Many interesting tips! My amateur Internet research had indicated that the tubes should be filled just enough so that an "eye" or curved meniscus shows up at the bottom of the tube -- but there are quite a few knowledgeable folks on this forum who prefer not to fill to that point.
So, I will see if I get any splash -- I never have before, in 15 years of using deep cycle batteries and filling them up to the bottom of the tube. But if I do get some splash, it is easy to drain a little water out of each cell with my hydrometer. (And yes, I know it's sulfuric acid!)
In terms of specific gravity, my hydrometer usually maxes out at 1300 when the battery is fully charged. So I will check the batteries at that point. I assume that the batteries, even though they are brand-new, were not fully charged at the factory. They each had a sticker saying it was manufactured this month (November of 2020), so I assume they have not been sitting around sulfating for more than a couple of weeks.
And oldwizard, I am not under 50. But I did not start paying attention to battery maintenance till I was in my early 50s, 15 years ago. So my "battery awareness" is fairly recent, much like a younger person's would be. I guess that is why I never saw a screw-on battery cap -- it turns out that it is old-school technology! ;)
One more thing about sulphation -- I have these two batteries charging in parallel on a BatteryMinder Plus, which pulses in order to reduce or eliminate sulphation. I know that there is some controversy over whether such a thing is possible. (Mexicowanderer is skeptical, and I value his opinion.)
But the manufacturer of the device has made a factual representation that the unit really can stop and even reverse the process of sulphation. (And there are quite a few reviews in which the review swears that the device cures sulphation.)
I don't have the expertise to evaluate this claim. But I can tell you that if this claim were demonstrably false, the manufacturer would have been sued for fraud.
I have checked, and no such suits have been brought. So my conclusion is that if no trial lawyer has challenged the manufacturer, these devices work as advertised.
