bi-directional relay

my 2012 newmar canyon star is having an electrical issue,
under the hood i have the bi-directional relay, next to it
the electrical solenoid and next to that is a black unit,
looks like some kind of coil or relay. what is it called?
discharging my chassis battery. and it is running very hot
over 130degrees , is it some sort of switch.. and could this
the reason my chassis battery is discharging.. please help