In response to Alistair's question on the EDTA use in batteries, my GUESS
is that the EDTA functions as a chelator for all divalent ions.  EDTA has
been used to reduce the activities of metals in solution (Activity refers
to the free ion concentration) In lead acid batteries, the lead exists as
Pb+2 when it is in solution.  Maybe adding EDTA complexes the Pb+2 such that
it doesn't react and form the slightly insoluble sulfate salts

it doesn't react and form the slightly soluble sulfate salts whixh can then
accumulate and short out the battery.....
christian