Hooking Up A Boat Battery Selector: A Step-By-Step Guide

Hooking up a boat battery selector is a simple process that can be done by following a few essential steps. It is recommended to have a second battery on your boat to provide backup power and prevent accidental battery drain. The first step is to choose a suitable battery selector switch, such as the Perko 8501 battery selector switch, which allows you to choose between batteries, combine them, or disconnect both. The next step is to install a second marine battery that meets the engine specifications and complies with safety standards. This includes securing the battery in a box or with tie-downs and covering the positive terminals with non-conductive boots. The third step is to select an accessible location for the battery switch, ensuring it is close to the batteries and has enough space. The fourth step is to connect the positive cables, followed by the negative cables, ensuring all connections are tight and using the correct cable sizes to prevent voltage drop. Finally, it is important to follow safety precautions when working with batteries and to refer to the American Boat and Yacht Council (ABYC) guidelines for circuit protection and wire sizes.

Understanding the types of marine batteries

Marine batteries are essential for providing electrical power to your boat's engine, dashboard, electronics, accessories, and more. When choosing a marine battery, it's important to consider the specific needs of your vessel, such as power requirements, weight, durability, and cost. Understanding the different types of marine batteries available is crucial for making an informed decision.

Starting Batteries:

Starting batteries, also known as cranking or boat cranking batteries, have a single purpose: to start the engine. They deliver high amperage bursts of current for several seconds when the ignition is activated and are then quickly recharged by the engine's alternator. These batteries are not designed to power electronics, lights, or other accessories. Starting batteries are similar to automotive batteries and are available in both flooded and sealed types.

Deep Cycle Batteries:

Deep cycle batteries are designed to provide steady and consistent power over extended periods. They have thicker plates compared to starting batteries, allowing them to withstand repeated deep discharging and recharging without damage. These batteries are ideal for powering lights, GPS, fish finders, trolling motors, and other accessories during your trip. Deep cycle batteries are available in flooded and sealed types, with lithium deep cycle batteries offering lighter weight and consistent power output throughout their discharge.

Dual-Purpose Batteries:

Dual-purpose batteries, as the name suggests, combine the functions of both starting and deep cycle batteries. They can start the engine and also provide power for electronics and accessories. While these batteries save space, weight, and cost, they drain quicker than deep cycle batteries and may not have sufficient power to crank larger engines. Dual-purpose batteries are available in flooded and sealed types, with some models offering exceptional durability and longer life expectancy.

Marine Battery Chemistries:

In addition to the three main types of marine batteries, there are also different battery chemistries to consider:

• Flooded Lead Acid (FLA): This type uses lead plates and a mixture of distilled water and acid. They are cost-effective but require regular maintenance, including topping off the fuel cells with distilled water. FLA batteries are bulky, heavy, and have a shorter life expectancy of around 2 to 4 years.
• Gel and Absorbed Glass Mat (AGM): These are sealed types of FLA batteries that don't require topping off. They are more expensive, leak-proof, and have a slower discharge rate. However, they still share the weight and bulkiness issues of traditional FLA batteries.
• Lithium Iron Phosphate (LiFePO4): Lithium marine batteries address many of the shortcomings of FLA batteries. They are exceptionally durable, sealed, and weigh significantly less than flooded lead-acid batteries. Lithium batteries offer longer life expectancy, higher capacity, and faster recharging capabilities. However, they come with a higher upfront cost compared to other options.

Selecting the right battery for your boat

The battery is one of the most vital parts of your boat's electrical system. It is important to select the right battery for your boat to ensure optimal performance and avoid being stranded on the water. Here are some factors to consider when choosing a marine battery:

Type of Battery

There are two main types of marine batteries: starting batteries and deep-cycle batteries. Starting batteries are designed to provide a separate power source to get the engine going, while deep-cycle batteries are used for the trolling motor and various electronics, offering a steadier source of power for long periods. Deep-cycle batteries are also designed to be used and recharged repeatedly. If you need a battery for both starting and deep-cycle functions, consider a dual-purpose battery, which can be used interchangeably for starting and house electrical loads.

Size of the Battery

The size of the battery will depend on the application, either engine starting or deep cycle for energy use. For starting batteries, consult the engine manufacturer's recommendations and consider the battery's marine-cranking amps (MCA), which measure the battery's power delivery in a short burst. A good rule of thumb is to have 1 cranking amp per cubic inch for gasoline engines and 2 cranking amps per cubic inch for diesel engines. For deep-cycle batteries, check your owner's manual for the CCA rating required for optimum performance.

Number of Batteries

Smaller boats may be able to use a single battery for both starting and deep-cycle functions. However, larger boats or those with high power usage should opt for two separate batteries to minimise the chance of killing the starting battery. Most boats with dual-battery systems use one starting battery and one deep-cycle battery.

Battery Chemistry

Marine batteries come in different chemistries, including flooded lead-acid, gel, AGM (Absorbed Glass Mat), and Lithium-ion. Flooded lead-acid batteries are commonly used in starting applications and have a no-spill design. Gel batteries are perfect for boats as they can jostle around without causing problems and require little to no maintenance. AGM batteries are great for both starter and deep-cycle functions as they hold a charge for long periods without losing energy. Lithium-ion batteries are known for their low weight and high energy density, reducing the load on the engine.

Safety and Maintenance

When selecting a marine battery, consider safety and maintenance requirements. Lead-acid marine batteries should be rated to stand up to the abuses of time on the water, fully sealed to prevent leaks, and vibration-resistant. Additionally, ensure that the battery meets safety standards set by organisations like the American Boat and Yacht Council (ABYC) and the US Coast Guard.

By considering these factors, you can choose the right marine battery for your boat and ensure optimal performance and safety on the water.

Installing the second battery

If your boat has only one battery, consider installing a second battery to double your battery capacity. This will ensure that you have a reserve bank to fall back on to start the engine in case you drain the first battery.

To install the second battery, start by choosing a marine battery that meets your engine specifications. You can either use a starting battery, which has high current rush capacity, or a deep cycle battery, which can handle repeated deep discharging and recharging without damage. Lithium deep cycle batteries are a great option as they are lighter and provide consistent power throughout discharge.

Next, pick a location for the battery switch that is easily accessible and complies with Coast Guard and ABYC standards. The switch should be as close to the batteries as possible and may be flush-mounted for a cleaner look, but ensure it is protected from spray.

Now, connect the positive cables first. Connect the positive terminals of both batteries to the corresponding posts on the back of the switch, and then connect the positive cable from the engine to the output post of the switch. Also, connect the positive accessory wire to the output post.

Finally, connect the negative cables. For the dual-battery system to function properly, you need a crossover cable between the negative terminals of the two batteries. Also, connect the negative cable lug from the engine/ground and the negative accessory wire to either of the negative battery posts, ensuring all terminal nuts are tight.

You can now use the second battery to start the engine and then switch to the low battery to charge it while the engine is running.

Connecting the positive cables

Firstly, it is important to select cables that are appropriately sized for your boat's electrical system. Cables that are too small can lead to a voltage drop, resulting in underccharging and increased charging time for your batteries. As a general guideline, size 2/0 cables are suitable for most outboards and gasoline inboards. It is also crucial to ensure that the cables are specifically designed for marine use and meet the necessary safety standards.

Once you have selected the appropriate cables, you need to prepare them for installation. This includes stripping the insulation from the ends of the cables and crimping or soldering marine-grade cable lugs onto the exposed wire. It is important to ensure secure and waterproof connections by using heat-shrink tubing to seal the cable-lug connections.

The next step is to connect the positive cables to the batteries and the battery switch. Connect the positive terminals of both batteries to the corresponding posts on the back of the switch. Then, connect the positive cable from the engine to the output post of the switch, along with the positive accessory wire. Ensure that all connections are tight and secure.

Finally, you can finalise the setup by mounting the battery switch in an easily accessible location on your boat. ABYC standards dictate that the switch should be as close to the batteries as possible and protected from spray. You may also want to consider using terminal caps for each positive battery terminal to prevent short circuits.

Connecting the negative cables

Firstly, you will need a crossover cable between the negative terminals of the two batteries. This is crucial for the dual-battery system to function properly.

Next, connect the negative cable lug from the engine/ground and the negative accessory wire to either of the negative battery posts. It is recommended to replace wing nuts with locking hex nuts to ensure a tight connection.

The negative cables should be the last cables connected when installing a dual-battery system.

Before beginning any work on your boat's electrical system, it is essential to prioritise safety. Always remove the positive battery cables from the battery terminals to prevent the risk of a short circuit and potential electrocution. Additionally, wear safety glasses to protect your eyes from battery acid, and keep a water hose or another method to flush out battery acid nearby.

By following these steps and taking the necessary safety precautions, you will successfully connect the negative cables for your boat's battery selector, ensuring a functional and safe dual-battery system.

Frequently asked questions