No 9-Volt Test Exists: What 28 AA Batteries Revealed

If you searched for 9-volt alkaline battery testing, here is the honest answer up front: no hands-on 9-volt battery test exists in the data this guide draws from. What does exist is an unusually thorough 28-brand AA battery test, the same alkaline chemistry used in most 9-volt batteries, just packaged differently. The capacity, voltage sag, and cold-weather findings below translate directly to what you should expect from an alkaline battery generally, even though the physical format tested was AA, not 9V.

That distinction matters less than it sounds. Alkaline battery chemistry behaves the same way whether it is packaged as an AA cylinder or a 9V rectangular block: the same tradeoffs around capacity, internal resistance, and cold performance apply. If you came here for a 9-volt buying decision, this is the closest real data available, and it is worth reading with that substitution in mind.

What the testing showed

The numbers below come from Project Farm, who tested 28 brands of AA batteries (alkaline and lithium) for device drain capacity, high-drain voltage, subfreezing performance, and fan runtime. No 9-volt batteries were part of this test. You can watch the full breakdown on the AA batteries test. Blinkspower was named the overall winner, with Power Owl called out as the budget pick.

Capacity claims varied enormously across brands

• Blinkspower: the overall winner of the test, though the specific capacity figure that earned it the top spot is drawn from the full device-drain and fan-runtime comparison across all 28 brands.
• Thunderbolt (Magnum), the Harbor Freight house brand at 23 cents per battery: delivered 2,130 mAh of measured capacity and ran a 2-cell fan for 5 hours 36 minutes, a strong result for a house-brand battery.
• Varta, at 20 cents per battery: delivered 1,829 mAh of capacity but ran the 2-cell fan for only 3 hours 14 minutes, the shortest runtime of all 16 alkaline brands measured in that specific test.
• Power Owl: named the explicit budget pick of the entire 28-brand test, the best value option once price and performance were weighed together.

Cold weather performance separated batteries that looked similar on paper

The subfreezing test, run at approximately 0F, showed real voltage differences between brands that performed similarly at room temperature. Thunderbolt held 0.75V under subfreezing conditions versus Varta's 0.83V, despite Thunderbolt's stronger capacity result at room temperature, a reminder that a battery's warm-weather number and its cold-weather number do not always move together.

How to read this for your own purchase

Since no 9-volt test exists, the practical move is to buy on brand reputation and retailer return policy for 9V specifically, while using this AA data as a guide to which alkaline battery brands generally deliver on their capacity claims versus which ones fall short.

If you need a 9-volt battery for a smoke detector or similar low-drain device, capacity claims matter less than shelf life and leak resistance, neither of which this AA test measured directly. Stick with a major national brand and check the manufacture date on the package.

If you need batteries for anything high-drain, the voltage-sag and capacity data here is a genuine warning: several brands that market aggressively delivered noticeably less real capacity than their stated rating, a pattern likely to hold across battery formats, not just AA cells.

If you are stocking up on batteries broadly (AA, AAA, and 9V) for a household, this test's overall winner and budget pick give you a real, tested starting point for the AA and AAA portion of that shopping list, even if the 9V portion is still an educated guess.

It also helps to understand why a 9-volt battery behaves somewhat differently from an AA cell even sharing the same alkaline chemistry. A 9-volt battery is actually built from six small alkaline cells stacked internally to reach its higher voltage, which means it starts with a much smaller total energy capacity than a single AA cell despite the higher voltage reading. That construction also makes 9-volt batteries more prone to a sharper voltage drop under sustained load, which is one reason smoke detectors chirp a low-battery warning well before the battery is fully dead, the device is designed to catch that steeper decline early. None of this changes the core lesson from the AA test, that claimed capacity and brand marketing do not always match real measured performance, but it is worth knowing the physical difference before assuming AA data translates one-to-one onto a 9-volt buying decision.

A few universal rules the alkaline battery data supports regardless of format:

• Check the manufacture date, not just the brand. All alkaline batteries lose capacity sitting on a shelf, whether packaged as AA or 9V.
• A cheaper battery is not automatically a worse one. The named budget pick in this 28-brand test was chosen specifically because it balanced price against real measured performance.
• Cold performance and room-temperature capacity are separate questions. A battery that tests well warm is not guaranteed to hold its voltage in a cold garage or an outdoor device.

Want to see how these AA and lithium batteries compare in full detail? Browse the rest of the batteries and power banks tests for the complete 28-brand breakdown.