What Is A AAA Battery? | Tiny Power Facts

AAA battery basics

AAA, or “triple-A,” is a standard cylindrical cell size that delivers portable power in slim devices like remote controls, wireless mice, thermometers, toys, and headlamps. The size trades capacity for a narrow body, so it fits grips, pens, and slim battery bays where a wider AA will not. The AAA format works with several chemistries, most commonly alkaline for single use and nickel-metal hydride for recharge.

Every chemistry that shares the AAA shell follows common dimensions so the cell slides into the same holder. That interchangeability lets you pick between long shelf life primary cells or rechargeable packs that cut waste and save money across many cycles.

AAA quick specs by chemistry

What is AAA battery size and code names

An AAA cell measures 10.5 mm across and 44.5 mm long. Makers and standards bodies label the same size with different short codes tied to chemistry. Alkaline AAA carries the IEC code LR03 and the ANSI code 24A. Nickel-metal hydride AAA carries the IEC code HR03 and the ANSI code 24H. Zinc-carbon AAA uses IEC R03 with ANSI 24D. Lithium iron disulfide AAA uses IEC FR03 with ANSI 24LF. You will also see brand codes like MN2400, E92, or E96 that map back to the same size.

Those letters tell you both the shell size and the chemistry inside. The “R” marks a round cell, while L, H, F, or none mark alkaline, NiMH, lithium iron disulfide, or zinc-carbon. The numbers point to the AAA size. If you match both size and chemistry, device behavior will match the spec on the label.

Dimensions in detail

The 10.5 mm by 44.5 mm size includes the small positive button on top and the flat negative base. That tight tolerance lets spring contacts grab the ends cleanly. Do not force a cell that binds in the tray; mismatched sizes damage holders and can deform the jacket.

AAA cell: voltage, capacity, and runtime

Primary AAA alkaline cells list 1.5 V on the label. Rechargeable NiMH AAA cells list 1.2 V. Many readers see that lower number and worry. In practice, most gadgets work fine with either because the voltage curve and internal resistance differ. Fresh alkaline starts near 1.6 V at light loads but sags as it discharges. NiMH holds near 1.2–1.3 V through much of the cycle and can supply higher current with less sag.

Capacity depends on chemistry, load, and cutoff. Alkaline delivers more at light loads, while NiMH outpaces it in cameras, toys, or flashlights that draw more current. A quality NiMH AAA usually lands between 800 and 1100 mAh. That number is measured at a defined discharge rate and cutoff voltage, so real runtime varies by device design.

Why 1.2 V works in devices rated for 1.5 V

Most devices that fit AAA cells use boost or buck converters or have wide input windows. Engineers design for the falling output of alkaline, so a steady 1.2–1.3 V from NiMH still meets the circuit’s needs. Series packs also raise the total: four NiMH AAA cells deliver about 4.8–5.2 V across the pack when loaded, which sits close to the range the same pack of alkaline cells provides under use.

Chemistry types you’ll see

Alkaline (LR03)

Single-use alkaline dominates retail shelves. It offers a long shelf life and low self-discharge, which suits remotes and clocks that sip current. Look for maker data sheets if you want service hours at specific loads and temperatures. One quick reference is the Energizer E92 sheet, which lists AAA as LR03 and ANSI 24A and charts runtime under varied loads. Energizer E92 technical sheet

Zinc-carbon (R03)

This older primary chemistry costs less and targets light-duty gear. Service life is shorter, and performance drops in the cold. Many brands now steer users to alkaline for better consistency unless a manual calls for zinc-carbon for a light, infrequent draw.

NiMH rechargeable (HR03)

Rechargeable NiMH AAA pairs well with cameras, toys, trimmers, and LED lights. Modern low-self-discharge types keep a charge on the shelf and work across many cycles. Rated capacity often sits at 800–1100 mAh. A typical datasheet marks the AAA code as HR03 and the nominal voltage as 1.2 V. Energizer HR03 datasheet

Lithium primary (FR03) and lithium-ion 10440

Lithium iron disulfide AAA is a primary cell that holds voltage under load and works better in the cold than alkaline. The label still reads 1.5 V. Separate from that, some vendors sell 10440 lithium-ion cells in an AAA-sized can. These are 3.6–3.7 V nominal and must only go in devices that state they accept 10440 or Li-ion. Never mix a 10440 with standard AAA cells in the same device.

Runtime tips and charging notes

Match chemistry to the job. For a TV remote that sits idle for weeks, alkaline works well and resists self-discharge. For gear that drains cells fast or gets daily use, low-self-discharge NiMH pays off. Keep two sets and rotate. Label sets so the cells that live together charge and discharge together.

Use a smart charger made for NiMH with independent bays. Charging by time or in pairs leads to weak packs. A charger that terminates on −ΔV or temperature rise protects cells and shortens the time from empty to full. If the charger offers refresh cycles, run them a few times each year to balance packs.

Cold weather lowers available capacity. Store spares in a room-temperature drawer, not in a hot car or a freezer. If a cell leaks, handle with gloves, wipe the bay with a cotton swab and isopropyl alcohol, and recycle the damaged cell.

Storage, safety, and disposal

Remove cells from seasonal devices before long storage. Keep packs away from metal parts that could bridge the terminals. Do not mix old and new cells in one device, and do not mix chemistries in a series pack. If a device shows erratic behavior, replace the full set at once.

Recycling policy varies by location. Single-use alkaline may go in household trash in many areas, yet recycling is the better choice. Rechargeable cells and any lithium type should go to drop-off programs or a hazardous-waste site. The U.S. EPA battery guidance outlines safe transport and drop-off basics, like taping terminals on loose lithium cells to prevent shorts.

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