My Itasca Suncruiser 37F is parked on my driveway. Last week, I heard the propane alarm going off, but the propane was shut off at the tank. I removed the detector and noted that it still had 2 years until it's expiration date. Made a note to order a new one. I am planning a short trip, so yesterday I decided to check the battery acid levels. The caps were popped up on three cells of one battery and the levels were low. I checked the battery voltage on the control panel and it read 13.5 volts, with and without shore power. I added distilled water to the 3 low cells. This morning the RV smelled of sulfuric acid. I rechecked the batteries and the caps on the 3 cells were popped up again. The battery was extremely warm. I removed the cables and it only read 6.5 volts. The second battery was maintaining the 13.5 volts. The propane detector had alarmed due to the explosive gas being given off by the bad cells.