When I was a student at GMI, one of my work periods was at AC DELCO Batteries. I not only was trained in the design,manufacturing but also rebuilding batteries. About 75% of those rebuilt had nothing more than the electrolyte changed and the case washed clean of the sediment that shorted the plates at the bottom. The batteries of that era had asphalt tar type material as a top seal. We used heated air to melt and flow the top to look as new. These batteries were then returned to other GM facilities and returned to service. I've seen batteries being rebuilt 15 times and many years. Of course 12 volt was coming on in 1953(I think), so most everything was 6 volt. We did have a high number of 8 volters. Bringing back memories. Happy Trails Beep Beep from Houston.
I can still smell that old plant