Nickel-iron Battery Specifications Energy/weight 30 -50 Wh/kg Energy/size 30 Wh/l Power/weight 100 W/kg Charge/discharge efficiency 65% - 85% Energy/consumer-price 1.5 – 6.6 Wh/US$ 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 max.46 °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.