Best Marine Boat Battery 12V Guide

Best Marine Boat Batteries – A Complete Guide

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Best Marine Boat Batteries

Below is our selection for the best marine batteries. While these are our top picks, be sure to read the remainder of the article to ensure you are purchasing the right battery for your needs. Links will open in a new tab.

Best Cranking / Starting Marine Battery

Best Marine Boat Battery Optima Starting Cranking Deep CycleOptima BlueTop Starting Battery

For a starting battery, you need one that’s going to be reliable, durable, and able to perform when you need it to. That’s why the Optima BlueTop Starting battery is our top pick for a cranking/starting battery. Optima is a well-known brand and uses spiralcell technology to build their batteries which offers a more energy-dense cell.

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Best Deep-Cycle Marine Battery

Best Boat Battery Renogy Deep Cycle Gel Renogy 100Ah Deep Cycle Pure Gel Battery

Renogy is better known for their solar power charging kits, which you should check out if you’re in the market for one. However, they make a pretty damn good battery too. With or without a solar kit, this battery simply performs. Utilizing high purity lead and a patented gel electrolyte, this battery is the best deep-cycle option available. A perfect option for building a battery bank.

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Best Trolling Motor Battery

Best Marine Boat Battery GreenLife Lithium Ion Deep CycleGreenLife GL Lithium-Ion Series or Universal Deep Cycle AGM

For small watercraft weight tends to play a factor in the battery you purchase. If you have the funds, purchasing a lithium-ion battery is ideal. Lithium ion batteries are incredibly lightweight, and are very compact compared to other types. Depending on your power needs, a 50Ah or 100Ah is the way to go.

For 50Ah (pictured), try the GreenLife GL50 50Ah Lithium-Ion Battery. For 100Ah, try the GreenLife GL100 100Ah Lithium-Ion Battery.

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Best Marine Boat Battery Universal Deep CycleIf the price for a lithium-ion battery is a bit out of your budget, try Universal’s 100Ah deep cycle AGM battery. It’s a great battery at a reasonable price.

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Best Lithium-Ion Battery

Best Marine Boat Battery Renogy Lithium ion Deep CycleRenogy Lithium-Iron Phosphate 100Ah Battery

Renogy takes another spot! Offered both in 100Ah, and 170Ah options, their lithium-iron (yup, you read that right, lithium-iron) phosphate batteries are a fantastic option for storing energy for multi-day use. If you plan on building a battery bank and have a larger budget, this is the way to go. The 100Ah model weighs under 30lbs, and the 170Ah model weighs less than 50lbs.

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Best Boat Battery Value

Best Marine Boat Battery Universal Deep CycleUniversal 100Ah Deep Cycle AGM Battery

Nothing fancy about these batteries, but they’re tough and they’ll do their job. This is the economic option for a deep cycle AGM style battery. Each puts out 100Ah and if you’re working on a budget battery bank or need to replace another deep cycle battery and keep it cheap, here’s your best option.

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Best Battery for Boat Lift Motor

Best Marine Boat Battery ExpertPower Boat Lift Deep CycleExpertPower 33Ah Deep Cycle Battery

You’ll want to consult the owner’s manual for your boat lift, but you generally won’t need a battery with a lot of power. ExpertPower’s battery is an AGM 33Ah deep-cycle battery. Hook this up to a drip feed solar charger and you’ll have all the power you need to operate your lift whenever you need it.

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Best Dual-Purpose Marine / RV Battery

Best Marine Boat Battery Odyssey Thunder Dual PurposeOdyssey Thunder Marine Dual-Purpose Battery

Don’t have the space for a cranking battery and deep-cycle? Here’s your next best option. Odyssey batteries are built to last. They’re strong, reliable, and have a strong warranty behind them. This model in particular provides 880 CCA and a RC of 135 minutes. Perfect for a boat or RV.

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Types of Marine Batteries

Buying a battery for a marine vessel is a little bit different than buying one for your car or truck. There’s different types of batteries and different needs that need to be taken into account throughout the purchase process. By the end of this guide, you’ll have answers some of the most common questions like:

Cranking (aka starting) vs. Deep-Cycle Boat Batteries

Cranking Starting Batteries Vs Deep Cycle Batteries

What is a Cranking  or Starting Boat Battery?

Whenever starting any sort of large engine, whether a boat or a car, there’s a large amount of energy needed in a short amount of time. In order to provide this burst of energy, cranking, or starting, batteries are designed with this intent in mind. No need to get into what these batteries look like on the inside just yet, we’ll cover that shortly.

What to look for

Most likely you’re boat came with a battery, which should be a good indicator for the kind of Marine Cranking Amps, or MCA, you’ll need for you new battery. Regardless, it’s recommended to check the owner’s manual to be sure the battery in previously was providing enough power. The MCA rating on the new battery needs to meet or exceed the recommended rating.

If your boat is recommended to have a 700 MCA battery, you’ll need a 700 MCA or 700+ MCA rated battery. A 800 or even 900 MCA battery will work just fine. Just be sure to take measurements of the old battery, or better yet, take it with you. The new battery will have to fit in the limited space the old battery was living in.

CCA vs. MCA vs. HCA Cranking Amps

What is a Deep-Cycle Boat Battery?

If you have a trolling motor on your boat or plan on constructing a battery bank, a deep-cycle battery is the way to go. A deep-cycle battery is different from a starting battery in it’s meant for a longer, slower pull of power. Instead of a quick burst in a second or two, these batteries are built for hours of gradual pull.

What to look for

If all you’re powering is a trolling motor and a few small accessories, you’ll be able to add up the power usage from those, the estimated time you’ll be using them and make some calculations. There are other factors you will need to account for such as depth of discharge. DoD is basically how much of your battery use before recharge. Since it’s not good to run batteries all the way to 0%, most manufacturers recommend not going anywhere below 20%-25% of power. Doing so significantly reduces the battery’s lifespan.

The exception to this rule is lithium-ion batteries. A lithium-ion battery can run 100% DoD, without harm to the battery. However, with all batteries, the shallower the discharge, the more cycles you’re able to get out of the battery. For example, if you get get 1000 cycles out of a battery at a 50% DoD, then you may be able to get 1200 cycles at a 70% DoD, ignoring other factors.

For even smaller batteries, some manufacturers do not recommend going below the 50% threshold. Your functional power is essentially cut in half.

If you have a lot of gadgets to power, BatteryStuff.com has a simple calculator. (Opens in a new tab)

A Realistic Example

Let’s say you have a single trolling motor that provides around 40lbs of thrust. This is roughly 2/3 of a HP, 500 watts, or 40 amps at 12.6 VDC. Here, were rare assuming 746 watts equals a single horsepower and 58lbs of thrust equals a single horsepower.

You decide to purchase a deep cycle wet cell battery which has a 100Ah (Amp hour) rating at 20 hour rate, meaning it functions at a draw of 5 amps per hour. Since this is a smaller battery, you won’t want to discharge this past the 50% point, leaving you with about 50Ah of functional power.

If you use the battery for 30 minutes every time you’re out fishing, the result is 20Ah of use (.5 x 40 amps). With 50Ah of functional power, you could take 2, 30-minute trips before needing to recharge the battery. However, these calculations don’t take into account other factors, like battery age, temperature, etc.

In a perfect world, you could get 2, 30-minute trips. However, in reality you’re safe getting in that single trip with some extra time to spare if you want to take the long way home. Rate of discharge and other accessories will draw power from the battery and simply said, you’ll want to charge the battery after every trip.

A Word of Caution

Do not switch out one battery type for the other. These batteries will be clearly labeled and if for some reason the label has become unreadable, don’t risk it. Using a cranking battery in a deep-cycle application will cause it to overheat, fail, and / or possible start a fire. A deep cycle battery in a cranking application typically won’t work. In the event it does, it’s likely to not start up the second time since deep cycle batteries take a significantly longer amount of time to charge. Better to be stranded ashore, then on the water.

 

Other Factors

Temperature

Batteries don’t like the cold! In colder climates, and generally any temperature below 70 to 80 degrees Fahrenheit, you’ll likely see a drop in performance. In sub-freezing temperatures, wet-cell batteries can even freeze and become useless. There isn’t a hard-and-fast rule for battery usage in colder climates, but just know you’ll likely need a stronger battery if the weather around you isn’t 70+.

Additionally, wet-cell batteries self-discharge during warmer temperatures at around 1% every 24 hours. In a few weeks’ time, it’s not unlikely the battery could have lost 20Ah of power. It’s recommended to purchase a solar panel charger in order to prevent this. More on solar chargers here.

This chart shows that as the temperature drops, so does a battery’s ability to hold a full charge. On the other hand, the battery’s ability to hold that charge increases. Remember Grandpa storing his batteries in the freezer? | Source: Donovan D. Devore – https://wiki.uiowa.edu/display/greenergy/Battery+Systems+Overview

Power Draw

The rate at which power is drawn from the battery also has an effect on the battery’s lifespan and use. This pertains more so to deep-cycle batteries. When a lot of power is drawn in a short amount of time, this not only shortens the lifespan, but also lessens the total functional power you can utilize. A significant portion of that energy is lost as heat.

Dual-Purpose Batteries

If you’re town between a cranking battery and a deep-cycle battery, there is a middle ground! Dual-purpose batteries give the best of both worlds without having to worry about frying a battery in the process. If possible, it’s best to have a separate starting battery and a separate deep-cycle if you have the need for both types. However, there scenarios where that isn’t possible, like if you’re limited on space.

What to look for

For a dual-purpose battery, you’re looking for the same factors and specs you would on a cranking or deep cycle battery. You need to make sure your CCAs meet or exceed the requirements of your motor, and make sure the reserve capacity will suffice for your intended usage.

 

Four Types of Batteries: Wet-Cell (aka Flooded, Flooded Cell, Lead Acid), Gel, AGM (Absorbed Glass Mat), and Lithium-Ion

Wet-Cell Batteries

Wet-cell, or flooded-cell batteries are your most basic batteries in boats, cars, SUVs, trucks and pretty much anywhere you need to draw a large amount of power in a short amount of time. They’re the most affordable option available, but also tend to require the most maintenance.

These batteries contain many lead plates that live in a mixture of distilled water and sulfuric acid. While we won’t get into how they work (that was for high school physics), the important thing you need to know is they’re capable of up to 1000 discharge/recharge cycles. This means they can last for years if well taken care of, at a low cost.

These batteries are less likely to be damaged by overcharging and for weight to energy output, they tend to weight the least. The problem with these batteries is you need to be checking the water levels to ensure they’re full. The additional problem with having to check these levels is insides of the battery are accessible which means they could potentially spill or leak battery acid in applications where there’s lots of movement – like a boat. When opened these batteries release hydrogen gas, which is flammable, so maintenance needs to be done in a well-ventilated area.

Lastly, these batteries do self-discharge. So when left off of a charger and not being used they typically discharge somewhere between 1% a day to 7%-8% per month, depending on factors like age and temperature.

Gel Batteries

Gel batteries solve many of the problems wet-cell batteries have, but at a cost. These batteries are sealed at the time of production, so these batteries are maintenance free. Instead of lead plates living in an acidic solution, these batteries are filled with a liquid electrolyte that is gelled with silicates.

As mentioned earlier, these batteries are meant to be used (or discharged) at lower rates over longer periods of time. Because of these, they can be stored for extended periods of time without worrying about losing power. Compared to a wet-cell’s of up to 1% per day, these batteries lose less than 1% of power per month.

Downside to these batteries is they’re typically more expensive and a special charger, or at least one with a gel-setting needs to be used. These are recommended to be charged to 13-14 volts.

AGM Batteries

AGM stands for Absorbent Glass Matting, meaning these batteries are composed of a dense filling of glass threads that are woven together to form a literal mat. These designed to wick the battery electrolytes between the lead plates.

Similar to gel batteries, these are sealed at production, meaning essentially no maintenance is required but some external cleaning. The downside to these batteries is they are sensitive to overcharging (rendering them virtually dead if overcharged), and are more expensive than their wet-cell cousins.

Lithium-Ion Batteries

Whether or not you know it, you use lithium-ion batteries on a daily basis. They’re in our cars, phones, power tools, and other electronics. The largest benefit with lithium-ion batteries is their lifespan and the energy density. Compared to other battery types they can hold more energy in a smaller amount of space and for a longer period time. When it comes to weight, these batteries win again. A 100Ah battery will usually weigh around 30lbs or so, compared to a AGM that will weigh 70lbs+. Lastly, there isn’t any reason to worry about depth of discharge. Lithium-ion batteries can be fully discharged without damage – this makes them great for building a battery bank.

The downside is, these batteries are far from cheap, however, they will typically last up to 7-10 times longer than some of the batteries already mentioned.

Other Specifications

CCA vs. MCA vs. HCA

Marine Cranking Amps and Cold Cranking Amps are essentially the same thing, just with a 32 degree Fahrenheit difference. You may see that your car battery has a CCA rating. What the CCA rating means is it tells how many amps the battery can send for 30 seconds at a 0 degrees Fahrenheit before the voltage drops to 1.2V per cell or 7.2V for a 12V battery.

Thus a 12V battery rated at 800 CCA, will provide 800 amps for 30 seconds at 0 degrees Fahrenheit before the voltage drops to 7.2V.

MCA on the other hand, is same measure, but at 32 degrees Fahrenheit. Sometimes ‘MCA’ is simply referred to as ‘CA’, or ‘Cranking Amps’. So, a battery rated at 1000 MCA (or CA), will provide 1000 amps for 30 seconds at 32 degrees Fahrenheit before the voltage drops to 7.2V.

HCA is less common, but sometimes you’ll see this rating too. HCA stands for Hot Cranking Amps and refers to the same measurement, but at 80 degrees Fahrenheit.

Reserve Minutes

Earlier we went through the calculations for a battery powering a trolling motor. There is another measure you can use for either building a battery bank or powering a trolling motor and that’s the reserve minutes, or also called the ‘reserve capacity’. This measure is expressed in minutes and tells how long a fully charged battery can provide a constant load (typically 25 amps), before it’s fully discharged.

For a 12V battery, it is fully discharged, once it has fallen to 10.5 volts.

Group Size

The group size is a categorization given by Battery Council International, or simply BCI. These sizes are apply to all battery types, including automotive, utility, and commercial applications. There’s a lot of different sizes and if you really want to dive through all of them, a chart is on this site here.  Group size isn’t super important, just make sure you take your old battery with your to compare sizes and purchase a battery with the same or higher CCAs.

 

Tips for Optimal Battery Performance

General Maintenance

This is specific for wet-cell batteries but cleaning any sort of corrosion that builds up around the terminals is a must. Too much corrosion can lead to a bad connection. Use a disposable shop towel to wipe away corrosion and other debris into a trashcan – don’t sweep this into the water.

If the corrosion is really bad, you’ll want to remove the connections and take a wire brush to terminals and wires. Once the metal has been cleaned, using a battery corrosion preventative such as NCP2, is highly recommended.

Lastly, doing some basic visual checks can go a long way. Make sure the case isn’t bulging or cracked. This could indicate overcharging and you will want to check your charger and alternator as well.

Winter Storage

If you’re winterizing your boat, you will want to full charge your battery and then disconnect them from the terminals. If you have a flooded cell battery, be sure it has enough water before charging. Depending on how long the battery is in storage, you’ll want to check it periodically and ensure it’s fully charged. If you don’t have the ability to check/charge the battery on a least a monthly basis, it’s highly recommended to purchase a trickle charger or a solar trickle charger if left out in the sun.

Consider a Battery Box

A battery box is exactly what it sounds like – it’s a protective housing for your battery. A battery box is excellent protection against the elements while still allowing the cables to be ran inside of the box. Boxes are typically vented to allow any gasses that might need to ventilate. These boxes will collect any battery acid that may leak and they make it incredibly easy to tie down and secure the battery.

Charging and Discharging

As was mentioned earlier, batteries should not be pushed past their depth of discharge as specified by the manufacturer. For deep cycle batteries, they should not go below a 20% capacity, with starter batteries, they generally shouldn’t go below 70% of their charge.

Always charge your batteries after use and do not mix different types of batteries together. Whenever replacing a battery, be sure all the batteries in your system are replaced at the same time. Older batteries tend to decrease the lifespan of new batteries. Never leave batteries deeply discharged for any significant period of time.

What to do with old batteries?

Whenever you purchase a new battery, automotive, marine, or whatever, there will be a core charge added to the cost. This will depend on the size of the battery, but it’s typically around $10-$20 in the US. This core charge is refunded when an old battery is returned to be recycled.

Where To Recycle Old Batteries Graphic

Most of the time, if you have multiple batteries, retailers will be happy to take those batteries off your hands for recycling. Home Depot, Lowe’s, AutoZone, and Rural King are a couple just to name a few. Be sure to call ahead to check. Otherwise, check with your city’s recycling program. EarthCity911.com and  Call2Recycle.Org are also 2 additional resources that can point you in the right direction.

 

Boat Battery FAQ

Can a boat battery get wet?

A marine grade battery can get wet, but only to an extent. Don’t forget, we’re dealing with electricity here. Electricity and water don’t mix, so avoid contact as much as possible. No battery should ever be sitting in any pool or puddle of water. However, most batteries will be fine if they get a little bit of rain on them. It’s highly recommended to store your battery in a battery box to protect it from the elements.

Can a boat battery be used in a car?

It depends on the application. If you plan on using it to start the car, then you need to use a cranking battery that meets the CCA required by your vehicle’s 12V electrical system. In general, if you’re using a cranking battery and the boat battery meets or exceeds the vehicle’s requirement for CCA, then yes you can.

Can you overcharge a boat battery?

Yes you can. While certain batteries are more sensitive to overcharging, like the AGMs mentioned in this article, all batteries can be overcharged. Once overcharged, they can be dangerous to handle and rendered almost useless in certain situations.

What boat battery do I need?

The type of battery you will need depends heavily on the use and requirements of your boat. Generally speaking, if this battery is only used to start up the motor, then a cranking battery is needed. If you are using a trolling motor or looking to power electronics on board, you’ll need a deep-cycle battery.

How long will a boat battery last?

The lifespan of a boat battery will vary greatly based on age, climate, use, and other factors. As each year passes, the total lifespan of the battery loses its ability to hold a charge. For example, a battery that could provide 100% of power at the start of its life, will likely only be able to provide 75% of its total power in 3 years. This number begins to increase significantly has time goes on.

How do I test a boat battery?

To check the voltage of any battery, you’ll need a multimeter. These can purchased fairly inexpensively from Amazon or your local hardware store. To test the battery you’ll want to disconnect the battery from the boat, set the multimeter to DC (or direct current), and connect the alligator clips to the correct terminals.

A fully charged battery will be around 12V or higher. If the reading comes less than 10.7V to 11V, it may be time to replace the battery. You may opt to purchase a multimeter than can perform a load test. A load test is simply a measure of how the battery performs under simulated use. While under a load test, the reading should be somewhere around 9.5V to 10.5V for 30 seconds total.

How do I charge a boat battery while out on the water?

To charge a boat battery while on the water you must have a charger or alternator built into your engine or some other means of replenishing power such as through a solar charger.

Do outboard motors recharge the battery?

Yes, most modern outboard motors have an alternator built-in to recharge the battery.

 

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