Question: Why can't SVR batteries be opened? (What happens if they are?) Answer: SVR (Sealed Valve Regulated), sometimes called SLA (Sealed Lead Acid), work on the recombination principle. This means that during charging, the hydrogen produced on the negative plate recombines with the oxygen produced on the positive plate to form H20 or water. This water replaces the moisture in the gel or absorbed mat separators. To work properly, this recombination process must take place in a pressurized cell of about 1 1/2 psi. If an SVR battery is overcharged, the hydrogen and oxygen will be produced faster than it can recombine and will be driven out of the cell... and lost. The gel or separators dry out and the battery fails. If an SVR battery is opened, the cell loses its pressure and the negative plate becomes contaminated with excess oxygen, which damages the battery. Also, when the valves are replaced, it is likely that they will leak which will damage the battery. That is why we preach DO NOT OPEN SVR BATTERIES!