When mine smelled like rotten eggs i.e. sulphur smell.
It was the CONVERTOR cooking the battery!!
My Convertor had a blown capacitor and couldn't regulate itself and was raging out of control frying the battery. Had to replace the convertor and of course a new battery.
On some MH's it is located along side the bed. There is your fuse panel, convertor and fan.
Get a reading on what it is putting out. Leave the tester on a good length of time to see if it is climbing past what is called for.
If you can't do it shut your convertor down and disconnect that battery asap. Go up to the CG office and ask them for the number of their local Mobile RV Repair guy. They carry everything you will need on board or get it within the hour and very reasonable prices while you sit back and have a cold one and chill out. Good Luck
