Well, I am no expert and will probably get in trouble idea for mentioning Stealth. It depends on the batteries and the charger. The on-board chargers are supposed to charge the batteries up, then monitor the charge. My stealth system charges the primary battery first then switches to the troller bats. There is a switch to disconnect the primary from the secondary, and they say to do this if you are going to let the thing sit for more than a month or two because the LED indication lights will drain the batteries. The primary will drain over time with the engine memory and gauge memory. Again, with good batteries, this will not happen unless the thing sits for a couple of months. If it was me, I would make sure they are charged BEFORE you leave the camp and not leave any kind of charger on the boat unattended. If the batteries are charged before you leave, even if you are gone a month, it shouldnt take more than 30 minutes to top them up again. An onboard charging system that lets the motor charge the batteries when running is the best investment you can make (IMHO). I have never run out of trolling motor juice in 4 years. Biggest deal is that the batteries are in good shape to start with. Milton