As the proliferation of on board electronic equipment with internal memories and presets has accelerated, we are now faced with what most of us considered a non issue 15 years ago, electrical parasites! This current draw needed to maintain the status of the on board equipment adds up to the point where it can bring a battery’s level of charge well below a safe level in terms of battery longevity and some cases even freezing, effectively destroying the battery. So, with all of this in mind, the new approach to all of this is to leave everything connected and in place but now connect the batteries in question to one of the charge maintainers shown above. These units put out just enough current to deal with the parasitic loads, measured in milliamps, without overcharging the batteries. With maximum outputs of 1.5 amps this type of unit is truly the answer on modern boats. Additionally, If your boat is equipped with a very modern smart battery charger with multi-phase capability it may be set up to maintain, but actually shut off once battery voltage reaches a prescribed level, again, maintaining charge level but not over-charging.