As a wee kid Me and a friend sold "X14" magic battery reconditioner.
for some reason which I dont quite understand, the maintance guy at the school buss lot , told me he would buy some, and test it in the old buss batteries, that were in need of replacment.
He got some inital good results, then 6mo or so later tracked us down in class and called us out, Long since forgotten by us by then. and told us that the short term quick fix of the magic X14 battery reconditioner was a total waste, and the batteries he put it in are now finished, as they were to begin with.
I could have known, that the maintance guy knew this stuff was not going to do anything usefull, then for him to actually test it for us, that was sort of special, then to do a followup, when we didn't even care anymore, that was cool.