You are here because you have a marine vessel with two batteries that need charging. As a buyer, choosing an onboard 2-bank marine battery charger can be frustrating, with so many available. While it can seem like a complicated process, there’s no need to worry, This article will make it easy.
To help you make an informed decision, I have developed this article in three parts. First, is a comparison table off all eight models. Next, are the in-depth reviews of each model. Third, I include a five-step buyer’s guide.
For ease of use there is a clickable table of contents to navigate to a specific product or section. Otherwise, scroll down to discover which of my eight picks are best for you.
Outdoors Informed is reader supported. We independently research and rate every product. When you buy through a link on our site, we may earn an affiliate commission. However, our opinions and evaluations are our own. Outdoors Informed does not accept free products from manufacturers. Learn more.
We updated this article in June 2021 to ensure the smart chargers we recommend meet current standards. For this year a new model hits our best-of list, from the Guest brand. Read on to discover the best 2-bank marine battery chargers for 2021.
June 22, 2021
Share This Article:
Share on facebook
Share on twitter
Share on reddit
Table of Contents
Click To View 4-6
Click To View 7-8
Dual Pro PS2
Minn Kota MK230PC
ProMariner 44012 ProSport 12HD
Ultimate Performance & Repairable!
Premium, Popular & Reliable
Newest Version With Heavy Duty Distributed-On-Demand Charging
For 2021 the Dual Pro “Professional Series 2” repeats as my pick for best 2-bank onboard charger. Unchanged from last year, Dual Pro continues to be the gold standard within the smart charger industry.
I love that it’s made in the USA, plus it’s the first choice of over 50 boat manufacturers and pro bass fishing boats. The professional series 2 (PS2) is a top of the line, 15 amps per bank charger. Compatible with 12/24v DC voltage, with AC input voltage o f115 VAC / 60Hz.
Approved for Wet cell or AGM batteries and can be special ordered for Gel cell batteries too. The PS2 is ideal for group 31 and larger trolling motor batteries. In fact, you can use it on land and in fresh or saltwater. Being this versatile it makes sense for hobbyists and pro’s to trust Dual Pro.
Dual Pro PS2 Features:
Worried about waterproof capability? Fear not, this 2-bank battery charger has the highest rating possible: an IP68 rating. This means the charger is submersible and hermetically sealed. For safety Dual Pro includes short circuit, reverse polarity protection and temperature compensation. I appreciate the simple LED charge mode indicators and onboard diagnostic coding. For installation, it’s easy and flexible.
What separates Dual Pro from the rest: it’s a “green” battery, meaning it is repairable! Unlike other brands, where if the charger gets damaged, you need to replace it.
DeltaVolt Intuitive Charging Technology
Dual Pro employs their “DeltaVolt” smart charging system on all its battery chargers. This is an advanced microprocessor inside the changer. Which provides a five stage controlled and intuitive charge technique.
Automatic charging can adapt to the needs for both cranking and deep cycle batteries. While allowing for safe charging a mix of battery sizes. As a result, this charger is able to connect to many 12-V battery configurations in series and/or parallel. In either 12 or 24 volts outputs, the PS2 provides unmatched charging performance.
I like that it removes the guess work for charging to proper specific gravity levels as well. Plus, it has a maintenance mode to keep your batteries at full charge during storage.
One issue that continues to plague the PS2 is the power cords are too short. Keep this in mind if you don’t have AC power close to your boat. Next is the weight, it weighs 14.5 pounds (6.58 kilogram), for some small boaters this might be a deterrent. For small boaters concerned with weight but want a Dual Pro, read the Sportsman Series 2 review in this article.
Choose the Dual Pro PS2 if you want the absolute best in class smart charger. It is the ultimate smart charger for reliability, safety and American quality. Rest assured that you will own the most versatile choice due to it being the one brand that is repairable. For peace of mind, the Dual Pro comes with a three-year warranty.
Short Circuit, Reverse Polarity, Arc & Ignition Protected
Compensates For Ambient Temperatures
Low Line Voltage Doesn't Lower Charging Ability
History Of Overheating
Minn Kota MK230 PC Review:
For 2021 the Minn Kota MK230 PC is a fast charging precision 2-bank charger. Higher amps per bank equates to shorter charge times, something all boaters like. If you aren’t familiar with Minn Kota, it is a powerhouse of a company founded in 1934, in Fargo, North Dakota. They make the hardest working trolling motors, shallow water anchors, and precision chargers. The company has a trusted following that continues to grow year after year.
Advantages of Minn Kota Precision Technology
Like others, this 12v or 24v charger uses specific technology to deliver fast charging. The difference from other brands is how precise the Minn Kota microprocessors are. To explain what this means lets look at four advantages of precision charging.
The first advantage is that each bank on the charger is independent and isolated from each other. Which means you can select and charge many battery chemistry types at the same time. Such as Wet cell, AGM/(HP) or Gel cell batteries. Like other chargers it can charge batteries in independent, series or parallel connections.
Second, is that it senses and compensates for outside temperature fluctuations. This is important because changing exterior ambient temperatures can damage batteries while charging.
Third, is the automatic compensation for low line voltage problems. For example, overloaded outlets or extension cords can’t provide the full 120 volts. As a result, this 2-bank marine battery charger will sense and adjust to keep a consistent charge.
The fourth advantage pertains to wet cell batteries, this charger has a precise equalization mode. This desulfator mode produces a sudden burst charge to clean the lead plates of sulfation build up.
Other Great Specifications:
Out of the box the MK230PC is a decent weight of 10.5 pounds (ca. 5 kg) and install is simple. Boaters like the LED display that shows charge status and when you need to check the connection. Included is an AC plug holder to keep the charger plug dry, safe and accessible. It’s waterproof with shock and vibration resistant construction for rough water days. The single issue that I found for the Minn Kota 230PC is one overheating complaint. Although Minn Kota’s excellent customer service provided a quick solution.
Buy the Minn Kota MK230PC charger if you are looking for lightning quick charging. With precise charging profiles that control current and voltage without cooking your batteries. It’s the perfect match if you already own a trolling motor of the same brand. Rest assured as Minn Kota offers a 3-year warranty with revered customer service.
In 2021 the ProSportHD 12 Generation 4 marine charger continues to be 2nd place and a top onboard charger. This is the big brother to the older ProSport12. It is a 2-bank heavy-duty charger that’s either 12v or 24v and has variable 12-amp charging capacity.
This charger uses Distributed-On-Demand™ Technology which is an enhanced microprocessor and software control charge. Using 5 automatic charge stages:
Auto Maintain (Energy Saver)
Equalization Mode (Once a Month Storage Recondition)
The final stage is a battery maintainer that allows for safe short and long term storage.
First this charger has a new aggressive heavy-duty tri-surface heat sink design. This upper, lower and rear heat sink provides faster charging with better cooling. At the same time it delivers true rated constant current charging amps during charge mode.
Second, the ProSportHD 12 is up to 40% lighter than most epoxy filled chargers. This is a bonus for small and medium boat owners that need a heavy-duty solution.
Third, is the new dashboard on the exterior of the charger. Now you have simple colorful led lights and gauges. Such as LED completion status, dual mode battery status, real time system check and more.
Other bonuses include built-in safety features buyers come to expect from ProMariner. Including dual inline waterproof fuses, reverse polarity, over-temperature, over-current, over-voltage and ignition protection.
* Note: If you use 4D or 8D large capacity batteries don’t use ProSportHD chargers. For these applications, see ProMariner’s ProNauticP Series.
If you want a lightweight on-board battery charger designed for use in the harshest environments this is a top choice. Best for group 24-31 Wet cell, AGM and Gel cell batteries. It’s easy to install, one that you can plug in and forget. For added confidence ProMariner offers a 2-year warranty on all their chargers.
Want a repairable charger but do not need 15 amps per bank? Do yourself a favor and consider the Dual Pro Sportsman (SS2). This is a 2-bank marine battery charger that’s smaller, lighter and more affordable than the Dual Pro PS2.
At first look the SS2 is a 12v or 24v, 10 amps per bank, temperature compensating battery charger, made in the USA! The size is of the charger means its simple to install. It’s a tough charger that boat manufactures and tournament fishermen trust.
Like the PS2, the SS2 is near waterproof except with a diminished waterproof rating of IP67. Although, for real world applications this change is negligible. Where the SS2 shines is vibration resistance which is paramount for small boats. Plus the body features a powder coated aluminum base suitable for either fresh or salt water.
PROVolt® Intuitive Charging Technology
Inside it uses the 5 stage PROVolt® charging technology using separate microprocessors for each battery bank. This results in each bank’s microprocessor controlling its own charging algorithm. This tech allows for batteries of differing age, size, state of charge, or type to mix on this boat charger. Its also a battery maintainer that’s temperature compensating.
Which is great if your boat is using one starting battery and one trolling motor battery. Keep in mind though that this charger is best for deep cycle batteries up to 110 amp hours. For batteries over 100 AH save weight elsewhere and pick the Dual Pro PS2 15 amps per bank charger.
The best advantage of the DualPro SS2 is like it’s big brother it’s repairable. When something goes wrong the brand will fix it instead of you having to trash it.
One downside of the SS2 is a nuisance this brand is famous for, for some reason they use short power cords. Most companies provide 6-foot cords but Dual Pro gives 3 foot AC power cords and 5 foot DC cords. You will need to ensure power close to the boat which isn’t always available.
Buy the Dual Pro Sportsman Series 2 (SS2) if you want a capable USA made 2-bank marine battery charger. The SS2 is the perfect choice for small boaters. It’s a well priced capable charger from a trustworthy company and repairable. Plus they offer a 3-year warranty, what is not to love? The Nema AC power cord that’s what.
For 2021 the Guest ChargePro 10/10 onboard charger is the model for boaters wanting one that’s simple to use. As of last year, Guest introduced new technology from the inside and out.
This new design has a low profile flange-less body wrapped in extruded aluminum. To ensure the unit is waterproof (IP67), it uses sealed gaskets and heavy-duty end caps. The end product is shock resistant for both fresh and saltwater use. Plus this design delivers an increase in charging and thermal management.
By adding new materials and enhanced tech you’d think it must weigh a ton right? Nope, in fact it’s up to 40% lighter over prior generations. Coming in at 6.6 pounds (2.99 kg), its lighter than most epoxy filled plastic body chargers.
It shouldn’t be hard for you to understand what’s happening during a recharge. To keep it simple Guest provides super easy to understand status lights. With expanded LED display and even battery fault detection display for each bank. It doesn’t get any easier than that.
5 Stage Automatic Charging
Every Guest charger has individual dedicated charging, sensing and control for each bank. This model uses digital automatic 5-stage performance charging. Below is a brief explanation of each stage:
Analyze Mode. First AC Power gets applied and the red charging LED flashes. This stage analyzes for proper connection/polarity, voltage level and ability to pre-charge. If there aren’t any faults are present, the red charge LED will illuminate solid red.
Pre-charge Mode. If battery is under 10v, this pulse charges the battery up to 10.5 volts. At this point the battery can accept constant current (stage 3). During this mode the red charging LED will stay illuminated.
Charging Mode. Red charging LED stays on to indicates each battery is charging in constant current mode. This stage controls temperature of the charge until the battery voltage raises to 14.6 volts DC. At the end of this stage the red charging LED will shut off.
Conditioning Mode. Now the amber conditioning LED will turn on. This mode charges the batteries at 14.6 volts for up to 3 hours until full. After it finishes, the amber light will turn off.
Energy Saver Auto Maintain Mode. The last mode uses a blue LED for AC power and green for auto maintain LED. This mode monitors each battery while in standby mode (long term storage). It consumes little to no power until the battery drops under 12.8 volts. If it does the charger will turn on and auto maintain the battery back to full charge.
Like other high-quality models the Charge Pro 10/10 comes with all the built-in safety needed. I appreciate the heavy-duty strain reliefs for the think cables. Plus, DC wire protection with reverse polarity, over-current, over-voltage, over-temperature and ignition protection. Likewise, the cables are six feet long for easy hook-ups.
Installing it is simple as everything has a simple label and detailed instructions. One thing to note, marketing materials state you can install horizontal and vertical. But the instructions states a vertical install only, that’s the one confusing part.
This is an easy-to-use charger that truly takes care of the guess work. You can hook up and charge without any concerns, something we should all appreciate.
Downsides of the Guest ChargePro 10/10:
The first negative about this battery charger is that it’s only capable of charging Wet cell and AGM batteries. You can’t mix and match other types. The second downside is that Guests’ warranty period is short compared to other brands. It would be nice if they would provide a bit longer period for peace of mind. Third is the speed of charging, it’s not terrible but don’t expect lightning quick recharges.
Buy the Guest 10/10 if you are looking for a simple to use and rugged 20 amp onboard charger. This one is a breeze to install and use but doesn’t charge as fast as others.
Charges Deep-cycle and Starter Batteries up to 230Ah
100% Sealed And Waterproof Rated: IP68 (highest possible)
Charges Multiple Battery Types
Long 5-Year Warranty
Only One 12 Volt Battery Per Bank
Wakes Up/Test Battery Levels Only After 24 hours
Some Recent Quality Complaints
User Manual Could Be Better
NOCO Genius Gen2 Review:
For a budget minded buyer in 2021 the NOCO Gen2 2-bank waterproof charger is a good choice. NOCO as a company has been producing power products since 1914 in Cleveland, Ohio. So you can be confident in their ability to produce a high quality product.
The NOCO Genius series has 100% sealed construction and rated at IP68, as a result it is a submersible onboard charger. Which is great because you do not have to stress about this model operating in extreme environments. Another feature is its versatility for handling many chemistry types. Including: Wet, Gel, Calcium, and AGM (from 25-230 Amp hours). This particular charger is capable of recharging 12v batteries.
Since safety is crucial for automatic onboard chargers, it is good to see NOCO providing a lot of protection. Such as reverse polarity, short circuit, open circuit, sparks, overheating, over-current, and overcharge.
NOCO claims to provide a special mode known as “Abnormality protection.” To clarify, this will automatically turn off the charger if it is in bulk charge mode for an extended period of time. Although I read some complaints that this mode has not functioned for many boaters. If this mode doesn’t function batteries can “boiled off” and die. For boaters using Wet cells this is a factor to consider.
Another feature I find impressive about the Genius 2 is the technology inside. NOCO includes one of the most advanced microprocessor systems for intuitive smart charging. This VosFX microprocessor, monitors input to diagnose, recover, charge, and maintain batteries. It completes this via an 8 stage charging process. The intended result is to give you superior power performance and longevity.
8-Step Intelligent Charging Process
Below is an image eight stages of charging for the Noco Genius Gen2. Followed by a brief explanation of each step.
Step 1 & 2: Analyze & Diagnose. To start, the smart charger checks initial condition, voltage, state-of-charge and health. Both these steps help determine the stability before actual charging starts.
3rd step: Recovery. This is for flooded lead acid or Wet cells. Starts the recovery de-sulfation for discharged or sulfated batteries via short bursts of charges to clean the lead plates of sulfate buildup.
4th Step: Initialize. Begins a slow and gentle start of the charging process.
5th Step: Opportunity & Bulk Charge. Increases the volume of current to 80% of total capacity.
6th Step: Absorption. Lowers the volume of the current to deliver a safe and efficient charge, ups charge to 90% battery capacity. By lowering current, the charger limits off gassing and prolongs useful life.
7th Step: Optimization (Float charge). Finishes the charging process and brings the battery to complete capacity. Known as trickle charging, it stabilizes the charge to optimize the specific gravity.
8th Step: Maintenance: Maintenance will turn on if the battery tells the charger it needs more current. Like the float stage, except it recharges the battery if voltage is below the right threshold. It recharges the battery until it reaches its optimal state. In effect the battery charger can stay on all the time without the overcharging risks.
Buy the NOCO Genius2 20 amp 2-bank charger if you want a budget friendly, waterproof smart charger. One that is capable of charging two individual 12v marine batteries. But be aware of the overcharging issues with this smart charger.
Want a cheap lightweight marine battery charger that doesn’t skimp on performance? The best choice for you is the ProMariner ProSport 12.
This is an onboard battery charger with two banks, variable 12-amp charging capacity and up to 24-volt output. It’s versatile, since you can use it with many battery types. Including Wet cell/AGM, High Performance (HP) AGM, and Gel cell batteries.
As a smart charger, it uses digital microprocessors and includes “Distributed-On-Demand Charging.’ In addition, it has safety features like dual in-line DC safety fuses for trolling/house battery banks. As well as built-in over-voltage, overload, over-temperature, reverse polarity and ignition protection. Given this combination of technology and safety, you can rest easy using this charger on your boat.
100% Distributed-On-Demand Charging
This is the key feature for this charger and beloved by customers who choose the ProSport 12. This is automatic multi-stage charging, for example if the starting battery has the least amount of charge left it will receive more amps. While the remaining charging amps go toward maintaining the trolling motor or house battery(s). As a result, this controlled pulse charging technology delivers cooler charger operation and fast efficient charging.
The ProSport 12 is a rugged 2-bank battery charger made of extruded aluminum, that’s waterproof and shock-proof. It is easy to install and operate.
I like the LED display for at-a-glance status of the different modes. Such as AC power, charging status, battery type, and energy saver/reconditioning modes. The latter are 2 special modes distinctive to this charger. Energy saver mode tracks and auto maintains batteries to ensure they keep a full charge. Which reduces AC power consumption, lowers operating costs and maximizes reserve power performance.
For more versatility the ProSport 12 has the special reconditioning mode. In short or long-term storage, this smart charger will check and top up all batteries on board a single time a month. Having this feature ensures you can be confident that your marine batteries will last long and have proper performance.
Bigger Than Other Chargers
After lengthy research, some concerns boaters have been their mixed feelings about total life expectancy of this charger. Other issues were common to most purchases, including cosmetics, size, or price. Regarding the size, this charger is a bit bigger than other chargers, so be aware if you own a small boat. On the other hand, the appearance or cost issue is up to you.
Buy the ProMariner ProSport 12 if you value a lightweight and simple to use smart charger. One that has impressive on-demand charging mixed with high quality built-in safety features. For added confidence ProMariner offers a two-year warranty.
This 2-bank marine charger is for buyers who own cruisers, sailboats, yachts and commercial/large fishing boats. As I am sure you know, boats like these power setups are different. They use a common ground, set up for AC shore power and some times use an onboard generator/inverter. These set-ups use larger batteries such as 4D or 8D mixed with group 24-31 batteries and an inverter to power the boat.
To speed up charging of these battery set-ups knowledgeable boaters trust the ProNauticP Series of vented battery chargers. If you use a 4D or 8D mixed with another group battery on your boat choose the ProMariner ProNautic 1210P as your 2-bank charger.
ProMar Digital Charging
The ProNautic 1210P employs the ProMar digital performance charge platform. Which combines digital control and software-based power conversion technology with global energy management. In layman’s terms it means you have 12 digitally-controlled performance charge profiles. Combined with 4 main charge profiles including the following:
In fact the ProNautic 1210P can charge batteries that are under load or not in use.
5 Exclusive Features Of The ProNauticP Series:
First, the 1210P has power factor correction with auto-ranging global AC input. Allowing it to operate off standard household power connections throughout the world.
Next the second feature, like all ProMariner chargers, uses distributed on demand charging. This will sense and distribute the available charging amps to the bank which needs it the most. As well as maintaining the other battery bank.
Third to help conserve energy, this charger has a special energy save mode. In this mode after 72 hours of not seeing a load greater than 5 amps, float voltage will lower. As a result it consumes less energy during storage periods. Lowering operating costs and maximizing reserve power.
Fourth, I love the simple-to-read LED indicators on this charger that show service and fault mode. Showing real time wiring faults or adverse conditions. Other indicators show charging voltage, amperage and AC power-on diagnostics.
Fifth is the automatic fan inside the charger to keep it cool during operation. The high quality fan the ProNauticP uses is quiet and efficient. Plus the innovative front exhaust prevents restriction of air flow and cooling.
An added bonus to the ProNautic 1210P is the included remote temperature probe. It’s simple to use as it is plug and play. Connecting it will make the charger adjust its charge based on battery temperature.
Old 2-Bank Marine Battery Charger Issues Addressed
I don’t have 4D or 8D batteries, any issues noted in this article I found via online forums. In 2017 customers noted overheating issues for older models. Although, if users follow the manual to set up the custom charge profile the issue fixes itself. Other than this, I didn’t find any more issues.
If you own a boat that uses large capacity batteries like 4D or 8D pick this charger. You get an awesome smart charger that plugs in around the globe. With the ability for deliver efficient charge to batteries in use or during storage.
How To Choose A Boat Battery Charger:
Follow these 5 steps to help you choose the right marine battery charger. Doing so will ensure that you avoid buying the wrong charger for your needs. Alright, let’s get started.
Step 1: Identify What Battery Type You Use
Most boaters use 3 chemical types of marine batteries: Wet cell, Gel, and AGM batteries.
Wet cell battery: Needs Maintenance & Considered Hazardous Material
A wet cell or flooded lead-acid battery, is the traditional choice for hand-on boaters. This is due to the simple lead-acid internal construction which you need to maintain. The lead-acid system inside the battery comes in two parts, first are some lead plates and second is the acid solution. To create power, the acid comes in contact with the lead plates creating a chemical reaction.
To further explain, lets look at the interior construction of this type of battery. The acid is an electrolyte fluid, water (distilled)makes up one half, which needs refilling and the other half is sulfuric acid. Since the water needs periodic refilling the cap is removable. Plus the chemical reaction creates hazardous off-gases. To be safe, the installation of this battery needs to be in a vented area of a boat. This traditional battery type is popular because it handles overcharging better than Gel Cell or AGM batteries. Likewise, it is inexpensive and will not overheat as much as the other types. Keep in mind, you have to mount a wet cell battery vertical or it will leak through the unsealed top cap.
One thing to look out for with a wet cell is that it requires a battery charger with an “equalization mode.” An equalizing mode is a deliberate overcharge to the battery to remove sulfate crystals that build up on the lead plates over time. Sulfation build up lowers the capacity of the battery and can render the battery useless. Another factor to watch out for is hazardous hydrogen off gassing during the equalization mode. This off gassing is a fire hazard and promotes corrosion to chargers installed near the batteries.
Gel cell batteries: Maintenance Free
A Gel cell is the next technological advance of a lead-acid battery. Where it differs from a wet cell is that it is a sealed battery, as a result it is maintenance free and spill proof. Another difference from a wet cell is the interior construction. Inside it has a thickened electrolyte fluid from adding a gelled substance. In fact a Gel cell operates under pressure, forcing gases created during charging to remix into the water. For this reason it eliminates the need to refill water for the battery.
The downsides of these batteries are overcharging and over heating. As a result, many boaters have moved on to AGM batteries. For those boaters that do choose to charge a gel cell battery, you must use a charger with both voltage and temperature monitors.
Learn More:How To Choose A Marine Battery
Absorbed Glass Mat (AGM): Maintenance Free
An AGM Battery is a combination of the two previous types with one key difference. This difference is a lead plate separator made of woven glass fiber sheets. Adding this separator aids in providing more consistent power. To explain, each glass sheet soaks in electrolyte which in turn absorbs and suspends the fluid. This results in the electrolyte fluid always being in contact with the battery plates. Constant contact with the plates enhances both the discharge and recharge efficiency. Likewise, the container comes sealed which is spill proof and vibration resistant.
Similar to gel cell batteries, AGM batteries are sensitive to overcharging. To explain, overcharging boils off the acid, damaging the plates, and killing the battery.
In general, AGM and gel batteries need special smart chargers to prevent overcharging. Unlike a wet cell battery that can use a digital charger. Either way, I prefer safe and fast charging for my marine batteries and recommend using smart chargers.
“Smart” chargers can charge a variety of battery types. While being safe and accurate using multi-stage charges, but more about that later. To ensure safety, check for a label that states it will work with the chemical type you use. Since every smart charger is different.
One last note, do not try to charge a gel cell at the same time as the other types on one charger. Gel cells need a lower voltage at the bulk and float stage. As a result, if you mix with the other battery types, one battery (the gel cell) may become damaged beyond repair.
Step 2: Determine The Number Of Banks Needed
Simply put, the number of banks needed, is the number of batteries the charger is able to charge at the same time. So if the charger has the “2 banks” label, it can charge 2 batteries within your boat at the same time. Although, if you have one 12V starter battery and two 12V trolling motor batteries you need a three bank charger. Otherwise, if you use one battery you can use a single bank charger.
To add confusion, there are instances when a “bank” is several batteries wired together. This is to allow these batteries to act as if they were a single, larger battery. With this in mind, smart chargers will allow one output per bank.
Each charger has outputs with separate positive and negative terminal connections. Plus per-bank microprocessors. To allow a charger to handle different types, sizes, and state of charges. Remember to be careful, what you can connect to a charger depends on the battery charger size.
We don’t mean physical size of a charger but the actual capability of the charger. This refers to its amp and voltage rating. The amp rating will answer the amount of time the charger takes to charge batteries. While a voltage rating determines if the charger matches the wiring of your batteries.
For amps the simple answer is: the higher the amp rating, the faster the battery will recharge. To calculate what is a suitable amp rating you will do some simple math.
Amp hour rating on battery(s) X 10% = charger amp rating
Example (group 31 battery) 100 amp hours X 10% = 10 amp rating
To determine your total charge time, do another quick calculation.
For voltage, it is critical to make sure that your output voltage matches the voltage on the charger.
Most small/medium-sized boats use 12 volt batteries, some will use one battery but most use two or more. Most boaters will use two batteries to gain more amperage, but want the voltage to remain the same. To accomplish this they wire the batteries in parallel.
Two 12 volt batteries wired in parallel, will output 12 volts, so you need a 12 volt charger.
If you want increase the voltage but keep amps constant, you wire batteries in series. Two 12 volt batteries wired in series makes 24 volts, like when powering a trolling motor.
For two 12 volt batteries wired in series, they change to outputting 24 volts, now you will need a 24 volt charger.
Many boaters get confused, a 24 volt charger will not charge a 12 volt battery faster. Attempting this destroys the battery, the charger, and can cause a fire on your boat. To reduce this hazard 12/24, 36, and 48 volt specific chargers exist.
Step 4: Choosing A Power Source
You will either power your chargers with continuous or intermittent AC power. So you will have some things to consider which factor into what kind and the size of the charger you want.
Many boats spend most of their week at a dock, with a charger connected to shore power. For this situation you can buy smaller amp rated chargers that have constant 120 VAC power. Find one that can handle the DC system and deliver proper power to float-charge your batteries. A good rule is the following:
Have enough amperage to equal the sum of the DC loads plus 10% of the amp-hour rating of the batteries.
Or if you spend more time out on the water than on shore you need to factor in intermittent power. Keep in mind the amount of capacity you need until the next recharge. One helpful tool is a battery monitor, such as the Victron BMV-700 Monitor. Some large boaters use an inverter generator to provide power to chargers on the water. But these may overcharge Gel and AGM batteries. So I recommend adding more battery capacity to be safe. Large battery banks accept more charging amps, so they replenish faster. As a result, you spend less time worrying and more time cruising the waters.
Step 5: General Considerations
The following list contains some general things to look out for, with a basic explanation of each.
Multi-stage Charging: A smart charger is “smart” because of how it charges and protects your batteries. To provide precision charging a smart charger will it take temperature and battery chemistry into account. It does this with built-in microprocessors that charge each battery in multiple stages. How many stages and which safety options are available will depend on the charger you choose. When using a smart charger the batteries will charge fast, be safe and will maintain them when not in use. Yes, a smart charger is more expensive than a digital model but it’s worth the extra cost. Due to it aiding in extending the life of the battery.
Vibration resistant: A high quality 2-bank battery charger should withstand shocks from wave impact.
Waterproof construction: It is critical that water cannot leak inside a charger. Water will destroy the microprocessor inside as well as produce shock and fire hazards. High quality manufacturers will build to a specific (IP) waterproof standard. The chart below explains each.
IP Waterproof Chart
Mountable: If you choose an onboard 2-bank battery charger it should be easy to install. Some charger companies will include mounting hardware and others won’t. If they aren’t included, it’s important to find corrosion resistant hardware approved for use on your vessel. As well as following the manufacturer’s installation methods when mounting. Finding and installing with proper hardware will ensures a clean installation and reduce the risk of damage to the charger or your boat.
Choosing the best marine 2-bank charger in 2021 doesn’t have to be hard. Follow the five steps to choose a charger above, and buy based on what you have learned.
In the end, thanks for letting Outdoors Informed help with your research, so you can spend more time out on the water.