Arent all batteries solid state? I know a few use flywheels for stationary use, but most are chemical vs mechanical in nature?
I use to be an avid reader of popular mechances/science and got tired of all the future far fetched ideas that never saw the light of day.
I think in all honestly lifepo4 batteries arent as light or good as lead acid is. I notice my enginer lifepo4 kit has a reduced capacity with 100 degree heat, below 32 degree temp with the cells in my passenger compartment and while the car is being heated and cool. I dont think lead acid had a reduction of almost half capacity in extreme temps, not that below 32 or above 100 is really that extreme for industrial equipment.
When I use to work for a company that sold hydrolic equipment, we could only guarantee it would work to -40 degrees, -60 and the pipes and hoses would burst.