Gone Outdoors

How to Wire Up a Perko Dual Battery Switch on a Boat

by David Curtis

A dual marine battery switch allows you to use two marine batteries and isolate them from each other. This avoids problems with both batteries accidentally draining, leaving you stranded. It also allows you to turn off all power to the boat. Some models are equipped with keys and locks to prevent unauthorized use of the watercraft by locking the batteries in the "Off" position. Place the battery switch in the "ALL" position to use and charge both batteries.

Locate a convenient place to install the battery switch. The best place is near the engine compartment and current battery. Mount the second battery box near the primary battery and secure it with the brackets and screws provided with the kit, using a Phillips screwdriver. Place the second battery inside the box.

Remove the battery box cpver and disconnect the negative or black lead from the primary battery for safety. Most marine batteries use a stainless-steel wing nut to hold the cables to the battery terminals.

Locate the red or positive lead going from the primary battery to the starter. Remove the cable from the starter using an open-end wrench. Connect this end of the cable to the terminal labeled "1" on the Perko dual battery switch.

Connect a new red battery cable from the second battery's positive terminal to the number "2" terminal on the Perko switch.

Connect the second new red battery cable to the common connection point labeled "COM" and connect the other end to the starter's wiring post. Secure the connections with an open end-wrench.

Connect a new black battery cable to the negative terminal on the second battery and connect the other end to a grounding point on the engine block. Use the same connection point as the first battery if convenient.

Reconnect the primary battery's ground cable on the negative terminal. Secure the protective marine battery box covers to the boxes and strap them down.

Items you will need
  • Marine battery box kit
  • Second battery
  • 2 marine grade red battery cables
  • 1 marine grade black battery cable
  • Open-end wrench
  • Phillips screwdriver

Warning

  • Always keep marine batteries inside approved spark resistant boxes for safety.

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