due to higher current efficiency. And, as is known, acidic solutions for applying a zinc-nickel alloy are ideal for deposition of a coating on cast iron products under the influence of direct current, for example, for deposition electroplating on the brake calipers.
The process of obtaining a zinc-nickel coating from an acidic electrolyte has certain difficulties, which makes it less convenient for use in industrial conditions. Zinc anodes dissolve in acidic chloride electrolytes, causing difficulties in controlling the concentration of zinc in the solution.
To do possible use soluble nickel anodes, double current rectification is used. IN Lately patented insoluble anodes were introduced to avoid double rectification. When the electrolyte is depleted of zinc or nickel, special salts are used. The use of these measures will increase the cost of the process (compared to the method using soluble anodes), however, in the first case, the procedure for obtaining the coating as a whole is significantly simplified, and its overall total cost will be half the cost of the alkaline process.
The distribution of the alloy at a given current density in an acidic electrolyte depends on the type of conducting salt and the presence of a complexing agent in the solution. To achieve the alloy composition required by the automotive industry for corrosion resistance, workpieces must be coated with a layer of 12-15% nickel distributed evenly over the surface of the part. According to Baldwin and his colleagues, an alloy in which the nickel content exceeds 21% is not capable of providing cathodic protection to a steel surface. In terms of appearance, a zinc-nickel alloy with a nickel content of more than 21% forms a black layer during electrochemical deposition.
EXPERIMENTS AND CONCLUSIONS
Three different alkaline zinc-nickel alloy deposition processes, described in Table I, were investigated in the experiments, all of which are widely used in modern manufacturing plants. Solution I was prepared on the basis of ammonium chloride, solution II, which did not contain a complexing agent, was prepared on the basis of potassium chloride. Solution III was also based on potassium chloride, but a mild complexing agent was also added to the electrolyte.
Table I.
Results of a study of acidic electrolytes for the deposition of a zinc-nickel alloy
| Electrolyte 1 | Electrolyte 2 | Electrolyte 3 | |
| Zn, g/l | 32 | 55 | 36 |
| Ni, g/l | 25 | 29 | 30 |
| NH4Cl, g/l | 253 | - | - |
| KCl, g/l | - | 245 | 232 |
| Ammonium hydroxide, ml/l | 60 | - | - |
| Boric acid, g/l | - | 20 | 20 |
| pH | 5,7 | 5,4 | 5,5 |
| Proprietary Additives | 60 ml/l | 180 ml/l | 25 ml/l |
| Complexing agent | - | - | 200-350 ml/l |
Mild steel cathodes, measuring 20 by 8 cm, were electrochemically treated in a 500 ml Tosei cell (also known as a long Hula cell) with magnetic stirring. The treatment duration was 10 minutes, the current density was 10 A. The alloy content was examined by X-ray diffraction using a Seiko spectrometer, model SE 5120. Measurements were taken at several points located at a distance of 2 cm from each other on the site high density current
The results of studies of a sample treated in electrolyte 1 based on ammonium chloride are shown in Figure 1. As can be seen from the table, the sample demonstrates a deviation from the norm, typical for the deposition of zinc with elements of the iron group. As the current density decreases, a decrease in the nickel content in the deposited layer is observed. Increasing the temperature of the solution increases the nickel content in the coating, but does not change the characteristics of the coating.
Picture 1.
Electrolyte 1. Ratio of alloy distribution to current density.
From a practical point of view, the areas on the cathode starting from the high density edge and ending at a distance of 10 cm from it are an indicator of the current density of the surface being treated. This property makes it possible to apply an alloy with a content of 10 to 15%, which provides the necessary level of corrosion resistance and the so-called sacrificial protection of steel.
The results of studies of a sample processed in electrolyte 2 are shown in Figure 2. The behavior of solution 2 during alloy deposition differs from the behavior of solution 1. Electrolyte 2 is characterized by a deviation from the norm at any current density, but at a minimum current density it exhibits behavior close to normal deposition . As the temperature increases, this property increases.
Table II. Dependence of alloy composition on current density
| 4.0ASD | 2.0ASD | 1.0ASD | 0.2 ASD | ||
| Electrolyte 1 | %Ni | 12,0 | 12,3 | 4,3 | 1,2 |
| (ammonium chloride) | Thickness layer, µm |
13,8 | 7,0 | 4,3 | 1,2 |
| Electrolyte 2 | %Ni | 12,1 | 12,2 | 13,4 | 15,5 |
|
(potassium chloride with/without complexing agent) |
Layer thickness, µm14.38.23.81.1
Concerning practical application, electrolyte 2 is not economically profitable. The nickel content in the layer obtained at standard current density varies from 6 to 15%.
Although this solution provides high corrosion resistance and sacrificial protection to steel, it poses some challenges in meeting the precipitated alloy requirements of automotive standards. In addition, when executing the process, it is necessary to maintain operating temperature solution at 33 ±2°C to avoid exceeding 20% nickel concentration, which has a negative impact on appearance deposited layer, as well as its ability to provide tread protection for steel.
Figure 3 shows the test results of samples treated in solution 3. The characteristics of the resulting coating are similar to the results of tests of coatings obtained using electrolyte 2, however, the tendency towards standard behavior is suppressed by increasing the concentration of the complexing agent. To obtain a coating that meets the requirements of automakers, the concentration of nickel and complexing agent in the solution must be carefully controlled. As practical experience shows, electrolyte 3 makes it possible to deposit a layer with a nickel content varying from 12 to 14% in the suspension line. The ability of the solution to deposit alloys containing 12 to 14% nickel without the addition of ferrous high-alloy alloys at low current densities in drums depends on product configuration, current intensity, and agitation.
Figure 2. Electrolyte 2. Alloy distribution.
For X-ray diffraction, mild steel samples were electrochemically treated in a standard Hula cell with propeller agitation at 2 A for 10 minutes. Alloy compositions depending on current density are given in Table II. The chemical composition and thickness of the deposited alloy were determined by X-ray diffraction using a D8 Discover diffractometer equipped with a GADDS detector from Bruker Analytical X-Ray Systems, Inc.
Figure 4.
In Fig. Figure 4 shows the result of X-ray diffraction of a sample processed in electrolyte 1. Regardless of the current density, Ni 5 Zn 21 phases are detected in the alloy. Changes in the current density do not affect the alloy phases in any way, only slightly changing the texture of the formed alloy. Qualitative analysis of the x-ray revealed the only orientation visible at 4 ASD - orientation (330). As the current density increases, the (600) orientation appears, which continues to grow even as the current density decreases.
Figure 5.
Rice. 5 is the result of X-ray diffraction of a zinc-nickel alloy deposited from electrolyte 2. At any current density, a single phase Ni 5 Zn 21 is present. Changes in current density have a significant effect on the surface texture. Qualitative analysis of the image showed that orientation (600) is dominant among those that were recorded at 4 ASD. As the current density decreases, the (330) orientation increases. At 0.2 ASD, the 330 orientation dominates over the (600) orientation.
A layer deposited from a potassium-based solution has characteristics opposite to those deposited using an ammonium chloride-based electrolyte.
CONCLUSION
The layer obtained by deposition of a zinc-nickel alloy from an acidic electrolyte has a Ni 5 Zn 21 phase with a mass fraction of nickel from 12 to 15%. Coatings deposited from ammonium chloride exhibit a crystalline orientation with respect to current density that is opposite to that observed in coatings prepared using a potassium chloride solution. The influence of this factor on coating properties such as internal stress and plasticity, as well as the possibility of subsequent deposition, requires additional research.
Ammonium chloride solutions for the deposition of a zinc-nickel alloy make it possible to obtain coatings whose nickel content at a given current density is more preferable for the enterprise from an economic point of view. In addition, ammonium chloride based electrolytes are suitable for both drum processing and hanging line applications. In cases where the use of ammonium chloride is prohibited for any reason, a facility can effectively replace it with a potassium chloride solution offered by many suppliers.
To control the composition of the alloy in areas of minimum current density, it is recommended to use a soft complexing agent. Despite the fact that the industry market has a large number of technologies based on potassium chloride, which do not require the use of a complexing agent, have not found widespread use in industrial enterprises due to the increased nickel content under the influence of a minimum current density and the need to maintain a strictly defined temperature.
It’s been a year since nickel-zinc batteries appeared on one widely used model site (store).
In size - they are about the size of a finger (or AA)
Voltage - Nominal - 1.6 Volts.
Say what you like, but batteries - metal hydrides with their nominal voltage of 1.2 Volts - no longer look so interesting. After all, sometimes it is the voltage that is not enough in the same flashlight or receiver. And here - even a non-freshly charged battery will have the same voltage as a fresh battery. It must be noted that the capacity of this type There are still fewer batteries than nickel-metal hydride batteries of the same size. But I think that this is often not required, since we usually do not discharge the batteries “all the way” anyway, but it is understood that we diligently monitor the operation of the batteries and charge them on time.
Let's start with security measures.
What the instructions tell us about safety measures:
Attention! Violation following operating rulescan lead to damage to Ni-Zn battery, explosion, fire and serious injury!
It is forbidden to throw Ni-Zn battery on fire or expose to heat!
It is prohibited to expose Ni-Zn
Do not short-circuit the contacts Ni-Zn battery directly without load.
Do not place the Ni-Zn battery at a height of more than 1.5 meters in case of a fall. Do not throw it from a height of more than 1.5 meters.
Use special insulating containers for transportation and storage.
Use Charger for charging specifically designed for Ni-Zn batteries.
Do not disassemble Ni-Zn batteries. This will lead to external or internal short circuiting the damaged parts, which will lead to a chemical reaction and then to heat generation, explosion, fire or electrolyte release.
It’s already quite scary and reminiscent of lithium polymers...
And let's continue:
Do not allow Ni-Zn batteries to come into contact with water, sea water or other oxidation reagents which may cause rusting and heat dissipation. If the batteries get rusty , then the emergency pressure relief valve may not work and this will lead to an explosion.
Do not recharge Ni-Zn batteries, i.e. do not leave Ni-Zn batteries , in the charger after the charging time has expired. If Ni-Zn batteries are not fully charged with this type of charger, please stop charging. Long charge may cause heating and explosion.
Do not connect more than 20 pcs batteries sequentially. This may cause electrolyte leakage, short circuit or heating.
Do not disassemble Ni-Zn battery as this could lead to short circuit, electrolyte leakage, heating, fire and explosion.
Do not use Ni-Zn batteries if detected electrolyte leaks or anychanges in battery color, shape, or other visible changes. Otherwise it may not heat up, ignite or explode.
Keep Ni-Zn batteries and electronic equipment using Ni-Zn batteries away from children to prevent the batteries from being swallowed by children.
AND use only new ones Ni-Zn batteries when The battery has already performed a large number of charge-discharge cycles - recycle the battery.
Wow - funny batteries... A kind of jar with a mixture of TNT and potassium cyanide....
So how do you charge these Ni-Zn batteries?
The instructions clearly tell us that we must charge batteries of this type with a special charger for these Ni-Zn batteries. And the model store offers to buy these chargers.
This is what this charger looks like - like a normal one for AA batteries.
Agree, I don’t really want to spend at least another 10 dollars to buy a non-name charger and charge it with it, while I’ve already bought some kind of smart (computer) charger, for example, Accucel-6, and have already spent money on it. But it doesn’t have a charging mode for Ni-Zn batteries!!! What to do?
The solution is quite simple. The manufacturer indicates the charging end voltage for the can - this is 1.9V. And the capacity of each jar is 1500mAh.
Now we can move on to charging methods:
First.
If charging allows you to limit the charge voltage in some mode (Voltage Cut-Off) - simply set the value of this limitation (Voltage Cut-Off) based on 1.9V per can (for two cans it is 3.8V, for three - 5, 7V, etc.) Next - using this mode - we charge the batteries with a current of 0.5C-1C (C is the battery capacity), i.e. 750-1500mA (milliamps).
Second.
This is the method I use. In my Accucel-6 tourniquet there is no charge voltage limit (or I didn’t find one), so I use the capacity limit. In the settings menu (USER SET PROGRAM -->) there is a Capacity Cut-Off item. For many (including me), this item is set to OFF. You need to put it in ON and set the value to 1500mAh. And then switch to the charging mode for nickel-metal hydride (NiMh) or nickel-cadmium (NiCd) batteries and set the current as recommended by the manufacturer - 0.5C-1C, i.e. this means for these batteries 750-1500mA (milliamps). And charge in this mode. Some users on the forums raise the installed capacity in chargers to 1900mAh, but it is up to you to decide how best to manage your batteries.
Third.
You can charge Ni-Zn batteries using the mode for charging LiFe batteries, but be careful - in this mode, the number of Ni-Zn batteries should be two per LiFe can. That is, if you put 2 LiFe banks in the charger, then in reality you should connect 4 series-connected Ni-Zn batteries, if you put 3 LiFe banks in the charger, then in reality you should connect 6 series-connected Ni-Zn batteries, if you put 1 LiFe can in the charger, then in reality you should connect 2 Ni-Zn batteries connected in series, etc. And of course, we (you) cannot use the balancing modes for these batteries. The disadvantage of this charging method is that Voltage Cut-Off for each Ni-Zn battery bank occurs at 1.8V, which is 0.1V less than the standard cut-off value for Ni-Zn batteries, and therefore the batteries will not take a full charge.
I think that if you observe your batteries for a couple of charge cycles and analyze what is happening, you will decide for yourself which charging method to use or what capacity to put in the battery so that it takes a full charge.
Attention! All information described in this article is not official instructions, nor the instruction manual. It only expresses the opinion of the author. The author of this article is not responsible for any actions and consequences that you take after obtaining information from this article. All yours further actions You do so at your own peril and risk...
I purchased NiZn batteries (not from this link, though). AA were declared as 2800 mWh (just elements in a green shell with a signature like on dot matrix printer printed), AAA - 1150 mWh (these are in a normal shell, under the UltraCell brand). In real life, AA cells produced 1400-1480 mAh (i.e., very similar to PowerGenix cells) or 2250 mWh when discharged with a current of 500 mA. AAA cells produced 560-580 mAh (or 900 mWh) when discharged with a current of 200 mA. So there is the usual Chinese embellishment of characteristics, but nothing more. About 10-15% of them had a high self-discharge (sellers sent replacements without any problems).
As for charging the Z4... it was clearly made initially for Li-ion, and only then additional voltages were added for LeFePO4, NiZn, NiMH. As for its circuitry, it is a standard blocking generator that converts 220 V to approximately 12 V, and pulse converter on MC34063 with 12 V the desired voltage (from 1.46 to 4.20 V depending on the switch position). There is no microprocessor or specialized charge controller - it's just a stupid voltage regulator with current limitation. For the specified microcircuit there is a whistle, hissing, etc. sound effects- a completely normal phenomenon, they are caused by the very principle of operation of the microcircuit (the conversion frequency is not fixed, and its change is heard as a whistle and hiss). Does not affect safety. Much more attention must be paid to not turning on the network and external source nutrition. They are not untied in any way, i.e. It will be difficult to predict the outcome.
The MC34063 outputs a voltage programmed by the switch (1.46 V for NiMH, 1.86 V for NiZn, 3.63 V for LiFePO4 and 4.20 V for Li-ion), which is then applied from one point to all 4 batteries through resistors 0.3 Ohm. Actually, the entire decoupling of batteries from each other is these resistors (it can be even worse - just parallel connection). I would like to note that 1.46 V is not enough for charging NiMH, and 1.86 V is not enough for charging NiZn. In order to charge them normally with this charger, you need to modify it with a file (solder in a couple of resistors, which will cause the voltage to rise to 1.49 V and 1.91 V, respectively). There is no need to modify anything for Li-ion.
About 1200 mA - a lie, total current is unlikely to exceed 500-600 mA for all batteries (this limitation is inherent in the MC34063 current limiting circuit). In principle, you can move it a little (the microcircuit itself can output up to 750 mA without the danger of overheating), but whether the 220-12 converter will handle this is unknown.
As for indicators, you don’t have to look at them. They are turned off stupidly by voltage (1.42 V for NiMH and 1.80 V for NiZn, and only for Li-ion at 4.20 V). 1.42 V and 1.80 V are very little; in fact, the batteries are at most half charged. Even when the indicators go off, the batteries continue to charge as if nothing had happened. For fully charged pairs of AA NiZn batteries need 20 hours (after modification the time is reduced to about 10 hours), it can be determined more accurately with a multimeter (the voltage on the battery will reach 1.85-1.86 V).
Bottom line: NiZn batteries are quite interesting, although they may not be suitable for certain equipment (I do not recommend using them in devices powered by 2 batteries - they may contain a boost converter that cannot produce a voltage lower than the input, but 3.7 V may be too much for chips designed for 3.3 V). Charging is a constructor for an amateur. After modification, it is suitable for charging an odd number of NiZn batteries (normal chargers usually only charge them in pairs).
Even though the camera was not new, it worked fine, took high-quality photographs and was completely satisfactory to me - it was a pity to throw it away. The search for a solution to the problem led me to ALIexpress, and the Internet suggested possible options, one of which was the use of Ni-Zn batteries with a voltage of 1.6 V and a capacity of 2500 mAh. The price was quite high, $2 per battery, but the alternative looked even sadder, since it was quite expensive to “feed” Rekam with disposable salt or alkaline batteries with a recommended voltage of 1.5 V. Let me remind you that it’s good AA battery at Magnit it costs about 60 rubles.
It’s decided, I order 4 batteries from Aliexpress and the package arrives at the beginning of September. I insert it into the camera and am pleased to see that everything works fine. The batteries arrived charged, let's see how long they last.
Later I will supplement the article with operating experience.
More than a month has passed since the start of operation of Ni-Zn batteries. Two batteries are always in the camera, but I didn’t have to take many pictures, so there’s nothing to say about the battery life. I read on a photographers forum that these batteries have (seemingly) two positions - “on” and “off”, that is, if it discharges below certain limit(about 1.4 V), then it stupidly turns off and stops working. After a month of operation, the voltage of my batteries remains 1.81 V.
Another package from Aliexpress delivered me a charger for a Li-Ion battery and a box for two AA batteries. All this stuff is designed to charge my Ni-Zn batteries. The idea is that the Li-Ion battery in such a charge can be replaced with two Ni-Zn batteries. However, such a replacement cannot be called complete, since the Li-Ion charging voltage is 3.7-4.2 V (divided by two, we get 1.85-2.1 V), and it is slightly higher than required. For normal charging, manual control is required, i.e. It is necessary to periodically measure the voltage at the battery terminals with a voltmeter and prevent overcharging. The voltage should be in the range of 1.92-1.95 V. Let me remind you that Ni-Zn batteries are very afraid of overcharging and, judging by the reviews, they instantly fail (not all, but you should be careful).
The photo shows a do-it-yourself charger for Ni-Zn batteries. I soldered two wires (+ red) and (- black) from the box to the board, glued the board itself to the box with double-sided tape, and also glued a piece of white plastic to the double-sided tape to protect the module. Any food will do USB port, in the photo I have a phone charger and an adapter cord from standard USB To mini USB. The red LED is on - indicates that charging in progress. In my case - 1.93 V per battery.
Nickel - zinc alloy. Nickel-alloyed zinc coatings (50% Ni and 50% Zn) have higher corrosion resistance than zinc and are able to provide anodic protection to steel parts against corrosion. The most optimal electrolyte for this purpose is (in g/l):
Ammonium chloride 200-250
Zinc oxide 15-17
Nickel chloride 25 - 40
Boric acid 20-25
Dextrin 5 - 10
Electrolysis mode: electrolyte temperature 15-20 °C, iк = 1 ÷ 2 A/dm 2, anodes - separate Zn:Ni = 1:1, pH = 6.3 ÷ 6.7.
The coatings are shiny and adhere well to the base. The duration of action of the dextrin additive (brightener) is 5 g/l per 10 Ah/l.
Along with this composition, an electrolyte is used containing (in g/l):
Zinc sulfate 75-125
Nickel sulfate 25 - 75
Ammonium sulfate 35 - 40
Ammonia, ml/l 250
Electrolysis mode: electrolyte temperature 15 - 20°C, ik = 1 ÷ 2 A/dm 2, (ik at the beginning of electrolysis 2 - 3 A/dm 2 for 1 min), anodes are made of an alloy that is deposited on the cathode.
Decorative and light-absorbing coatings made of black nickel in the optical industry are deposited from an electrolyte (in g/l):
Nickel sulfate 65 - 75
Zinc sulfate 30 - 40
Nickel - ammonium sulfate 45 - 50
Sodium rhodanate 15
Boric acid 25
Electrolysis mode: electrolyte temperature 45 -55°C, ik = 1.0 ÷1.5 A/dm 2, separate anodes Ni: Zn = 1:1 or from an alloy that is deposited on the cathode.
First, at 0.02 - 0.05 A/dm 2, it is recommended to deposit a certain layer of ordinary nickel as a sublayer, and then increase i to 1.3 A/dm 2 and apply black nickel. This increases the adhesion of the coating to the base. To work in temperate climates (in addition to the underlayer of copper and nickel on steel), black nickel coatings are additionally treated in a hot solution of potassium dichromate.
Coatings obtained from rhodanium electrolyte, in addition to nickel and zinc, include sodium rhodanium and double nickel-ammonium salt.
At small i k = 0.2 ÷ 0.4 A/dm 2, gray nickel is deposited on the cathode, firmly adhered to the base. An increase in ik from 0.4 to 1.0 A/dm 2 leads to the formation of black precipitation. At the same time, the quality changes - the coatings become fragile. When the electrolyte temperature drops to 20°C, the coatings become rough and scorched. The transition from gray nickel to black occurs abruptly. In Fig. 43, section 1 of the curve corresponds to the release of nickel, and section 2 to the release of zinc. In the transition section, Ni-Zn reduction occurs at the cathode. At 50°C this moment corresponds to i k = 0.35 ÷ 0.4 A/dm 2. Gray coatings contain traces of zinc, 14 - 15% black nickel sulfide, 74% zinc hydroxide, 9% ordinary nickel sulfide.
Rice. 43.
1—nickel release; 2 - release of zinc
The cathodic reduction of a Ni-Zn alloy boils down to the fact that at a value of ik corresponding to a potential jump on the cathode surface, the release of hydrogen bubbles begins. As the pH of the cathode layer increases, zinc hydroxide is formed in it, which, being adsorbed by the cathode surface, passivates the faces of the growing crystals and stops their growth.
As a result of the reduction of thiocyanates, metal sulfides are formed, and when deposited on the passivated faces of the cathode, the latter become electrically conductive. This ensures the emergence of new centers of metal crystallization, the further growth of which is inhibited by passivation of the crystal faces with zinc hydroxide.
The microhardness of Ni-Zn alloy coatings is 400-500 kgf/mm 2 and increases with increasing nickel content in the alloy. The Ni-Zn alloy can be used as an independent coating or sublayer before applying chromium-nickel coatings to steel.
Petr Stepanovich Melnikov. Handbook of electroplating in mechanical engineering, 1979 .