Perhaps they are not sulfated. I'm about to replace my charger due to a flakey charging bank which is likely to be my problem with this set of batteries but more importantly, if I'm going to replace the charger and the batteries I want to do everything I can to setup for the longest battery life possible including desulfating.
Not knowing exactly what is going on with the flakey charging bank, it's conceivable that it was not fully charging the battery leading to sulfation. Further, if the battery wasn't being charged up enough to avoid sulfation, the rest of the series were likely discharging and potentially sulfating.
I am by no means a battery expert but my understanding is that sulfation starts occuring when batteries are drawn down to about 80% of their charge. I have no idea how long the battery must be at this state for sulfating to occur but I'm guessing there isn't a magic time frame and there are other factors involved (temperature, etc). I'm also under the impression that this is at least one of the reasons why you want to charge your batteries as soon as possible and that if done quickly, the charging process can remove the sulfates.
There are times however that I do not get my boat on the charger as soon as I'd like and I'd suspect are least minimal sulfication occurs even when I do although I have no proof. The boat is sometimes in the shop, I go camping and fish for multiple days without a charger, I fish in high currents and high winds. I've drawn my batteries down so they only move the boat at 2mph rather than the typical 3mph, forget to plug the boat in, park the boat where there is no power, etc, etc.
It just seems to me that desulfating wont hurt, so why not do it?
- Ray