Does plain mineral oil extend the life of RV lead acid batteries? Edison marketed a “Battery Oil” that was nothing more than mineral oil. A thin layer of mineral oil covered the electrolyte solution floating on top inside the battery cell to prevent both evaporation and absorption of CO2 in Edison Primary Batteries. Edison’s batteries were used in commercial applications like railroad crossing signals. RVers have been using mineral oil this way in their RV batteries for years. What is the theory behind this concept? Well, the idea is that when batteries are discharged and charged (which happens frequently in RVs) increased water consumption occurs through evaporation. During this process sulfuric acid fumes discharge from bubles rising to the top of the cells. This results in external corrosion problems. The thin layer of mineral oil acts to retard the rapid bubble explosions thereby reducing the amount of sulphuric acid that escapes. I do not have scientific data to determine whether this actually works or not, but I do know many RVers have told me this treatment has increased the life of their batteries and significantly reduced the amount of corrosion on battery posts, cables and trays. They also report less evaporation resulting in less maintenance. A down side to this is you have to get the tube of your electrolyte tester down past the layer of mineral oil in order to do an electrolyte test. I’m not recommending that you do this. I could not find sufficient data to support doing it, but, I am using my RV batteries as a test bed for this project to see if indeed these claims are true. So, today I put two ounces of plane white mineral oil in each of my battery cells using a one ounce syringe.
I had to remove some of the electrolyte to ensure a proper level in each battery cell. I purchased the mineral oil at the WalMart pharmacy. I’ll report back in a year and let you know how my batteries are performing. Doing stuff at home without adult supervision - Jim Twamley, Professor of RVing