Ultimate Miata Battery Guide – Get Juiced!

Finding the perfect Miata battery can become confusing, so we’ve simplified everything you need to know for each generation in this guide.

• Which battery is best for my Miata?
• Why is my Miata battery draining?
• Miata battery lifespan
• Can I use a cheap lawn/tractor battery in my Miata?
• Should I buy a used Miata battery?
• How to replace a Miata battery
• Best NA/NB Miata batteries
• Best NC/ND Miata batteries
• Our Miata battery winners

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In a hurry? Here are our Miata battery winners

Car batteries are usually one of the most straightforward parts of routine maintenance.

Still, given the nature of the Mazda MX-5 Miata, they’re somewhat of a headache compared to your typical daily driver.

Over the years, we’ve had an insane amount of messages from Miata owners asking which battery we’d recommend for their specific Miata generation since they’re struggling with the conflicting advice found online.

So, we’ve decided to put the matter to bed with this guide, which we shall call: “The guide of all guides for Miata batteries”! We’re hoping we will finally put the matter to rest.

You no longer need to spend countless hours reading arguments on the various MX-5/Miata forums, as we’ve answered every Miata battery question in this guide.

If you feel that we’ve missed something, then feel free to drop us a line. We’ll get back to you and then add your questions to our guide, hopefully helping other Miata/MX5 owners further down the line.

As a Miata owner, you’re likely to know they’re fantastic at chewing through batteries quicker than most cars on the road.

Given the age of NA/NBs and even some NCs, they will likely have already been replaced.

If not, we’re not surprised that they’re reaching the end of their lifespan.

Since most NAs are celebrating their thirtieth birthdays, it’ll be a real cause for celebration if your battery has somehow survived along the way, which we unfortunately doubt is the case.

Although many owners believe that the OEM batteries had a far better lifespan than the modern-day replacements.

The good news is that battery advancements have allowed for cheaper-than-ever prices, which softens the blow when replacing.

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Which battery is best for my Miata?

Mazda designed the NA/NB generations to run their battery in the car’s trunk rather than under the hood.

Given these cars’ lightweight design, something as small as a battery can significantly impact weight distribution, so putting the battery in the rear helps provide optimal handling performance.

Heat can become a big issue for batteries, especially on a forced induction setup, where the temperatures of a turbocharger or supercharger will be far higher than your typical naturally aspirated setup.

Since Mazda opted to move the battery under the hood for the later generation NC/NDs, enthusiasts squeezing additional power out of their Miatas typically opt for a battery relocation kit.

This moves the battery to what most die-hard Miata fans believe to be the ‘correct’ location – the trunk.

When choosing the best battery for your Miata, it’s easy to opt for the cheapest possible solution, but we do not recommend doing so.

The cheaper batteries on the market are often wet cells, causing a real mess if not maintained correctly, but they can also leak over time.

If that doesn’t put you off, we’ve also heard far too many horror stories of them exploding, which could potentially cause many issues, and the small financial trade-off suddenly doesn’t feel quite so appealing.

So, for that reason – wet cell batteries are a no-no for us.

Thankfully, Mazda shares the same mindset regarding the wet cell battery, so they fitted the Miata with Absorbed Glass Mat (AGM) batteries as a standard OEM part from the factory, even way back in 1990.

Placing a battery in the trunk has disadvantages. You need to figure out how to vent the hydrogen fumes expelled from the battery, which can potentially harm or cause severe rust problems.

Thus, Mazda devised its vented tubing from the battery to eliminate potential risks or disasters.

If you opt for a non-vented battery, you can expect to suffer from severe corrosion issues in the battery area.

For this reason, AGM batteries are also sealed and vented, making them the perfect choice for your Miata.

What is an Absorbed Glass Mat (AGM) battery?

AGM technology provides increased safety, performance, and service life over alternative battery types.

We feel that this simplified explanation from DC Battery explains it best:

“In AGM sealed batteries, the acid is absorbed between the plates and immobilized by a very fine fiberglass mat. No silica gel is necessary. This glass mat absorbs and immobilizes the acid while still keeping the acid available to the plates. This allows a fast reaction between acid and plate material”.

“The AGM battery has an extremely low internal electrical resistance. This, combined with faster acid migration, allows the AGM batteries to deliver and absorb higher rates of amperage than other sealed batteries during discharging and charging”.

“In addition, AGM technology batteries can be charged at normal lead-acid regulated charging voltages, therefore, it is not necessary to recalibrate charging systems or purchase special chargers”.

The benefits of this are that AGM batteries won’t potentially spill acid into your boot over time, unlike other batteries, which would also require far more routine care and maintenance to ensure optimal performance.

If you’re after a ‘set and forget’ method with your battery, then AGM is undoubtedly the best choice for you.

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Why is my Miata battery draining?

We’ve heard of Miata owners accepting that their battery needs replacing, only to die again just a few weeks later.

There are several reasons that this could be happening, and since you’ll still have your warranty, we’d recommend getting a replacement battery to ensure it’s not the culprit.

Once you’ve confirmed that and you’re still having issues, it’s time to investigate what could be causing them.

Aftermarket alarms and head units are often the leading cause of this problem, but OEM alarms are also known to cause an issue.

Draining an AGM battery can severely damage or even kill the battery entirely.

Not only that, but you can’t jump-start AGM batteries using the traditional methods, as they need a 1-12 amp power delivery, which can take up to 24 hours for a full charge.

Therefore, we highly recommend avoiding a complete battery drain with AGM batteries whenever possible.

Our first two checks, besides obvious things, like ensuring you’ve remembered to turn the lights off, would be the following:

Aftermarket head unit – Have you recently had a new stereo installed? If so, this will be the most likely issue, and it would appear that the electrics are malfunctioning somehow.

Alarm – Even if you’ve not activated your Miata alarm, it can still cause battery drain. We recommend disconnecting the alarm and seeing if that solves the problem.

If this is the case, we recommend getting yourself a car battery maintainer.

However, it will be worth investigating the issue, as you’ll inevitably want to arm your alarm away from home where you can’t leave the car on charge sometime.

On a problem-free Miata, we would still expect to see a few weeks of battery life from a frequently-driven car before any issues arise with a healthy battery and electronics.

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Miata battery lifespan

Typically, we expect around ten years’ lifespan from the OEM Mazda batteries on a frequently-driven Miata.

Replacement batteries will often not last as long as the OEM battery, with most owners expecting around a five-year lifespan, which is why the best warranty can often be significant.

Climate and weather can often play a huge role in the lifespan of your battery. If you live in an exceptionally hot or cold region, we would expect the battery lifespan to decrease dramatically.

Temperature extremes are where a decent warranty on your battery will be more vital than ever.

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Can I use a cheap lawn/tractor battery in my Miata?

Cheap batteries have been a common trend among owners looking to save a few bucks, but as we explained previously, it’s a false economy in the long run.

You’ll need to frequently check the battery, top it up with water, worry about venting, and run the risk of it exploding. On top of that, the cheaper batteries typically only come with a 6-month warranty, which isn’t ideal.

Not only are you likely to end up using the ‘buy cheap, buy twice’ theory here, but you also risk damaging your Miata in the process.

We don’t feel it’s worth the risk for such a small saving every few years.

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Should I buy a used Miata battery?

We’re surprised how many owners consider this; the simple answer is no.

New batteries come with a warranty and a limited lifespan unless you know when the original owner had it fitted.

In addition, you have the original receipt for an exchange. We definitely wouldn’t consider a used battery.

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How to replace a Miata battery

Once you’ve purchased your new Miata battery, you’ll need to follow this simple process for installation of your fresh new battery:

• Remove the negative terminal using a 10mm wrench or socket
• Next, remove the positive terminal
• Loosen both 12mm (or 14mm) battery tie-down nuts
• Remove the tie-down by angling the hooks towards the front of the car and lifting
• Remove the insulating shroud
• Lift the battery from the car
• Now that you’re ready to fit your new battery reverse the process above, ensuring that you connect the positive terminal before the negative terminal
• Stand back and admire your hard work!

If you’d prefer a Miata battery replacement instruction video, we recommend following this guide:

NC Miata (MK3 MX5 owners) will likely need to reset the DSC (Dynamic Stability Control) after replacing the battery.

If you replace your battery, if the DSC is off with no response from the button, or if your ‘DSC OFF’ light flashes, you’ll need to follow these steps.

This can also be found on page 152 of the manual:

• Ensure the new battery is connected
• Turn the key in the ignition to the ‘ON’ position, but don’t start the engine
• Turn the steering wheel full-lock to the left until it hits the lock stop (it can be somewhat challenging without power steering!)
• Turn the steering wheel to the right until you hit the lock stop
• Re-center the steering wheel
• Ensure the ‘DSC OFF’ light turns off
• Turn the ignition to the ‘OFF’ position
• Turn the ignition to the ‘ON’ position
• Ensure that the ‘TCS/DSC’ light goes off. If not, repeat the above steps carefully.

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Best NA/NB Miata batteries

Now that you know everything regarding replacing your Miata battery, it’s time to find the ideal replacement to restore your car to its former glory.

Although most Miata owners would like to buy the OEM Panasonic replacement, unfortunately, they aren’t even available from the Mazda dealerships, which will likely provide you with a third-party gel/wet cell equivalent. Which, once again, we advise avoiding at all costs.

Since there are superior batteries on the market to Mazda’s offerings, we’ve listed the best products to help you choose the right battery for your NA or NB Miata.

If you’re looking for NC or ND batteries, scroll down to find our favorite picks.

WestCo 12V31M Miata Battery

• Voltage: 12 Volts
• Capacity (C20): 31 Ah
• CCA (Cold Cranking Amps): 320 A
• Length: 194 mm
• Width: 130 mm
• Height: 180 mm
• Weight: 25 Lbs
• Battery type: AGM (Absorbed Glass Mat)
• Warranty length: Typically 1 year (Check with reseller)
• Value for money: 🔥🔥🔥🔥
• Purchase link: Buy your WestCo 12V31M Miata battery here

Our comment: The WestCo 12V31M is typically one of the most popular choices among NA and NB Miata owners, with many reporting that the battery is still going strong after five years of use.

Some have opted to trim the rubber vent tubes to ensure the perfect fit since they are rounded rather than rectangular.

However, a quick trim with scissors is all it takes to eliminate possible breathing issues.

The WestCo 12V31M provides an excellent OEM replacement for NA/NB owners. We would have given it five stars if it had an improved warranty.

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Odyssey Extreme PC925MJT Miata Battery

• Voltage: 12 volts
• Capacity (C20): 28 Ah
• CCA (Cold Cranking Amps): 330 A
• Length: 168.6 mm
• Width: 179 mm
• Height: 148.1 mm
• Weight: 26 Lbs
• Battery type: AGM (Absorbed Glass Mat)
• Warranty length: Limited 3 and 4-year full replacement warranty
• Value for money: 🔥🔥🔥🔥🔥
• Purchase link: Buy your Odyssey Extreme PC925MJT Miata battery at Amazon or eBay

Our comment: Like the WestCo above, this battery comes from East Penn Manufacturing Co., except this is the superior alternative.

It comes at a little extra cash but includes improved performance and a much better warranty.

With a 3-10 year service life, it’s the ultimate ‘set and forget’ battery you’ll only need to check on every few years.

It has a 70% longer life cycle than conventional batteries and a fast recharge feature capable of fully charging in 4-6 hours.

A slight modification to the mounting bracket required a snug fit, but we certainly wouldn’t let that put us off.

Although the Amazon rating isn’t the best, this is down to owners complaining that it doesn’t fit their car. Perhaps we need to write a battery guide for their cars, too!

Manufacturer description: “Some batteries provide enormous cranking power. Others, deep cycle reserve power. The revolutionary ODYSSEY battery is designed to do both.”

“How is this possible? The answer begins with flat plates made of 99.99% pure virgin lead – not lead alloy. Pure lead plates can be made thinner, so we can fit more of them in the battery. More ODYSSEY battery plates mean more plate surface area. And that means more power – twice as much as conventional batteries.”

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Deka/East Penn 8AMU1R Miata Battery

• Voltage: 12 volts
• Capacity (C20): 31 Ah
• CCA (Cold Cranking Amps): 320 A
• Length: 198 mm
• Width: 132 mm
• Height: 182 mm
• Weight: 24 Lbs
• Battery type: AGM (Absorbed Glass Mat)
• Warranty length: Typically 1 year (Check with reseller)
• Value for money: 🔥🔥🔥🔥
• Purchase link: Buy your Deka/East Penn 8AMU1R Miata battery on eBay

Our comment: Once again, the Deka battery is another offering from East Penn Manufacturing Co. and is remarkably similar to the WestCo 12V31M, which they also make.

The Deka is a like-for-like replacement of the former popular Marathon battery, made by the same manufacturer.

Given that they both have incredibly similar specs, we would choose either of these as a budget, depending on which you can get cheaper.

Many owners have stated that this battery fits without any modification so it may be the more convenient option for a straight fit.

The Odyssey above will be the better choice for those of you after a superior battery for your NA/NB.

Manufacturer description: “The Deka AGM Battery was designed for more than performance; it was designed for the enthusiast. Completely spillproof and leakproof; frequent replacement and high maintenance are over“!

“The AGM technology increases power while improving driver and environmental safety. The key to this technology is the highly porous microfiber separators, which completely absorb and trap the electrolyte. Molded top and side connection terminals provide versatility, increased strength and durability. The Deka AGM Battery provides the most advanced power and value in the industry.”

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Best NC/ND Miata batteries

For the NC/ND models, Mazda opted to move the battery under the hood, much to many Miata enthusiasts’ disappointment.

From the NC onwards, Mazda began providing far more electronics.

Therefore, a more substantial battery is recommended for maximum efficiency in theNC and ND Miata.

We’ll show you our favorite batteries before ending the list with a battery relocation kit for those looking to return the NC/ND to the ‘true’ Miata-style, returning the battery to the trunk.

Optima Batteries 8073-167 D51R YellowTop Dual Purpose Battery

• Voltage: 12 volts
• Capacity (C20): 38 Ah
• CCA (Cold Cranking Amps): 450 A
• Length: 234 mm
• Width: 126 mm
• Height: 227 mm
• Weight: 26 Lbs
• Battery type: AGM (Absorbed Glass Mat) SpiralCell Technology
• Warranty length: Typically 3 years (Check with reseller)
• Value for money: 🔥🔥🔥
• Purchase link: Buy your Optima Batteries 8073-167 D51R YellowTop Dual Purpose Battery here

Our comment: Optima’s YellowTop D51R has proven a fantastic option for NC/ND owners.

Utilizing their SpiralCell technology, this is fantastic for those looking to upgrade your in-car entertainment or run additional power on your battery.

Although this may look and sound like the perfect option, Optima has received criticism recently.

After moving their manufacturing plant from the US to Mexico in 2008, many have stated the former quality expected from the company declined.

Although this is a somewhat mixed opinion, we would ensure that a decent warranty with the reseller was in place before going ahead with the purchase, just in case.

Manufacturer description: “The OPTIMA YellowTop high-performance AGM battery is one of the only true dual-purpose automotive batteries available.”

“With premium cranking power and unparalleled cycling capability (rechargeability), it is perfect for modern accessory-loaded vehicles. With a 40-year history of technological innovation and engineering OPTIMA products offer unstoppable power for extreme enthusiasts.”

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Braille B3121 No-Weight Extreme Use Carbon Fiber Battery

• Voltage: 12 volts
• Capacity (C20): 31 Ah
• CCA (Cold Cranking Amps): 550 A
• Length: 168 mm
• Width: 132 mm
• Height: 173 mm
• Weight: 21 Lbs
• Battery type: Advanced AGM (Absorbed Glass Mat) Racing Technology
• Warranty length: Typically 2 years (Check with reseller)
• Value for money: 🔥🔥🔥🔥🔥
• Purchase link: Buy your Braille B3121 No-Weight Extreme Use Carbon Fiber Battery here

Our comment: For those planning a substantial engine swap, want the best performance for your race car, or want to treat your Miata to the best battery, look no further.

This tiny, lightweight, carbon fiber battery packs more of a punch in a smaller, lightweight package than its competitors.

If you’re serious about racing, then each pound counts, and this could present the perfect opportunity for enhanced performance and weight saving at the same time.

Braille has an excellent reputation; many owners have been delighted with their batteries in the long haul.

It is a fantastic choice that will be a convenient fit in the front or rear (with a relocation kit) of your NC/ND Miata, and best of all; it’s currently at the same price as the Optima.

Manufacturer description: “At under 22 pounds, the B3121 is our lightest do eveything battery yet. Using our Advanced AGM racing technology we have put a lot of power into a very small package.”

“With 1380 pulse cranking amps this has enough power to start more than any other battery in its weight class. This is the perfect model for those who want to shave half the weight of a stanard Group 34 battery and still have enough power to crank over a large V8.”

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Duralast Gold Battery 51R-DLG

• Voltage: 12 volts
• CCA (Cold Cranking Amps): 500 A
• Length: 238 mm
• Width: 129 mm
• Height: 223 mm
• Weight: 28 Lbs
• Battery type: Wet Cell
• Warranty length: Typically 3 years (Check with reseller)
• Value for money: 🔥🔥🔥🔥🔥
• Purchase link: Buy your Duralast Gold Battery 51R-DLG here

Our comment: If you’re after a cheap, cheerful, reliable NC/ND Miata battery, look no further than the Duralast Gold battery.

The Duralast Gold has become the most popular choice among NC/ND owners looking to conveniently swap out their tired OEM battery for a quick, easy, and reasonably priced replacement with a good warranty.

Although we advise against wet cell batteries for the Miata, given that the NC/NDs typically have the battery under the hood, this wouldn’t be a problem given the adequate ventilation compared to the trunk.

If you’re using a battery relocation kit to put the battery in the trunk, we certainly wouldn’t recommend using this option but opting for the Braille alternative above.

All in all, this presents an excellent option for those of you wanting to straight-swap your under-hood NC/ND battery at a reasonable price.

Manufacturer description: “Duralast Gold is engineered to deliver the maximum Cold Cranking Amps and Reserve Capacity ratings to meet or exceed your vehicle’s original specifications.”

“Even in extreme conditions, Duralast Gold is designed to give you the starting power you need, combined with robust construction for dependability and long life. Install it with confidence“!

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Flyin’ Miata Mazda ND battery relocation kit

• Value for money: 🔥🔥🔥🔥
• Purchase link: Discontinued

Our comment: These kits have been designed with V8 conversions in mind and provide the perfect solution for those unhappy with Mazda’s decision to move the battery under the hood.

Many owners have voiced their opinions on the battery moving to the front of the Miata, and with this kit, you’ll be able to turn it back to its rightful place.

Flyin’ Miata recommends using the Odyssey PC925T from earlier in our guide with this kit for the ultimate fitment.

They state that it will work with an OEM setup but require some problem-solving.

Although it’s not the perfect solution, it’s worth considering, especially for those of you swapping out your engine.

Manufacturer description: “Anyone who’s been around Miatas knows that the battery only belongs in one place: the trunk. Mazda forgot this in 2006 with the NC, and forgot it again with the ND redesign. Well, we’ve accepted it for too long and now we’re taking action.”

“Includes a Sparco battery switch, a 350A fuse and fuse holder, a kill switch bracket, and all of the wiring (4ga) and hardware needed to move the battery and mount the various bits other than the battery bracket itself. We recommend using an Odyssey PC925T and the matching Odyssey bracket, available all over the place.”

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Our Miata battery winners

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NA/NB Drifted Choice

Our NA/NB winner is the Odyssey Extreme PC925MJT Battery

With the best performance and warranty to match, we feel it’s worth paying a little extra to get the best battery for your NA/NB.

We know many owners who have had fantastic long-term results from this battery.

Also, this is the perfect choice for those looking for a battery to suit the Miata ND relocation kit from Flyin’ Miata.

With an extended life cycle, a fast-charge feature, and an excellent warranty, we believe this has firmly earned its spot as the winner on our list.

Odyssey Extreme PC925MJT Battery

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Budget Miata NA/NB Choice

Our Budget NA/NB Choice is the Deka/East Penn 8AMU1R Battery

A straight replacement for your OEM NA/NB battery, this fantastically-priced offering from Deka just edged past the popular WestCo due to price, but you can’t go wrong with either battery.

If you’re looking for a hassle-free replacement to run on your stock or lightly modified Miata, look no further than the Deka Gold.

Deka/East Penn 8AMU1R Battery

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Miata NC/ND Drifted Choice

Our Miata NC/ND Battery winner is the Braille B3121 No-Weight Extreme Use Carbon Fiber Battery

If your eyes are already watering at the potential cost when you see the words ‘carbon fiber,’ you can wipe them now.

Despite its unique, tiny, lightweight design, this Braille battery is, in fact, a genuine bargain when compared to some of its competitors.

Designed with Corvette V8s in mind, your Miata certainly isn’t too much of a challenge for this incredible battery.

Braille B3121 No-Weight Extreme Use Carbon Fiber Battery

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Miata NC/ND Battery Runner-Up

Our Miata NC/ND Battery Runner-Up is the Duralast Gold Battery

You won’t do better for your money than the exact OEM fit Duralast Gold.

If your original Mazda battery has given up, fear not, as the Duralast Gold comes recommended by just about every NC/ND owner and presents an excellent value-for-money option, with a great warranty included.

Duralast Gold

Thank you for reading our Miata Battery guide.

We hope we’ve helped you decide when figuring out which battery is best suited for your Miata. Now that it is sorted, why not treat your little roadster to a new shift knob?

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Photography credits

We want to thank the following sources for the use of their images:

• eBay
• Amazon
• Flyin’ Miata
• Adrian Kot
• Logan LeGrand
• Jonathan Moreau
• hushypushy
• visualraws
• Robert Couse-Baker
• Michael

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