I talked with a tech at the Trojan Battery factory in Georgia (USA not Russia)
I asked if R.O. water was Ok to fill batteries (Thought it was, but...) He said it was fine, also how long I should wait to check the specific gravity after filling, he said a few hours would be good.
He did say that if the check revealed a 1.270 reading, to charge, or wait if on-charge until the number moves up from there.
He said if a battery was bad, the balls in solution would not even move. Also, usually one or maybe two cells usually are bad in a 6 Volt battery, not all of them. He verified that if the electrolyte was even with the top of the plates, they should be Ok.
All predicated on healthy batteries going into this deal..
I also asked how they check batteries, with an electronic meter, or the bulb, glass tube, and little Gerbil balls. He said they use both.