Comparison of AA battery chemistries

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In this article I will look at the 4 different AA battery chemistries: zinc-carbon, Alkaline, Lithium and NiMH. Zinc-carbon, alkaline and Lithium are primary batteries, i.e. not rechargeable, NiMH is rechargeable.

The standard size of AA batteries is 50.5 mm long (including plus pole) and 14.5 mm in diameter, this was standardized in 1947 by IEC (but the battery was in use long before that).



Naming

The AA battery has been around a long time and during that time many different names has been used, both from manufacturers and from standard organizations.
IEC uses R6 for the AA battery size and then places a letter before, depending on chemistry, the most common are: LR6=Alkaline AA, FR6=Lithium AA, HR6=NiMH AA
ANSI uses 15A for alkaline AA, 15LF for lithium AA and 1.2H2 for NiMH AA.
Some of the other names used for the AA cell size is: penlight, mingon, MN1500, M



Voltage, capacity and other info

Zinc-carbon

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These batteries are rated 1.5 volt, their actual capacity is seldom specified, because it varies with load.
The Varta datasheet for these batteries specifies 1000mAh when discharge at unspecified low current. They are rated for a 36 months self life and can be used from -10C to 50C.
The battery weights about 18 gram.

Today they are very rare, because they have been replaced by alkaline batteries, that has considerable better performance.



Alkaline

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These batteries are rated 1.5 volt, their actual capacity is seldom specified, because it varies with load.
Energizer has a datasheet with specifications and their AA has about 2900mAh at 25mA load, but only about 1400mA at 500mA load.
According to Energizer the Alkaline battery will work down to -18C, but with reduced capacity.
The shelf life can be up to 10 years.
The battery weights about 23 gram.

Alkaline batteries is also known to leak and destroy equipment, even unused cells can leak.



Lithium

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These batteries are rated with 1.5 volt and has around 3000mAh.
According to Energizer the battery will work down to -40C, but with reduced capacity.
The shelf life can be up to 15 years.
Unloaded voltage will be around 1.8 volt.
The battery weights about 15 gram.

The lithium batteries compared here is lithium-iron (Li-FeS2) batteries, there does also exist lithium batteries with 3 volt, they are usual sold in other sizes (CR123, CR2), but can also be found in AA size, but cannot be used instead of ordinary AA batteries.



NiMH

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These batteries are rated with 1.2 volt, capacity is marked on the cell and is usual in the 2000mAh to 2700mAh range.

According to Sanyo the battery will work down to 0C, but with reduced capacity.
The shelf life it not rated for rechargeable, but depending on type they can retain charge from a few weeks to a couple of years.

The battery weights 26 to 30 gram.



Comparison

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First curve is at fairly low current. The alkaline battery lasts about 22 hours (2.2Ah at 0.1A), half the time is has higher voltage than the NiMH batteries, the rest of the time lower.
The lithium battery is the only battery that stays close to 1.5 volt and it is also the battery that delivers most energy.
Zinc-carbon cannot compare at all.

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Increasing the current to 1A is very hard on the alkaline battery, the voltage drops below the NiMH after a few minutes and continues down.
Again the lithium battery is the best, with highest voltage and most capacity, the capacity drop from 0.1A to 1A is small.
Zinc-carbon cannot compare at all and is mostly useless at this current.


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At 3A the alkaline battery cannot do much. NiMH works fine.
The lithium cell is also having problems, first the voltage drops, then it increase again while the cell heats.
Zinc-carbon cannot be used at 3A.

capacity

The capacity shows how much current is in the batteries.

energy

With energy it is the product of voltage and current that is summed, a buck or boost can use this energy, i.e. it can use extra voltage for more brightness or runtime.

time

This table is just the capacity converted to time.



Conclusion

The voltage printed on the cells, does not have much relation to actual voltage when using the cell. Alkaline marked with 1.5 volt has lower voltage than NiMH marked with 1.2 volt at higher loads (Like a flashlight on high). At very low loads alkaline will be better than NiMH.
Lithium has the highest voltage in most cases and can handle high loads.



Battery reviews

AA rechargeable
Eneloop AA HR-3UTGB 1900mAh (White)
Eneloop AA HR-3UWXB 2450mAh (Black)


AA primary
Panasonic Pro Power AA
Energizer Ultimate Lithium AA
Varta SuperLife AA