I have a newly installed Minnkota 3 bank onboard charging system.
I fish usually 1 or 2 days a week.
Batteries never get worn out....should I keep the unit plugged in all the time or only the night before a trip.
Learning as I go folks.
If it's a new Minn Kota, then you are able to leave it plugged in 24/7. As said above, it will cut off when the batteries are fully charged, then it will periodically "test" the batteries to see if they've drawn down. If so, it will charge it until full again then repeat.