A battery combiner automatically connects the banks when charging, so only the master switches have to be turned on.
A NOVEL CONCEPT Upgrading master panel battery switches could be a big project until Blue Sea introduced the Dual Circuit Plus battery switch, an innovative replacement for the four-way switch.
MAKING THE SWITCH Swapping out the master switch is straightforward—these switches are the same diameter and share the same mounting screw spacing as most of the older, four-position switches.
Before starting this project, to reduce the likelihood of an short circuit or arcing, disconnect the batteries by removing the positive cable from both battery banks.
The engine starter may even draw enough current to cause a momentary drop in voltage deep enough to shut down the navigation instruments.
Most new electrical panels have several master switches—one for the starting bank, one for the house bank, and one to combine or parallel the banks if either gets discharged.
Connect the wires leading to the house panel to the stud below the house battery bank.
Thread on the nuts and loosely tighten to hold the cables in place.
Depending on how the old switch was wired, connect the existing wires that may power the bilge pump to the top terminal of the house battery to directly connect the pump to the battery.As you disconnect the battery banks, positively identify each cable running from battery bank one and two at the master switch and mark them (wear safety glasses when working around batteries).Then remove the cables from the back of the master switch. Some may be connected to the common stud on the old switch and are turned on and off by the switch, like the feed for the DC main panel.Wires leading to the bilge pump or from the battery charger are usually connected to the individual battery terminals and are not switched.Loosen the bolts that hold the old switch to the panel and remove it.The four-position master switch that controls a boat’s 12-volt system has been the standard for years; it’s simple to install and reliable, but it has several drawbacks.First, it requires the operator to remember to change the position of the switch to use either battery bank one, or battery bank two, or combine the two banks to start the engine and power the 12-volt lights and electronics.The output of your alternator determines the size of these wires and fuses.The higher the amperage output from the alternator, the heavier the wiring.Drop in the Dual Circuit Plus Switch and bolt it in place.You may need to purchase longer bolts depending on how the old switch was mounted.