Tech's Files: Battery Power—Conventional or Rechargeable?

Jan 1, 2010 12:00 PM, By Eddie Ciletti



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Five 9-volt variations flank a simple AA battery load tester. In front are AAA and AAAA cells, which can be found inside a 9V battery.

Five 9-volt variations flank a simple AA battery load tester. In front are AAA and AAAA cells, which can be found inside a 9V battery.

Batteries have a language all their own. At the heart of all batteries is a single electro-chemical device called a cell. Examples are the AAA, AA, C and D. In non-rechargeable form, each cell generates 1.5 volts, and when “stacked” (wired in series) multiple cells create a battery; the 9-volt “transistor” and 12-volt “automotive” are the most common. Using simple mathematics, it is obvious that six 1.5-volt cells add up to 9 volts.


More Tips From Eddie Ciletti

Disposable batteries are referred to as a primary power source and are most commonly made from alkaline (zinc-manganese dioxide) and zinc carbon; there are lithium-based disposables, as well. Rechargeable batteries are made from many different materials; nickel cadmium (NiCd), nickel metal hydride (NiMH) and lithium ion are popular with electronic devices; each has properties that make it suitable for certain applications over others.

Relative to primary batteries, the most obvious trade-off with rechargeable batteries is current capacity over time measured in milliAmp-hours (mAh), output voltage (typically less, but improving) and cost. As with many green technologies, the initial investment is higher. Local store prices on single quantities are most discouraging. Bulk buys at specialty stores can cut prices almost in half, yet the cost is easily three times more than, say, a conventional 9-volt battery at $2 a pop in a box of 12.

The Hidden Feature

Modern gizmos are typically rechargeable by design and include power management — an essential feature that's built in to maximize our pleasure and minimize our pain. Familiar examples include laptops, cell phones and cameras that dim or power-down their screens but are otherwise fully capable, ready to do our bidding at the touch of a button.

The magic behind any energy management system is the software equivalent of having a voltmeter, ammeter, chart recorder and a brain, all in one compact package. Not only is energy transfer optimized during discharge (normal use), but also when charging, to maximize the total number of charge/discharge cycles. In plain English, for dealing with more complex and power-hungry gear, power management squeezes every last drop of juice out of the power source.

Elevated Awareness

Using rechargeable batteries in gear designed for disposable batteries requires a higher consciousness. The initial cost is higher, and it's also necessary to buy at least two batteries for every device — at minimum, there should always be one charged spare/backup. All should see regular activity.

When the best a vintage stomp box can offer is being “off” when no ¼-inch plugs are inserted, the onus is on us to be “the brain” that handles the power-management chores. How often have you left something on overnight, only to find it dead in the morning? For this reason alone, rechargeable batteries really do pay for themselves several times over in the long run.


Most rechargeable cells produce in the range of 1.2 to 1.45 volts instead of the typical 1.5 volts. This might not seem to be such an issue for one cell, but in applications where multiple cells are in series, the end results may be just above the minimum threshold for operation. Consider these worst-case examples, based on 1.2-volt cells: a camera expecting to see 6 volts from four AA's instead sees 4.8 volts; walkie-talkies and audio analyzers expecting 4.5 volts from three AA batteries see 3.6 volts.

Dissection of a 9-volt alkaline battery reveals six 1.5-volt cells capable of 565 mAh. The same number of NiCd or NiMH cells — 1.2 volts each — produces only 7.2 volts, so one or two additional cells must be added to make 8.4 or 9.6 volts, respectively. (Lithium-ion cells generate 3.2 volts.)

Primary battery manufacturers are varied, yet we tend to rely on the two popular brands: Energizer (Eveready/Union Carbide) and Duracell. Rechargeables take us into unfamiliar territory, where brand recognition is an oxymoron.

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