People do have real world experience with Nickel Iron Batteries. I personally know a friend running a large set for his Ham radio station at home. A smaller set that used to be in his TC till it was sold and he has not installed them in his class A as they would be in the nose and doesn't want to add all that weight up there. Best places to get info about them, that I have found, is on off grid solar forum boards. I personally would not use them in a mobile environment as they are very heavy and have different charging requirements than FLA battery. Seems that FLA is still the most bang for the buck. For the money it would cost for new ones, I could buy LOTS of FLA.