Best Marine Battery – Dual Use, Starting, and Deep Cycle Batteries Explained and Reviewed

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Ever been on the water and had your trolling motor die? Worse still, ever been miles from the boat ramp, tried to start your outboard, and got nothing?

That’s a heart-sinking feeling you only need to experience once to learn to take batteries seriously!

Marine batteries can be tricky business, and if you don’t know what to look for, it’s easy to be disappointed. We’d like to help, and below, you’ll find a careful explanation, thorough guide, and list of batteries you can trust. We only have space to focus on Group 31 and 27 batteries, but if you need something else, just ask in the comments!

Quick look at the best marine batteries available today:

Cranking/Starting Batteries

Dual Use Batteries

Deep Cycle Batteries

Check out our guide for the Best On-Board Battery Chargers

Battery School: What You Need to Know When Choosing a Marine Battery

Battery Basics

Batteries are a simple idea: a way to store electrical energy so that you can use it later. But to be realized, that simple idea demands some pretty complex chemistry. A good basic grasp of battery technology can really help you make the best choice for your needs.

Batteries have three internal components that you need to understand: a negative and a positive electrode and an electrolytic medium. In conventional batteries, these take the form of lead plates and an acidic liquid or gel. In some very advanced batteries, these materials are replaced by carbon and lithium salts, respectively.

Battery Tech: Wet-Cell vs. SLA/VRLA/AGM vs. Lithium-Ion

Battery tech has come a long way over the last 20 to 30 years, and you may not be aware of the various kinds of battery systems on the market. Understanding their strengths and weaknesses can help you pick the right one for your needs.

Sealed Lead-Acid (SLA), Valve-Regulated Lead-Acid (VRLA), and Absorbed Glass Mat (AGM) – Essentially three terms for the same chemical system, SLA/VRLA batteries use lead plates and acid as their basic components. AGM batteries add one additional chemical trick. The result of this tech is that they’re all heavy and safe–and that they don’t require the maintenance of traditional wet cell batteries.

These batteries hold a charge well, but they are quite a bit more expensive than typical wet-cell alternatives, and they can be damaged by overcharging.

Gel batteries – Gel batteries also use lead plates and acid, but the addition of silica to the electrolyte turns it into a thick gel. This provides them with superior long-term storage capacity, and like standard AGM batteries, they’re very safe and maintenance-free.

But they don’t like sudden, powerful discharges, which can lead to damage to the plates. And they must be recharged carefully, never exceeding a maximum charge.

Lithium-Ion (Li-ion) – These batteries trade up from lead and acid to carbon and lithium salts to deliver power. The result is that they’re easily rechargeable and generally smaller and lighter than the SLA or AGM batteries of the same power. They’re simply better battery tech.

The downside? They can be insanely expensive, and 12v systems designed for marine use can cost thousands!

Wet-Cell Batteries – Wet-cell batteries have remained pretty much unchanged since their introduction in the late 19th century. Their low initial price-point has kept them popular, and if cared for, they can survive quite a few charging cycles. They’re also resistant to damage from overcharging and weigh-in a bit under typical SLA or AGM alternatives.

But they require proper ventilation, can leak and spill acid, don’t hold a charge as well in storage, and can be damaged by the vibrations typical in marine use.

Types of Marine Batteries

There are three types of battery commonly found in boats:

Starter or cranking batteries – Lead/acid starter batteries use many light, spongy plates to increase the surface area of the chemical reaction. This dramatically increases how much power they can generate over a short time, allowing them to turn your engine over and deliver the power necessary to run pumps, fuel injections, and other vital engine components.

But they can’t supply low levels of power for long periods–the plates just aren’t designed for that. And if you try, two things will happen. First, you’ll drain the battery very quickly, and second, you’ll permanently damage the battery by discharging it deeply.

Simply put, starter batteries are designed to start an outboard, not run a trolling motor. And unless you’re running your outboard (and its alternator) pretty much constantly, you’ll quickly deplete a starter battery if you attach it to anything more than a fishfinder and a live well.

Even then, you’ll want it on a good on-board charger.

Deep cycle – Lead/acid deep cycle batteries use heavy, solid plates to create the chemical reaction that allows them to store and discharge power. As a result, they can supply low levels of electrical current for very long periods, and their plates and acid are designed for very deep discharging and repeated recharging.

Unlike conventional batteries, they can be discharged down to 20 percent of their capacity again and again, without suffering damage.

But deep cycle batteries don’t have plates that can generate a quick burst of high power, and most will struggle to start an outboard. Even if they do manage to turn it over, they may still lack the power to get it running.

Simply put, deep cycle batteries are designed to run electronic devices like fish finders, GPSs, radios, live wells, and trolling motors.

Dual use batteries – Dual use batteries are the sweet spot between these two types, and they’re designed with enough surface area to generate a quick burst of power, as well as enough plate mass to sustain deep discharges without damage.

While not as good at starting motors as a dedicated cranking battery, and while not as long-lived as a true deep cycle battery, they combine the strengths of both alternatives.

Dual use batteries can usually be safely discharged down to 50 percent of their capacity.

Marine batteries – Sometimes used as a synonym for “deep cycle,” marine batteries can consist of any of the other types, depending on their purpose.

How Can You Pick the Right Battery for Your Needs?

As we note in the intro, we’re focusing on batteries for small boats of the kind used for crappie, bass, perch, and inshore fishing for reds, speckled trout, flounder, etc. You’re almost certainly running a trolling motor and some electronics, not just starting an inboard or massive outboard engine. And you’re not offshore trolling for hours at a time on your main engine.

Note: What we recommend here is not necessarily true for off-shore boats that do not run electric trolling motors.

If you think carefully about how you use your boat’s batteries, you’ll realize a simple truth. The vast majority of the time–99.9 percent–you’ll be asking them to power your trolling motor, fish finder, live well, and lights. But given the power demands of modern electronics, you need to think through your battery selection very carefully.

And though just a fraction of the battery’s time is spent starting your outboard, that’s a critical task!

Space and Cost Are the Limiting Factors

The larger your boat, the more space you’ll have for batteries. But given how much tackle we tend to pack with us, filling all that space with batteries isn’t practical. And given how much they cost, you’ll be broke by the time you do!

If you’ve only got space for one battery in your boat–and you’re running a trolling motor as we assume–you really don’t have a lot of options. You’ll need a dual use battery with enough oomph to start your outboard.

Consult your owner’s manual carefully, and always choose a battery with at least the manufacturer’s recommended cold-cranking amps (CCA) or marine cranking amps (MCA).

If you have space for more than one battery, consider a dedicated cranking battery plus at least one deep cycle battery to run your trolling motor. Ideally, you’ll run several identical batteries in tandem to supply power to your 24v or 36v trolling motor, reserving that cranking battery for the live well, electronics, and of course, getting your outboard started.

Another option is to select dual use batteries with sufficient cranking power to start your outboard.

Whichever option suits your needs, be sure to use a quality on-board charger. That’s especially critical for the battery connected to your outboard!

What We Consider When Selecting a Marine Battery

CCA or MCA

Cold Cranking Amps or Marine Cranking Amps are a measure of how much amperage a battery can deliver over a short time–in cold temperatures–to turn a motor over and get it running smoothly.

As experts can tell you, “CCA is a rating used in the battery industry to define a battery’s ability to start an engine in cold temperatures. Generally speaking, it is easier to start an engine in a warm environment than in a cold one. The rating refers to the number of amps a 12-volt battery can deliver at 0°F for 30 seconds while maintaining a voltage of at least 7.2 volts. The higher the CCA rating, the greater the starting power of the battery.” MCA is essentially the same rating, applied at 32°F, and should always be a larger number than the CCA.

It is essential that your battery at least meet the minimum requirements of your outboard, and we recommend that you give yourself a reasonable margin above that for starting in the cold or when the battery is less than fully charged.

Reserve Capacity

As Simon Slayford of Hunker explains, “Reserve capacity is defined as the number of minutes a fully charged 12-volt battery at 80 degrees Fahrenheit can provide 25 amperes at 10.5 volts until the voltage decreases.” Essentially, it’s a measure of a battery’s capacity when not being charged by an alternator.

You may have heard that RC is “just a number.” That’s not exactly true, but a battery’s RC is not an accurate assessment of how many minutes of run-time you get from it. Instead, that depends on a number of factors, including temperature and total power draw.

Weight

Even “light-weight” batteries are heavy, and the heavier your boat, the more this matters. With a large enough bank of batteries in a heavy fiberglass bass boat, outboard performance can suffer.

This is something to think about when you’re deciding how large a bank of batteries to run, and it can really help justify the added cost of lithium-ion batteries.

Size

Measure carefully! Batteries come in multiple sizes, and generally speaking, bigger batteries are more powerful.

But if a battery won’t fit where you need it to go, it’s not going to do you much good!

Price

Batteries range in price quite a bit, and it’s worth considering the difference between upfront and long-term costs. An expensive battery that lasts for years may be cheaper in the long-run.

Battery Tips

Never Mix Battery Kinds

Never mix AGM, gel, wet-cell, and lithium-ion batteries. You want to charge your batteries on the same system, in the same way, every time.

Never Mix Old and New Batteries

Adding new batteries to a bank of older ones will quickly deteriorate the new addition. When it’s time to change one battery, it’s time to change them all.

Keep the Terminals Clean

Periodically check the terminals on your batteries, and remove any corrosion or oxidation.

Keep Your Batteries Cool

No battery likes to be hot or cold, and temperature extremes affect performance and storage life. You probably already know this if you’ve tried to start your car when it was really freezing outside, but be aware that extreme heat is a problem, too.

When you’re not using your battery, you need to keep it cool and dry. You’ll also want it to be charged rather than depleted when you store it, so before you put it away, be sure to top it off.

Recharge Slowly

Unless you choose a battery pack which plugs into a standard outlet, you’ll need to invest in a battery charge. Slow charging is always better than fast, and it’s important to ensure that you never overcharge your battery. Most batteries can be recharged overnight.

Don’t Run Them to Death

Most deep cycle batteries can be discharged and recharged hundreds of times. Expensive lithium batteries offer thousands of cycles, eventually breaking even with cheaper SLA and AGM alternatives–if you take care of them. Try to avoid completely draining your battery; it’s best to stay above 50 percent charge if you want to get the longest service life from it.

Best Starting/Cranking Marine Batteries

Cabela’s X-900 Pure Lead AGM Battery Group 31 – Our Pick!

Type: AGM
RC: 220 minutes
MCA: 1370 Amps
CCA: 1150 Amps
Weight: 74 lbs.
Size: Group 31; 6.77 x 12.91 x 9.78 (with terminals)

Cabela’s X-900 AGM batteries have won a solid reputation for anglers, and they’ll reliably start your outboard as long as they match or exceed the manufacturer’s recommendations for CCA and MCA ratings. Indeed, with 1150 cold cranking amps, you can be confident that this battery will start your outboard even on the coldest mornings.

And with an RC of 220 minutes, plenty of anglers use these batteries to run their electronics, live wells, and trolling motors, too.

If you do that, we strongly recommend that you reserve one battery for the outboard!

These batteries have been torture-tested by anglers in freezing winter conditions as well as the worst heat summer can supply. They’ll start your motor every time, all the time, if you do your part. And since the X-900 is a sealed AGM design, that means nothing more than proper storage, keeping the terminals clean, and careful recharging.

At 74 pounds, the Group 31 X-900 is no feather-weight, and if that’s an issue for you, it might be worth investing in the Lithium Pros M3180.

Pros:

  • Dependable in all temperatures
  • Incredible CCA and MCA
  • Great RC

Cons:

  • Heavy

Cabela’s X-900 Pure Lead AGM Battery Group 27 – Our Pick!

Type: AGM
RC: 195 minutes
MCA: 1080 Amps
CCA: 930 Amps
Weight: 68 lbs.
Size: Group 27; 6.77 x 12.44 x 8.74 (with terminals)

For smaller spaces, Cabela’s Group 27 X-900 delivers lots of starting power and a fantastic 195 minutes of RC. That’s impressive, and it goes a long way in explaining why this battery is so highly respected.

Like its larger sibling, many anglers use these to start their outboards and run their electronics and trolling motors–which is perfectly acceptable given that they tolerate relatively deep-discharge well.

But play it safe with your outboard and reserve one battery just for starting (if you have the space)!

And like its big brother, this battery has been put through its paces by anglers all over the country. It’ll start your outboard no matter the conditions as long as you take good care of it. That’s good news, because caring for an AGM battery is a snap.

Pros:

  • Dependable in all temperatures
  • Excellent CCA and MCA
  • Great RC

Cons:

  • Heavy

Lithium Pros M3180 12V 80Ah Marine Starting Battery

Type: Lithium-Ion
RC: 184 minutes
MCA: 1200 Amps
CCA: ?
Weight: 25.2 lbs.
Size: Group 31; 6.81 x 13 x 8.43

Lithium Pros M3180 is a high-tech starting battery that competes with the best AGM batteries in terms of power output, while cutting weight to a minimum. Delivering a full 1200 Amps of MCA, and an RC of 184 minutes, it weighs-in at just 25.2 pounds!

For weight-conscious anglers with a huge budget, that’s not something to miss. Just be sure to recharge this lithium-ion battery correctly.

In a word, this battery is incredible–and incredibly expensive!

Pros:

  • Ultra light-weight
  • Incredible MCA
  • Great RC

Cons:

  • Expensive!

NorthStar Ultra High Performance Group 31 AGM Battery

NorthStar Ultra High Performance Group 31 AGM Battery

Amazon 

Type: AGM
RC: 220 minutes
MCA: 1370 Amps
CCA: 1150 Amps
Weight: 76 lbs.
Size: Group 31; 6.8 x 12.9 x 9.2

Northstar’s Group 31 AGM starting battery is a popular choice for anglers running large outboards. And like the Cabela’s X-900, its awesome RC allows it to be used in dual roles. Of course, if you do, you run the risk of discharging it to the point that it can’t start your motor, and so we recommend reserving one for just that purpose.

The heaviest of the starting batteries we recommend, we give the edge to the X-900 series from Cabelas.

Pros:

  • Dependable in all temperatures
  • Incredible CCA and MCA
  • Great RC

Cons:

  • Heavy!

Best Dual Use Marine Batteries

Odyssey 31M Trolling Thunder Marine Dual Purpose Battery – Our Pick!

Odyssey 31M-PC2150ST-M TROLLING Thunder Marine Dual Purpose Battery

Amazon 

Type: AGM
RC: 205 minutes
MCA: ?
CCA: 1150 Amps
Weight: 77.8 lbs.
Size: Group 31; 6.80 x 13 x 9.41

Odysseys’ Group 31 “Trolling Thunder” is a fantastic dual use battery, delivering plenty of starting power and an incredible 205 minutes of RC. That’s enough juice to keep your trolling motor running all day if you’re careful with the throttle!

And while not as light as the “Blue Top,” Odyssey’s been delivering top-notch quality control and enviable performance, stealing many former fans from the cult of Optima.

With enough cold cranking amps to start an outboard on the coldest mornings, this is an incredible battery–though at about twice the price of an Optima!

Pros:

  • Dependable in all temperatures
  • Incredible CCA and MCA
  • Incredible RC

Cons:

  • Heavy

Deka 8A27 AGM Deep Cycle and Starting

Deka Battery 8A27 Battery

Amazon 

Type: AGM
RC: 185 minutes
MCA: 900 Amps
CCA: 580 Amps
Weight: 63 lbs.
Size: Group 27; 6.75 x 12.75 x 9.86

For anglers in the know, Deka’s Intimidator AGM batteries have been a perennial choice when they need a versatile, dependable power system.

Deka’s Group 27 AGM battery can start most outboards, though its performance suffers a bit in the cold with only 590 cold cranking amps. Still, for smaller outboards, that’s plenty, and this battery has earned its reputation as a solid performer.

Indeed, with 185 minutes of RC, this battery can be relied on to power basic electronics and still hold enough charge to get your motor started–all with little to no real maintenance.

Pros:

  • Good MCA and CCA
  • Great RC

Cons:

  • Not great for starting in cold temperatures

Deka 8A31 AGM Deep Cycle and Starting

Deka Battery 8A31 Battery

Amazon 

Type: AGM
RC: 210 minutes
MCA: 1000 Amps
CCA: 800 Amps
Weight: 69 lbs.
Size: Group 31; 6.75 x 13 x 9.5

Deka’s larger Intimidator delivers impressive cold starting amperage and a full 210 minutes of RC. That’s enough oomph to crank your motor on finger-numbing mornings, and it’ll give your trolling motor the power it needs for an entire day of fishing if you keep the throttle under control.

That goes a long way toward explaining why it has the reputation it does, but for the price, the Odyssey has it beat in performance.

Pros:

  • Dependable in all temperatures
  • Good CCA and MCA
  • Great RC

Cons:

  • Lags behind the Odyssey in performance at roughly the same price-point

Optima Batteries D31M Blue Top Starting and Deep Cycle

Optima Batteries 8052-161 D31M BlueTop Starting and Deep Cycle Battery

Amazon 

Type: AGM
RC: 155 minutes
MCA: 1125 Amps
CCA: 900 Amps
Weight: 59.8 lbs.
Size: Group 31; 6.56 x 12.81 x 9.38

Optima’s “Blue Top” batteries have won a huge following on the water, though quality control has slipped lately. When these batteries are well-made, they’re among the best you can buy. Otherwise, they tend to fail quickly, necessitating warranty claims.

The bad news is that Amazon is not a licensed dealer, and if you purchase through them, Optima will not honor the warranty. NAPA and O’Reilly are both licensed retailers, and these batteries are available directly from the manufacturer as well.

Why are they popular?

With a CCA of 900 Amps and 155 minutes of RC, this Group 31 battery still weighs in at a svelte 59.8 pounds! As you can see, its unique spiral-core technology delivers a lot of juice while keeping weight down. And whether you’re using it to start your outboard or power your trolling motor, the “Blue Top”–at its best– has proven to hold a charge long enough for all-day fishing while reliably delivering enough cranking power to start a big outboard, even in bitterly cold weather.

Pros:

  • Dependable in all temperatures
  • Incredible CCA and MCA
  • Great RC
  • Relatively light

Cons:

  • Poor quality control can lead to short life

Best Deep Cycle Marine Batteries

VMAX MR127 AGM Deep CycleOur Pick!

VMAX MR127 12 Volt 100Ah AGM Deep Cycle Maintenance Free Battery Compatible with Boats and 40-100lb, minnkota, Cobra, sevylor and Other trolling Motor (Group 27 Marine Deep Cycle AGM Battery)

Amazon 

Type: AGM
RC: 200 minutes
MCA: 800 Amps
CCA: ?
Weight: 68 lbs.
Size: Group 27; 6.75 x 12.1 x 8.2 (8.46 with terminals)

It’s hard to find a more popular deep cycle battery than the VMAX MR127, and for the price, this is probably the best option on the market.

Delivering 200 minutes of RC and tolerating deep discharges season after season, this is among the best trolling motor batteries you can buy. It takes virtually no maintenance, and if charged properly, will last for years.

Pros:

  • Dependable
  • Awesome RC
  • Tolerates deep discharges, season after season

Cons:

  • Heavy

Interstate Batteries SRM-27

Type: Wet-cell
RC: 160 minutes
MCA: ?
CCA: 600 Amps
Weight: 50.3 lbs.
Size: Group 27; 6.75 x 12.75 x 9.5

Long trusted by anglers and battery experts alike, Interstate Batteries’ SRM series are consistently solid performers, delivering the power you need to run live wells, electronics, and trolling motors. Using old-school wet-cell tech, they deliver if you do your part to keep them working properly.

Their Group 27 battery offers a full 160 minutes of RC while weighing in at only 50.3 pounds. That’s a pretty good performance-to-weight ratio, and they tolerate deep discharges for years.

But be aware that you need to attend to their acid-water level carefully, avoid spilling, and wear eye protection when working on these batteries!

If you’re willing to do that, the reward is long-service, excellent performance, and a bargain price!

Pros:

  • Dependable
  • Good RC
  • Inexpensive!

Cons:

  • Lags behind the VMAX in performance

Interstate Batteries SRM-31

Type: Wet-cell
RC: 210 minutes
MCA: ?
CCA: 675 Amps
Weight: 59.7 lbs.
Size: Group 31; 6.69 x 13 x 9.63

Interstate Batteries’ Group 31 deep cycle model delivers incredible performance at a relatively light-weight–just 59.7 pounds! And with 210 minutes of RC, you can run a trolling motor all day, no problem.

Using wet-cell tech, the SRM-31 is among the least expensive options on our list, making it an easy choice if it fits your needs.

Pros:

  • Dependable
  • Great RC
  • Inexpensive!

Cons:

  • Lags behind the VMAX in performance

Lithium Pros M3140-36 36V 40Ah Trolling Battery

Type: Lithium-Ion
RC: 92 minutes
MCA: ?
CCA: 675 Amps
Weight: 30.3 lbs.
Size: Group 31; 6.81 x 13 x 8.43

Lithium Pros 36V deep cycle battery is designed to replace an entire bank of lead-acid alternatives, delivering up to nine hours of power to your trolling motor. And at just 30.3 pounds, those 92 minutes of RC won’t bog down even the heaviest boat.

The downside? Prepare yourself for the price!

Pros:

  • Dependable
  • Good RC
  • Replaces three 12v batteries at only 30.3 pounds!!!

Cons:

  • Insanely expensive!

Final Thoughts

There’s no “best” battery–only the best one for your needs and boat. But whether you’re looking for a good starting battery to get your outboard running in early spring, or just need a reliable bank of deep cycle batteries to keep your trolling motor powered all day, we’ve got you covered.

We hope you find what you need on our list, but we only had space to review Group 27 and 31 batteries.

If you need a recommendation for another size, please leave a comment below. We’d love to help!

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