Best Onboard Marine Battery Chargers of 2021 – Buyer’s Guide

| Last Updated June 1, 2021

Along with being an incredibly convenient method of charging boat batteries after a long day in the water, onboard marine battery chargers also recharge batteries in a safer and faster way, maintaining the charge until your next trip. 

With so many different types of batteries having their own charging requirements, it's essential to choose a battery charger that provides the correct charge every time. To help you make the correct decision, this guide includes reviews of some of the best models available, along with tips on how to correctly install one.

Comparison Chart of the Best Onboard Marine Battery Chargers

  • Waterproof and shock-resistant for durability
  • Equipped with LED indicator lights
  • Comes with ignition protection
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  • Features a waterproof and rugged construction
  • Can independently maintain two 12-volt batteries
  • Makes use of spark-proof technology
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  • Best for the Money
  • Offers durable aluminum construction
  • Body is completely corrosion-resistant
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  • Best 3 Bank Onboard Marine Battery Charger
  • Can charge all types of lead-acid batteries
  • Durable construction makes it waterproof
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  • Has a useful desulfate cycle
  • Can auto-charge while boat's in storage
  • Is able to charge deep cycle high-perform batteries
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What to Look For When Buying an Onboard Marine Battery Charger

Choosing the best onboard charger can be a complicated decision, especially if you're doing it for the first time. To ensure you make the right choice, here are some things you should keep in mind before you finalize your purchase:

Recovery Time 

Recovery time can be simply defined as the speed at which batteries are completely recharged after being drained. Quality chargers are able to recharge your batteries in 3-5 hours, delivering 15 amps per bank. Some chargers can also take 6-12 hours to recharge your batteries. If you're planning on fishing several days a week, then it's essential to choose a unit with a faster recovery time. 

Battery Type

Choosing a charger that's not compatible with Gel or AGM batteries can permanently damage your batteries. Usually, Gel and AGM batteries need more specialized and high-quality chargers to maintain their longevity. 

Make sure you check the type of battery you have and then choose a charger that supports it. High-end chargers are designed with microprocessors that identify the battery type and change the voltage and amperage to meet its demands accordingly. 

Safety and Durability

It's advisable to choose a unit that's completely waterproof and corrosion protected. High-quality models are also designed with safety features, including low-line voltage compensation, reverse polarity protection, temperature compensation, and spark-proof technology. It's also better to choose models that are accredited by authoritative bodies, such as UL and ABYC. 

Review of the Best Onboard Marine Battery Chargers

With such a wide range of chargers available today, choosing the best one can be incredibly difficult. To help you find a quality model that will protect your battery for years, we've reviewed some of the best onboard marine chargers available in the market. Let's take a look:

Best Overall:
Boating Accessories New MINN KOTA

Minn Kota Digital On-Board Battery Chargers


  • Backed by a 3-year warranty
  • LED status display quickly informs you of charging progress 
  • Designed to be shock-resistant, vibration-resistant, and waterproof 
  • Automatic multi-stage charging ensures a safer and more precise charge 
  • Automatically adjusts to temperature fluctuations for an accurate, fast charge 


  • Heavier than other models
  • Might stop working after two years 

What Recent Buyers Report

Almost everyone who invested in this unit was extremely happy with it. Users loved its multi-stage charging and stated that they had no issues with it. One user even said that their model had been going strong for three years. However, some customers reported receiving defected units that failed within two years. 

Why it Stands Out to Us

This model constantly monitors the voltage and temperature of the battery to prevent it from overcharging. Its exceptional digital charging technology ensures the proper conditioning, maintenance, and charging of your boat. It's further designed with an LED light indicator to display the charging status, making the unit safer and more efficient.

Who Will Use This Most

One of the most popular models for fishing boats, this unit is perfect for lead batteries and AGM batteries. Since it's waterproof and shockproof, it can be used in every weather condition. Its size also ranges from a four bank 40-amp to a single bank 60-amp, making it suitable for almost everyone.

Bottom Line

All in all, this premium quality charger is incredibly reliable and affordable. It's available in different charging capacities, making it perfect for all your charging needs. Although it's a bit heavy, the efficiency and safety it provides make the weight a minor issue.


NOCO Genius GENM2, 2-Bank, 8-Amp (4-Amp Per Bank) Fully-Automatic Smart Marine Charger, 12V Onboard Battery Charger and Battery Maintainer


  • Comes with a 5-year warranty
  • Certified to be ISO 8846, UL1236, and 33 CFR 183.410
  • Automatically shuts off power once the battery is fully charged
  • Waterproof and rugged construction makes it capable of being submerged down to 3 meters 
  • Designed with reverse polarity protection, overcharge protection, and spark-proof technology 


  • Takes up a lot of space
  • Can overcharge the battery at times
  • Does not include self-tapping screws

What Recent Buyers Report

The majority of the buyers were extremely satisfied with this unit, with some stating that they were confident it would maintain and protect their batteries. Users found it incredibly easy to install and use, and liked the separate charging light indicators that informed them of the charging status. However, customers were disappointed with the quality of the included screws, while some reported that the unit boiled the water out of their batteries and until they were ruined. 

Why it Stands Out to Us

This unit provides the perfect combination of rugged construction and high-technology. Designed with an onboard microcomputer, it constantly monitors battery activity to ensure efficient and safe charging, automatically reduces energy consumption, and offers numerous levels of safety protection, like spark-proof technology, and overcharge and reverse polarity protection. Lastly, it features Rapid Charging technology, allowing it to charge batteries two times faster than ordinary battery chargers. 

Who Will Use This Most

This model can be quickly installed and mounted onto several different applications, including tractors, boats, and a wide range of equipment. Specifically manufactured for use in tough marine environments, this unit can charge all kinds of lead-acid batteries, including gel, deep-cycle, wet, and AGM batteries. 

Bottom Line

NOCO is one of the most reliable brands in the US, and the NOCO Genius GENM2 is undoubtedly one of the best models available today. Several authoritative bodies have accredited its construction, so it will certainly last you for years to come. However, you might need to purchase better quality screws for mounting the device.

Best for the Money:
Minn Kota Precision On-Board Charger

Minn Kota Precision On-Board Charger


  • UL listed to standard 1236 and FCC complaint 
  • Features aluminum and corrosion-resistant construction 
  • Reverse polarity, ignition, arc, and short circuit protected
  • Automatically protects and cleans flooded lead-acid batteries 
  • Designed to be shock-resistant, vibration-resistant, and waterproof


  • Heavier than other models
  • Face of the charger might warp if left in high temperatures 

What Recent Buyers Report

Almost everyone who bought this unit was extremely pleased with its operation, with some stating that they would definitely purchase it again. Users loved the fact that they could leave the batteries in their boat with the unit plugged in all winter without any worries. However, some customers reported receiving defected models that stopped working after a few months. 

Why it Stands Out to Us

This model primarily stands out to us because of its durability. It's designed with some of the most sophisticated and complex charging technology, including selective battery type, digital controls, battery equalization, and low power-line compensation. It further has a compact footprint, making it perfect for cramped boat compartments.

Who Will Use This Most

This model is ideal for anglers using expensive battery types, such as gel, HP AGM, and AGM. If you need the best for your boat, then this model is certainly the one for you! Since it's capable of charging different types of batteries simultaneously, it's also perfect for those using an AGM battery for their motor engine, and a Gel battery for trolling

Bottom Line

When it comes to onboard marine battery chargers, this model offers the best value for money. Boasting some of the best charging technology, it's undoubtedly one of the most advanced and fast chargers available.

Best 3-Bank Onboard Marine Battery Charger:
NOCO Genius GEN3

NOCO Genius GEN3, 3-Bank, 30-Amp (10-Amp Per Bank) Fully-Automatic Smart Marine Charger, 12V Onboard Battery Charger and Battery Maintainer


  • Can diagnose, recover, and charge all kinds of lead-acid batteries
  • Charges two times faster compared to traditional battery chargers 
  • Stabilizes battery chemistry for longevity and enhanced performance 
  • Rated NEMA 6P and IP68 for continuous operation in extreme environments 
  • Protects batteries from short circuits, reverse polarity, thermal runaway, and sparks 


  • Included screws are of poor quality 

What Recent Buyers Report

Most buyers loved this model and recommended it to other people as well. They loved the fact that it could maintain the charge and health of three different batteries at the same time. While one user stated that the unit worked perfectly after 4.5 years of use, one reported that it boiled three new batteries. 

Why it Stands Out to Us

This model's optimization and recovery benefits are what make it stand out from its competition. It restores lost performance by stabilizing the internal battery and also tackles and recovers batteries suffering from lost capacity or sulfation. It further constantly monitors the battery's health to ensure it doesn't overcharge.

Who Will Use This Most

This three-bank unit is ideal for all kinds of lead-acid batteries, ranging from 25-230AH, including AGM, deep-cycle, wet cell, and gel cell batteries. It's suitable for all standard types of marine batteries and can be installed on tractors, boats, and other equipment. 

Bottom Line

To put it simply, this model is a high-performance onboard marine battery charger and undoubtedly deserves a place on our list of top picks. It constantly observes the battery to ensure optimal battery maintenance, but the quality of the screws could be improved.

Editor's Pick:
ProMariner ProSport 12 Gen 3

ProMariner ProSport 12 Gen 3 Heavy Duty Recreational Series On-Board Marine Battery Charger - 12 Amp - 2 Bank


  • Covered by a 2-year warranty 
  • Able to charge multiple batteries at the same time 
  • Energy saver mode reduces AC power consumption 
  • Impressive lighting system displays the status of the batteries 
  • Built-in safety features protect batteries from high temperatures and overload 


  • Might not fully charge the second battery
  • Extending the cables will void the warranty 
  • Doesn't include any hardware for securing the charger 

What Recent Buyers Report

This unit has received numerous positive reviews. Buyers found it incredibly easy to install and stated that it kept their batteries charged for a long day on the water. They said that it charged batteries quickly and loved the customer service provided by ProMariner. However, some users reported receiving models that stopped working after a few months of use. 

Why it Stands Out to Us

We love this model because it's incredibly easy to use and charges the batteries in an extremely efficient way. It senses increased demand from auxiliary batteries and diverts all the available power to that battery. Lastly, it also reconditions all batteries automatically, ensuring maximum battery performance and life.

Who Will Use This Most

An intelligent 12 amp charger, this model is designed with two charging profiles for gel cell batteries and flooded or STD AGM batteries. Since it's waterproof, you can install it almost anywhere on your boat.

Bottom Line  

Boasting numerous positive attributes, this model offers different charging solutions, so the health of your battery is maintained. Although it delivers efficient and fast charging, the lack of hardware needed to secure the charger might be a hindrance to some.

How to Install an Onboard Marine Battery Charger

Installing an onboard marine battery charger is not a complicated process and can be easily completed by a competent DIYer on the weekend. Before you start the installation process, it's important to know that some chargers feature an AC lead that's already connected to the model. 

For installing an onboard marine battery charger, you can follow these simple steps:

  1. Mount the unit in a dry and well-ventilated spot with stainless steel nuts and bolts or self-tapping screws. 

  2. If you have a model that delivers a maximum output of around 20 amps, then it's better to choose a bigger fuse, such as a 25-amp terminal-mounted fuse. 

  3. For DC wiring connections, secure a length of adhesive heat-shrink tubing inside the wiring compartment to make a waterproof connection. If the wiring is terminated with alligator clips, cut them off using proper ring terminals to prevent sparks.

  4. Make sure the cables are properly supported about every 18 inches. You can do this with cable ties and plastic clips. 
  5. Once the DC connections are made, start making AC wiring connections. 

  6. Cut off the unit's AC plug and connect the charger to the compact shore power AC inlet. Make sure you use the wire size that's mentioned in the model's installation instructions. 

  7. Lastly, check all the connections again before you start up the system.

To get a better understanding of how to install a marine battery charger, check out this video below:


Hopefully, this guide will help make your decision easier. Just make sure you choose a unit that supports your batteries and recharges them within the time you need. Make sure you go through all the reviews to find the model that best suits your needs!

People Also Ask 

Choosing the best onboard marine battery charger can be an extremely technical and difficult task. To ensure you don't end up wasting your money, and to clear any confusions you might have, following are some of the most frequently asked questions:

How Does an Onboard Marine Battery Charger Work?

Onboard battery chargers are computer-controlled and allow users to leave their batteries in the boat. To charge the battery, you just need to plug it in the unit's AC cord, giving you the sufficient energy load you need.


Can I Charge a Marine Battery Charger With a Regular Charger?

Although you can charge your marine battery with a regular charger, it's better to use a marine battery charger as it's specifically designed for that purpose. This reduces the risk of damage to the battery as marine battery chargers identify the needs of each battery and deliver power accordingly.

How Long Does it Take to Charge a Marine Battery?

The time it takes to charge a marine battery depends on its physical size. Also, the more discharged a battery is, the more time it will take to recharge. Batteries generally take several hours to charge. If a battery is extremely discharged, it might take more than 12 hours to recharge. 

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