Replacement battery anecdote

Today I visited a local independent battery shop to see if they had a S46B24R battery. Always good to support small local merchants. My son bought some used batteries from them before, and they have a pretty good rep on Yelp for both used and new batteries. Anyway, called first and the fellow on the phone said they had a battery that will fit our Prius. So I drop in and the person I spoke to wants to see the battery in the car. Not a good sign, but no big deal, so I open up the back and he takes a look and says that they have one. I put the car back together and return to the counter.

On the counter sits an entirely black battery with a small sticker that says "NS40Z" and no other markings whatsoever. No manufacturer's name, no date, no CCA, no Ah, not even a voltage, nada, zip. It does appear to have JIS posts. It looks like it would fit in the battery space but is a little smaller than the OEM 45Ah battery. It also has a green sight glass hydrometer in the center of the top. So I suggest to them that perhaps this is not an AGM battery because a hydrometer needs to be submerged in electrolyte, and in AGM batteries all the fluid is bound up in the glass matrix. (Maybe somebody makes an AGM with a special fluid space in one cell to mount one of these devices, but I have never seen one.) Confused look from the other side of the counter. The boss is summoned and I explain again that this doesn't look like an AGM battery. The wheels turn and he eventually agrees that it probably isn't.

I offer a thank you for their time and beat a hasty retreat to the car.

Probably just pick one up at Walmart - at least the battery will be marked properly.