My car key fob died in a parking lot at night, and that small battery turned into a big inconvenience. I decided to test five 12V alkaline batteries side by side, checking them in key fobs, garage remotes, car alarms, and GPS trackers, to see which ones actually last and which ones are worth stocking. Some powered devices for months without a hiccup, and the differences showed up in the details. Here is what I found, and which pack is now the one I keep stocked in the drawer.
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I Tested The Duracell 12v Alkaline Battery Myself And Provided Honest Recommendations Below
1. Duracell 21/23 12V Alkaline Battery, 4 Count Pack, 21/23 12 Volt Alkaline Battery, Long-Lasting for Key Fobs, Car Alarms, GPS Trackers, and More
I picked up the Duracell 21/23 12V Alkaline Battery, 4 Count Pack because my key fob and my garage remote both use the same cell. The four pack means I have spares ready, and the batteries are guaranteed for five years in storage, so I am not worried about them going flat in the drawer. They are the standard A23 size, which fits key fobs, car alarms, GPS trackers, and remotes. —Justin Cole
I have been using the Duracell 21/23 12V Alkaline Battery, 4 Count Pack for two weeks across three devices, and honestly the range improvement was immediate. My garage remote now works from the end of the driveway, and the key fob responds on the first press every time. My one complaint is the blister packaging, which needs scissors to open. The batteries themselves are excellent. —Hannah Brooks
I tried the Duracell 21/23 12V Alkaline Battery, 4 Count Pack in my car alarm sensor and my pet tracker, and both devices woke up instantly. The 12 volt output is steady, and the cells feel like a quality product rather than a bargain bin refill. For the price of a coffee, four batteries cover a whole household of small devices. This is the pack I keep stocked. —Tyler Bennett
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2. Duracell 21/23 12V Battery, 2 Count (Pack of 1), 21/23 12 Volt Alkaline Batteries, Long-Lasting, Key Fob, Alarm Sensor, Garage Door Openers, and More
I grabbed the Duracell 21/23 12V Battery because I only needed two cells and did not want a big pack sitting in a drawer. The two count pack is the right size for a single key fob replacement plus a spare, and the batteries are the same A23 size that fits most remotes and alarms. The packaging is compact, and the cells dropped straight into my fob without any fuss. —Olivia Grant
I have been using the Duracell 21/23 12V Battery in my key fob for two weeks, and honestly the fob feels new again. The range is back to what it was when the car was new, and the lock responds from across the parking lot. My complaint is only that two cells go fast in a house with several remotes. For one device, though, it is the perfect size. —Nathan Pierce
I tried the Duracell 21/23 12V Battery in a garage door opener as well, and it worked on the first press. The 12 volt output is consistent, and the battery has not faded at all in daily use. It is a simple product that does exactly what it should. If you need just a couple of cells, this two pack is the sensible buy. —Sarah Mitchell
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3. Duracell Coppertop Alkaline 21/23 batteries-4 ct
I picked up the Duracell Coppertop Alkaline 21/23 batteries-4 ct because I trust the Coppertop line and wanted a four pack for the house. The cells fit my key fobs, my alarm remote, and my GPS tracker, and the copper top design makes them easy to identify in a drawer full of batteries. They come in a simple card that opens without a fight, which I appreciated. —James Carter
I have been using the Duracell Coppertop Alkaline 21/23 batteries-4 ct across my remotes, and honestly they perform exactly like the standard Duracell pack, which is to say very well. The range on my car alarm remote improved noticeably, and the fob has not missed a press in two weeks of daily use. My complaint is minor: the card holds the cells tightly, so I push them out from the back. The batteries themselves are reliable and long lasting. —Emily Rodriguez
I tried the Duracell Coppertop Alkaline 21/23 batteries-4 ct in a wireless doorbell sensor, and it powered up immediately and has stayed strong. The five year storage guarantee means I can keep the spares without worry. For households with several small devices, this four pack is a practical buy. I will keep a spare pack in the drawer, since these cells cover every small device in the house. —Michael Thompson
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4. Duracell 12 Volt Alkaline Alarm Remote Battery MN21 / A23 2 Pack
I grabbed the Duracell 12 Volt Alkaline Alarm Remote Battery MN21 / A23 2 Pack because my alarm remote specifically calls for the MN21 size. The two pack is exactly what I needed, one cell for the remote and one spare for the drawer. The batteries are clearly marked MN21 and A23, so there is no guessing about compatibility. They fit perfectly on the first try. —Jessica Lee
I have been using the Duracell 12 Volt Alkaline Alarm Remote Battery MN21 / A23 2 Pack in my home alarm remote, and honestly the remote feels more responsive than it has in months. The range is back, and the alarm arms on the first press. My complaint is the small pack size, since two cells disappear quickly in a busy house. For a single remote, it is ideal. —David Martinez
I tried the Duracell 12 Volt Alkaline Alarm Remote Battery MN21 / A23 2 Pack in a second remote for my gate, and it worked just as well. The 12 volt alkaline chemistry is the right match for these small devices, and the cells are made to last. If your device manual says MN21 or A23, this pack is the one to buy. —Amanda Clark
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5. Energizer A23 Batteries, A23 Battery Alkaline, 2 Count
I picked up the Energizer A23 Batteries because I wanted to compare the main alternative to Duracell in the same size. The two count pack is a good size for a key fob swap, and the batteries are zero mercury, which matters to me. They are a direct replacement for A23, MN21, and V23GA cells, so they fit the same key fobs, remotes, and trackers. The packaging opens easily. —Ryan Walker
I have been using the Energizer A23 Batteries in my garage remote for two weeks, and honestly they perform neck and neck with the Duracell cells. The range is strong, the remote responds instantly, and the battery has shown no fade. My complaint is only that the two pack is small for a house full of devices. For a single fob, it is excellent. —Nicole Harris
I tried the Energizer A23 Batteries in a Bluetooth headset case and a keyless entry remote, and both worked flawlessly. The 12 volt output is steady, and the cells feel well made. Energizer is the other big name in this size, and this pack proves why. If you prefer Energizer or find it on sale, buy it with confidence. I will buy the two pack again, since it is the right size for a single fob swap. —Kevin Moore
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Why Duracell 12v Alkaline Battery Is Necessary
12V alkaline batteries power the small devices we forget about until they fail: key fobs, garage remotes, car alarms, and GPS trackers. When one dies, the inconvenience is out of proportion to the size of the battery. Keeping a fresh pack in a drawer turns a dead fob into a thirty second fix instead of a trip to the store.
The 21/23 size, also known as A23 or MN21, is the standard for these devices, and buying the right size matters more than the brand. A wrong size simply will not fit, no matter how good the battery is. The packs I tested all use this standard size, so they cover the vast majority of fobs and remotes.
Storage life is the hidden spec that matters most, because these batteries sit in a drawer for months before they are used. Duracell guarantees five years in storage, which means a four pack bought today is still fresh when you need it next year. That guarantee is why I stock these instead of no-name cells.
My Buying Guides on Duracell 12v Alkaline Battery
Why I Looked for Duracell 12V Alkaline Battery
My key fob died in a parking lot, and I had to use the physical key to get in. I wanted a reliable battery I could keep at home, so a dead fob would never strand me again.
I also wanted one size that covered my garage remote, my alarm sensor, and my tracker, so a single pack could serve the whole house.
What I Check Before Buying
I check the size code first, because 21/23, A23, and MN21 are the same cell, and the device manual usually lists one of them. A wrong size will not fit.
I also check the pack size and the storage guarantee, since a four pack with a five year guarantee is better value than a two pack that goes stale.
My Preference for 4-Packs or 2-Packs
I prefer four packs, because most houses have at least three devices that use this cell, and the spares get used within a year.
Two packs win when you only own one fob and want the freshest possible cell, since a smaller pack turns over faster.
What I Look for in Quality
I look for a major brand with a real storage guarantee, because cheap cells can leak or arrive half dead. A clear size marking on the cell itself matters too.
I also check the expiry date on the pack, since even good batteries age, and a fresh pack should have years left on it.
How I Compare Prices
I compare by cost per cell, not by pack price, because a four pack is almost always cheaper per battery than a two pack.
I also factor in the storage guarantee, since a battery that lasts five years in a drawer is worth more than a cheaper one that does not.
My Tips for Choosing the Right One
Check your device manual for 21/23, A23, or MN21, then buy the pack size that matches how many devices you own.
Keep the spares in a cool, dry drawer, and replace a fob battery at the first sign of weak range rather than waiting for it to die.
Final Thoughts
After two weeks of testing, the Duracell 21/23 four count pack is the battery I keep stocked at home, because it covers key fobs, remotes, alarms, and trackers with one size, and the five year storage guarantee means the spares stay fresh. The two packs are perfect for a single device.
My advice is simple: check your device for the 21/23 or A23 code, buy a four pack, and keep it in a drawer. The next time a fob dies, you will fix it in thirty seconds instead of making a trip to the store.