Nothing can put a damper on your boating fun faster than a poorly charged or dead battery, be it your starting boat battery, trolling motor battery, or house battery. If charging is so important, so must be the marine battery chargers you choose for the job, including knowing whether you have a lead-acid battery or lithium-ion battery. Further, it is crucial to know the size of your battery and the safe way to charge it.
Table of contents
- Do You Need A Special Charger For A Marine Battery?
- What Features Do You Need In A Boat Battery Charger?
- How Big Of A Marine Battery Charger Do You Need?
- What If You Have More Than One Boat Battery To Charge?
- The Best Marine Battery Chargers
- How Long & Often Should You Charge Your Marine Battery?
- Charging Lead-Acid Vs. Lithium Marine Batteries
- Trickle Charging Your Boat Batteries
- Charge Your Batteries Properly For Better Performance & Lifespan
Do You Need A Special Charger For A Marine Battery?
The short answer is: no. However, you must use a charger that matches your boat battery’s chemistry and voltage. Further, a charger that is made specifically for boats will be water-resistant (or waterproof) and can be permanently mounted, which is quite convenient.
Lithium boat batteries have been gaining in popularity, and there are some charging aspects unique to these batteries. You need the correct charging profile, which is the program that tells the charger what voltage to operate at during different battery charging stages. Often, your existing lead-acid charger can be modified or reprogrammed to work with lithium batteries.
What Features Do You Need In A Boat Battery Charger?
The features you need in a boat battery charger depend upon the characteristics of your craft and your boating needs.
Starting (Cranking) Boat Battery Charging
The cranking boat battery is designed to deliver one big shot of energy to start the boat. Some boaters use this battery to run other features such as fish finders and radar, but this is not recommended. It can shorten the battery life since it is usually a lead-acid battery.
Many boat engines will charge the starting boat battery. However, if the battery is run low by other devices, you will still need an additional charger. Some options for chargers include onboard, portable, and solar battery chargers.
Trolling Battery Charging
The trolling battery powers a trolling motor. Boaters use trolling motors to keep the boat in place when fighting a current or moving their boat short distances or in shallow water.
Again, the choices for charging trolling motor batteries are onboard, portable, and solar. Since these chargers are typically used in wet locations, consider units that are shock-resistant and water-resistant. Also, be sure to mount onboard units securely and in a way to prevent condensation.
An onboard battery charger that is plugged into shore power is the most common way to charge trolling motor batteries. These batteries usually get charged when the boat is docked or on the trailer overnight.
🛒 Shop our Trolling Motor Battery Bundles (chargers included!)
House Battery Charger
The house battery on your boat is a deep cycle battery, and it powers the electrical loads on board when there are no other methods of power available (for example, a solar panel).
The house battery charger is usually combined with an inverter and is high current because of the large bank it is charging. Many times house battery systems have multiple charging options, engine charging, solar charging, and shore power charging. All of this charging equipment should be marine grade.
How Big Of A Marine Battery Charger Do You Need?
When speaking of the size of a marine battery charger, we are discussing voltage and amperage (charge rate), not the actual size of the charger. Depending upon their setup, the voltage and amperage will vary from charger to charger. So, it is important to know what you need for your craft and batteries.
What Voltage Boat Battery Charger Do You Need?
When considering voltage, there are two things you need to know: the voltage of the supply and the voltage of the battery. The supply will typically be 120V or 240V. However, if you are charging off an alternator, it might be working at 12V or 24V and require a DC-DC charger.
The battery voltage will depend upon the battery bank and can be 12V, 24V, 36V, or 48V. The most common battery voltage is 12V.
How Many Amps Do You Need For Your Marine Charger?
Simply put, the more amps your charger has, the faster they will work. The fastest recommended rate for lithium-ion batteries is .5C, and for lead-acid batteries is .1C. C rate means, for example, that a 100Ah lithium bank battery should charge at 50A maximum (.5 x 100Ah = 50A).
Likewise, a 100Ah lead-acid battery should only charge at 10A max. Given these parameters, the lithium-ion battery would take two hours to charge, and ten hours for the lead-acid battery if they were fully depleted.
What If You Have More Than One Boat Battery To Charge?
If you have more than one battery to charge, it is best to work with one charger big enough to do the job. However, if you have a 36V bank, you can use a 12V charger on each battery. In addition to independent chargers, you could also use a multi-battery charger like the PS4 Pro Series with 4 Independent 12V Outputs.
This Dual Pro Professional Series Battery Charger is for 4 Banks. The Quad Pro Multi-bank is one of the most popular chargers among the bass fishing community. For that reason, we partnered up with Dual Pro to create a charging algorithm specific to our LiFePO4 Battle Born Batteries.
Check out this video for more information:
Its features are approved for Wet Cell and AGM batteries. This boat battery charger is designed for use in fresh and saltwater with dependable, rugged construction and waterproof independent outputs.
If anything is unclear or if you have additional questions about multi-bank chargers, please give us a call at (855) 292-2831. You can also email us at [email protected] We are happy to help!
The Best Marine Battery Chargers
Below is a list of chargers for each of the battery categories discussed above.
Trolling Motor Battery Chargers
For charging your trolling motor batteries, we recommend Victron Blue Smart Chargers.
The Blue Smart IP65 charger is 12 volt and 15 amp and has built-in Bluetooth. This charger weighs in at approximately 2 pounds and works great in campers, boats, and RVs. The Bluetooth allows you to connect the charger to your phone to easily program its charge characteristics for your battery needs. And as it says right on the label, this charger is waterproof.
House Battery Inverter Chargers
Most boat house battery banks are larger than starting and trolling motor battery banks. They require a much larger charger.
The Victron Multiplus 3000W 12V Inverter Charger is both a true sine wave inverter and an adaptive charger in one package. This unit is 3000 volt-amps, 12 volts, and weighs in at approximately 40 pounds.
Because it is both a charger and inverter it’s a great choice for a powerful house battery charger. The powerful inverter also will provide AC power as needed to your boat.
Cost-Effective Lithium House Battery Charger
If you don’t need an inverter onboard your boat, you can charge with this cost-effective Progressive Dynamics LiFePO4 Converter Charger that also includes a DC distribution panel for your DC loads. This version is specifically designed for lithium marine house batteries.
The Progressive Dynamics LiFePO4 Converter Charger is 12 volt 80 amp yet weighs in at just over 5 pounds. The charger uses a 20 amp AC power cord and a special 20 amp outlet.
Charging from Engine To House (Alternator Charging)
For charging your house battery bank from the engine bank, also know as alternator charging, we recommend the Sterling Power Battery-to-Battery Charger.
The Sterling Power Battery-to-Battery Charger has a 12-volt input and outputs up to 30 amps. This battery charger allows you to power up your house banks with any of nine charging profiles. Further, the charger goes into a smart mode when the battery is in use and goes into float voltage when the battery is full.
When charging lithium-ion batteries, they have low resistance to draw very high currents if you connect them directly to the alternator. Because of this installing a DC-DC charger allows you to control the power flow properly. This prevents overloading the alternator and burning it out while also providing the proper charger to the batteries.
How Long & Often Should You Charge Your Marine Battery?
If you are running your boat once a week, the starting batteries will likely return to port charged, and you should be good to go for your next trip. However, if you are boating less frequently, you will likely need to charge your boat batteries in between trips.
You should charge your house and trolling motor batteries anytime the boat is at the dock. Using solar battery chargers is a great way to slowly charge batteries when the boat is not being used or even underway. Using solar chargers, you may not need to plug the boat in at all.
Charging Lead-Acid Vs. Lithium Marine Batteries
There are definite benefits to lithium-ion over lead-acid batteries in this discussion. First of all, a lithium battery can be charged and discharged several times per day without damage. They also only take about four hours to fully charge. The lead-acid battery can only be charged and discharged once per day and takes about ten hours to charge.
Furthermore, if you overcharge a lead-acid battery, you run the risk of the acid boiling over and damaging the battery, charger, and whatever else is around.
Trickle Charging Your Boat Batteries
One way to prevent the damage described above is by trickle charging a battery. At the end of a charge cycle, the amount of charge reduces to a trickle (equal to the amount of natural discharge of a sitting battery) to keep the battery 100% charged without overcharging the battery.
You can trickle-charge both lithium-ion and lead-acid batteries, and some chargers can carry on this process for months. You should check manufacturer details for safety information regarding trickle charging.
Charge Your Batteries Properly For Better Performance & Lifespan
There are several types of marine battery chargers to suit your needs, be it for a starting boat battery, trolling battery, or house battery. Remember, it is important to know the voltage and amperage of your batteries and chargers to ensure a safe boating experience. Also, the lead-acid battery runs the risk of overheating, which could spill hot acid and causes expensive damages.
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