The supposed effect of VX-6 and other, similar additives was supposed to break down "sulfation", the formation of the crystalline form of lead sulfate that accumulates on battery plates when a battery is left in a partially-discharged condition for an extended period of time. The problem is that most battery failures are mechanical, not chemical. The reactive material falls off the plate grids and accumulates at the bottom of the cell group, where it cannot enter into the charge/discharge chemical reaction. Additives don't help the mechanical deterioration of battery cell groups.
Lead sulfate is a normal byproduct of battery discharging, but on a freshly-discharged cell plate it is a spongy material that readily reconverts into lead on the negative plate and lead dioxide on the positive plate as the battery recharges. Crystalline lead sulfate can be broken down by repeatedly discharging and recharging the battery, but it's a long, slow process. Additives might help slightly, but the series of tests my father and I ran under pretty scientific conditions at Nashville Auto-Diesel College in preparation for rewriting the school's battery and charging system training program didn't show any measureable advantage to using additives such as VX-6.
Jerry
