Re: Voltage puzzle
"The only true method of determining the charge state is to use a hydrometer."
Consider this, Gary. If that were so, then there would be no way to determine the charge state of AGM, gel, and sealed wet cells.
So, how do you think battery makers, distributors, and warranty services are done on all these other batteries? Right, with digital voltmeters, and internal resistance testers, aka electronic "load" testers.
The main purpose of a hydrometer is to burn acid holes in fabric, so folks can sell you new clothing and upholstery. It has some other minor uses, but that's the main one these days.
The electronic tools are easiily misused, but you can't blame the tools for poor workers.