How to Install a Selector Switch on a Boat Battery
- 1). Select the type of battery switch that will work best for you. A small boat with a single battery can get the most out of a simple switch that will turn off house power to extraneous systems, such as a stereo, lights or anything not required to power the boat in an emergency. Larger, more complicated boats, at the very least, need a switch that will alternate between two batteries. An even better solution for a dual battery system, or larger, is a switch that allows alternating between batteries (or battery banks) and an off switch that can turn the entire system, including ignition, off completely so it is impossible to drain the battery.
- 2). Choose the area to mount the battery switch. The best place to mount a switch is in a place that is easy to reach but out of the way. Out of sight is even better. Some people prefer under a back seat. Another consideration is the distance from the engine/battery compartment. You can mount your system up near the helm for easy access, but you will need to run a lot of wiring back to the engine and batteries.
- 3). Decide beforehand which battery position will be your engine and which battery position will be your house. The engine battery is responsible for powering anything that is required to run the boat. This includes the engine compartment blower, the starter and basically any item on the helm of the boat, such as running lights and windshield wipers. The house battery is responsible for everything else. The house battery is largely considered a luxury battery because it powers items, such as microwaves, running water, televisions, air conditioners, stereos and lights. You can choose either "A" or "B" for either purpose, whichever suits you so you remember it, as long as you always use those designations for that purpose.
- 4). Use an open-end wrench to connect the positive ports of the circuit breaker and the engine to the selector switch. Connect the negative terminals of both the "A" and "B" batteries to the alternator. Connect a negative terminal of the alternator to the engine. Connect the positive terminals of both the "A" and "B" batteries to the corresponding position on the switch.
Source...