Nickel-cadmium batteries, nickel-metal hydride batteries and the charging method of the principle (part 1)
Ni-Cd / Ni-MH development of battery
In 1899, the Waldmar Jungner-open type nickel-cadmium, the first use of the plate nickel, almost at the same time, Thomas Edison invented the electric car batteries for nickel-iron. Unfortunately, due to the time of this alkaline plate battery those other materials were more expensive, so the effective implementation has been considerably restricted. ThinkPad R50 battery ThinkPad R51 battery
Later, Jungner of nickel-cadmium batteries, after several important improvements, performance improved significantly. One of the biggest improvements in 1932, scientists began using the battery nickel active material. They are active substances in porous nickel plates in nickel plate and then in metal hull. Battery Nickel-cadmium, another milestone in the history of development in 1947 and “sealed nickel-cadmium type developed. In this cell, a chemical reaction to produce a variety of gas should not drain the battery in combination chemical may be. Sealed nickel-cadmium successful development of nickel-cadmium range of applications has increased significantly. ThinkPad R52 battery ThinkPad T40 battery
Sealed nickel-cadmium batteries, high efficiency, long life cycle, the energy density, small size, light weight, compact structure, and does not require maintenance, so in the industrial and consumption were widely used.
With the development of space technology, people have become more demanding food. Mid-70s, the United States has successfully developed a powerful, light weight, long life, low-cost batteries nickel metal hydride, and in 1978 successfully applied to satellite cells navigation as, batteries nickel-metal hydride and nickel-cadmium with the same volume over capacity can be doubled, and there are no pollution problems caused by cadmium. Its operating voltage is identical to the nickel-cadmium, hope of life in much the same, but it has a good over-charge and over-performance discharge. In recent years, nickel-metal hydride is the world’s attention, a constant stream of new technologies. Ni-MH is published, we should use the containers to high-pressure hydrogen storage, then the people using metal hydrides to store hydrogen, which is made up of low atmospheric pressure and even nickel-metal hydrides. In 1992, Sanyo in Japan to produce 2 million per month batteries nickel metal hydride. Currently, over 20 development units and production of nickel-metal hydride batteries, nickel metal hydride made the overall performance reached the advanced international level. ThinkPad T41 battery ThinkPad T42 battery
Battery Parameters
Battery of five main parameters: the battery capacity, rated voltage, internal resistance, termination voltage discharge and tension-end load. The battery capacity is generally Ah (AH) said, 1Ah is able to 1A of current, discharge 1 hour. Unit cell of the number of active substances contained in the decision level battery charge, while the active substance from materials of the drums and the volume of the decision, therefore, generally the longer the battery size, more capacity. And battery capacity of the relevant parameter is the battery charge current. Charging the battery’s current charge rate C is generally said, C is the rated capacity of the battery. For example, with 2A being on 1Ah battery, charge rate is 2C; Similarly, with 2A current from the battery 500mAh, the loading rate is 4C. ThinkPad T43 battery ThinkPad T60 battery
The battery runs the factory, unlike positive and negative electric potential between the nominal voltage of the battery. Rated voltage from the electrode materials, electrode potential and electrolyte concentration internal decision. When the temperature of the environment, use of time and changes in working conditions, output voltage of the unit is a slight change in the stack, in addition, the battery voltage and output power the battery is left is a certain relationship. Nickel-cadmium cell nominal voltage of about 1.3V (it is generally considered to 1.25V), cell Ni-MH rated voltage of 1.25 V.
The battery internal resistance determined by the plate resistance and resistance to the flow of ions. In the process of charge-discharge, the plate resistance is unchanged, but the impedance of the ion current to changes in electrolyte concentration and to increase or decrease the change of charged ions. ThinkPad R32 battery ThinkPad R40 battery
Battery power sufficient, the board of the same active substance has reached the saturation point, then continue to charge the battery voltage does not increase the tension at present known to voltage charge termination. Nickel-Cadmium battery charging voltage termination of 1,75 ~ 1.8 V, Ni-MH voltage battery charge termination of 1.5V.
Termination voltage discharge is the minimum allowable battery voltage discharge. When the voltage is below the battery voltage termination discharge to discharge, the battery voltage decreased rapidly at both ends to form a depth of discharge, so that the resultant formation of a council where he is not easy in the resume normal load, thus affecting the battery life. Discharge voltage and the rejection rate of termination. Battery voltage nickel-cadmium discharge and flow of the termination of the relationship, as shown in Table 1-1, Ni-MH discharge battery voltage termination is generally defined as 1V.
Ni-Cd Ni-MH battery charging principles and methods - Nickel-cadmium works September 23, 2009 Auteur: anonymous: ATEX Battery Test Lab Editor: nickel-cadmium WorksThinkPad X60 battery FRU 92P1141 40Y6799
Nickel-cadmium cathode material for nickel hydroxide and a mixture of graphite powder, the negative electrode material for the sponge like powder and cadmium oxide powder of cadmium, the electrolyte is usually sodium hydroxide solution or potassium hydroxide. When the temperature is high, using a density of 1.17 ~ 1.19 (15 ℃ h) solution of sodium hydroxide. When the temperature is low, the use of density is 1.19 ~ 1.21 (15 ℃ h) a solution of potassium hydroxide. To -15 ℃ below, using a density of 1.25 ~ 1.27 (15 ℃ h) a solution of potassium hydroxide. To account for low-temperature performance and retention capacity load, sealed nickel-cadmium with a density of 1.40 (15 ℃ h) solution with potassium hydroxide. To increase the capacity of the battery cycle life, often in the electrolyte by adding a small amount of lithium hydroxide (about the electrolyte per liter plus 15 ~ 20g). Inspiron 1100 battery Inspiron 1150 battery
Nor-Cd rechargeable batteries, the cathode active material of a board of nickel hydroxide NiOOH〕 〔, active material for negative electrode in a board of cadmium metal battery discharge nickel-cadmium, cathode active material of a board of nickel hydroxide, the material of negative electrode active board hydroxide cadmium.
1. Discharge in the process of an electrochemical reaction
(1) negative reaction
Cadmium on the anode after the loss of two electrons in a bivalent cadmium ions Cd2 +, and then immediately to the solution of hydroxide of two OH-binding generates hydroxide cadmium Cd (OH) 2 deposited on the plate cathode.
(2) the positive reaction
Cathode material asset is a board of nickel hydroxide (NiOOH) crystals. Nickel is positive trivalent ions (Ni3 +) Network of nickel ions for both the external circuit for the negative change in two electronics, generating two divalent ions 2Ni2 +. At the same time, the solution of ionization of water molecules for both of the two hydrogen ions in the positive plate, and the lattice oxygen anions on the two combined to produce two hydroxyl ions, then with the network the original two hydroxide ions, and the two nickel ions bivalent generated two crystals hydroxide nickel. Inspiron 1300 battery Inspiron 1318 battery
The sum of the two types above, ie, nickel-cadmium discharge in May the general reaction:
2. Pricing in the process of chemical reaction
Pricing, charging positive and negative, respectively positive and negative battery is connected to the discharge of the battery in the event and the exact opposite of the electrochemical reaction that occurs to restore the negative reaction, the reaction of oxidation cathode occurs.
(1) negative reaction
Negative pricing hydroxide board, cadmium, first ionized into ions and hydroxide ions of cadmium and cadmium ions from the outside or access to electronic circuits to produce atoms of cadmium bound to plate pole, while the hydroxide ions in solution involved in the positive feedback:
(2) the positive reaction Inspiron 1420 battery Inspiron 5100 battery
Under the influence of power outside of the council cathode, lattice of nickel hydroxide, two nickel ions bivalent loss of one electron is generated nickel ions trivalent, while the mesh of the two hydroxide ions free hydrogen ion, remain in the network of anions of oxygen, releasing hydrogen ions and hydroxide ions in solution combine to produce water molecules. Then the two nickel ions trivalent and two anions of oxygen and two hydroxyl ions combine to produce two crystals of nickel hydroxide:
The sum of the two types above, which is too Charger Ni-Cd when the electrochemical reaction:
The end of the battery charging when the charge current of the battery decomposes into water, the reaction took place in the positive plate and negative will be plenty of oxygen and deposition of the hydrogen, the electrochemical reaction is as follows: Latitude D620 battery Latitude D800 battery
The electrode reaction above may be considered that the exclusion of sodium or hydrogen, potassium hydroxide is not directly involved in the reaction, only play the role of electrical conductivity. From the reaction of the battery, the water molecules produced during filling and discharge in the consumption of water molecules, the loading and unloading to process the concentration of electrolytes is very small, can not be detected per meter of density level loading and unloading.
3. Terminal voltage
Enough power immediately after uncoupling charging circuit, nickel-cadmium electromotive force of up to 1.5V or so, but quickly abandoned 1,31-1.36 V.
Battery voltage nickel-cadmium administration charge-discharge process changes can be expressed as:
U load = E + charger I load R
U = E could put I put in R
The style can be seen that the charging of the voltage across the battery above the discharge and charge current larger, higher voltage, discharge current increased, the lower voltage. Latitude D810 battery Latitude D820 battery
When the battery nickel-cadmium discharges discharge current standard, the average working voltage of 1.2V. 8am rejection rate of adoption when the battery voltage to 1.1V, the battery or the end of electric discharge.
4. Strengthening and capacity of the main factors influencing
After the battery is fully charged, under certain conditions of release, the release of provisions for the termination voltage, the battery release of total capacity when the battery nominal capacity, the ability of Q the discharge current and the time unloading the product to represent this type are as follows:
Q = I * t (Ah)
Battery capacity nickel-cadmium and the following factors:
① The number of active substances;
② rate of discharge;
③ electrolyte.
The discharge current directly affect the termination voltage discharge. The closure of the discharge voltage required, the discharge of the battery of larger capacity current of the smallest. Latitude D830 battery Latitude X300 battery
The use of different components of the electrolyte, the battery capacity and life expectancy have some impact. In general, the environments of high temperature to improve battery capacity, often add a small quantity of electrolyte in the lithium hydroxide to form a mixed solution. The results show: l electrolyte by adding 15 ~ 20g lithium hydroxide in water at room temperature, the capacity can be increased by 4% ~ 5% to 40 ℃, capacity may be increased by 20% . However, the concentration of electrolytes in lithium-ion batteries too, not only increases the resistance of the electrolyte, but also that the board left in the anode of lithium-ion (Li +) slowly infiltrated into the network within pairs of positive effects harmful chemical changes.
Temperature of the electrolyte on the battery capacity of greater impact. Because the temperature of the electrolyte material chemical reaction of active plate is also gradually improving. XPS M140 battery XPS M1210 battery
Harmful impurities in the electrolyte batteries smaller capacity. The main impurities harmful is carbonate and sulfate. They can increase the resistance of the electrolyte, and crystallization at low temperature easier to plug porous plate so that the battery capacity has decreased significantly. In addition, the carbonate ions with the role of negative plates, producing carbonic acid cadmium negative electrode plate attached to the surface, causing the drivers side, so that the battery internal resistance increases, the capacity decrease.
5. Resistance
Nickel-cadmium batteries internal resistance and conductivity of electrolytes, the plate structures and their size related to the conductivity of the electrolyte also with the density and temperature. Resistance Resistance battery electrolyte mainly by the decision. Potassium hydroxide and changes in sodium hydroxide solution resistivity with density. 18 ℃ when the solution of potassium hydroxide and sodium hydroxide solution minimum resistivity. Usually, the internal resistance of nickel-cadmium batteries can be calculated by: 6Y270 75UYF C1295
6. The efficiency and lifetime
Under normal conditions, the effectiveness of nickel-cadmium batteries ηAh capacity for 67% -75%, ηWh efficiency of 55% ~ 65%, the life cycle is about 2000 times. Capacity and power efficiency efficiency ηWh formula ηAh is as follows:
(U loading and unloading must be considered as the voltage average U)
7. Memory effect
Process of nickel-cadmium batteries, so not all given the power end started to load, unload, next time, you can not provide all the power. For example, nickel-cadmium batteries is only 80% of capacity after the release start charging later, fully charged, the battery can deliver 80% of electricity, a phenomenon called “memory effect . GD761 TD347 U4873
Full press release after the battery power, very small crystals board. The drum part of the discharge, the nickel hydroxide is not completely in the nickel hydroxide and nickel hydroxide remaining will be combined to form larger crystals. Larger crystals of nickel-cadmium are the main reason for the memory effect generated.
Works of Ni-MH
Nickel-metal hydride and nickel-cadmium with the same volume compared to a doubling of capacity, load life cycle of discharge is also longer, and no memory effect. Ni-MH active material of positive electrode for NiOOH (discharge) and Ni (OH) 2 (Load), material negative plate active for H2 (discharge) and H2O (load) of the electrolyte with 30% of the hydroxide potassium solution, charge and discharge when the electrochemical reaction is as follows:
According to the equation: pricing, precipitation negative hydrogen, stored in a container, the positive nickel hydroxide into nickel hydroxide (NiOOH), and H2O; discharge of hydrogen at the electrode negative is used, the positive change of nickel hydroxide in nickel hydroxide. D5318 HD438 KD186