I'll add if it smeel sweet it's not ether or sulfuric acid. Added wird of advice... don't rely on smell to decide. Even small. amounts of sulfutic acid fumes can be harmful if it's acidic enough.
You could take a top off a battery in the RV and take a whiff. Not too deeply draw the gases toward you by using a hand to drag it toward you.
Don't just stick your nose over one of the cells and inhale... odds are that coils end poorly.
It most well could be something plastic out gasing. Be safe open windows if you can should you be using your rig right now.