The motor in your boat needs a battery to start, just like a land-based vehicle. Boats have different power needs than cars and trucks, and the wet conditions add extra challenges. The best marine battery needs to provide consistent power and have protections against moisture, vibrations, and temperature fluctuations.
We’ve picked out our favorite marine batteries and compared them side by side so you can figure out which is the best option. Factors like portability, reliability, power, and price were all included in our decision. Read on to learn which models performed the best and which give you the best value for your money.
- 1 Comparison Table – Best Marine Batteries
- 2 Buying Guide
- 3 Product Reviews
- 3.1 Belter PK12350 DC Power 12-Volt Marine Deep Cycle Battery
- 3.2 Mighty Max ML55-12 Electric Trolling Motor
- 3.3 Universal UB121000-45978 12V Deep Cycle AGM Battery
- 3.4 Optima Batteries 8006-006 34M BlueTop Marine Starting Battery
- 3.5 Renogy Li 12V Smart Lithium Iron Phosphate Battery
- 3.6 Optima Batteries 8016-103 D34M BlueTop Starting and Deep Cycle Marine Battery
- 3.7 Optima Batteries 8027-127 D27M BlueTop Starting and Deep Cycle Marine Battery
- 3.8 Odyssey 34M-PC1500ST Trolling Thunder Marine Dual Purpose Battery
- 3.9 Optima Batteries 8052-161 D31M BlueTop Starting and Deep Cycle Battery
- 3.10 Odyssey 31M-PC3150ST-M Trolling Thunder Marine Dual Purpose Battery
- 3.11 The Bottom Line
- 4 FAQs
- 4.1 How do I add water to these batteries?
- 4.2 What does “group type” mean, and how do I know which one I need?
- 4.3 What kind of charger is best for marine batteries?
- 4.4 How often should I charge a marine battery?
- 4.5 What’s the difference between a marine battery and a deep cycle battery?
- 4.6 Do I need two batteries in my boat?
- 4.7 How long do marine batteries last?
Comparison Table – Best Marine Batteries
Optima Batteries 8006-006-FFP 34M Marine Battery
Optima Batteries 8052-161 D31M Battery
VMAX MR127 12 Volt 100Ah AGM Battery
|Dimensions||12.1 x 11.8 x 11.5 inches||12.8 x 6.5 x 9.4 inches|
|Reserve capacity (minutes)||100||155||200|
What is the Purpose of Your Marine Battery?
There are three main types of marine batteries based on what role they serve. Deep cycle batteries are designed to give up more of their stored energy before they take damage. They’re most often used for trolling motors because they can provide continuous power for several hours.
Starting batteries serve a similar function on boats that they do in land vehicles. They put out a high amount of power in a short burst to start the boat’s engine. While they can provide more one-time power, they aren’t designed to provide continuous power. Using a starting battery for trolling could permanently damage it.
Dual-purpose batteries are a hybrid of the two types above. They can provide short bursts of power to start an engine, or provide a lower level of power continuously to run electronic systems and trolling motors.
What Do You Expect Out of the Battery?
Now that you know about the different types of marine batteries, the next step is to figure out which one you need. Here are some questions to ask yourself as you’re shopping.
- Does your boat have a lot of electronics and creature comforts? Along with starting the boat, the battery powers on-board electronics. This includes everything from the lights on the dash to aftermarket sound systems and appliances. The more electronics your boat has, the more battery capacity you’ll want to power them.
- What conditions will the battery be used in? All marine batteries need to be durable to stand up to the vibration and moisture they encounter out on the water. If you’ll be using the battery in extreme heat or extreme cold, though, you’ll want to look for one with extra protection against the elements.
- Will the battery be sitting for a long time between uses? Batteries lose charge over time when they sit on the shelf. The battery’s self-discharge rate tells you how long holds its power. If you use your boat seasonally or occasionally, look for a battery that lasts a long time in storage.
Cranking Amps and Capacity: Do You Need the Best Performance?
There’s a lot of variation in the size of boat engines. As a result, they’ll need drastically different power levels to start. Generally speaking, the larger the engine and the boat, the more cranking amps it takes to get it moving.
For starting and dual-purpose batteries, you’ll want to look at the Marine Cranking Amps (MCA) and Cold Cranking Amps (CCA) to determine what kind of one-time power it can produce. The CCA rating will be lower, and tells you how much power the battery produces at below-freezing temperatures.
When considering trolling and deep cycle batteries, the amp hour (Ah) rating is the more crucial stat. This tells you about how much power the battery can deliver over a sustained length of time for running trolling motors or on-board electronics.
How to Care for Your Marine Battery
Proper maintenance is the best way to maintain your battery’s health in the long-term. Here are some tips for getting the most out of your marine battery.
- Check the terminals periodically for corrosion. This will look like a white powder on the terminals or around the bases. If you see any, you can clean it away by mixing equal parts baking soda and water into a paste. Use a toothbrush or other soft-bristled brush to scrub this paste onto the terminal.
- Lightly grease the terminals with dielectric grease before attaching the connections. This makes it easier to get a secure connection and can prevent corrosion before it happens.
- Make sure your battery is tightly secured when you install it. Extra vibrations from loose brackets can cause internal damage that lowers the battery’s maximum lifespan.
- Keep track of the age of the battery so you can better assess when it needs to be replaced. This information is printed on the battery’s label but can often wear off in the conditions experienced by a marine battery.
- When storing batteries, keep them in a cool, dry, and dark environment. An ambient temperature of around 50°F is ideal. Direct sunlight and high heat accelerate the battery’s internal reactions and will make the battery lose charge faster.
- Fully charge your battery before installing it if you’ve recently had it in storage. The correct charge for a full battery ranges from 13-13.4 volts, depending on its chemistry. The battery’s manual will tell you which is ideal for yours.
Belter PK12350 DC Power 12-Volt Marine Deep Cycle Battery
- Treated plates are stronger and more reliable
- High resistance to damage from shocks and vibration
- Heavy duty construction extends service life
- Stands up well to repeated deep discharges
- Sealed and maintenance-free
- Maximum lifespan isn’t as long as other batteries
Mighty Max ML55-12 Electric Trolling Motor
- Works well even in extreme heat and cold
- Rechargeable and maintenance-free
- Flexible mounting options
- Safe to use in enclosed spaces
- Good weight to power ratio
- Lasts up to 6 hours between recharges
- Takes a while to charge (up to 8 hours to full)
- Not as convenient to install and carry
Universal UB121000-45978 12V Deep Cycle AGM Battery
- Consistent deep cycling without any maintenance
- Thick protective casing withstands harsh weather conditions
- Large storage capacity
- Holds its charge well in storage
- Lasts up to 5 years
- Bulky, heavy design is tricky to mount
- Takes about 12 hours to fully charge
Optima Batteries 8006-006 34M BlueTop Marine Starting Battery
- High resistance to vibration damage
- Fast recharging rate
- Holds charge for up to a year in storage
- Durable, fully-sealed housing
- Reliable even in cold weather
- Price is a bit high for the capacity
- Not suitable for larger vessels
Renogy Li 12V Smart Lithium Iron Phosphate Battery
- Lasts for more than 2,000 recharge cycles
- Built-in protections against over-charges and short-circuits
- Integrated smart battery management system
- More flexible connection options
- Excellent in deep cycle applications
- Can’t be connected in series with other batteries
- Company’s customer service can be difficult to reach
Optima Batteries 8016-103 D34M BlueTop Starting and Deep Cycle Marine Battery
- Up to 870 marine cranking amps
- Weather-resistant casing
- Can be mounted in multiple positions
- Lasts for 5 times the charges of most batteries
- Recharges quickly even if fully discharged
- Easy to transport and store
- Not as effective for starting larger engines
Optima Batteries 8027-127 D27M BlueTop Starting and Deep Cycle Marine Battery
- Efficient power use with a long lifespan
- High cranking power (up to 800A)
- Reserve capacity of up to 140 minutes
- Double-posts and leak-free sealing
- Drains quickly when used by larger motors
- Doesn’t retain charge as long in storage
Odyssey 34M-PC1500ST Trolling Thunder Marine Dual Purpose Battery
- Holds charge up to 2 years in storage
- Works well in both extreme heat and extreme cold
- Easy to install and maintenance-free
- High crank amp rating
- Efficient power use for consistent, reliable operation
- Higher price
Optima Batteries 8052-161 D31M BlueTop Starting and Deep Cycle Battery
- Recovers well from deep discharges
- High cranking amp rating
- Long reserve capacity
- Lasts through 3 times the recharges of conventional batteries
- Runs well in hot weather
- Quick to recharge
- High self-discharge rate (drains quickly in storage)
- Max capacity diminishes over time
Odyssey 31M-PC3150ST-M Trolling Thunder Marine Dual Purpose Battery
- Twice the power of most marine batteries
- Lasts up to 10 years
- Resists corrosion
- High construction quality on cells
- Recharges fully in 4-6 hours
- Wide temperature tolerance range
- Most expensive option
- Heavy and bulky
The Bottom Line
If pressed to pick just one overall best option, we’d have to go with the Optima BlueTop D31M. Every battery in the BlueTop line is a consistent and reliable choice, but the D31M is the right size and power level for most people.
That said, those specifically looking for a starting battery will want to check out the Optima BlueTop 34M. It has high cranking amps for such a compact battery, and the price is right, too.
Those looking more for a dedicated deep cycle battery will want to consider the Beiter PK12350. Its weight to capacity ratio is high, and it can run even 50-pound trolling motors for hours without failure.
Obviously, all of these batteries have their strengths—that’s the reason we’ve included them on the list! Choosing the right one for you really depends on your boat and lifestyle. Before you buy, decide how much power you need (and for how long) to get the most out of your purchase.
How do I add water to these batteries?
You don’t, because you don’t need to. Those who are used to traditional flooded lead-acid batteries are probably in the habit of adding water every couple of months. The batteries on this list are sealed and won’t lose water, so you don’t need to check the fluid levels. Adding water to AGM batteries isn’t just unnecessary, it can actually cause damage to the battery.
What does “group type” mean, and how do I know which one I need?
The battery’s group gives you a basic idea of its dimensions and can be helpful in figuring out if the battery will fit your boat. The most common marine battery groups and their dimensions are:
|27M||12” X 6.8” X 8.875”|
|31M||13” X 6.8” X 9.4”|
|34M||10.25” X 6.8” X 7.875”|
|U1||7.7” X 5” X 7”|
Different groups also typically offer different levels of power, though this varies more from one battery to the next than the size. The “M” after these group names is for “marine” and differentiates the batteries from those of the same size for land vehicles.
What kind of charger is best for marine batteries?
You can use the same charger for marine batteries that you would for any other 12-volt battery. That said, which charger you need depends on how you use your battery.
Many battery chargers come with a deslufation or recovery mode that can undo the damage caused to batteries by use over time. These chargers cost a bit more but can also extend your battery’s lifespan, so they’re often a worthwhile investment.
If you’ll be using your battery seasonally, it’s a good idea to get a trickle charger or battery maintainer. Even batteries that hold their charge well in storage will stay healthier if they’re kept fully charged. Trickle chargers use a low amp level. While this takes longer to charge a depleted battery, it’s also less likely to cause over-heating or other damage.
How often should I charge a marine battery?
It’s smart to check your battery’s charge about once a month, whether it’s installed on your boat or in storage. If it reads lower than 12.6 volts, you should put it on the charger until it’s refilled. If you’re storing it long-term, your other option is to use a smart battery maintainer and keep the battery on it all the time.
What’s the difference between a marine battery and a deep cycle battery?
The term “marine battery” can mean different things to different companies. From most manufacturers, it means a dual-purpose battery that can both start the engine and provide continuous power. In this case, a deep cycle battery is different because it’s not meant to provide high short-term charge.
A true deep cycle battery uses thicker, heavier plates than dual-purpose batteries. This is what allows them to recover so well from deep depletions. That said, some companies use the terms “marine battery” and “deep cycle battery” interchangeably, so it’s always a good idea to check the specs of whatever model you’re looking at.
Do I need two batteries in my boat?
Many boats use a dual-battery system with both a starting battery and a deep cycle battery. Smaller boats may be designed to use a single dual-purpose battery. The best way to find out what your boat needs is to check out what’s already installed.
How long do marine batteries last?
Most boat batteries last between 2 and 5 years. Some durable marine batteries can last up to 10 years with proper maintenance but this is fairly rare. Following the maintenance tips above is the best way to get the longest possible lifespan from your battery.