Disconnecting Boat Battery: When And Why?

Boat batteries can be left dormant for long periods, which can lead to a dead battery when you want to use your boat. If you store your boat on land, you should disconnect the battery to prevent it from draining. However, if you store your boat in the water, you should not disconnect the battery to ensure that the bilge pumps have power in case the water level rises. In this case, you can use a charger to keep the battery fully charged.

Disconnecting boat batteries on land

If you are storing your boat on land, it is recommended that you disconnect the battery to prevent it from draining. Even when the boat's motor is turned off, the battery could still be drawing power from things like the radio, bilge pump, fish finder, or a clock. Over time, these items will slowly drain your battery, especially if the battery is wired directly to any of these objects.

How to Disconnect the Battery

• Get the necessary tools: You will need an adjustable wrench or a similar tool that fits the terminal bolts properly. Although not required, it is highly recommended to wear latex gloves for safety.
• Locate the battery: Depending on your boat, the battery may be in a compartment that you need to open. You may need to refer to your boat's manual to find it.
• Open the battery compartment: If there is a hold-down strap or an ON/OFF switch, make sure to remove or turn it off.
• Remove the negative cable first: Use your wrench to unscrew the bolt on the negative terminal (usually the black wire) until you can pull the cable off. Be careful not to let the negative and positive cable terminals touch each other. Set the cable aside in a safe place.
• Remove the positive cable: Loosen and remove the positive (red) cable from the battery. Again, be careful not to let the terminals touch each other. Tuck the cable out of the way.
• Store the battery: During the winter months, it is best to store your battery in a cool, dry place, such as a basement or workshop. Marine batteries should not be left outside in the cold as they can freeze and get damaged. The ideal temperature for storing your boat battery is around 50°F-60°F (10°C-16°C).
• Maintain the battery: If you plan to store your battery for a long period, ensure it is fully charged and maintained. Clean any dirt or corrosion from the battery terminals using a solution of water and baking soda. Check the battery every 4 to 6 weeks to ensure it is holding a full charge.

When Not to Disconnect

It is important to note that there are circumstances when you should not disconnect your boat battery. If you are storing your boat in the water, you will want to keep the battery connected to power the bilge pumps in case the water level rises inside the bilge. In this case, consider using a charger to keep the battery fully charged.

Keeping batteries in the boat while in water

It is recommended to keep your boat battery connected if you plan on storing your boat in the water. This is because you will need to ensure that the bilge pump has power in case the water level rises inside the bilge. If you disconnect the battery, the pump will not work, and your boat could flood.

Keeping the battery charged

If you plan on leaving your boat in the water for over a week, you should ensure that the battery remains charged. You can do this by connecting the boat to a power source provided by your marina, or by using solar panels or a trickle charger.

Battery maintenance

Boat batteries should be properly installed and maintained. They should be kept clean, cool, and dry. They must not be left on wet surfaces or placed directly on the ground. It is also important to regularly check the condition of the battery terminals and for acid leaks. Any leaks or build-up around the terminals should be gently cleaned, and any oxidation or corrosion of the cables should be removed.

Battery replacement

If your boat battery is properly installed and maintained, it is not uncommon to get 5, 6, or even 7 years of good service out of it. However, at some point, you will need to replace it. To do this, follow these steps:

• Open the battery compartment.
• Check the condition of the battery terminals and for acid leaks.
• Gently clean any leaks and build-up around the terminals.
• Remove any oxidation or corrosion of the cables.
• Remove the negative (black) cable terminal from the battery. This may require a wrench or pliers.
• Remove the positive (red) cable terminal from the battery. Be careful not to let the negative and positive cable terminals touch each other.
• Carefully remove the old battery and place it aside.
• Place the new battery in the battery compartment, making sure it is seated properly.
• Attach the positive (red) cable terminal to the positive terminal post on the battery and tighten the nut with care.
• Replace the negative (black) cable terminal to the negative terminal post on the battery and tighten the nut with care.

How to disconnect a boat battery

Firstly, locate the battery on your boat. You may need to open a compartment to access it. If your battery has an on/off switch, make sure it is turned off.

Next, check the terminals for any corrosion or acid leaks. If there is corrosion, use terminal spray and a rag to clean it off. If there are leaks, gently clean them and any build-up around the terminals. Remove any oxidation or corrosion from the cables.

Now you can begin to disconnect the battery. First, remove the negative (black) cable. You may need a wrench or pliers to do this. Be careful not to let the negative and positive cable terminals touch each other. Never touch the terminals with your hands if you have a screwdriver or metal in them.

Once the negative cable is removed, carefully pull up on the cable near the end and slowly slide it off the terminal. If the cable doesn't move, do not use a screwdriver to pry it off as this could cause damage. Instead, use a battery terminal puller.

Tuck the cable out of the way, then remove the positive (red) cable from the battery. Again, be careful not to let the terminals touch each other.

Now the battery is disconnected, carefully remove it and place it to one side.

If you are storing your battery, it is recommended to keep it in a cool, dry place. Batteries should not be left on wet surfaces or placed directly on the ground. Place them on a piece of wood while working with them. Keep them clean, cool, and dry.

Removing boat batteries in winter

Leaving your boat's battery connected during winter can cause a host of problems. Firstly, low temperatures can drain your battery. Cold weather naturally lowers a battery's capacity, reducing performance. If the battery is not removed and properly charged, it can drain completely, causing irreparable damage.

Secondly, freezing temperatures can cause physical damage to the battery. If a battery freezes, it expands, which can lead to cracked casings, leaks, and broken components.

Thirdly, long periods of disuse reduce the battery's lifespan. Even when the boat is turned off, electronic systems such as bilge pumps or lights can slowly drain power. Over time, this can shorten your battery's lifespan.

Lastly, corrosion can worsen in storage. When left connected, a battery's terminals can corrode due to moisture or residual electrical flow, affecting battery connections and leading to poor performance and costly replacements.

Boat batteries should be removed and stored for winter if temperatures are expected to fall below freezing.

How to Remove Boat Batteries for Winter Storage:

• If your battery has an on/off switch, turn it off.
• Remove the hold-down (if there is one) and open the battery housing.
• Use a wrench to unscrew the negative (black) cable first, then the positive (red) terminal.
• Take out the old battery.
• Install the new battery (if applicable).
• Screw in the positive terminal, then the negative.
• Close the battery housing.

How to Store Boat Batteries in Winter:

When storing your boat battery for the winter, follow these best practices:

• Charge the battery: Ensure your battery is fully charged before storing it.
• Clean the battery: Wipe down the battery and clean the terminals with a mixture of baking soda and water.
• Store in a cool, dry place: Keep the battery in a controlled environment, safe from freezing temperatures and condensation. The ideal temperature for storing boat batteries is around 50°F-60°F (10°C-16°C).
• Check the charge periodically: All batteries lose some charge over time, even when not in use. Check the voltage monthly and recharge as needed.

Types of Boat Batteries and Specific Winter Care Instructions:

Different types of boat batteries have varying levels of cold tolerance and specific care requirements for winter storage:

• Flooded lead-acid batteries: These are prone to water loss and corrosion. Ensure they are cleaned and stored carefully.
• AGM (absorbent glass mat) batteries: These handle cold weather better but should still be stored in a safe, dry place.
• Lithium-ion batteries: While more resistant to freezing temperatures, lithium-ion batteries require careful charging and storage to maintain performance. For lithium-ion batteries, only charge to around 50% before storing, and recharge if the charge drops below 40%.

Always consult the manufacturer's recommendations for specific winter storage guidelines for your battery type.

Charging a boat battery

When to Charge

If your boat is stored on land, you should disconnect the battery and ensure it has a full charge. This will allow it to sit safely for several weeks without draining. If you plan on leaving your boat in the water for over a week, you should have a way to charge the battery.

Choosing a Charger

Boat batteries have different voltage and amperage requirements, so it's important to match your charger to your boat battery's chemistry and voltage. All boat battery chargers fall into one of two categories: onboard and portable. Onboard chargers are convenient as they are already connected to the battery system, whereas portable chargers are less expensive and can be used anytime, anywhere.

Charging Process

Before charging, clean the battery terminals as grime can disrupt the charging process. When you're ready to charge, connect the red (positive) cable to the red terminal, and the black (negative) cable to the black terminal. Plug in the charger and turn it on. If you're using a smart charger, you can set it and forget it. Once the battery is fully charged, disconnect the charger, then remove the black cable from its terminal, followed by the red one.

Charging Time

The time it takes to charge a boat battery depends on the type of battery and charger used. A marine battery typically takes about four to six hours to charge from 0% to 80%.

Maintenance

To maintain a healthy boat battery, always keep it fully charged and never let it dwell for long at a partial charge. Additionally, try not to discharge it completely; the best deep-cycle batteries will manage over 800 cycles at 50% depth of discharge.

Frequently asked questions