Nickel-iron battery
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| Battery specifications | |
| Energy/weight | 50 Wh/kg |
| Energy/size | |
| Power/weight | 100 W/kg |
| Charge/discharge efficiency | |
| Energy/consumer-price | |
| Self-discharge rate | 20%-40%/month |
| Time durability | |
| Cycle durability | |
| Nominal Cell Voltage | 1.2 V |
The nickel-iron battery is a storage battery having a Nickel(III) oxide-hydroxide cathode and an iron anode, with an electrolyte of potassium hydroxide. The nominal cell voltage is 1.2V. It is a very robust battery which is tolerant of abuse, (overcharge, overdischarge, short-circuiting and thermal shock) and can have very long life even if so treated. It is often used in backup situations where it can be continuously charged and can last for 20 years. Its limitations, namely, low specific energy, poor charge retention, and poor low-temperature performance, and its high cost of manufacture compared with the lead-acid battery led to a decline in usage along with it having the lowest energy-to-weight ratio. [1]
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 Fe3O4, which is good and bad. It is good because the slow formation of iron crystals preserves the electrodes, bad because it limits the high rate performance: these cells charge slowly, and give it up slowly.
Nickel-iron batteries have long been used in European mining operations because of their ability to withstand vibrations, high temperatures and other physical stress. They are being examined again for use in wind and solar power systems and for modern electric vehicle applications.
[edit] History
The battery was claimed to have been developed by Thomas Edison in 1901, and used as the energy source for electric vehicles, such as the Detroit Electric. In fact Edison stole the idea from the Swedish inventor Waldemar Jungner who had invented the Nickel-Cadmium battery 2 years earlier in 1899. Junger experimented with substituting iron for the cadmium in varying proportions, including 100% iron. Jungner had already discovered that the main advantage over the nickel-cadmium chemistry was cost, but due to the poorer efficiency of the charging reaction and more pronounced formation of hydrogen (gassing), the nickel-iron technology was wanting and was abandoned. Jungner never patented the iron version of his battery. Edison, nevertheless, made exaggerated claims for 'his' nickel-iron design, claiming them to be, "... far superior to batteries using lead plates and acid". Jungner's work was largely unknown in the US until the 1940's when Nickel Cadmium batteries went into production there.
There is a (possibly apocryphal) claim, that an oil company stole the battery blueprints due to fears of being put out of business by electric batteries. The theft was allegedly aided by the employee who claimed to really have invented the battery, annoyed because Edison would never allow any name to appear on a patent other than his own.
Edison's batteries were made from about 1903 to 1972 by the Edison Battery Storage Company located in East Orange, NJ. They were quite profitable for the company. In 1972 the battery company was sold to the Exide Battery Corporation. They continued to manufacture the battery until about 1975, then abruptly discontinued making the battery. Edison was disappointed that his battery was not adopted for starting internal combustion engines and that electric vehicles went out of production only a few years after his battery was introduced. He actually developed the battery to be the battery of choice for electric vehicles which he thought would be the preferred transportation mode in the early 1900's. The battery enjoyed wide use for railroad signaling, fork lift, and standby power applications. There are no Nickel Iron batteries manufactured in the United States at this time (2006).
