I have read about Nickel-Iron batteries and from what I have understood they have very long life and large cycles. They are heavier than lead-acid batteries, but even lead acid cells are used in places where weight doesn't matter much.
So, my question is why don't manufacturers innovate or develop this chemistry much? I guess the cost is due to the limited production. Is it because of the long life manufacturers hesitate to produce it which will reduce profit due to reduced replacement cycles? Also this cell chemistry doesn't have any toxic heavy metals either.