The Best Onboard Battery Chargers: Maintenance for Boat Batteries

Last Updated on June 21, 2021 by Donnell Henderson

The simplest way for charging your marine batteries is with an onboard battery charger.

The battery charger plugs into an electrical outlet when your boat is docked, most often a 120-volt outlet. It converts alternating current (AC) electricity from the outlet into direct current (DC) electricity that is fed into and stored in your marine batteries. 

You will not run short of onboard battery chargers to choose from. But you wouldn’t truly know what’s best for your marine batteries unless you do a little research. So, my roundup for the best onboard battery charger took into consideration all the important features you would want an onboard battery charger to have.


My Top Pick

Minn Kota Precision Onboard Charger is the most liked and the bestseller. This smart charger is digitally controlled and automatic, which means it charges faster and effectively without your intervention. It features automatic temperature compensation and low-line voltage compensation. Not to mention that it is super easy to install.


Here are My Best Onboard Marine Battery Charger Reviews:

  1. Minn Kota Precision Onboard Charger — Overall Best Onboard Battery Charger for Boats
  2. ProMariner 43012 ProSport Onboard Battery Charger 
  3. ProMariner 44020 ProSportHD Series Onboard Battery Charger 
  4. Guest 2707A ChargePro Onboard Battery Charger 
  5. Noco Genius2D Direct Mount Onboard Charger — Best Value Model
  6. Noco Genius GEN3 Onboard Battery Charger
  7. Extreme Max Battery Buddy 4-Bank Onboard Battery Charger

1. Minn Kota Precision Onboard Charger — Overall Best Onboard Battery Charger for Boats

Minn Kota Precision Digital Chrgr MK 440 PC 4 bank x 10 amps

The marine onboard battery charger review I’m going to do is one for my top pick — the Minn Kota Precision Onboard Charger. Charge, maintain, and keep all your marine batteries healthy with this one, which outperforms every other charger in its category.



  • Automatic multi-stage charging
  • Digital control
  • Automatic temperature compensation
  • Low-line voltage compensation
  • Saltwater tested
  • 1- to 4-bank models available


This high performing charger is available in four styles, one-bank, two-bank, three-bank, and four-bank. So, you can conveniently choose what works best for your application.

You can select each bank depending on the type of marine battery you want to charge and maintain. Automatic multi-stage charging and digital control ensure your onboard marine batteries charge optimally, faster, and safely. Automatic temperature compensation; on the other hand, provide fast and accurate charging in both hot and cold weather conditions.

Another good feature that comes with this charger is battery equalization. This technology helps clean and protect flooded lead-acid marine batteries. You can effortlessly activate the cleaning process with a single push of a button.

But the thing is, the charger may not be suitable for charging AGM batteries.



  • It is waterproof, vibration-resistant, and shock-resistant
  • Controls current and voltage for precise charging
  • Senses and adjusts charge performance to ambient temperature changes
  • Low-line voltage compensation delivers consistent charging
  • It cleans and protects your marine batteries



  • It may not be the best choice for charging AGM batteries
  • Some models may take longer to charge



Get the fastest and smartest charging performance with Minn Kota Precision. This onboard charger will charge, maintain, and protect your marine batteries effectively.

Overall Rating: 4.9


2. ProMariner 43012 ProSport Onboard Battery Charger 

ProMariner 43012 ProSport 12 12 Amp, 12/24 Volt, 2 Bank Generation 3 Battery Charger

Stop buying new marine batteries for your boat and start taking care of the ones you have with this incredible onboard charger from ProMariner.



  • Two bank battery
  • Compatible with AGM, Gel, and flooded
  • Digital multi-stage charging
  • Energy saver mode
  • Multi-safety features


What makes this amazing onboard battery charger stand out is the multi-safety features. With the ProSport, you don’t have to worry about reverse polarity, over-temperature, overload, or over-voltage. The charger also comes pre-wired for quick and easy installation.

ProMariner ProSport features digital multi-stage charging, which is good because it fully charges your marine batteries and extends their lives. Apart from charging boat batteries, the charger also conditions and auto-maintains all marine batteries on board.

I particularly appreciate the energy saver mode of this model, which monitors and maintains batteries only when it is necessary. Another good feature is the storage recondition mode, which ensures your boat batteries are automatically reconditioned once a month.

What is disappointing about the ProSport is the quality of battery identification plugs, which can misidentify your marine batteries.



  • Compact, light, and super easy to install
  • Multi-safety features ensure your batteries are protected
  • It ensures all the charging amps are used to charge the batteries
  • Intuitive LED keeps you informed about the charging status
  • Energy saver mode reduces AC power consumption



  • May come with poor quality battery identification plugs
  • Cutting the ring terminals to extend wires voids the warranty



With the ProMariner 43012 ProSport, you get a compact, light, fast-charging, and easy to install onboard marine battery charger.

Overall Rating: 4.8


3. ProMariner 44020 ProSportHD Series Onboard Battery Charger 

ProMariner 44020 ProSportHD Series Battery Charger - 20 Amp

The ProSportHD from ProMariner is the smartest and safest onboard marine battery charger you have been looking for all this time.



  • Two-bank charger
  • Distributed on-demand technology
  • Digital multi-stage charging
  • Built-in safety and quality
  • Expanded LED display


At first glance, you will appreciate the light, tri-surface heat sink design that delivers fast and efficient charging without overheating.

The fully automatic digital multi-stage charging process does a great job of enhancing battery performance as well as extending battery life. It features distributed on-demand technology, which is great because it ensures the charging amps are distributed to the two banks depending on what the individual batteries demand. The charger helps to maintain a full state of charge only when needed to reduce AC power consumption and maximize reserve power performance.

What makes this model truly stand out is the expanded LED display. Apart from the charging, conditioning, and auto-maintaining status, the intuitive LED also shows the completion status gauge. You do not need special skills to install and operate ProSportHD.

But the thing is, the pre-wired inline DC fuses are a little bit short.



  • The extruded heat sink design ensures cool charging
  • Compatible with AGM, Gel, and flooded marine batteries
  • It charges batteries according to the demand
  • Large LED includes completion status gauge
  • Digital multi-stage charging improves performance and battery life



  • The pre-wired inline DC fuses are somewhat short
  • The gauge of the charging wires is not stated



If you want an onboard marine battery charger that will optimally charge your trolling and engine start batteries, then the ProMariner ProSportHD is your best bet.

Overall Rating: 4.8


4. Guest 2707A ChargePro Onboard Battery Charger

Guest 2707A ChargePro On-Board Battery Charger 8A / 12V, 2 Bank, 120V Input

This high performing smart onboard marine battery charger from Guest boasts over-temperature, over-voltage, and overcurrent protection. So, it is one of the safest options to seek out.



  • Two bank battery
  • Digital charging technology
  • Five-stage charging performance
  • Multi-safety features
  • Auto-maintain energy saver mode


The ChargePro comes in a heavy-duty design that is shock-resistant and waterproof. This unique construction will offer years of service for saltwater and freshwater applications. I appreciate the fact that the DC inline fuses come pre-wired because they make installation much easier.

The new ChargePro guarantees the safest charge cycle with its built-in ignition, over-temperature, overcurrent, reverse polarity, and over-voltage protection. All these protection measures help to prolong the life of your trolling and engine start batteries. You’ve got a high performing battery and wiring fault detection system that ensures proper connections. The LED display is expanded for better visualization of the charge status monitor.

The automatic five-stage charge cycle ensures your marine batteries are properly cared for. It analyzes, precharges, charges, conditions, and then auto-maintains when needed. This helps to maximize performance as well as battery life.

But the thing is, the ChargePro may fail to resuscitate completely dead marine batteries.



  • The pre-wired design is easy to install
  • In-line fuses provide superior DC wire protection
  • Multi-stage charge cycle improves battery life and performance
  • It is designed to detect faulty wiring and battery
  • It only auto-maintain a marine battery when needed



  • It may fail to revive completely dead boat batteries
  • Tends to get warmer when used over an extended period 



This is a great onboard charge for marine batteries that have as low as two volts. But it may get warmer if used for a long time.

Overall Rating: 4.7.


5. Noco Genius2D Direct Mount Onboard Charger — Best Value Model

NOCO GENIUS2D, 2-Amp Direct-Mount Onboard Charger, 12V Battery Charger, Battery Maintainer, Trickle Charger, And Battery Desulfator With Temperature Compensation

If you are looking for an ultra-compact direct mount onboard battery charger that will help improve the performance and life of your marine batteries, look no further than Noco Genius 2D.



  • Auto-detects up to one-volt battery capacity
  • Compatible with AGM, maintenance-free, Gel, and flooded
  • Universal AC input
  • Direct mount
  • Monitors and auto-maintains


The first and most impressive feature of the Noco Genius2D is the direct mount, which allows you to mount near the batteries. It is engineered to automatically detect marine batteries that are as low as one volt.

This charger is completely automatic, which is great because you don’t need any technical knowledge or special codes to make it charge your marine batteries. It will safely and efficiently charge boat batteries and auto-maintain them after a full charge. The charger is also capable of detecting and repairing damaged marine batteries. In other words, this unit will continuously monitor, charge, condition, and auto-maintain batteries without your intervention.

What concerns me about this onboard battery charger are the cords, they may turn out to be too short when installing the new unit.



  • Direct mount design allows for easy installation
  • It is tested to withstand high-heat engine compartments
  • Completely automatic, no technical knowledge necessary
  • The charger is optimized to deliver optimal charging in any climate
  • It is reverse polarity, over-voltage, and over-temperature protected



  • The cords may be too short for your application
  • It is possible to receive a model that has quality issues



The Noco Genius2D is a high performing two-bank onboard battery charger that is super easy to install. It has lots of technical features that will improve the performance and life of your marine batteries.

Overall Rating: 4.7


6. Noco Genius GEN3 Onboard Battery Charger 

NOCO Genius GENM3, 3-Bank, 12-Amp (4-Amp Per Bank) Fully-Automatic Smart Marine Charger, 12V Onboard Battery Charger And Battery Maintainer

Do you have more than two marine batteries that need charging and maintenance? The Noco Genius GEN2 is a great option.


  • Three-bank charger
  • 100 percent waterproof
  • Multi-safety features
  • Multi-level safety barrier
  • Excellent optimization


The Noco Genius GEN3 comes in a completely sealed construction, which is great because it is protected against saltwater and the elements. The design also features built-in protection against overheating, overcurrent, overcharging, and reverse polarity. The multi-level safety barrier; on the other hand, prevents abnormal and unsafe conditions.

I appreciate the unique optimization feature of this unit, considering how effectively it stabilizes the internal chemistry of marine batteries. This helps to improve battery performance as well as longevity.

When compared to conventional chargers, the GEN3 charging performance is faster and more efficient. It can detect low capacity, sulfation, and low voltage and it applies a high-voltage pulse to recover the battery.

What is disappointing is that it is possible to receive a charger without battery clamps.



  • The waterproof design is protected against the elements
  • Multi-safety protection features improve battery performance and life
  • Great for detecting lost capacity, sulfation, and low voltage
  • The interactive process allows for more efficient charging
  • It is compatible with most marine batteries



  • It may come without battery clamps
  • May take longer to charge three marine batteries



This 30-amp marine battery charger does a good job of charging and auto-maintaining marine batteries. But make sure it comes with battery clamps.

Overall Rating: 4.6


7. Extreme Max Battery Buddy 4-Bank Onboard Battery Charger 

Extreme Max 1229.4023 Battery Buddy 4-Bank Battery Charger/Maintainer

Do you have a boat that has one standard battery and two deep cycle batteries? The Extreme Max Battery Buddy is what you need to keep them charged and auto-maintained.



  • Four-bank charger
  • Overheating protection
  • Wiring and battery fault detection
  • Compatible with lead-acid marine batteries
  • LED light indicators


This good quality battery is designed to charge all six-volt or twelve-volt lead-acid marine batteries. It features four intelligent modes for faster and more efficient charging. It is capable of detecting lost capacity, low voltage, and sulfation and it uses a high voltage pulse to revive marine batteries. The LED indicator lights will tell you when the batteries are charging and when they are full.

It features exceptional built-in safety features for improving performance and battery life, such as reverse polarity and short circuit protection. You’ve also got wiring and battery fault detection for added protection.

But the thing is, this battery charger is only suitable for charging and maintaining lead-acid batteries.



  • It can detect lost capacity, low voltage, and sulfation
  • The four-stage charge cycle improves charging performance and battery life
  • LED indicator lights tell you when the batteries are full
  • It has reverse polarity and short circuit protection
  • It does not overheat



  • The charger is only suitable for lead-acid batteries
  • You can receive a model with quality issues



Extreme Max may not be a very popular brand, but their Battery Buddy has proven to be a very reliable choice for most boat owners.

Overall Rating: 4.6


best onboard battery charger


Things to Consider When Looking for the Best Onboard Battery Chargers

All the electrical apparatuses in your boat need consistent and reliable power. So, you need the best onboard marine battery charger to make sure that your marine batteries never die. Here are a few things to consider during your search.


The Number of Banks Needed

Each of your boat’s trolling batteries will need one bank.

You may also need an extra bank for your starting battery.

For example, if you have a 36-volt trolling motor, then you have three batteries that need charging and maintenance. When you include your starting battery, you will have a total of four marine batteries and four banks. In this situation, you will be better off with a four-bank onboard battery charger for consistent and reliable charging and auto-maintaining.

A 24-volt trolling motor; on the other hand, will have two batteries. So, when you add the two batteries to your starting battery, you will have three banks. This means you will need a three-bank onboard battery charger.


The Types of Batteries You Have Onboard

Your marine battery charger must be compatible with the types of trolling and starting batteries you have onboard.

Lead-acid batteries come in several types, including flooded (wet), deep cycle, maintenance-free, Gel, and absorbed glass mat (AGM). Some onboard battery chargers you will come across use one-setting to charge and maintain all battery types. But other chargers will need you to select your marine battery type before the charging cycle starts.

In either case, I urge you to choose a battery charger that is compatible with your batteries.


Battery Voltage and Capacity

The voltage and size of your marine batteries matter. Whatever you select must be compatible with your boat battery’s voltage. Most marine batteries are rated at 12 volts, and most battery chargers are designed for 12-volt boat batteries.

The best onboard marine battery charger delivers the correct amount of charging amps for your particular marine battery. If you charge at a higher amperage, you can easily overheat and damage your boat battery. A too low amperage will lead to longer charge times. Your marine battery capacity is rated in amp-hour.

So, determine the amp-hour rating of your boat battery and choose an onboard battery charger that is suitable for that range. You can find this information on the name of the battery or from the side of the battery.

As a rule of thumb, your charger’s amp rating should be approximately 1/10th of the amp-hour rating of your boat battery. If you are in search of an onboard charger that will maintain your batteries’ charge while not in use over an extended period, a charger rated at two amperes or less is ideal. You can also consider a charger with multiple charge settings for added versatility.


Special Features to Look for

A good onboard battery charger must have maintenance or float charge.

This feature allows you to keep the charger safely connected to your marine batteries indefinitely without overcharging. An onboard charger with a reconditioning feature can help get rid of sulfate buildup on the internal plates of your boat batteries.

This helps to restore optimum performance and capacity. A battery charger with an automatic temperature compensation feature helps to maintain optimum charging temperature in extreme weather conditions.


Final Thoughts

The winner of this round is Minn Kota Precision Onboard Charger. What makes this charger stand out is its versatility. It is available in one-bank, two-bank, three-bank, and four-bank styles. It has a rugged design that has been saltwater tested for superior rust and corrosion resistance. The design is also waterproof, vibration-resistant, and shock-resistant.

This charger is suitable for charging multiple batteries onboard. It is an appropriate choice for Gel, absorbed glass mat (AGM), maintenance-free, and flooded lead-acid marine batteries. It also comes with several special features, including automatic temperature compensation, low-line voltage compensation, digital control, and automatic multi-stage charging.

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