Ecologieforum

In 1901 Thomas Edison developed a new type of battery using nickel and iron for the plates, and alkaline potassium hydroxide for the electrolyte. He intended them to be used in electric cars and for automotive starting, and you'll see them referred to as nickel-iron (NiFe) or Edison cells. They are making a bit of comeback in the renewable energy world and are especially popular among “preppers” for one reason—they are extremely long-lasting and resistant to abuse from over- and undercharging. It's not uncommon for 50-year-old NiFe batteries to still be functioning just fine.

Unfortunately they also have major disadvantages, which are why they never caught on for Edison's planned uses. They are very expensive to manufacture, don't store as much energy for their size and weight as lead-acid batteries, have a high self-discharge rate, are very inefficient when charging or discharging, and are subject to thermal runaway if not charged carefully. Currently they are only made in China, and there is only one company in the USA that imports them. That company is currently working with charge controller manufacturers to develop programming to better suit NiFe cells.

I usually advise clients to avoid NiFe and go for industrial lead-acid batteries instead, but I can't deny that the idea of a battery that can last decades is very attractive. If you are going to use NiFe batteries, I recommend that you size both your solar array and battery bank at about twice the normal capacity, and be certain that all your charger equipment has specific settings just for NiFe.