Home Blogs-LiTime Lithium Blogs Understanding Marine Boat Batteries Voltage
knowledge about battery

Understanding Marine Boat Batteries Voltage

Mike Smith
Mike Smith
—
09/07/2024

When it comes to marine vessels, having a reliable battery is essential for ensuring your boat's electrical systems run smoothly. Understanding the voltage of marine boat batteries is crucial for selecting the right battery and maintaining its performance.

In this article, we will explore the fundamentals of marine boat batteries voltage, why is it important and how to check.

Why Is Voltage Important

Voltage measures the amount of energy a battery can store. Although different batteries have varying capacities, ensuring you have enough energy for your needs is essential. A battery’s electrical potential is primarily determined by the type of chemical reaction and the concentration of electrolytes within it.

By measuring a battery’s voltage, you can gauge how well it’s charged. Low-voltage cells can’t output much energy, but most batteries can be recharged by introducing an electric current into the system.

How Many Volts Should a Marine Battery Have

A healthy lead-acid or AGM marine battery should register between 12.6 to 12.7 volts, while a healthy 12V lithium marine battery should be over 13.33V when it’s fully charged. For more information, please check The Guide to Battery Voltage.

To accurately measure the resting voltage, test the battery after it has been sitting for at least an hour without being charged or connected to the boat’s charging system. Testing immediately after charging or while the boat is running will give an inaccurate reading.

Ideally, let your boat sit overnight with all systems off, then test the battery the next morning before starting the boat or recharging the battery. This method will provide the most accurate gauge of your battery's health.

Check Battery Voltage Using a Multimeter

Marine batteries are often located in the engine bay, but some manufacturers may place them elsewhere. If you're unsure of the battery's location, consult the owner's manual. The batteries may be housed in a plastic box, shroud, or cover, which can be unclipped, lifted off, or unfastened with bolts or screws. Once the batteries are exposed, you might find a red cover on the positive terminal and possibly a black cover on the negative terminal. These covers can be lifted off or pulled back to expose the terminals.

When both terminals are exposed, be extremely careful not to touch them with anything metal, as this will cause a short circuit.

How To Test a Marine Battery With a Multimeter

To ensure your multimeter (also known as a digital voltmeter) is correctly set to measure DC voltage, look for the setting indicated by a dashed line and a solid line above the letter "V." Set the dial to 20, which will accurately measure between 0-20 volts. If the reading blinks when not attached to anything, you may need to replace the multimeter’s internal battery.

Step-By-Step Guide

Testing a marine battery with a multimeter is a straightforward process. Follow these steps to accurately measure the battery's voltage:

Materials Needed:

  • Multimeter (digital or analog)
  • Safety gloves and goggles (optional, but recommended)

Steps:

1. Turn Off All Electrical Systems:

  • Ensure that all electrical systems on the boat are turned off.
  • If possible, let the battery sit for at least an hour to get an accurate resting voltage.

2. Locate the Battery:

  • Find the battery. It is often located in the engine bay, but check your owner’s manual if unsure.
  • The battery may be in a plastic box, shroud, or cover. Remove any covers to access the terminals.

3. Set Up the Multimeter:

  • Turn on the multimeter and set it to measure DC voltage (VDC).
  • Ensure the multimeter is set to a range that includes 12 volts. For most multimeters, setting it to 20V DC is appropriate.

4. Connect the Multimeter Probes:

  • Connect the red probe to the positive terminal (usually marked with a “+” or “POS”).
  • Connect the black probe to the negative terminal (usually marked with a “-” or “NEG”).

5. Read the Voltage:

  • Observe the reading on the multimeter display.
  • A healthy marine battery should read between 12.6 to 12.7 volts.
  • If the reading is below 12.4 volts, the battery may need to be charged or replaced.

6. Interpret the Results:

  • 12.6 - 12.7 volts: Battery is fully charged and in good condition.
  • 12.4 - 12.6 volts: Battery is partially charged and may need recharging.
  • Below 12.4 volts: Battery is discharged and likely needs recharging. If it remains low after charging, it may need to be replaced.
  • Above 12.7 volts: The battery may be overcharged, or there could be a surface charge present. Let the battery rest and test again.

7. Disconnect the Multimeter:

  • Remove the probes in reverse order: black (negative) probe first, then red (positive) probe.

8. Re-secure the Battery:

  • Replace any covers or shrouds that were removed.
  • Ensure the battery is securely fastened and terminals are properly covered.

Safety Tips:

  • Avoid Short Circuits: Do not let the metal parts of the probes touch each other while connected to the battery.
  • Wear Safety Gear: Consider wearing safety gloves and goggles to protect against accidental sparks or battery acid.
  • Proper Disposal: If the battery is found to be faulty and needs replacing, dispose of it properly according to local regulations.

By following these steps, you can accurately test the voltage of your marine battery and determine its condition.

LiTime LiFePO4 Lithium Battery Voltage Chart

State of Charge

12V

24V

36V

48V

100%

≥13.33V

≥26.66V

≥39.99 V

≥53.32V

75%

13.3~13.33V

26.6~26.66V

39~39.45V

53.2~53.32V

50%

13.15~13.2V

26.3~26.4V

39.45~39.6V

52.6~52.8V

25%

13~13.15V

26~26.3V

39~39.45V

52~52.6V

0%

10~12V

20~24V

30~36V

40~48V

How to Test the Alternator with a Multimeter

The alternator’s job is to produce electricity and charge the battery, ensuring the boat has sufficient charge to start the motor next time. While the motor is running, the alternator supplies power to the boat's electrical systems and charges the batteries. Note that deeply discharged batteries cannot be fully charged by the alternator alone; this requires a dedicated battery charger.

To check if the alternator or charging system is supplying the correct amount of charge, follow these steps:

1. Prepare the Multimeter:

  • Ensure your multimeter is set to measure DC voltage (VDC) with the dial set to 20V.

2. Start the Engine:

  • Start the boat’s engine and let it run at idle.

3. Connect the Multimeter Probes:

  • Place the red probe on the positive battery terminal.
  • Place the black probe on the negative battery terminal.

4. Read the Voltage:

  • A healthy alternator should produce between 13.6 volts and 14.4 volts at idle.

5. Interpret the Results:

  • Below 13.6 volts: The charging system is not supplying enough power, which can lead to flat or discharged batteries. Simply replacing the batteries will not fix the problem; the charging system needs to be checked and repaired.
  • Above 14.4 volts: For flooded lead-acid battery and AGM, the charging system is overcharging the batteries, which can cause damage by boiling away the electrolyte. Overcharging will significantly reduce battery life and requires professional inspection and repair. But for lithium battery, the charging voltage is just properly. Suggest reading: Best Ways to Charge Deep Cycle Lithium Batteries

By following these steps, you can accurately test your boat’s alternator and ensure it is functioning correctly. If you find that the alternator is not charging within the specified range, seek professional help to diagnose and fix the issue, as both undercharging and overcharging can severely impact battery performance and lifespan.

Why Lithium Marine Batteries Have Higher Voltage

The nominal voltage of a 12V lithium marine battery is 12.8V, which is higher than AGM and flooded lead acid.

voltage of lithium marine battery

Lithium marine batteries have higher voltage for several reasons, primarily related to their design, chemistry, and performance advantages over traditional lead-acid batteries. Here are some key factors:

1. Higher Energy Density

Lithium batteries have a higher energy density compared to lead-acid batteries. This means they can store more energy in the same amount of space. As a result, lithium batteries can provide higher voltage and more power without significantly increasing their size or weight.

2. Stable Voltage Output

Lithium batteries maintain a more stable voltage output throughout their discharge cycle. Unlike lead-acid batteries, which experience a significant voltage drop as they discharge, lithium batteries can sustain a higher voltage until they are almost fully depleted. This stable voltage output ensures consistent performance for marine applications.

2. Stable Voltage Output

Lithium batteries maintain a more stable voltage output throughout their discharge cycle. Unlike lead-acid batteries, which experience a significant voltage drop as they discharge, lithium batteries can sustain a higher voltage until they are almost fully depleted. This stable voltage output ensures consistent performance for marine applications.

3. Efficiency in Power Delivery

Lithium batteries are more efficient in delivering power. They have lower internal resistance, which allows them to deliver higher currents without substantial voltage drops. This efficiency makes lithium batteries ideal for high-power marine applications, such as running trolling motors, inverters, and other demanding electrical systems.

4. Weight and Space Savings

Lithium batteries are lighter and more compact than lead-acid batteries. This weight and space savings allow boat owners to install higher voltage battery systems without adding significant weight or taking up valuable space on their vessels. Higher voltage systems can improve the efficiency and performance of onboard electrical systems.

agm vs lithium marine battery

LiTime 12V 100Ah LiFePO4 Lithium Trolling Motor Battery

5. Longer Lifespan

Lithium batteries typically have a longer lifespan compared to lead-acid batteries. They can endure more charge and discharge cycles without significant degradation. This longevity means that over the life of the battery, boat owners can benefit from sustained higher voltage and performance, reducing the need for frequent replacements.

6. Advanced Battery Management Systems (BMS)

Lithium batteries are often equipped with advanced battery management systems (BMS) that monitor and regulate the battery's performance. The BMS ensures that each cell within the battery is balanced and operates within safe voltage limits. This advanced technology helps maintain optimal voltage levels and protects the battery from overcharging or deep discharging.

lithium marine battery with battery management systems (BMS)

Why Choose LiTime Lithium Marine Batteries?

Lithium marine batteries offer numerous advantages over lead-acid batteries, though the high initial cost often deters upgrades. LiTime provides high-value, tech-driven lithium marine batteries specifically for trolling motors and electric outboard motors. These batteries feature an upgraded Battery Management System (BMS) with the following benefits:

  • Moisture-Proof Design: The innovative moisture-proof design ensures that LiTime lithium batteries are resilient against moisture ingress, making them ideal for marine environments where exposure to water is common.
  • Salt-Spray Resistance: With salt-spray resistance, LiTime batteries are more durable and able to withstand the corrosive effects of saltwater, ensuring reliable performance even in harsh marine conditions.
  • Low-Temperature Cutoff Protection: The advanced low-temperature cutoff protection feature enhances safety during charging by preventing battery damage in cold weather conditions. This ensures optimal performance and longevity of the battery over its lifespan.

Lithium Battery for Electric Outboard Motor

The LiTime 12V 100Ah Lithium Electric Outboard Motor Battery is perfect for boaters seeking reliable and high-performance power for their 24V-60V electric outboard motors. For higher voltage systems, the 36V 100Ah outboard motor battery is recommended. Key features include:

  • Smart Bluetooth 5.0: Automatically connects to your phone for intelligent control of discharging, real-time monitoring of battery status and data, and effortless system checks.
  • Max. 5S5P Configuration: Capable of building a powerful 60V 500Ah battery system (up to 32kWh of energy) with a continuous discharge current of up to 500A.
  • High Performance BMS: Supports continuous charging/discharging at 100A, with peak performance reaching 500A for up to 1 second.

Why Choose LiTime for Your Marine Battery Needs?

At LiTime, we are dedicated to providing high-quality, reliable, and efficient lithium batteries tailored for marine, RV, golf cart, and other off-grid applications. Our products are designed to meet the rigorous demands of boating, ensuring you have the power you need when you need it. Visit LiTime’s warranty policy and YouTube reviews for more information.

Mike Smith
Mike Smith
Mike Smith is a marine energy expert with 15+ years of experience and a Master’s in Electrical Engineering from Stanford. Passionate about lithium battery integration, he also enjoys sailing and exploring coastal waters in his free time.

Join LiTime

Life & Discovery
Email Address *

You May Like

LiTime 12V 100Ah Group 27 Bluetooth LiFePO4 Lithium Battery
LiTime 12V 100Ah Marine Battery for Electric Outboard Trolling Motor
LiTime 12V 100Ah Xtra-Mini Bluetooth Small LiFePO4 Battery
LiTime 12V (14.6V) 20A LiFePO4 Lithium Battery Charger

Recent Post

8 Frequently Asked Questions About Trolling Motor Batteries
29/11/2024
How Long Will A 100ah Battery Run A Trolling Motor?
26/09/2024
How to Charge Your Trolling Motor Battery Step-by-Step Guide
20/03/2023
What's the Best Type & Size Battery for Trolling Motor
21/03/2023