BU-106a: Choices of Primary Batteries

Knowing the difference in run-time performance

By far the most common primary battery is the alkaline. The reason for its success is high specific energy but the specific power is less commendable. Alkaline is environmentally friendly, leak-proof even if fully discharged (almost), provides an up to 10-year storage life and has good safety record. The battery can safely be carried on board an aircraft without subject to UN Transport and other regulations.

Moving into other primary batteries with higher capacities leads to lithium-metal batteries. These have very strict air shipping guidelines and must mostly be shipped under the Dangerous Good Regulation. If exceeding a level of lithium metal in the cell, the batteries must be shipped under Class 9 hazardous material. (See BU-704a: Shipping Lithium-based Batteries by Air.)

Lithium-thionyl chloride (LiSOCI2) is one of the most rugged lithium-metal batteries. High specific energy and low weight make it suitable for medical applications and sensors. The ability to withstand high heat and strong vibration enables the battery to serve for horizontal drilling activities, known as fracking.

Like alkaline, lithium-thionyl chloride has relatively high resistance and can only be used for light discharge loads. If stored for a time, a passivation forms between the lithium anode and the carbon based cathode that can be dissipated by applying with a brief load. This layer protects the battery by granting a relatively long shelf life by preventing self-discharge. The lithium-metal imposes strict air shipment regulations and different rules apply to Li-ion.

The nominal voltage is 3.50V/cell; the end-of-discharge cut-off voltage is 3.00V. The specific energy varies and some cells go up to 500Wh/kg. The Temperature range varies from -55°C to +85°C (-67ºF to 185ºF), some specialty cells go up to +130°C (266 ºF).

Lithium Iron Disulfide (Li-FeS2) is a newcomer to the primary battery family and offers improved performance compared to alkaline. Lithium batteries normally deliver 3 volts and higher, but Li-FeS2 has 1.5 volts to be compatible with the AA and AAA formats. It has a higher capacity and a lower internal resistance than alkaline. This enables moderate to heavy loads and is ideal for digital cameras. Further advantages are improved low temperature performance, superior leakage resistance and low self-discharge, allowing 15 years of storage at ambient temperatures.

The disadvantages of the Li-FeS2 are a higher price and transportation issues because of the lithium metal content in the anode. This causes restriction in air shipment. In 2004, the US DOT and the Federal Aviation Administration (FAA) banned bulk shipments of primary lithium batteries on passenger flights, but airline passengers can still carry them on board or in checked bags if the lithium content if not exceeded. Each AA-sized Li-FeS2 contains 0.98 grams of lithium; the air limitation of primary lithium batteries is 2 grams (8 grams for rechargeable Li-ion). This restricts each passenger to two cells but exceptions have been made in which 12 sample batteries can be carried.

The Li-FeS2 includes safety devices in form of a positive thermal coefficient (PTC) that is resettable and limits the current at high temperature. The Li-FeS2 cell cannot be recharged as is possible with NiMH in the AA and AAA formats. Recharging, putting in a cell backwards or mixing with used or other battery types could cause a leak or explosion. (See BU-304a: Safety Concerns with Li-ion.)

Figures 1 and 2 compare the discharge voltage and internal resistance of Alkaline and Li-FeS2 at a 50mA pulsed load. Of interest is the flat voltage curve and the low internal resistance of Lithium; Alkaline shows a gradual voltage drop and a permanent increase in resistance with use. This shortens the runtime, especially at an elevated load.

Voltage and internal resistance of Alkaline on discharge

Figure 1: Voltage and internal resistance of alkaline on discharge.

The voltage drops rapidly and causes the internal resistance to rise.

Courtesy of Energizer

Voltage and internal resistance of Lithium on discharge

Figure 2: Voltage and internal resistance of Lithium on discharge.

The voltage curve is flat and the internal resistance stays low.

Courtesy of Energizer

The AA and AAA are the most common cell formats. Known as penlight batteries for pocket lights, the AA became available to the public in 1915 and was used as a spy tool during World War I; the American National Standard Institute standardized the format in 1947. The AAA was developed in 1954 to reduce the size of the Kodak and Polaroid cameras and shrink other portable devices. In the 1990s, an offshoot of the 9V battery produced the AAAA for laser pointers, LED penlights, computer styli, and headphone amplifiers. (See BU-301: A look at Old and New Battery Packaging) Table 3 compares carbon-zinc, alkaline, lithium, NiCd, NiMH and nickel-zinc and the AA and AAA cell sizes.







Capacity*  AA






Nominal V






Discharge Rate

Very low




Very high







Shelf life

1-2 years

7 years

10-15 years

3-5 years

3-5 years

Leak resistance






Retail **  AA
(2015)     AAA

Not available
in most stores



Not available
in most stores


Table 3: Summary of batteries available in AA and AAA format. The capacity on the AA is double that of the AAA at similar price, making the energy storage cost of the AAA twice than that of the AA.

The AA cell contains roughly twice the capacity of the smaller AAA at a similar price. In essence, the energy cost of the AAA is twice that of the AA. In an effort to downsize, energy cost often takes second stage as device manufacturers prefer to use the smaller AAA over the larger AA. This is the case with bicycle lights where the AA format would only increase the size of the lighting device slightly but deliver twice the energy for the same battery expense. Proper design considerations also help the environment.

Retail prices of the Alkaline AA vary, so does performance. Exponent Inc. a US engineering firm, checked the capacity of eight brand-name alkaline batteries in AA packages and discovered an 800 percent discrepancy between the best and lowest performers. Counting the shots of a digital battery provides such a test as the elevated current of the digital camera stresses the battery more than a remote control or a kitchen clock.

Figure 4 illustrates the number of shots a digital camera can take with discharge pulses of 1.3 watts on alkaline, NiMH and Lithium Li-FeS2 in an AA format. (With two cells in series at 3V, 1.3W draws 433mA.) The clear winner is Li-FeS2 with 690 pulses; the second is NiMH with 520 pulses and the distant third is standard Alkaline producing only 85 pules. Internal resistance rather than capacity governs the shot count. (See BU-801a: How to Rate Battery Runtime)

Number of shots a digital camera can take with Alkaline NiMH and Lithium

Figure 4: Number of shots a digital camera can take with Alkaline NiMH and Lithium

Li-FeS2, NiMH and Alkaline have similar capacities; the internal resistance governs the shot count on a digital camera.   

Li-FeS2, 3Ah, 690 pulses
NiMH, 2.5Ah, 520 pulses
Alkaline, 3Ah, 85 pulses

Test: ANSI C18.1

Courtesy of Exponent

The relationship between battery capacity and current delivery is best illustrated with the Ragone Chart. Named after David V. Ragone, the Ragone chart evaluates an energy storage device on energy and power. Energy in Ah presents the available storage capacity of a battery and is responsible for the runtime; power in watts governs the load current.

Figure 5 illustrates the Ragone chart with the 1.3W load of a digital camera using lithium (Li-FeS2), NiMH and Alkaline. The horizontal axis displays energy in Wh and the vertical axis provides power in Watts. The scale is logarithmic to allow a wide selection of battery sizes.

Ragone Figure 5: Ragone chart illustrates battery performance with various load conditions.

Digital camera loads NiMH, Li-FeS2 and Alkaline with 1.3W pulses according to ANSI C18.1 (dotted line). The results are:

- Li- FeS2 690 pluses
- NiMH 520 pulses
- Alkaline 85 pulses
Energy = Capacity x V
Power = Current x V

Courtesy of Quinn Horn, Exponent Inc.

The performance of the battery chemistries varies according to the position of the Ragone line. NiMH delivers the highest power but has the lowest specific energy and works well at high loads. Lithium Li-FeS2 has the highest specific energy and satisfies moderate loading conditions, and alkaline offers an economic solution for lower current drains.


Presentation by Dan Durbin, Energizer Applications support, Medical Device & Manufacturing (MD&M) West, Anaheim, CA, 15 February 2012

Presentation by Quinn Horn, Ph.D., P.E. Exponent, Inc. Medical Device & Manufacturing (MD&M) West, Anaheim, CA, 15 February 2012


Last Updated 2015-07-06

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On May 29, 2012 at 11:25pm
TVSSubRamanian wrote:

Articles are excellent and are highly Informative.I wish that I get more and more opportunities on practically application of these and disseminate these technically information among interested students

On May 29, 2012 at 11:28pm
TVSSubramanian wrote:

My comments earlier to be read as practical and technical informations

On November 10, 2012 at 9:52am
Jesse Ifarunde wrote:

Excellent article.

On November 7, 2014 at 2:31pm
Michael wrote:

Read the whole 20+ articles here but not being an electrician or anything related to the science leaves me with a question if I may. It all comes down to $$ in my case and trying to find out given an equal battery (or what seems to be) is it worth paying the extra bucks for certain batteries. In my case I am mainly referring to AA, AAA, and small batteries found in watches, calculators etc. Now yes I’ve seen the really cheap batteries not being worth it at all as they don’t last long but what are good tips regarding such purchases. Is Duracell really that much better than Eveready, Panasonic or others? As you know even the same manufacturer has the same type of battery which isn’t the same, and having different prices. Thanks

On November 23, 2014 at 4:45am
Jeff wrote:

Alkaline cells have only one role and are not worth purchasing at all in anything else. I use them only in clocks. They have too much of a tendency to leak to be trusted in any of my remotes. I use rechargeable cells in everything else. The development of the lifepo cells have been a huge advance. I really could care less if Duracell makes a better alkaline cell than everyone else. Alkaline cells are mostly junk. They can’t handle high current loads, leak when exhausted, expensive, non-rechargeable, and have a poor discharge curve. They perform well only when compared to carbon-zinc and zinc chloride cells. Why people still purchase them is beyond me. The cursed cells come included in a lot of items and I save them for my clocks.  In fact, if I were to actually purchase a primary cell for my clocks, it would be the zinc chloride chemistry as they perform nearly as well in low drain devices for far less cost. As far as watch batteries, silver oxide is superior to alkaline as the little alkaline cells swell up as they are exhausted. Lithium is the way to go for primary cells and batteries. In my small flashlights and laser pointer which normally uses 3 LR44 cells in series, I have been able to substitute a rechargeable 10180 li-ion cell with superior results. There is now an equivalent to to the alkaline LR44 cell using LiFeS2 chemistry, but until the prices come down on those, I will continue to use the silver oxide cells with the EPX76 superior to the 357 types in my experience.

On November 23, 2014 at 9:28am
Michael wrote:

Jeff thanks. It seems to me that perhaps you are suggesting the rechargeables have improved significantly since 5 years ago. My problem in the past with such cells was that they lost power too quickly. I’d rather pay a little more than have to change and charge batteries that often. I say ‘‘pay a little more’’ because to me after calculating the price of such rechargeables and the charger itself I didn’t really see much of a difference compared to the stats. This does seem to change from manufacturer to manufacturer, type to type and construction to construction of all parts involved. I still have the original battery inside my ipod 3G making it I think 6 years old now and yet other similar batteries needed replacement after a year or so—camera, cell phone. I find it interesting whereby you say alkalines ‘can’t handle high current loads’ I didn’t know batteries were used for high current loads with a few exceptions. When I think of such batteries I think of where I use them: a mouse. keyboard, stylus pen, mp3 player, xbox controller, flash light, clock, whereby the xbox is the only one that drains them quickly enough all others last a long time compared to those things I have which have their own rechargeables inside them: cell phone, ipod, camera. I also have a camera flash which has both its own rechargeable pack (with AA’s) or whereby I can place alkalines instead and alkalines last a lot lot longer—though yes, in this case there is a difference in price

On January 20, 2015 at 12:23am
Jeff wrote:

Hi Jeff, Where are you from, Why you are so professional about the battery? I want to learn more from you. zzrm316@163.com