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Disconnecting alternator charging at a voltage setpoint
There are scenarios where one might want to prevent an isolator from combining the house and chassis 12v systems:
- the house battery needs less voltage than lead-acid (lithium, for example)
- the combined circuit can feed higher-than-optimal voltages back from solar charge controller to the chassis' electronics.
how it works
Isolator/relays/solenoids, etc, use mechanical or electrical means to combine the chassis and house 12v systems. These mechanical or electrical means will require a small amount power to operate.1)
If the device's own power source is disconnected it will turn off and 12v systems will be separate again.2) Using a High Voltage Disconnect to kill power to the device will stop the alternator from charging the house battery at a given voltage setpoint.
Shutting down the device will require different approaches, depending on where it gets the power to operate itself.
disconnecting isolators and simple relays
by 12v trigger. Example: 12v source that's only active when the key is in the RUN position. These have 4 lugs: starting+, house+, trigger+, trigger-; or,
disconnecting voltage sensing relays
These usually have 3 lugs: starting+ in, house+ out, starting-. The starting- “ground” is only used to complete a small circuit so the relay can run itself. So it's usually very thin.
