Thor Forums

[javelin]

Two position (center off) momentary switches are normally used with latching relays in RVs. In the up position they provide a certain polarity (+,-) voltage to the control pins of the latch relay; in the down position they provide the opposite polarity (-,+) voltage to control pins of the same latch relay. This enables the latch to operate or release and stay that way when the momentary switch is released to center off (no voltage applied) position. Read OldWEB’s post #19 in this thread to learn how the typical latch relay works in more detail.


By the way, I referred to “old Ford style starter relay” in my previous entry only to give you a comparative relay function (that you are probably aware of) for the isolator relay in the Intellitec schematic. You should note though that an old Ford style starter relay is not meant for continuous duty (always on; or on for long periods). There are special relays built to be able to stay operated and used as an isolator relay for RV battery control circuits.



The isolator relay can be used to momentarily connect the coach and chassis battery together to allow you to start your RV engine (if chassis battery is discharged); or the isolator relay can be operated for much longer times, to allow the alternator to also charge the coach batteries when the engine is running and the coach batteries require charging. The BIRD electronics and the aux start switch in my previous diagram determine when the isolator relay operates. Hope that helps.