The nickel–iron battery (NiFe battery) are batteries made of iron, nickel, and hydroxide. They are very strong, and do not break easily. They can last for more than 20 years. They are slow to charge. They are often used on trains.
Nickel-iron batteries are very durable. They can be charged many times. They are often associated with Thomas Edison, although he did not invent this type of battery. Edison's company manufactured the batteries until the early 1970s. Today they are made by several Chinese companies. They are often used in applications where a very long service life is required, such as large off-grid solar power systems.