Originally Posted by VinceU
Good research Lou, I had a Thermoil battery in a motor home from Gulf Stream built late 1999. The Oil looked like salad dressing oil, thin and just laid on top. The purpose was to retard gas bubbling from leaving the battery (hydrogen). It may have reduced it but its obvious the gas is very light and some will break through. Oil mfg. I've known to use this principal, adding water puts the H20 back in! Can't see how it retards freeze temp however.
Totally seemed like a gimmick to me. If you have a proper 3 stage charger there should be very little or no H2 released as a gas and the hydrogen should stay in solution as Hydrogen ions (H+).
The only time H2 would be released is if the battery was overcharged or charged at a rate too high for the battery to accept and the water would be torn apart by the excess current releasing hydrogen and oxygen as gas. If not vented, this explosive mixture would collect faster than the vents could release it and BANG.
Fully Discharged: Two identical lead sulfate plates
In the discharged state both the positive and negative plates become lead(II) sulfate (PbSO4) and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit.
Negative plate reaction: Pb(s) + HSO−4(aq) → PbSO4(s) + H+(aq) + 2-e
Positive plate reaction: PbO2(s) + HSO−4(aq) + 3H+(aq) + 2-e → PbSO4(s) + 2H2O(l)
The (aq) means aqueous or dissolved in water; so no gas is produced. When discharging, the sulphate from the acid bonds with the lead and the sulfuric acid becomes pure water.
Fully Charged: Lead and Lead Oxide plates
In the charged state, each cell contains negative plates of elemental lead (Pb) and positive plates of lead(IV) oxide (PbO2) in an electrolyte of approximately 33.5% v/v (4.2 Molar) sulfuric acid (H2SO4). The charging process is driven by the forcible removal of electrons from the positive plate and the forcible introduction of them to the negative plate by the charging source.
Negative plate reaction: PbSO4(s) + H+(aq) + 2-e → Pb(s) + HSO−4(aq)
Positive plate reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO−4(aq) + 3H+(aq) + 2-e
Again, the (aq) means aqueous or dissolved in water; so no gas is produced when charging at a rate that the battery can accept. When charging at the correct pace, the sulphate from the plates bond with the Hydrogen ions in the water and the water becomes sulfuric acid again.
Oil would have no use in either process.