Primaries

Single-use cells are often referred to as "primaries" or "disposable." Primary cells are not rechargeable, secondary cells are.

Carbon-Zinc

1.5V/cell. These were the original flashlight battery first developed and marketed in 1886. With many refinements over the years, they remained in widespread use through the mid 1970s and are still available today. Also marketed as "Heavy-Duty." These do not last as long as alkaline batteries and do not tolerate heavy loads at all well. Tend to leak when asked to produce more than a few tens of milliamps and when exhausted. Are not able to power devices requiring large current such as digital cameras or flashguns.

The size "D" cell was the original size and remains readily available, along with C, AA, and AAA sizes. Batteries made up of multiple carbon-zinc cells were historically important, notably including the "square" lantern size (2.6" x 2.6" x 3.9") in 6 volts, the larger "rectangular" lantern size (2.75" x 5.75" x 4.875") in both 6 volts and 12 volts, and the 3R12 "flat pack" 4.5 volt battery (67mm x 62mm x 22mm). Other sizes were produced and were occasionally used in flashlights.

Flashlights designed for carbon-zinc batteries most commonly used two or three cells in series, or a battery made from three or four cells internally, though other configurations were also used.

As with alkaline cells, pre-1995 carbon-zinc cells typically contained small amounts of mercury to reduce the incidence of leakage.

Alkaline

1.5V/cell. Alkaline cells were introduced in the early 1970s in the same sizes as the carbon-zinc cells and batteries then available, and reflected an improvement in power capacity and energy capacity over carbon-zinc. They remain in widespread use due to their low initial cost.

Prior to 1996, mercury was used as part of the cathode (negative electrode) in both carbon-zinc and alkaline cells to reduce corrosion and leakage potential. In the mid 1990s, as part of a broader effort to reduce the mercury content of landfilled waste, legislation was enacted in numerous countries prohibiting the addition of mercury to most consumer batteries, leading to a reformulation of these cells. Post-1996 cells are more prone to leakage when stored in a discharged state.

Alkaline cells have higher internal resistance than NiMH rechargeables and lithiums, so they do not perform as well with high-drain applications. They can be very economical in low-drain uses like clocks and remote controls where they will last for years without needing replacement. There are different levels of performance available and Duracell, for instance sells an Ultra Advanced version that has more capacity than their regular copper tops.

Alkaline cells and batteries have been made in many sizes and shapes. The most common sizes used in flashlights have been the D, C, AA, and AAA cells. Lantern and flat pack sizes are also available and still in use. Smaller sizes, including LR44 button cells, N cells, and AAAA cells, are occasionally seen in keychain lights and lights incorporated into writing instruments.

Lithium Iron Disulfide (Li/FeS₂)

Important: ***These are not the same as lithium-ion batteries that can be recharged. These are "primaries" and therefore can be used once and then recycled. If you attempt to recharge them, they will explode (example).***

Lithium Iron Disulfide batteries have been commercially available since 1989. At 1.7 volts they offer rough voltage compatibility with alkaline and carbon-zinc cells and are available in some of the same sizes. They are notable for low-temperature performance and long calendar life, and remain popular for standby applications. At present (2025) the only commercially available with this chemistry is Energizer Ultimate Lithium, and the only sizes being manufactured for use in flashlights are AA and AAA (a 9v battery is also available).

After 10 years, they might retain 80% of their original charge. They are a good choice for an emergency flashlight or one that is not used that often. Because of the extra capacity, some people use them to get the longest possible runtime. They also weigh noticeably less than other batteries.

The higher voltage makes some flashlights brighter than on alkalines or NiMHs but can lead to early failures of incandescent lamps or driver electronics for LEDs. Energizer retains a patent on lithium AA and AAA batteries in the US and therefore are the only company to offer this chemistry there. These batteries are widely available and come in two varieties: "advanced" and "ultimate". The "ultimate" has blue on the label and is the same thing as the earlier e2 lithiums (both versions have the same part number: L91 for AA and L92 for AAA batteries). These are advertised as lasting 8 times as long as alkaline batteries (realistically it might be 4 times as long, but they cost 3 times as much). While they have an initial voltage in excess of 1.7V, this bleeds off very quickly and the temporary increase in brightness compared to alkaline cells is short. Their real advantage is very long shelf-life and low-temperature tolerance, they will still produce useful current at lower temperatures than just about all other cell chemistries. Otherwise they are extremely expensive for the capacity they offer.

Cells in C and D sizes were formerly available. A cost-reduced "Energizer advanced" version was formerly available, with about 75% the capacity.

Lithium Manganese Dioxide (LiMnO₂)

The CR123a cell using LiMnO₂ chemistry was introduced in the mid-1980s and was originally intended for camera applications. It was used by Surefire in 1988 to produce a line of small, high-performance flashlights that were innovative for their time and widely adopted. The cells are nominally 3 volts, but are notable for delivering 1500 mA, much more power for their size than the alkaline cells then in widespread use.

The same chemistry is widely used in button cells, some of which are used in keychain flashlights. LiMnO₂ button cell sizes are expressed as diameter in mm followed by thickness in tenths of a mm. The most common size is 2032, that is, 20mm diameter and 3.2 mm thick. Larger 2450 cells are also in widespread use, and are sometimes seen in flashlights.

Other

Saft - This company has a line of lithium primaries (LiSOCl2 - Lithium-thionyl chloride chemistry) that are 3.6 volts per cell.

Nickel Oxyhydroxide

Now discontinued; introduced in 2006 and discontinued around 2011. 1.7V/cell (?). Duracell PowerPix batteries use a nickel oxyhydroxide (NiOx) chemistry that is supposed to last twice as long as alkalines in digital cameras (high drain) and has a higher voltage, similar to lithiums. However, the actual performance does not seem to be that much higher than alkalines and in low and moderate drain use, there is no advantage.