Probably this question is better suited for the motor home channel however I will give it go here . I am trying to understand the purpose of a latching relay and then another solenoid (relay) to contr...
RV latching solenoids have a second small solenoid that mechanically latch the main solenoid in the on position and hence use no power, except when switching states. Typically used to turn off unwanted power like lights when you exit the rig. Prior rig turned off the refer (really dumb) and the current rig does not.
Typical charging solenoids are controlled by the ignition or smarter electronics and they are NOT latching solenoids.