Download Nickel Iron battery • This rechargeable battery was introduced in

Nickel Iron battery
• This rechargeable battery was introduced in 1900 by Thomas Edison.
• Also called Nickel Alkaline or Edison batteries.
The open circuit voltage of these cells is 1.4 V, and the discharge voltage is
about 1.2 V.
• The ability of these batteries to survive frequent cycling is due to the low
solubility of the reactants in the electrolyte.
• The formation of metallic iron during charge is slow because of the low
solubility of the ferrous hydroxide.
• While the slow formation of iron crystals preserves the electrodes, it also
limits the high rate performance: these cells charge slowly, and are only able
to discharge slowly.
• The nickel-iron battery (NiFe battery) is a storage battery having a
• nickel(III) hydroxide : cathode
• Iron: anode
• Electrolyte: potassium hydroxide
• The above active materials are held in nickel-plated steel tubes or perforated
pockets.
• The half-cell reaction at the cathode:
• 2 NiOOH + 2 H2O + 2 e− ↔ 2 Ni(OH)2 + 2 OH−
•
at the anode:
• Fe + 2 OH− ↔ Fe(OH)2 + 2 e−
Fully charged condition:
• Positive plates : nickel hydroxide [Ni(OH)3]
• Negative plate : iron
•
When the cell delivers current to load,
• positive plate changes from Ni(OH)3 to Ni(OH)2
• negative plate changes from iron to Ferrous hydroxide (Fe(OH)2).
Advantages
• Very robust.
• Withstands overcharge and over-discharge
• Accepts high depth of discharge - deep cycling.
• Can remain discharged for long periods without damage, whereas a Lead
Acid battery needs to be stored in a charged state.
• Lifetime of 30 years possible
Shortcomings
• Low cell voltage.
• Very heavy and bulky.
• The low reactivity of the active components limits the high rate performance
of the cells. They cells take a charge slowly, and give it up slowly.
• Low coulombic efficiency, typically less than 65%
• Low energy density.
• High self discharge rate.
Applications
• Traction applications
Fork lift trucks
Costs
• Less expensive than Nickel- Cadmium cells
Characteristics of Nickel Iron Batteries
The emf of a fully charged Edison battery is 1.4 V. The average discharge voltage
is about 1.2 V and the average charging voltage is about 1.7 V per cell. The
characteristics of this type of battery is shown below in the figure.
The voltage characteristics of the Nickel Iron battery are similar to that of lead–
acid cell. As the fully charged emf 1.4 V and it slowly decreases to 1.3 V and then
very slowly to 1.1 or 1.0 V during discharge. From the graph, we can see that there
is no lower limit for discharging emf beyond which the output of the battery will
be zero. That’s why after a certain period the battery stop to any output. The emf of
a battery is directly proportional to the temperature, which means the emf of the
battery increases with increase in temperature. The average time of charging of a
battery is 7 hours and discharging time is 5 hours. Another characteristic of Edison
battery is that continuous operation at higher temperature decreases the life of the
battery, same thing happens if the battery is charged for more than the average time
of charging. The ampere-hour and watt-hour efficiency of this nickel iron battery
are 85 % and 60 % respectively. At 4°C temperature, the capacity of Edison
battery falls to zero, that’s why the battery should be heated up before operation
though during operation the I2R loss keeps the battery hot and running.
Advantages of Nickel Iron Batteries
There are various Advantages of Edison battery , these are listed below.
1. The weight of these battery is lower than other types of battery because they
need less amount of electrolytes and plates are also lighter.
2. The service life of the battery is much higher because of various provisions
made.
3. These types of battery are stronger, have rugged construction because of steel
body. For this reason they are not affected by vibrations, jolts or shocks, heavy
currents and do not suffer during short circuits.
Disadvantages of Nickel Iron Batteries
There are certain disadvantages of Edison battery, like the initial cost needed for
making these battery are pretty high as the materials used are highly priced.
Another drawback of these type of battery is the low efficiency. For this few
reasons the use of these battery are restricted, they are mainly used in the areas
where high mechanical strength, lightness, freedom from acid fumes are needed.
Application of Nickel Iron Batteries
From the above discussions, we already know that the said battery are mainly used
in extreme conditions or it can be said that where there is no other way than using
Edison battery. These battery are mainly used in industrial trucks for propulsion
purpose. They are also used in mine locomotives and for railway, car lighting and
air conditioning because they have pretty high mechanical strength.
Maintenance and Care of Nickel Iron Batteries
We already know that the these battery need lower maintenance than other
types of battery. The main precaution taken for these types of battery is to
maintain the level of electrolyte present inside the battery. Because, if the level
of the electrolyte becomes lower than the plates inside, the battery get damaged
very quickly and the battery suffer irreversible damage. To prevent this, the
battery should get filled with distilled water at least once in a week. Another
maintenance which is needed for these battery is to change the electrolyte
solution time to time, whenever the specific gravity of the solution falls below
1.16 the electrolyte gets changed. Lastly, it is important to consider that the
battery should be discharged to zero volt before taking it out for servicing for a
long period.