Batteries boiling

[rheavn]

My two wet cell starting batteries have been boiling water out as the coach sits in the garage hooked up to power. Charger shows charging in float mode. Volt meter verifies batteries receiving float charge. My batteries have always started the coach without fail. They are just starting year eight so I assumed they needed replacement. I checked each cell with a hydrometer and they tested still good. As I was removing the caps I noticed a slight woosh, like the batteries were under pressure. I left the caps loose for a few days and no more water boiling out. I cleaned the battery caps in a baking soda solution. The batteries no longer boil water out with the caps back in place. It was a very simple solution, although in messing with automotive stuff for close to fifty years I have never cleaned battery caps before. Maybe my experience will help some one in the future.