A boat battery is a backbone of each trip, as it provides power to essential electronics, e.g., navigation systems, lights, trolling motors, and a fish finder. Marine batteries can lose charge over time, even without showing any warning signs. Therefore, it is crucial for every boater and angler to know how to check the boat battery voltage.
Testing a marine battery’s health shows the amount of charge it has and familiarizes you with the early signs of weakness before it fails. Whether you’re a seasoned angler or a weekend sailor, checking the battery voltage regularly ensures your boat is always ready whenever you need it. In this article, you will learn to measure the boat battery voltage with a step-by-step guide.
Why Does Voltage Matter for Your Boat Battery?
Voltage shows the amount of power or energy a battery can store. Different batteries may have different capacities. Therefore, it is important to make sure that you have enough energy to fulfill your power needs before you leave for the trip. When it comes to the electrical potential of a marine battery, it is determined by two parameters: concentration of electrolytes and the type of chemical reactions that occur within the battery.
The voltage measurement helps you know how well a battery is charged. If your battery cells have low voltage, they won't be able to output much energy. An electric current is introduced into the system to recharge most batteries.
How Many Volts Should Your Boat Battery Have
Wondering how many volts should a boat battery have? Well, it mainly depends on the type of battery installed in your boat, e.g., lithium, lead acid, or AGM. If a 12V healthy lithium battery is fully charged, it should show more than 13.33 volts. Similarly, if a healthy AGM or lead acid battery is fully charged, it should display a voltage between 12.6 and 12.7 volts.
If you want to measure the accurate resting voltage, test your battery after it sits idle for one hour, which means it is neither charged nor connected to the charging system. If you test the voltage immediately after charging your battery or when your boat is running, you will get inaccurate results.
Ideally, you should let your boat battery sit overnight after disconnecting it from all electronics or loads. Then, measure the battery voltage the next morning before recharging it or starting the boat. In this way, you can get the most accurate results and information about your battery health.
While checking the battery voltage, you should first know where it is placed in your boat. Generally, boat batteries are placed in the engine bay. However, some boat manufacturers may place the battery somewhere else. If you are not sure where exactly the battery is located, review the owner's manual. Batteries can be packed in a cover or plastic box, which can be opened with screws or bolts.
Once you see the batteries, you will see a red cover and a black cover on the positive and negative terminals, respectively. You can lift both the covers to expose the battery terminals. Once the battery terminals are exposed, don't touch any metal to them, as it may result in a short circuit or other similar issues.
How To Test The Alternator With a Multimeter
First, you need to adjust the multimeter settings for the accurate measurement of DC voltage. Check the setting indicated by a solid and dashed line above the letter V. Then, set the multimeter's dial to 20. It will help you measure the accurate voltage levels between 0 and 20. If your multimeter is not attached to anything and its reading blinks, it is time to change its battery.
Material Required
- Goggles
- Safety gloves
- Analog or digital multimeter
Let's now look at the steps you should follow to measure the battery voltage using a multimeter.
Step 1: Turn Off Everything
Turn off all the electrical systems of your boat. Once done, it is recommended to let your boat battery sit for at least one hour. Doing this helps you get the accurate value of the resting voltage.
Step 2: Find the Battery
This step is all about locating the battery in your boat. Usually, marine batteries are placed in the engine bay, as mentioned earlier, but the place can be different in some boats.
Checking the owner's manual will tell you about the exact location of the battery in your boat. You may find the battery covered in a shroud or plastic box. Access the terminals by removing covers, if any.
Step 3: Adjust the Multimeter Settings
Turn on your multimeter device. Then, set it to measure DC voltage for you. Moreover, make sure you set the multimeter to a range that includes 12 volts. Setting the multimeter to 20V DC is a common practice when measuring the voltage of a 12V marine battery.
Step 4: Connect the Multimeter
When connecting the multimeter to the battery, connect the red probe of the multimeter to the positive terminal of the battery, which is usually indicated by “POS” or the “+” sign. Then, connect the black probe of the multimeter to the negative battery terminal, which is denoted by the “-” sign or “NEG”.
Step 5: Read the Voltage
Check the reading displayed on the multimeter's screen. If your marine battery is healthy, it should display voltage between 12.6V and 12.7V. If the multimeter shows that the charging is below 12.4V, you may need to charge or replace the battery. Nothing else will work in this case.
Step 6: Understand the Results
If your boat battery shows 12.6-12.7V on the multimeter, it means your battery is healthy and fully charged. If the battery shows its voltage between 12.4 and 12.6, it indicates that it is partially charged and you may need to recharge it for further use.
If the voltage is below 12.4, it shows the battery is discharged and you should recharge it as a priority. If it does not hold the charge, it may need replacement. On the other hand, if the battery voltages are above 12.7V, it indicates that it is overcharged. It may also be due to the surface charge. In such a case, allow your boat battery to sit for some time and check its health again.
Step 7: Disconnect the Multimeter
The process of removing the multimeter from a battery is different from connecting it to the battery. This time, remove the black probe first from the negative terminal of your marine battery. Then, remove the red probe from the positive terminal of the battery. This practice makes sure you don't experience problems like short circuiting.
Step 8: Re-Install the Battery
Cover the battery terminals with the shrouds that you removed earlier. Then, fasten the battery securely. Now, you can connect the electrical system and all essential electronics to your boat battery to enjoy a smooth trip on the water.
Important Note: If the battery is dead or faulty and you want to replace it, don't forget to follow the local regulations for disposing of it properly.
How To Test The Alternator With a Multimeter
The primary purpose of the alternator is to generate electricity and recharge the boat battery. It makes sure that the boat has enough charge to start the motor as and when needed. When the motor runs, the alternator not only supplies power to the electrical system of your boat but also charges the marine batteries.
One thing you should keep in mind is that the alternator can't fully charge a deeply discharged battery. A dedicated battery charger is needed for this purpose. Follow the steps below to check if the alternator is supplying the desired amount of voltage.
- Set the Multimeter: Set your multimeter to DC (VDC). Adjust the dial to 20V.
- Start the Engine: Start your boat's engine and allow it to run idle.
- Connect the Multimeter: Connect the multimeter's red probe to the positive terminal of your boat battery. Then, connect the black probe of the multimeter to the negative battery terminal.
- Read the Voltage: If your alternator is generating between 13.6V and 14.4V at idle, it means that the alternator is healthy.
- Understand the Results: If the voltage level is below 13.6V, it indicates that the charging system is unable to deliver enough power. It may cause discharged or batteries. If this is the case, you will need to replace the boat batteries and repair the existing charging system.
If the voltage for AGM and lead acid batteries is over 14.4V, it means the batteries are being overcharged by the charging system. Overcharging may lead to reducing the battery lifespan. However, lithium batteries operate with precisely regulated charging voltage.
Following these steps will help you determine whether or not your alternator is functioning properly. In case the alternator is not producing the desired amount of electricity and charging the batteries within a specific range, ask for professional assistance to find and fix the issue on priority.
Why Do Lithium Batteries Have Higher Voltage
A 12V lithium marine battery operates at a nominal voltage of 12.8V, which is higher than the nominal voltage of flooded lead acid or AGM marine batteries. Performance advantages, design, and chemistry contribute to providing lithium batteries with higher voltage. Below is a list of a few factors that come into play.
- Higher Energy Density: Lithium batteries can store more energy in the same space compared to AGM and lead acid batteries.
- Stable Voltage Output: Unlike traditional AGM and lead acid batteries, lithium batteries offer more stable output throughout the discharge cycle.
- Efficient Power Delivery: The low internal resistance of lithium batteries allows them to deliver higher currents and more power efficiently.
- Space Saving and Lightweight: Lithium batteries are more compact and lighter in weight compared to lead acid and AGM batteries.
Final Thoughts
Checking your boat battery voltage is not only required for maintenance, but it is also crucial to get consistent power while you are on the water. There is no rocket science behind checking your battery's voltage. A simple multimeter can help you check the battery's and alternator's health. All you need is to understand the results displayed on the multimeter's screen.
FAQs
How often should I check my marine battery voltage?
Make it a habit of checking the boat battery voltage before starting each trip. If you have stored the battery in a proper place, keep checking its voltage every month.
Can I check the alternator's voltage without removing it from my boat?
Yes, you can check it. All you need to do is connect your multimeter to the battery terminals appropriately while the boat's engine is running. This is how you can quickly check your alternator's health without removing it.
How do I know if my alternator is failing?
Well, there are multiple signs that indicate the failure of an alternator, such as electrical malfunctions, dead battery, flickering or dim lights, unusual noises, and a battery warning light on your dashboard.
Is it necessary to disconnect the battery before I check its voltage?
No, it is not necessary. You can easily test the battery voltage while it is connected to the electrical load. However, if you want to get highly accurate results, it is recommended to test the battery when it is at rest.
