Clicking sound with trickle charger

I called Pleasure Way about this. They told me the click is a solenoid that closes on a charge signal, as several sharp guys pointed out here. The simple solution is to disconnect the positive battery terminal and put the trickle charger directly on the post. Even driving the RV every 3 weeks or so doesn't always prevent a discharged battery which is the reason I went to a trickle charger in the first place. Thanks for the feedback.