Here's an interesting old book I stumbled on while searching for something else.
http://tinyurl.com/juc4kox
There are hyper links to take you to each chapter.
While skimming through it, I was reminded of something Dad used to do in the late '50s and early '60s when car batteries had a hard rubber case and the top was sealed to the case with bitumen. When the battery started to fail after 5 or 6 years, he would carefully drain the acid into a plastic bucket and then tip it on its side on the edge of the gully trap. (Remember them?)
He would then very gently use the garden hose to rinse out the accumulated sediment from each cell. Once drained again, he would carefully decant the acid back into each cell leaving any sediment in the bucket. The cells were then topped up with fresh acid to replace what had been lost. He would usually get another 2 or 3 years out of the battery.
I've also seen him use a hot blade to carefully cut through the bitumen around the top of the case, lift out the whole top and plate assembly, carefully rinse the plates and clean out the case, then reassemble the whole thing and reseal the top by running a large copper-headed soldering iron around the cut to reseal the bitumen. (Not an electric iron, but the kero blowlamp type).
In fact back then you could buy reconditioned batteries that had their plates replaced.
