Question DutchStar 4311 has both BIM and BIRD

[Kevin D Pem]

As usual, Joe, your research is impeccable! I was uninitiated, had no idea what a BIM was, of course had no reason to research it, but good to know.

 

[Joe Hogan]

The Bi Directional Interrupt/isolator solenoid/relay
(BIRD/BIM) serve similar functions. That is to join/disconnect the chassis battery circuit and the house battery Circuit.
This serves several purposes,
a) allows engine alternator to charge house battery in most cases
b) maintains chassis battery voltage from House battery when chassis battery is supplying camper electrical power.
c) provides a Boost to chassis battery for starting when requested By Boost switch.
d) limits duty cycle of charging based on various specs, typically time and voltage.

the programming in these units provide limited charging duty cycles and voltage limits to avoid ”cooking” alternator or batteries.
Additionally if you have dissimilar battery chemistry between house and chassis the isolator/interrupt should be programmed to take this into account.