Battery power can be a confusing topic for boaters, but battery power is vital to start engines, run the lights and power the accessories. Fortunately, for those not blessed with a wealth of detailed knowledge on managing charging needs of the spectrum of boating batteries, there are a whole host of chargers out there with built-in smart charging options available which make taking proper care of your batteries as easy as taking candy from a baby.
There are a number of questions you will need to consider when making the decision on the right charger for you. Consider the list of best marine battery charges below and you will soon be sailing away with the best boat battery charger for your needs.
Best 4 Bank Onboard Marine Battery Charger
NOCO Genius GEN3 30 Amp 4-Bank Waterproof Smart onboard Battery Charger Review
If your budget is at the higher end and you require a multi-battery charger then this NOCO Genius 4 bank advanced, high-technology marine battery charger is a great choice. This powerful onboard charger and battery tender is capable of charging and maintaining 4 12-volt marine, starter or deep-cycle batteries at the same time. It also works fine with all types of boat batteries – AGM, gel, wet and MF.
With rapid charging technology, the power of this charger does not fall short when it comes to speed, being 2 times faster than traditional linear battery chargers. It’s built in battery desulfator can recover batteries that are depleted, while at the same time it will monitor the activity of your batteries and diagnose their state, charge them to the optimum level and then maintain them so they are ready to go when you are.
You can also rest assured that this onboard marine battery charger is safe. Its advanced charging system makes sure batteries are never overcharged, and, in fact, will improve your batteries performance and longevity.
Built to withstand the environment in which your marine adventures take you, the NOCO Genius is 100% waterproof, shock and vibration resistant and is completely sealed so that it is safe even in the most extreme environments. The safety features of this charger do not stop there, it also has spark-proof technology and protects against reverse battery hookup. This safe and effective marine battery charger is the perfect option for those of you with boats on the larger side.
This onboard battery charger also comes in different sizes, so if your power needs are lower you can still choose this quality product but at a lower cost if you require fewer banks. In addition to the 4 bank model, the NOCO Genius comes in the following sizes: 1 bank (4 AMP and 10 AMP), 2 bank (8 AMP and 20AMP) and 3 bank (12AMP and 30AMP).
Q&A: Does this marine battery charger come with a mounting system?
A: Yes, this comes equipped with a spot mount for the onboard charger, although it may be easiest to mount on a board and attach to the hull with an adhesive.
Best 4 Bank Marine Battery Tender
Battery Tender 022-0148-DL-WH 12-Volt 4-Bank Battery Management System Review
If your budget is at the lower end and you require a multi-battery charger then this Battery Tender 022-0148-DL-WH is for you. This 4 bank station is designed to fully charge and maintain batteries to the proper storage voltage whilst avoiding damaging effects associated with trickle chargers. Its compatibility with AGM makes it an ideal choice for many boats’ batteries and the microprocessor control ensure you can have hassle-free four-step charging that is safe for all your boathouse vehicles.
The four-step charging includes initialization, bulk charge, absorption mode and float mode so that you can confidently maintain batteries at optimal performance levels. This 4-bank charger with help you to maintain battery life with minimal effort. For example, the charger’s ability to switch between output voltage to either a storage or a float level means that you won’t have to worry about the damage that can be caused by overcharging.
A useful feature of this unit is the user-friendly LED indicator light for each individual charging bank, helping you to ensure optimum charging. In addition, the reverse polarity and short-circuit protection, alongside the spark-proof connectors, means you can be sure in the safety of this device. It is also designed to meet both US and international safety standards, UL and CE respectively.
This super-lightweight design is great for those with large power needs and is available for a great price, considering the features it has to offer, from a brand you can trust.
Q&A: What are UL Standards?
A: UL (previously known as Underwriters Laboratories) is a global safety certification company who are approved to perform safety testing by the Occupational Safety and Health Administration (OSHA) in the US and Canada.
Best 3 Bank Onboard Marine Battery Charger
ProMariner 43021 ProSport 3 Bank Battery Charger Review
The ProMariner 43021 is a great value option if you are looking for a 3 bank battery tender and marine battery charger that is compatible with flooded and AGM batteries.
Its exclusive microprocessor ensures that all of your onboard batteries are charged in the most efficient way and that all unused amperage is distributed to trolling motor or house bank batteries thanks to Distributed-On-Demand Charging Technology. An incredibly efficient onboard marine battery charger and tender.
This charger is fitted with exclusive “System Check OK” and “Battery Bank Trouble” LED indicators so as soon as you connect this charger you are given feedback on the state of your batteries.
Once diagnosed, it will then fully charge and condition batteries and maintain them at their optimum charge. It’s super efficient Energy Saver Mode will then monitor and auto maintain the batteries when needed, with an automatic function to check them once a month to ensure maximum performance and to extend battery life.
The lightweight design of this charger makes it 40% lighter than conventional onboard battery chargers and it is also waterproof so perfectly adapted for your onboard marine needs. There are also important safety mechanisms built-into this charger, its dual inline fuses protect trolling and house bank batteries and the built-in over-voltage, overload and over-temperature protection make sure that your batteries are safe.
This easy to use charger is the best 3 bank onboard marine battery charger on the market.
Q&A: If I have a single starting battery and 2 deep cycle batteries in parallel, do I need a 2 or a 3 bank charger?
A: Actually you can use either a 2 or 3 bank charger with this setup!
Q&A: Does this charger also do a trickle charge?
A: It does, it will fully charge them and also maintain and condition them throughout the year.
Best 2 Bank Onboard Marine Battery Charger
Minn Kota Precision onboard 2 Bank Charger Review
While rated as the best 2 bank onboard marine battery charger on the market, the Minn Kota Precision charger actually comes in various sizes with 1 bank, 3 bank and 4 bank types also available if you need them.
This well-designed charger is a firm favourite amongst the boating community and we can see why. Its versatility means that it can be used for AGM, gel or flooded lead acid batteries and the precision chargers allow you to select and charge different battery types by bank. It’s LED display clearly shows you each individual battery’s connection status, power status, percent charged and selected battery type, keeping you fully informed.
The built-in Digital Microprocessor ensures a regulated and precise charge for your battery. Unsurprisingly, this smart technology has made Precision Onboard Chargers renowned for extending battery life, as well as providing shorter charge times and a longer running time. All of this ensures that you will be out on the water faster, and for longer, great for those who want to optimize their time out on the open seas.
With Automatic Temperature Compensation, you can also be reassured that your batteries will not over or under-charge – you can leave this plugged in all winter and not have to worry. It’s sturdy, durable design also means this charger is built to last – with heavy-duty housing that is resistant to freshwater or saltwater corrosion. Fully waterproof, shock and vibration resistant – this best 2 bank boat battery charger is built with adventures in mind.
This onboard marine battery charger is FCC Compliant and UL listed to marine standard 1236. It also comes with a 3-year replacement warranty. You can be confident that your money is well spent with the Minn Kota Precision onboard 2 Bank Charger.
Q&A: Can this be plugged in at all times?
A: Yes, this can be plugged in 100% of the time when you are not using your boat. Just unplug it when you are using the boat and plug it back in when you are not.
Q&A: Does this work with 220V input?
A: No, this only works with 120V input.
Best 2 Bank Marine Battery Charger
Battery Tender 022-0165-DL-WH 12-Volt 2-Bank Battery Management System Review
Another great 2 bank marine battery charger option is the Battery Tender 022-0165-DL-WH Suitable for all 12 volt AGM, sealed maintenance free and flooded batteries this best boat battery tender comes with 2 independent charging stations so you can charge two batteries at once. While a great option for maintaining boat batteries this charger can cater to a range of applications such as cars, motorbikes and gardening equipment.
If you are unable to get out on the water as often as you would like, or you store your boat away for the winter this dual-bank battery tender means you won’t have to worry about dead batteries as it provides a continuous flow of charge to make sure that your battery is at its peak performance level whenever you need it.
The inbuilt safety mechanisms mean that this system will only charge batteries when they need it, protecting them from over or under charging and prolonging the life of your marine batteries. Being spark proof and reverse polarity protected, you can leave this charger attached 24/7 without worrying about it.
This product comes with 2 alligator clips, 2 sets of ring terminals and a 2-year warranty.
Q&A: How long are the cables that connect to the batteries?
A: There is a total of 60 inches from the charger to the battery.
Best Portable Marine Battery Charger
MinnKota MK-105P Portable Battery Charger Review
At the cheaper end of the market, and a great option for those with smaller boats and smaller marine batteries is the MinnKota MK-105P. This is a 1 bank, 5 amp charger that can charge 12-volt batteries.
It is significantly more compact than the onboard marine battery charges so is a good option for smaller boats as it doesn’t take up much room. Plus, its design makes it a good portable option with its unique handle design making this charger easy to transport.
This best trolling motor battery charger uses smart technology to run a fully-automatic 2 stage charging programme and it is designed to fully optimize the charge of 12-volt batteries in your boat. This charger is protected from the risk of both over-charging or under-charging so you can plug it in and leave it as long as you like.
Protected from short circuits thanks to its smart and durable design, this charger also will not experience reverse polarity problems from improper connections. This charger is also easy to use, with just the push of one button it gets to work and the LED indicator lights make sure that you know what stage the charging is at.
Q&A: Can I use it on an AGM battery?
A: This is not suitable for AGM batteries as you will need a charger with a voltage meter or microprocessor to make sure you do not overcharge and damage the battery.
How many banks will you need?
A bank simply means the number of batteries which are harnessed together and so treated as if they are a single larger battery. Typically, you will need a number of banks equal to the number of batteries used by your boat. So, if you have a boat with two 12-volt batteries, then a 2 bank charger is what you should be looking at.
However, charging requirements relate to replacing the energy we consume, so to consider how many banks you will need you will also need to reflect on how much energy you require. The best estimate is to assume that your battery bank capacity should be around 3.5 times bigger than what you expect to consume, in terms of energy, per day.
What charger is best for your boat?
Whether you require 2,3 or 4 bank chargers it is important to check that the charger you buy stops charging each battery bank when it is fully charged, so that if only one battery needs charging, all the amps will be sent to that battery.
Although cheaper chargers may seem good value, it is best to pick a big marine brand name, such as ProMariner, NOCO or Minn Kota, as poor quality chargers are likely to overcharge your battery. Overcharging leads to reduced battery life and will force you into early battery replacement, so in the long run, you won’t be saving any money at all!
When choosing a charger, as a rule of thumb, it is good practice to have sufficient amperage to equal the total DC loads of the amp-hour capacity of your boat’s batteries, plus an additional 10%. You should also check battery type as not all chargers a compatible with Gel or AGM batteries.
What amp charger will I need?
Basically, the higher the amps the faster the battery will recharge. You will also need to consider the number of banks your charger can support. As mentioned a bank is essentially the number of batteries your charger can support. However, if you buy a 2 bank charger (or above) you will be able to charge one bank, just make sure to double up the leads and to consult the manual if you need to do this.
Whilst it is important to remember that because of Peukert’s Law (capacity will decrease as the rate of discharge increases), it will be difficult to estimate the exact time your battery will last. A general rule to help you choose the right charger for your needs is to check the amp hours associated with your battery size and multiply by 10%.
With this in mind, imagine you have a battery with size 24 volts, roughly equal to 85 amp hours. In order to estimate what charger you will need, multiply 85 by 10%, which is equal to 8.5. This means to charge efficiently you need a charger of at least 8.5 amps. However, it is highly recommended to round up, so you should go for a 10 amp charger in this example. Moreover, if you have 2 batteries to charge, then a 20 amp charger would be necessary and a 30 amp charger for 3 batteries.
Finally, be sure to remember that most chargers do not support mixing battery types, so all battery types connected to a charger at a given time will need to be the same.
Marine Voltages, what’s the difference between in parallel and in series?
The majority of marine batteries are 12V. If you are looking to charge these batteries in parallel then you can comfortably charge these with a 12-volt battery charger. However, if you are hoping to charge your batteries in series then the charger will need to reflect the total voltage of the batteries in the series. This is a common way to charge lead-acid batteries.
For example, if you have 2 12V batteries connected in series then you will need a charger cable of reaching 24-volts, and for three 12-volt batteries, this would require a charger capable of reaching 36-volts.
How to expand battery life
There are a number of things you can do to either extend or reduce battery life. A key thing to extend battery life is to charge it before storing it, otherwise, sulfates will build up in the battery causing corrosion and prevent the battery storing charge. Leaving batteries deeply discharged for any length of time is a big no-no. Get them charged as soon as you can!
You should also seek to avoid mixing old batteries with new ones if you want to keep your batteries healthy and where possible seek a shallow discharge and maximum of 80% discharge. This will help extend battery life greatly. You will get less life out of your battery with regular deeper discharges.
On the other side, you should avoid undercharging your battery. This with lead to the build-up of lead-sulfate which will harden on their plates, gradually reducing their performance. In addition, the increased resistance to charging, caused by sulfation, leads to false voltage readings which will trick your charger into thinking the battery is fully charged – thus creating a downward spiral!
Just like undercharging, overcharging is also damaging to battery life – especially for AGM and Gel batteries. This can lead to thermal runaway, with the battery becoming hotter and hotter as the electrolyte can be boiled out of the cells!
When selecting the best marine battery charger for you it is important to consider the size of your boat, and how many ‘banks’ you need to sufficiently charge all of the batteries on board. If you are needing to charge batteries fast, make sure you select a charger with a higher amperage.
You also need to think about the safety mechanisms within the charger and be confident that it will not overcharge your batteries, so that you can leave the charger attached, keeping your batteries in the best possible condition. Investing in a quality marine battery charger is an economical choice, as it will significantly improve the performance of your boat batteries as well as extending their life.