Originally Posted by Seneca Pilot

Gel and AGM are good, no doubt. Of course Tesla uses Lithium. The biggest advantage to nickel iron over any others is the lack of memory. They can be pulled to zero, charged to 100% and back to zero or maintained anywhere in the middle with little or no long term effect on battery life or ability to charge. Old tech but very stable and long lived. Too heavy for sail boats or vehicles but fine to anchor down a house.