- Battery low electrolyte density after topping up with distilled water

Hello,
Recently, I was charging the 90Ah car battery, after fully charging its resting voltage was 12.7-12.8V, i.e. correctly, but I checked the level and density of the electrolyte, the density was ok, on the green field on the aerometer (1.26-1.27 I do not know if this aerometer is mega accurate or not, but it was on the green), but the electrolyte level was below the max and those markers under the L-shaped stoppers, so I added distilled water to the L edge.

The electrolyte density dropped to 1.21 -1.22 (white field, almost red, measured after closing the plugs, gently mixing and waiting 30 minutes) so I connected it back to charging, with a low current of 2A for 10h, after this time and waiting 2h after charging I checked again the quiescent voltage and electrolyte density, voltage about 12.8V, but the electrolyte density was still at 1.22.

What to do about it? Continue loading it? Can it increase the charging current to 1/10 of its capacity so that excess water evaporates? Buy some battery acid and thicken the solution?

Because it actually looks like it is too thin. The electrolyte is clean, transparent, so the battery should not be sulphated. Pulling it out for charging was not caused by the fact that it discharged and no longer had the strength to spin the starter only purely prophylactically because he was sitting in a car that was rarely fired.

It's not that easy with this electrolyte, especially when charging the electrolyte stratifies. There are always higher concentrations of acid at the bottom than at the top. The situation is slightly improved by intensive gassing in the final phase of charging, but the final electrolyte density is best measured after a few days of charging.
If there was no leakage of electrolyte, it is by no means added acid, only distilled water.
As the battery was used in such a car, unfortunately it is partially sulphated. Wait a few days and check the density again. Any lower density than 1.28 will mean that part of the acid is trapped in lead sulfate crystals in the active mass of the plates or already at the bottom of the battery. But all this provided that the battery is properly charged, e.g. zero-duty Ca / Ca, you need to charge it until it reaches 16.2V. Normal Sb / SB with 14.5V, until the charging current drops almost completely.

Ok, I will throw it on a standard 1/10 capacity charging.
The battery is not old, it is from 3 years old, the battery is voltmaster 90Ah, from what I saw on one side, the model comes out that it is probably the one with calcium, but it is possible to remove the entire strip with plugs, always without a problem fired a 3-liter roller, the car was occasionally fired to leave the garage, occasionally it was driven.
During a few hours of charging, the voltage reaches 15.8V, which means that it still needs to be charged, the rectifier I use is the Soviet "electronics"
Recently, I put it in a second car that I drive every day, even in cold frosts without a problem, I didn't need to look into it, to the level of electrolyte.
Well, let's see what will happen after this standard charging and after a few days what will be the density and resting voltage.

Unless others say what to do about it

Added after 12 [hours] 39 [minutes]:

I guess everything will be ok, after 10h charging with 6A (this is the max gives this charger and turns itself off after 10h from switching on), the electrolyte density is already closer to the green field 1.25-1.26. Checked 2-3h after charging, voltage also around 12.7-12.8V
Now I put it on charging, I think that after this charging it will be ok, we'll see

I guess everything is fine, after approx. 36 hours from disconnecting the charge, the battery voltage is 12.6V, and the electrolyte density in the cells is ~ 1.27, i.e. approx.

12.6V voltage a bit too low for a fully charged battery. The density is the same for all purposes?

It was 12.8V after a few hours after charging, after two days 12.6V, so ok, the electrolyte density in each cell is the same. The load test was successful, 3 times loaded, the device hand did not leave the green field. That means it will work, it is already sitting in the other car.

Water with electrolyte must have time to mix.
As soon as you measure it, it won't be good.