In this video the fellow adds water to his AGM battery. I never thought about that much but duh, it is done by weight on an AGM, since one cannot just add water and look at the surface level. That is, if the "new" weight is known one can weigh the older battery (after cleaning all the dirt off of it) and just add the appropriate amount of distilled water to make up the difference. (How much to each cell? Well, no level to look at, so probably same amount to each unless there is some other indication that one has less water than another.) Unfortunately the OEM battery True Start S46B24R battery (0054421171325) doesn't have a spec sheet, at least not on the web parts site at the dealers. The Yuasa one does though: https://www.yuasabatteries.com/battery/s46b24r/ which shows the weight as 29.76 pounds. Does the True Start differ from the Yuasa in anything other than the label? Labels don't weight much usually. That the battery could be serviced this way assumes that once the label is cut off there are removable caps underneath to access the cells. That might not be true on this battery. The factory assembled batteries might have the whole top glued on over the cells, or the caps glued to the top. That would make them "Maintenance free" in the "Maintenance nearly impossible" sense.
Speaking for the Yuasa battery; electrolyte must cover the plates. An equal amount above the plates in the 6? cells. The end cells usually requires more distilled water than the ones in the middle. Hope this helps.....
Interesting that the fluid is over the top of the plates. I do recall a video where somebody tilted an AGM battery and the electrolyte could be seen (barely, through the translucent case) sloshing up the side. What are the cell caps like on that battery? Do they screw on one at a time like in that video or are they just "push in snugly as a group of three" like most flooded batteries?
Do we believe the True Start is identical to the Yuasa battery, or is it from whichever manufacturer will give Toyota the best deal each time Toyota makes a bulk order of S46B24R batteries? Another thought - is there a nondestructive test to show that the valve is still in the closed state? Or perhaps that isn't needed since my understanding is that if these valves ever open they tend to stay open, at which point the battery will dry out very rapidly and fail.
The one in my car is absolutely NOT a Yuasa battery with a different label. Pulled it out today and weighed it with an Accuteck All-in-1 Series W-8250 50 lb scale. I had previously tested the scale with water volumes (not having a calibrated weight for testing) and it was within a few percent of the right mass for 1 gallon of water. The error was probably from my fill of the container, it is impossible to see a couple of extra ml on top of a gallon. Anyway, the Yuasa site gives the weight of their battery as 29.76 pounds, or 13498.9 gm, and the one from my car weighed 10638 gm. There is no way a battery would work with 3 kg less water, this battery probably doesn't even have that much water in total when it starts. So not a Yuasa. Then I looked at the top more carefully and the cell covers were not right. I was expecting plastic "bolt" heads, or maybe those under rubber caps. Nope. Here it is: The cell covers are like a security screw, there is a flat face on those spokes that could be used to screw the part in, but to screw it out there are only slopes. It also was marked "Made in Korea" on the side (not shown). Looked at some pictures of this type of battery and found one with a similar pattern on the cell covers - the Everstart Maxx at Walmart. The specs there said that battery weighs "26 lb" which doesn't suggest a high precision value. That is 11793 gm. Closer, but again, hard to believe a battery would function if it was down a liter of water, and ours still works (just not a lot of capacity). So I think this Toyota battery is probably similar to the Everstart Maxx, but with even thinner lead plates to shave the weight down to 23 or 24 pounds.
