While I can't comment on the use of EDTA, I just want to point out that I've had limited results with pulse charging.
Not quite sure of the mechanism behind it, although I can follow a few theories.
Anyway, both pulse charging and discharging (ghurd controller for example) have given some interesting results from a few "testers" that I have experimented on.
Not that it applies here, but for anyone glancing at this in hopes of reviving an SLA with any of this. Stop right here, I can save you the trouble.
Only FLA have ever really been responsive.
Now, with all of that said, I'd be interested to see what the deal is if EDTA has sufficient effect that the two (or three, actually) concepts can be combined to give some really decent results.
One thing that bothers me about this however is this "battery must be recharged immediately" thing. One can take this a couple different ways - Does that mean you need to charge it immediately after adding it, then all will be ok? Or does it mean that you should have even less "dead" time than normal, lest one expect the thing to die a horrific death if discharged to any degree and left for more than a moment... ?
Food for thought. You're not the first one (by far) to mention EDTA, and pulse charging/discharging are not new concepts either.
Not saying experiment with all the variables on your bank at one time, but might be worth looking into this combination.
I know I wouldn't be the only one interested in the answer...
Steve