Top 5 Best Onboard Battery charger of 2021 – [Reviews & Buyer Guide]

Looking For The Best Onboard Battery charger In The Market

There was a very interesting discussion with a buddy about the best onboard battery charger recently. As strange as it may sound, he’d never heard of the concept of an onboard battery charger before.

And me, well, I’d just dealt with the worst possible nightmare that anyone can have, being caught with a dead battery in the middle of a fishing trip out in the wilderness. I’ll leave the back story for later.

If someone were to ask me ‘What’s the worst sound in the world?’

I’d say that it’s the sound of your car sputtering to death due to the battery running out of steam, or your boat, RV, mower or any other machine for that matter. There’s nothing worse than being caught with a dead battery when you are least prepared for it. And it is more common than you’d believe.

People make mistakes that borders on stupidity. They leave their radio on all night or a headlight. Sometimes, they fail to notice simple signs that the battery is about to go kaput. Either ways, having an onboard battery charger is like having insurance. It keeps you armed to fight a disaster when it creeps up on you and strikes.

If you, like my buddy are least aware of a battery charger or if you are looking to buy one for yourself, then you are in luck. I have just spent 10 days rummaging through the market trying to find the best onboard battery charger and here are my picks.

#1. NOCO Genius GENM2 8 Amp 2-Bank Waterproof Smart On-Board Battery Charger

[Editor Top Pick]

 NOCO Genius GENM2 8 Amp 2-Bank Waterproof Smart On-Board Battery Charger

My #1 pick is the Genius 8 Amp 2-Bank onboard battery charger from Noco. If ever there was a product that’s true to the brand name, it is this one. This is an ingeniously designed, compact onboard charger that can charge just about all commonly used types of rechargeable batteries. And you can pick from 7 different power configurations with the lowest one at 1-Bank 10 Amp and the highest one at 4-Bank 40 Amp.

Rugged PE casing

The Genius GENM2 features a rugged and durable polyethylene casing that is designed to be mounted in the most corrosive surroundings. It is 100% sealed and waterproof (IP68 rating), is saltwater tested for corrosion resistance and it can take more than a few knocks and nicks in its stride. While it is primarily advertised as a marine charger, you can easily use it for a variety of applications including electric cars, generators, boats as well as trolling motors.

Continual Monitoring

The Genuis GenM2 is designed to continually monitor your battery for signs of power drainage and maintain the charge. This is the 2 bank 8-Amp model which will help maintain the charge in a 12V Starter and Deep Cycle battery that includes Wet, Gel, AGM, EFB & MF. The charge cycle is constantly monitored and the charger automatically alters the power input based on the positive feedback from the battery. At the end of the day, it gives the battery a finishing charge while preventing overcharging.

Safe & Reliable

All of Noco’s genius range of best onboard battery chargers are 100% safe and protected against adverse conditions that may arise without a warning. So, you are covered against sparks, short circuit, overcharging or reverse polarity that may affect the lifespan of your battery. By charging at 8 AMPs per bank, it will have you ready to go in no time even if you hook this up when your battery is fully drained.

Best features

  • Compact and rugged design that can be mounted anywhere
  • Continually monitors your battery for signs of drainage
  • Alters charging cycle based on battery feedback
  • 100% waterproof and shockproof
  • Gives the battery finishing charge at the end of use


The Noco Genius M2 with its budget pricing is an unbelievable deal and a must have if you are looking to stay protected from unexpected dead batteries. It is hands down, one of the best onboard battery chargers in the market.

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

[Best Boat Battery Chargers]

ProMariner 43012 ProSport 12

Promariner is one of the most reputed brands that you will come across while searching for battery chargers. The ProSport 43012 is one of their popular offerings that boasts of a bunch of incredible features that keeps your battery from draining out completely.

Unlike some of the other models, it features a digital microprocessor with integrated LED lights that indicate whether the battery status is ok or whether it needs urgent attention every time you get started.

Lightweight, easily mountable

For a long time, buying even the best onboard battery charger meant making numerous changes to the existing marine engine set up or under the hood to allow easy installation. Not anymore. The ProMariner 43012 is 40% lighter than old battery chargers and is 100% shockproof and water resistant. The compact sizing means portability and compatibility with a wide range of applications. From a spacious motor boat to a space-constrained mower engine, this will fit right in.

Integrated Energy Saving Mode

Apart from automatically monitoring, charging and conditioning your batteries, the ProMariner 43012 also features an integrated energy saver mode that kicks in the moment your batteries are fully charged. This prevents unwanted applications from robbing your battery power when the engine is not in use. Also, this extends the lifespan of your batteries and reduces the need for continual ongoing charge.

Microprocessor and software controlled

The microprocessor and software control at the core of the ProMariner 43012 not only monitors the battery banks onboard for faults and possible glitches, it also reconditions all the batteries once every month. That’s irrespective of whether you connect it for a short term trip or whether it is permanently mounted. It primarily charges the main engine battery and once that is fully charged, all the remaining amps are distributed evenly to the other batteries on house.

Best features

  • Compact, lightweight and easy to mount
  • 40% lighter than old batteries
  • Microprocessor and software controlled
  • Automatically monitors all batteries on board
  • Battery status ok and battery bank status indicator LED lights
  • 100% waterproof and shockproof


The ProMariner 43012 is priced a tad higher than the #1 pick in this list. However, being packed to the brim with features and being completely digitally monitored, it is completely worth those few extra dollars. It gives you the much needed peace of mind and assurance that you need.

#3. MinnKota MK 315D On-Board Battery Charger (3 Banks, 5 Amps per Bank)

[Top Rated On-Board Battery Charger]

MinnKota MK 315D On-Board Battery Charger (3 Banks, 5 Amps per Bank)

If you have multiple batteries on board, like it is typically the case for boats with 1 battery for the electronics and two for the trolling motors, then my next pick, the MinnKota ML315D is the perfect choice for you. This is a 3 bank onboard battery charger with 5 Amps per bank.

Like the ProMariner 43012, it is also completely digital and microprocessor based which eliminates the chances of a potential glitch and ensures precision in the way the batteries are monitored and charged.

Multi stage charging

To ensure that your batteries which are most probably heavily and repetitively cycled do not deteriorate due to the constant use, MinnKota MK315D features a multi-stage charging system that will control both, the current as well the voltage that the battery receives through all-three stages of the charging process. This prevents problems like sulphation or stratification which can otherwise reduce the lifespan of your battery considerably. The M315D also features an integrated temperature sensor that adjusts the charging according to the outside temperature ensuring that constant temperature fluctuations don’t damage the battery.

Faster and accurate charging

Unlike epoxy based chargers which were heavy and slow to charge, the microprocessor based digital MinnKota MK315D provides a much faster charge that is also more precise and accurate. Another advantage is that you can use this to recharge even the most discharged battery that is completely dead. Once connected, the charger automatically detects the status of the batteries on board and displays it via the status code LEDs. If the charger has kicked into the float charging mode, the LED blinks yellow while green indicates that the batteries are full charged and being monitored. Red indicates a problem with one of the battery connections.

Practical design

The Minnkota MK315D looks minimalistic as compared to many other onboard battery chargers in the market. However, behind the simplistic exteriors are a bunch of practical design features that make it easy to use. It is 100% waterproof and resistant to shocks and impacts. The casing is saltwater tested too to repel corrosion. It also features an integrated AC plug holder which allows you to keep the plug from being damaged.

Best features

  • 3 Bank digital charger with 5 amp each bank
  • Multi stage charging to protect the battery from damage
  • Recharges even completely discharged batteries
  • Integrated status LED display
  • Waterproof, shockproof and corrosion resistant design
  • In-built AC plug storage


The Minnkota MK315D is certainly a worthy contender for the best onboard battery charger in the market currently.

#4. Schumacher SE-1-12S-CA Fully Automatic Onboard Battery Charger

[Best onboard battery chargers for price]

Schumacher SE-1-12S-CA Fully Automatic Onboard Battery Charger - 1.5 Amps

A lot of people will be surprised by my next pick in this list of best onboard battery chargers. This is the SE-1-12S-CA, an extremely barebones onboard trickle battery charger that is perfect for spendthrifts who are looking for reliability without blowing a hole in their wallets.

The SE-12S from Schumacher Electrics is priced under $20. But that’s not the best part. It is fully automatic and can be used handheld or even mounted on most of the commonly used vehicles. How’s that for versatility?

Molded Plastic Casing

The SE-1 is housed in a molded plastic case. It is durable but it is not waterproof or corrosion resistant. To be honest, that would be too much to ask at this price point. It can be mounted onboard next to the battery on most vehicles and even some fancy ones like a heavily modified street rod. The package includes hardware and mounting brackets that you need for easy mounting.

Consistent trickle charge rate

The Schumacher SE-1 is a trickle charger that has a 1.5 amp trickle charge rate. For the uninitiated, that’s akin to a maintainer. It will not charge a battery that is completely dead. Instead, it can prevent the battery from going kaput even if you don’t use your car or your truck every day. All that you need to do is hook this up to your car and it will trickle charge the batteries keeping it primed for use. There are LED lights that indicate the charging status as well as power status and it also features an integrated reverse hookup protection that protects your batteries from short circuits and reverse polarity. An automatic shut off feature shuts off the charger when the batteries are fully charged.

Multiple uses, great pricing

There are so many situations in which the SE-1 can be an invaluable addition to your tool kit. It can keep the batteries ready for start up on cold winter nights, it can prevent the battery from discharging during long periods of inactivity and it can prevent mowers from draining. It is so easy to install and you don’t have to constantly keep checking it either. To top it off, it has an under $20 price tag. You have nothing to lose really.

Best features

  • Compact 1.5 amp trickle charger
  • LED indicator for power on and full charge
  • Automatic shut off
  • Reverse hookup protection
  • Compact sized molded plastic casing
  • Can be permanently mounted in your car/bike during the winters
  • Priced under $20


I would rate this among the best onboard battery chargers in the market. It is inexpensive, very effective at what it does and so easy to use. If you mow, drive, ride bikes, own boats, then one of these will be a worthwhile purchase.

#5. Attwood 31710 On-Board 10 Amp Battery Charger

Attwood 31710 On-Board 10 Amp Battery Charger

The last pick in this list of the best onboard battery charger is the Attwood 31710 from Attwood Marine. This is a simple but very efficient onboard charger that is perfect for charging all the batteries on board and comes prewired to make it easy for you to hook it up on-the-go.

Being a reasonably new product, it is up against some very big names in the business. But from the initial response that it has generated, it looks pretty much like most of the other offerings from Attwood Marine, top notch.

Long Battery leads

One of the common problems with even the best battery chargers is a short battery lead which makes it impossible to permanently mount the charger without using extension cords. The 31710 has 3 feet long battery leads which lets you connect it to multiple batteries without needing extensions. The casing is compact enough to fit easily next to the engine crank battery and it is waterproof, shockproof and salt water tested making it perfect for all kinds of applications.

Fully Automated operation

Irrespective of whether you are trying to keep your batteries alive during winters or looking to recharge one that is almost dead, the Attwood 31710’s automated operation keeps you covered. You just have to hook it up to the terminals and the built-in maintenance mode kicks in which maintains the engine crank battery at optimum charge and then transfers 100% of the remaining amp to the trolling batteries.

It also features an integrated temperature sensor that protects the battery against extreme fluctuations. Other notable features include reverse polarity ignition. All in all, it is designed for plug and play use. You can install and forget about it.

Safe, multi-stage charging

The Attwood 31710 uses the gold standard in onboard charging technology. It uses a multi-level pulse charging system that automatically adjusts the charge according to the temperature, response and feedback from the batteries on board. This is the only safe and accurate way to charge your batteries and it protects the batteries from overcharging and helps increase the lifespan.

Best features

  • Completely automatic onboard charger
  • Multilevel pulse charging system
  • Automated shut off
  • Maintains the engine crank battery
  • Transfers 100% of amps to other batteries on board like the trolling battery
  • Temperature sensor to protect from fluctuation
  • 3 feet long battery leads
  • Prewired for easy installation
  • Ready to use

That sums up the list of the best onboard battery chargers. For someone who’s accustomed to onboard charging, that list presents five of the best options that have been handpicked from among hundreds of models marred by poor performance or lack of quality.

But for someone who’s new to this, that may seem like a bunch of technical features thrown in together, no matter how elaborately and simply the features have been laid out. And I wouldn’t blame you either if you feel that way. To that end, here’s a small buying guide with a list of features that you need to keep an eye out for while shopping for onboard battery chargers.

The Onboard Battery Charger Buying Guide

Onboard Battery Charger

One of the most popular applications that an onboard battery charger is used in is a boat. And hence, we have to consider a lot of factors that are more suited for marine application than not.

The conditions

While no battery charger will be exposed directly to water, except for ones that are used in small boats or fishing boats, it pays to have a waterproof battery charger because of the extremely high moisture that it will continually be exposed to. For this reason, we have picked the best on board battery chargers that are 100% waterproof.

The Application

Your choice of the best onboard battery charger will depend largely on where and why you intend to use it. Is it for keeping the batteries from dying down during winter? Or is it to keep the trolling battery as well as the engine crank battery continually? Both these are completely different applications and require different types of chargers.

Automated Monitoring

Most modern onboard chargers will constantly monitor all the batteries in your set up and warn you about possible flaws in connection or lack of charge. These chargers are the easiest ones to use and do not require monitoring. You can install them and forget until you see a low charge LED notification indicating that it’s time to recharge it.

Automatic Shut off

A charger that automatically shuts off when all the batteries are fully charged will help improve the lifespan of the batteries on board. Also, it is less likely to cause potential problems due to back charging or over charging.


You’d want to be able to install the charger along with your main batteries without modifying the set up too much. Thankfully, onboard chargers have undergone a sea of change in the past few years. The large and oversized battery chargers of yore have been replaced by compact and versatile units that can be installed just about anywhere.

The number of banks

The number of banks in the charger should correspond to the number of batteries in the set up. For example, if you have two batteries, then a 2-bank charger will work best. If you have a 3 battery set up, then consider using at least a 3 bank charger.

That’s about it. We hope that you enjoyed reading through our recommendations and would love to hear if you have any comments or feedback. Just give us a holler. Happy sailing!

You might also like our reviews on Optoma HD142X and Vortex Crossfire II 1-4×24.

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Updated: — 4:49 am