Deconstructing Pop Culture

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Battery Powered

December 15th, 2006 by David Kronemyer · No Comments

A. Overview

There are several different sizes of alkaline batteries used in portable consumer electronic equipment, such as, AAA, AA, C, D, and 9V. All of these put out 1.5 volts of electricity, except for the 9-volt battery, which (duh) puts out 9 volts.

The alkaline battery was invented in 1959. There are several other types of batteries besides alkaline, for example, carbon zinc, nickel-cadmium, nickel-metal hydride (“NiMH”), lithium-ion, and lithium. Alkaline batteries, however, comprise some 80% of the consumer market. There also are many other odd sizes of batteries for cameras, watches, hearing aids, etc.

The three major brands of batteries available for purchase in the U.S. are: Duracell, Energizer, and Rayovac. While all of these companies are publicly-traded, it is impossible to discern from their financial reports how many batteries each company sells, much less anything about revenue or profitability.

In 1998, the U.S. Dep’t of Justice, Office of Justice Programs, Nat’l Institute of Justice, published a peculiar document entitled “New Technology Batteries Guide,” NIJ Guide 200-98 (widely available on the www). Ostensibly designed to appraise law-enforcement personnel about batteries, it is a useful compendium of otherwise-arcane battery lore.

B. Statement of the Problem

For some reason I got interested in how much residual electrical power capacity the United States has, at the level of batteries currently powering portable consumer electronic equipment, and also those available for sale at retail.

In principle, this inquiry should be similar to the one posed during the 1973 – 1974 oil crisis, when the U.S. government was flabbergasted at the extent of residual gasoline capacity on hand in people’s gas tanks (actually, the gas tanks of their cars), and available for purchase at retail filling stations.

The Hunt Brothers found out just how much residual silver capacity there was, when they tried to put the squeeze on the silver market in 1977 – 1978. As the price of silver continued to rise, more and more of it appeared on the market, as people started cleaning out grandmother’s trunk in the attic they hadn’t opened for the last decade, melting down their flatware, etc.

Federal statistics aren’t much help. According to the Environmental Protection Agency (“EPA”), every year in the U.S., “billions” of batteries are bought, used, and discarded – three billion in 1998 alone. And, every year, over 15 billion batteries are produced and sold worldwide. Although interesting, these vague pronouncements aren’t particularly useful.

As a general proposition, it’s unquestionably true increased demand for batteries can be traced largely to the rapid increase in cordless, portable products such as cellular phones, video cameras, laptop computers, and battery-powered tools and toys. More than $50 billion worth of portable products were sold in the U.S. in 2002. This market is estimated to reach nearly $68 million by 2007, an average annual growth rate (“AAGR”) of 2.6%. Furthermore, new technologies such as small fuel cells, with inherently higher energy density, will lead to longer operational time, which will be demanded by the next generation of portable electronics. These platitudes, however, don’t help us quantify the extent of residual battery-power capacity presently available.

There are several battery industry trade associations, but like all trade associations, they shy away from collecting and disseminating market data, out of concern for possible antitrust violations (e.g., price-fixing). Several consulting companies have prepared market research reports, but evidently those are highly proprietary, seeing as how they want thousands of dollars just to look at a copy.

C. Size of the Batteries Market

The most accurate information I could find on-line is, total sales for the U.S. in 2002 battery and battery-related markets was $11.4 billion, with a forecast to grow to $15.5 billion by 2007, resulting in an 6.4% AAGR. Sales of portable batteries are the largest component of U.S. battery market figures, forecast to reach $6.9 billion by 2007, an AAGR of 4.3%.

Another study, though, estimated the U.S. market for batteries at about $2.8 billion in 2003, projecting it will reach about $3.4 billion by 2008. Although the discrepancy between these statistics is large, it probably can be accounted for because the lower number is wholesale, and the larger number is retail; that is, the retail mark-up for consumer products, such as batteries, typically is on the order of 50%.

D. Field Investigation

Although annoyingly imprecise, I concluded the pricing figures most likely would be more accurate, than the quantity figures. I did some field work, and discerned retail prices for batteries were about as follows: “AAA,” $3.99 for 4; “AA,” $5.99 for 8; “C,” $2.99 for 2; “D,” $2.99 for 2; and 9V, $5.99 for 2. Of course there are many variations depending upon the identity of the manufacturer, the type of retail outlet, quantity purchased, and other variables. Let us surmise, though, the average retail price for an AAA battery is $.9975; for an “AA,” $.7488; for a “C,” $1.495; for a “D,” $1.495; and for a 9V, $2.995.

We still need to hypothesize some quantity figures. Based on the distributions in the stores I canvassed, there can be no question, “AA” is the most demanded size (perhaps this also accounts for its lower per-unit price). My guesstimate is it comprises approx. 50% of the market. It’s not possible to realistically evaluate the others’ contribution; in the absence of better data, I’m surmising they divide the remaining 50% of the market equally, that is, 12.5% each.

We also need to imagine how long a battery lasts, which is the main difference between sizes (AAA lasts for the shortest length of time, and D lasts for the longest). If we didn’t adjust for this, an over-all calculation would be impossible, because different-sized batteries would be running out of power at different times. We therefore need to develop a factor to “standardize” the rate of discharge. Since the voltage of a battery is relatively constant, its capacity to store energy is expressed in terms of “ampere hours,” which is the total amount of charge able to pass through it, in an hour’s time.

This won’t be a constant figure, because several other factors come into play, such as how much current is drawn, over what period of time, and even the temperature. For example, an AA-sized alkaline battery might have a capacity of 3000mAh (i.e., 3,000 milli-ampere hours, i.e. it will discharge 3,000 milli-amps over one hour) at low power, but at a load of 1000 mA, which is common for digital cameras, the capacity could be as little as 700 mAh. Source: Duracell Ultra Application Note MX1500 (6/98).

Coupled with this is an additional factor: different manufacturers use different materials, resulting in wide capacity fluctuations. For these reasons, batteries typically aren’t sold with any indications of their capacity. This is what makes using them so frustrating, because you never know how much charge they have left.

Energizer publishes a chart (at DataSheets.aspx) setting forth the nominal capacity of each size in mAh (“nominal” in this context means the shape of the discharge slope over time due to the above factors isn’t considered). It shows the following: “AAA,” 1,250; “AA,” 2,850; “C,” 8350; “D,” 20,500; and 9V, 625.

E. Calculations

Assuming the retail market for these sizes of batteries in fact is $6.9 billion, sales break down as follows: “AA,” 18,429,487,180 batteries sold; “AAA,” 864,661,654; “C,” 576,923,077; “D,” 576,923,077; and 9V, 287,979,967. [One thing that can be said in defense of these figures is, they do in fact comprise “billions.”]

This results in amperage, as follows: “AA,” 5,252,403,846A; “AAA,” 1,080,827,068A; “C,” 4,817,307,693; “D,” 11,826,923,080; and 9V, 179,987,479. For a total of 12,513,218,400 amps.

F. Conclusions

Exactly how much power is this? In the U.S., ordinary household current is 120VAC. If a circuit is rated at 20A, it therefore can power 2,400 watts. A typical U.S. home is wired for 200 amps, meaning, it could, at least in theory, handle 24,000 watts simultaneously (divided into ten 20-amp circuits). This can go pretty fast, though. For example, an electric clothes dryer consumes 4,000 watts/hour; a central air conditioner, up to 5,000 watts/hour; a dishwasher, 1,500 watts/hour. I’m sure everybody is familiar with the phenomenon of the “lights dimming” when a circuit is overloaded, e.g., the coffee-maker turns on at the same time the outdoor lights are on.

Let’s imagine the power grid goes down due to some catastrophic event, and for whatever reason we want to link all of our 1.5V batteries together, to get it up and running again, which will (we hope) take no more than an hour. How much power would we have? We have 12,513,218,400 amps available at 1.5V, which gives us 1,876,982,760 watts (1,876,982.76 kilowatts).

By comparison, according to its website, the ten-year (1996 – 2005) annual average amount of power generated by Hoover Dam was approx. 4.8 billion kilowatt-hours (i.e., one kilowatt of power acting for one hour), or 555,555 kilowatt hours in one hour, which is all the time we’ve accounted for. Thus, all of our batteries lined up end to end would last about 3.38x as long as the amount of power Hoover Dam could put out, over the same period of time.