how to tell if boat battery is bad

Last Updated on December 7, 2021

Boat owners should know how to tell if the boat battery is bad. There are certain signs that a bad battery shows which will inform you of its present state. Some of which include the boat not starting, voltage below 12 volts, and failing in load test. Our team at BoatingBuddy.com assembled the top information to help diagnose a bad boat battery, and how to improve the lifespan of your battery.

 Symptoms of a bad boat battery

To  decipher if your boat battery is in good condition, here are some signs which show your boat battery state :

Boat electronics won’t work

An important way to tell the condition of your boat battery is when all electronics on the boat go cold. You could also use onboard electronics to check if it’s working. Electronics to be checked include GPS, depth finder, bilge pump, and chart plotter. When any or all of these aren’t working, it may signify your battery is dead.

This is because every electrical appliance on the boat is connected to the battery. If the battery is good and any of these electronics fail to work, they are damaged.

The boat doesn’t start

These symptoms are linked to the boat that uses starters not those who use deep cycle batteries. Boats use a different kind of battery to start their motor, if your boat is bad, the boats won’t come alive. Usually, the starter battery is connected through the solenoid which is wired to the starter.

Immediately you switch on the key switch, it should send power via the motor. This motor is connected to the boat combustion engine to start the boat. Therefore, if the battery is bad, there won’t be any power sent to these components. But we warned that a bad battery isn’t the only reason why your boat won’t start. So it will be hasty of you to conclude. Other factors to consider include bad motor, solenoid, engine issues, and wrong connectors. Try to check other signs before replacing your battery.

Physical factors

Though this isn’t a popular opinion, it is true nonetheless. Rust, wear & tear, and leaking may show that your boat battery is bad. These bad visuals may tell you more than anything, the bad state of your battery.

Checking the bulging look of your boat battery and cracks will mean your battery isn’t in good condition. Moreover, broken or bad battery terminals are fatal and cause damage. When this happens, it is visible on the battery and tells you it needs to be changed.

Sometimes battery terminals look clean, however, they aren’t clean in the real sense. Remove clamps, clean thoroughly and tighten it back. You can then retest if it’s working. Another thing to consider is the ground connector wires of the battery, sometimes they lose and fall off easily. Physical inspection of the boat battery is important in deciding if the battery is bad or not.

What are the ways to improve your boat battery life?

To increase the lifespan of your boat battery here are some suggestions:

Avoid deep charge for your boat battery

When you constantly discharge your boat battery less than 70%, it will greatly reduce your battery number of cycles. When this happens, the amount of power discharge will be higher (up to three times) than required for proper efficiency.

Also, boat batteries that have been regularly discharged will take more time to be fully charged. When you occasionally discharge your battery, it’s fair.

Charge the battery fully and remove it when not in use

To improve your boat battery lifetime, charge to 100% before storing for a while. This is essential for those who aren’t regular users or who want to travel. All batteries will discharge after a while, it is inevitable.

However, when it isn’t charged fully, it worsens life and goes bad quickly. Moreover, consider disconnecting the boat battery during harsh weather like Winter. It is important because electrical devices will drain the battery even when not active. Therefore, fully charge and disconnect your battery if not in use for a long period.

Never leave a boat battery on a charge for long

While charging the battery regularly is great, avoid overcharging because it could ruin your battery. Have you come across batteries with a huge bulge, overcharging is hugely responsible.

When you overcharge your boat battery, it causes too much gassing (electrolytes become hot which generates hydrogen and oxygen gas). For sealed batteries, it could even be worse, because the batteries could burst.

Avoid putting your battery in hot locations

High temperatures affect boat batteries because they cause battery leaks and ruptures. Always take good care of your battery by keeping an average temperature. It is highly recommended to store your batteries at 59 Fahrenheit.

When the location temperature increases to around 100 Fahrenheit, your battery internal discharge is affected. When you leave your battery for 30 days in hot weather, your battery will likely not start.

Ensure your battery is always fully charged

For people who use their boat regularly, your battery will discharge. However, when you charge the batteries regularly, the life cycles will improve. Although it won’t exceed the manufacturer’s specifications, it will still work perfectly.

It is bad, however, when using batteries with a lower DOD(45% or less). It will damage your battery and put extra loads on it. This will affect the battery’s life when it discharges. At least twice weekly, ensure your boat battery reaches 100% for a better life cycle.

It’s good to use a boat battery around 55% to 65% while cruising, but nothing beats 100% charging because you will have fewer worries.

Take safety precarious on Flooded batteries

It is a good idea to check electrolytes on boat batteries. This is because it could give you shock and sometimes affect boat performance. Use gloves and safety types of equipment when handling batteries to avoid injuries.

Make sure you use a brush( with a solution of baking soda and water) to clean the battery. After this remove the covers from the cell ports and clean all dirt and rust.

Boat batteries need to be taken care of regularly to improve their lifespan. Also, ensure you take note of the many symptoms to tell when your battery is bad to avoid disappointments.