Yeah know what you mean there ghurd,have seen that on other batts esp when batt is moved ie electrolite shaken, but mine dont do that even when fully charged,
ive had mine for 3years and noticed when new it didnt glow that was in all 8 batts,
i should have queried this with the supplier but didnt
they are squadron 110amphr deep cycle been in constant use as i am and have been off grid for around 15years, 2 small turbines and ocassional genny use have kept them topped up.
since being on this site and only recently internet i thought i would ask the experts, and see if anyone else had the same thing.
nodge