The Edison Nickel Iron Cell...Outlasts Lead Acid Batteries by Decades!
Categories: Power Solutions
Lasting Energy Storage for Solar, Wind & Micro-Hydro
-Invented over 100 years ago by Thomas Edison as a non-polluting and non-consumable alternative to Lead Acid Batteries using no heavy metals!
-Now manufactured once again worldwide after lead acid battery companies closed Edison's Plant in 1972 in East Orange, NJ USA.
-This Information Is Provided by: The Nickel Iron Battery Association -dedicated to clean energy storage for renewable energy systems.
Thomas Edison with his Nickel Iron Battery in 1910
Building a solar, wind or other renewable energy system for a home or business can be discouraging if lead acid batteries need to be used. Lead acid batteries are "consumables" and last only a fraction of lifespan of your solar panels or other electricity sources. Massive battery banks of lead acid batteries need to be replaced every 10 years or less. However a better solution has been available since about 1911 using the almost forgotten storage battery that contains no toxic heavy metals and may outlast you or your house!
The purpose of this article is to collect information that will help people to use and maintain the Nickel Iron Battery technology for use in Solar homes and for Marine applications. The Nickel Iron battery often lasts in excess of 40 years and makes a perfect match for solar panels which also last for about 40 years or more. This site is focused on the re-popularization of nickel iron batteries in renewable energy applications. Nickel Iron Batteries contain no environmentally damaging heavy or poisonous elements. The electrolyte of Potassium Hydroxide is caustic but can be useful in farming when diluted to neutralize acidic soils.
This info is not specific to a manufacturer or supplier. This site supplies useful and accurate information on the Edison Nickel Iron Battery technology and its uses in alternate energy applications.
Nickel-iron Battery Specifications
|Charge/discharge efficiency||65% - 85%|
|Self-discharge rate||10-15% /month|
|Time durability||30– 100 years|
|Cycle durability||Repeated deep discharge does not reduce life significantly.|
|Nominal cell voltage||1.2 V|
|Charge temperature interval||min.-40°C |
The nickel-iron battery (NiFe battery) is a storage battery having a nickel(III) oxide-hydroxide cathode and an iron anode, with an electrolyte of potassium hydroxide. The active materials are held in nickel-plated steel tubes or perforated pockets. It is a very robust battery which is tolerant of abuse, (overcharge, overdischarge, and short-circuiting) 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 more than 40 years. Due to its high cost of manufacture, other types of rechargeable batteries have displaced the nickel-iron battery in most applications. Because of their long life NiFe batteries are ideal for backing up renewable energy applications. The reason for their disappearance in the North American market is largely due to the Exide Corporation's decision to abandon the technology in 1975 after purchasing it from the Edison Storage Battery company for several million dollars. The reason for acquiring the manufacturing process to make NiFe batteries and then simply abandoning the technology is unknown. Exide remains the second largest manufacturer of lead acid batteries in the world.
The proper float voltage is 1.45 volts per cell. If 10 cells were used, the proper charge voltage would be 14.5 volts. Charging Parameters
The charge voltage can vary from 1.46 to 1.55 volts per cell. Unlike other battery designs, the exact charge voltage is unimportant. A higher voltage will result in quicker charges but more water loss that will necessitate more frequent topping up with distilled water. Since the cells can withstand overcharge there is debate over what constitutes a proper charge voltage. The higher you go the quicker water will disappear from the batteries. At voltages greater than 1.5 volts/cell the batteries will store approximately 15% more power than they are rated for. If 10 cells were used, the charge voltage could range from 14.6 volts to 15.5 volts. It is probably better to use the 1.46 volts / cell level of charge in order to minimize water loss if the battery will be unattended for months at a time. Regenerative catalytic caps are available to combine the h2 and o2 back into water if unattended maintenance is required. There are also auto watering systems that are available.
The proper equalization voltage is 1.65 volts per cell. If 10 cells were used, the proper equalization voltage would be 16.5 volts. This equalization charge is applied for 8 hours using at least C/10 current. According to Edison's original manual from 1914, it is best to completely discharge the batteries from time to time before applying the equalization charge. Edison also recommends a 1.7 volt equalization charge and he recommends changing the electrolyte every 5-10 years.
This will all come as a surprise for lead acid battery users. In contrast to lead acid, the NiFe battery can be overcharged for decades at a time without damage and can be left discharged for years at a time and will still work perfectly when needed.
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. 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.  Nickel-iron cells should not be charged from a constant voltage supply since they can be damaged by thermal runaway; the cell internal voltage drops as gassing begins, raising temperature, which increases current drawn and so further increases gassing and temperature.
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.
The half-cell reaction at the cathode:
2 NiOOH + 2 H2O + 2 e− ↔ 2 Ni(OH)2 + 2 OH−
and at the anode:
Fe + 2 OH− ↔ Fe(OH)2 + 2 e−
(Discharging is read left to right, charging is from right to left.)
The open-circuit voltage is 1.4 volts, dropping to 1.2 volts during discharge.  The electrolyte mixture of potassium hydroxide and lithium hydroxide is not consumed in charging or discharging, so unlike a lead-acid battery the electrolyte specific gravity does not indicate state of charge.  Lithium hydroxide improves the performance of the cell. the voltage required to charge the cells is between 1.6 and 1.7 volts. Most people use 1.65 volts.