Ventilation would be my primary concern, unless you are planning to use fully sealed batteries like lithium. Even my "sealed" AGM car battery (mounted inside the passenger compartment) has a special venting system. Most batteries produce explosive gasses, and need to be well ventilated; perhaps if you add some exterior venting to the side of the trailer?
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2018 Nissan Titan Midnight Ed.