The curve is NOT linear, nor is it the same for differing density of electrolyte. Temperature makes a significant decrease in electron and chemical activity BUT BUT BUT BUT BUT sulfation still can form and still can lattice at -20C
A typically abused forgotten battery (disconnected not top charged) does not uniformly sulfate the surface area of a plate. Latticed sulfation is like cancer, a spot can form and then render the area inactive. A loss of capacity in percentile. But newer sulfate that joins with the latticed old sulfate is much more easily and quickly rendered "hard" and difficult or impossible to remove unless steps are taken at appropriate time spans to revert the sulfation back into solution.
The process is slower with Pb only plates, or lead calcium.
Another reason to hasten the development of lithium technology.
