I have two batteries and a standard master switch. I am used to using a battery charger as needed set at 10 amps. My charger has a 2 amp setting. I was wondering if I could leave the charger in the boat set at 2 amps for extended periods of time without worrying about overcharging. If OK would it be best to connect to one battery and set the master switch to Both or do them one at a time changing to the other battery every (?) days.