Connecting Boat Batteries: What Side To Start With?

Connecting a boat battery is a crucial skill for any boat owner, and it's important to understand the basics of boat electrical systems to ensure a seamless and safe integration. In this article, we will be discussing the steps involved in connecting a boat battery, with a specific focus on the order of connections and the safety precautions to be observed. By following these guidelines, you will be able to enhance the performance and reliability of your boat's electrical system while also maintaining the longevity of your battery.

Safety first: Disconnect the negative terminal, then the positive

When working with boat batteries, safety should always be the top priority. Before connecting or disconnecting batteries, it is crucial to turn off all electrical systems on the boat. This precaution eliminates the possibility of a short circuit or electrocution, ensuring the safety of both the boat and the person handling the batteries.

When it comes to battery terminals, the correct procedure is to disconnect the negative terminal first, followed by the positive terminal. This order of operations is essential for safety reasons. By disconnecting the negative terminal first, you eliminate the risk of creating a dangerous spark or short circuit. The negative terminal, also known as the ground strap or cable, is directly connected to the vehicle's engine, body, and chassis. If you were to loosen the positive terminal first, there is a chance that your wrench or tool could accidentally touch a metal panel or the chassis, resulting in a dangerous short circuit.

Additionally, removing the positive terminal first could lead to the battery continuing to discharge. This is because, with the positive terminal removed, the battery can touch the chassis or engine through a wrench or another metal tool, creating a path to ground. This scenario could result in fire or physical injury. Therefore, it is always recommended to disconnect the negative terminal first to prevent any potential hazards.

After disconnecting the negative and positive terminals, ensure that the cables are not close to the terminals to avoid accidental contact. Once you have finished working on the batteries, remember to reconnect the positive terminal first, followed by the negative terminal. This order ensures that the battery is reconnected safely and securely.

By following these safety guidelines and procedures, you can confidently work on your boat's electrical system while minimising the risk of accidents or damage to your boat's electrical components.

Battery type: Choose between lithium, lead-acid, or AGM

When choosing a battery for your boat, there are several factors to consider, including the type of boat, how often you plan to use it, and your budget. Here is a breakdown of the three main types of batteries: lithium, lead-acid, and AGM, to help you make an informed decision.

Lithium Batteries

Lithium-ion batteries, commonly used in the automotive industry, offer several advantages for boat owners. They are significantly lighter than lead-acid batteries, weighing only about 30% of their lead-acid counterparts, which is a huge advantage for boats where weight and space are limited. They also have a higher energy density, meaning they can store more energy in a smaller package. Lithium batteries can be discharged to almost 100% and are known for their extreme cycle stability, with a lifespan of up to 6,000 cycles. They are also considered more environmentally friendly than other battery types. However, they tend to be slower to recharge and are generally more expensive, especially for marine-class units.

Lead-Acid Batteries

Lead-acid batteries are the most common type of battery used in boats, as well as in automobiles, warehouse machinery, and golf carts. They are cost-effective and reliable, but they do have some drawbacks. Lead-acid batteries require more maintenance and tend to be more fragile, with a lower tolerance for hard impacts. They also have a shorter lifespan, typically lasting 3-5 years. These batteries are designed to deliver short bursts of high energy, making them suitable for engine-starting but less ideal for continuous energy draw.

AGM Batteries

Absorbed Glass Mat (AGM) batteries are a popular choice for marine applications due to their sealed design, which makes them spill-proof and able to mount in any orientation except upside down. They are more durable than lead-acid batteries and less susceptible to damage from constant vibration and pounding in a marine environment. AGM batteries have a faster recovery charging time and a greater depth of discharge (up to 80%) compared to lead-acid. They are also known for their higher cold crank amps and reserve capacity. However, AGM batteries are generally heavier and less durable than lithium batteries, and they tend to be more expensive.

In summary, each battery type has its own advantages and disadvantages. Lithium batteries are ideal for those seeking a lightweight, durable, and safe option, while lead-acid batteries are a more cost-effective choice. AGM batteries offer a balance between the two, with superior durability and performance but at a higher price point. When choosing a battery, consider your boat's specific needs, your budget, and the trade-offs between weight, performance, and cost.

Wiring: Decide between series or parallel wiring

When wiring boat batteries, you can choose between series and parallel wiring. The choice depends on the specific needs of the devices you are powering. Here are the key differences between the two wiring options:

Series Wiring

• Series wiring increases the voltage of the battery system while keeping the capacity the same.
• It is suitable for high-power applications, such as large boats that require high voltage.
• The number of batteries used in series can vary from 2 to 4, and all batteries must be similar in age, size, type, and manufacturer.
• To wire batteries in series, connect the negative terminal of one battery to the positive terminal of the next battery.
• Always use a charger that matches the battery system voltage when charging batteries in series.

Parallel Wiring

• Parallel wiring increases the total battery capacity while keeping the voltage the same.
• It is suitable for most situations and provides longer battery longevity.
• Similar to series wiring, all batteries in a parallel setup must be similar in age, size, type, and manufacturer.
• To wire batteries in parallel, connect the positive terminals of the batteries together and then connect the negative terminals together.

In summary, series wiring is ideal for high-powered applications that require higher voltage, while parallel wiring is suitable for most other situations as it provides increased capacity and longer battery life.

Battery switch: Choose a suitable switch, e.g. Perko 8501

When it comes to choosing a battery switch for your boat, the Perko 8501 series is a popular and reliable option. This battery switch is designed for surface mounting and is suitable for use with alternators and generators in 6-32 VDC marine electrical systems.

The Perko 8501 offers both standard and heavy-duty options. The standard-duty switch features a bright red polycarbonate housing with a large, easy-to-turn black knob, while the heavy-duty version has a red fibre-reinforced polycarbonate housing. The high conductivity studs can accommodate more than one cable and provide the torque needed for secure connections.

One of the standout features of the Perko 8501 is its "make before break" capability, which allows you to switch between the "1", "ALL", and "2" positions while the engine is running. This is especially useful for boats with dual battery systems, as it enables you to select specific batteries for starting the engine, running accessories, or recharging.

Additionally, the Perko 8501 includes an "Alternator Field Disconnect" feature, which provides protection for non-unitized alternators if the switch is accidentally turned off while the engine is running. This feature further enhances the safety of your boat's electrical system.

The Perko 8501 also offers installation versatility, as it can be mounted in various locations, including the engine rooms of gasoline-powered boats. The 90-degree rotation feature allows users to feel the switch's position even in low-light conditions, making it easy to operate.

When choosing a battery switch, it's important to consider your specific needs and requirements. The Perko 8501 is a robust and user-friendly option that has earned a reputation for its durability and performance, as evidenced by positive reviews from boat owners. Its ease of installation, sturdy construction, and effective battery management make it a popular choice for boats with dual battery setups.

Battery box: Secure the battery with a box or tie-downs/brackets

Securing your boat battery with a box or tie-downs/brackets is an important step to prevent damage to the battery and your boat. Here are some methods to achieve this:

Battery Box:

Using a battery box is a great way to protect your battery and ensure it doesn't move around. Here are some tips for securing a battery box:

• Choose a battery box that fits your battery snugly to minimize movement.
• Use a battery box with a strap and brackets. This combination will keep the battery secure and prevent it from bouncing around.
• If your battery is smaller than the box, consider using rags or foam pads to fill the extra space and prevent the battery from shifting.
• You can attach the battery box to the floor of your boat using screws or bolts. For aluminum floors, consider using an adhesive like 5200 or PC-11 to attach a piece of starboard, and then screw the battery box into the starboard.

Tie-Downs/Brackets:

If you prefer not to use a battery box, you can secure your battery directly to the floor of your boat using tie-downs or brackets:

• Battery tie-down straps are available in various lengths and widths and typically include a cam buckle and mounting hardware (e.g., stainless steel brackets and screws).
• Look for tie-down straps made from durable materials like stainless steel and polypropylene webbing.
• Ensure the straps are long enough to fit around your battery and the mounting points in your boat.
• Consider using a battery tray in conjunction with tie-down straps for added security.
• Brackets can be attached to the floor or walls near the battery to provide mounting points for tie-down straps.
• When tightening tie-down straps, make sure they are secure but not so tight that they damage the battery casing.

Frequently asked questions