How to Hook Up Two Batteries in a Boat Diagram

A fishing expedition will be more successful and enjoyable if you don’t have to worry about being stranded in the middle of the lake because your motor suddenly conk out, the battery completely depleted. For your peace of mind and to avoid such misfortune, it is best that you have two batteries on your boat for reserve capacity.

Aside from the batteries, you will need a dual power cell selector switch . The switch will allow you to choose if you want to turn on both batteries or use only one of them with a flick of a switch. There is a more complicated switch system that includes automatic charging but the switch we will use in this article is the simple one, but can also gets the job done.

Note: we are not specifying any brand of switch here.

The materials and tools you will need to hook up two batteries in a boat diagram

You can only enjoy the advantage of having two batteries on your boat if these are correctly and safely wired. In wiring two batteries on your boat, you will need the right tools and materials such as;

Tools and Supplies:

-Two marine batteries that meet the motors’ specification
-power cell selector switch
-Battery box w/tie-down or bracket
-2/0 cable (marine-grade), red & black
-2/0 cable (marine-grade) lugs, soldered or crimped
-Heat-shrink piping or tubing
-Terminal caps (positive terminals)
-Power drill including drill bits
-Mounting screws (Stainless-steel)
-Socket wrench
-Heavy-duty crimp
-Soldering gun
-Wire stripper
-Cable clamps and tie-wraps

You will also need safety goggles and gloves as protection when you are working with batteries. Before we go about hooking up two batteries in a boat diagram, let’s look at some safety precautions first.

Safety precautions

1.Batteries are made up of a huge amount of potentially dangerous stored energy. So, when you are working on an electrical system make sure to detach the battery’s positive cable from the terminals to prevent the risk of electrocution and/or a short circuit.

2. Use prescribed wire sizes and follow published safety standards for circuit protection.

3. See to it that the metal to metal connections are clean, the terminals are of the right size and properly waterproofed, and the mechanical fasteners are secured for a low resistance connections. This is imperative since the attachments in the battery circuit can carry hundreds of amps.

4. Hex nuts or nylock nuts instead of wing nuts are recommended for outboard motor applications. Lock washers should also be tightened to at most 10 foot pounds of torque. Clamp-on battery terminals attached to a battery cable with the correct gauge should be used for inboard motor application.

5. Wearing safety goggles and gloves is a must when working with batteries. Also, have a water hose ready that you can flush immediately on your face just in case battery acid is splashed on the face or eyes. Never, ever work on batteries close to an open flame and be cautious about using tools that are uninsulated, it might short across the terminals .

Steps in how to hook up two batteries in a boat diagram

Now that you have the right tools and supplies, and you have gone over the safety precaution to ensure that no untoward incident can happen while you are embarking on this DIY project on ways to hook up two batteries in a boat diagram, you can begin.

Step 1 – Select a switch

In choosing a suitable switch for hooking up two batteries in a boat diagram, make sure that you are getting one meant for two batteries and could handle the amperage for cranking the motor. A 250 constant amp rating is enough for most inboard or outboard motors. There are some switches equipped with lock as protection from theft and others with field disconnect circuits as protection for the alternator in cases where you switch off the batteries while the engine is still running.

Step 2 – Install the batteries

First, make sure that the batteries meet the specification of the motors. If your battery is a wet cell battery, make sure that it is secured in a battery box. But, if you’re using an AGM, a battery box is not needed. Brackets or tie downs are needed, though, for both batteries, with their positive terminals protected by non-conductive boots.

Step 3 – Find a convenient location for the switch

According to boating standards the switch should be accessible but as close to the batteries as possible, so look for a place that corresponds to both. Also, the surface should be at least 4 to 6 inches wide, the usual size of a standard switch. You can choose to flush-mount it above deck, but make sure that it won’t be reached by sprays. Don’t install the switch yet, not until you have attached the positive cables to the switch.

Step 4 – Connect the positive cables

Make sure that your cables are marine cables and with the right size., 2/0 cables are appropriate for most inboard or outboard motors. Connect the positive terminals of both batteries to the equivalent posts at the back of the switch. Next, attach the positive cable from the engine to the switch’s output post. Connect also the positive accessory wire to the switch’s output post.

Step 5 – Attach the Negative Crossover

A crossover cable connecting the batteries’ negative terminals is needed for the proper operation of a dual battery system. The, next step in this DIY project of a hook up of two batteries in a boat diagram is to attach the negative accessory wire and negative cable lug from the motor to either of the battery’s negative posts. In doing so, make sure that all the terminal nuts are tightly in place.

You have successfully hooked up two batteries in a boat diagram. This is a simplified DIY project of hooking up two batteries in a boat diagram. If you’re not confident that you can do it right,ask the help of an expert mechanic.

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