Hardware Hacking Projects for Geeks

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D

Many hacks require a portable power source. Batteries are easy to replace

and an inexpensive source of electrical power. Solar cells provide electricity

when exposed to light, and generators are also available. Let’s take a look at

the pros and cons of each.

Batteries

Batteries are probably the easiest portable power source to work with.

Battery capacity is typically measured in amp-hours or milliamp-hours.

This number is the product of the amount of current (in amps or milliamps)

times the number of hours it can operate. For example, if a battery is rated at

1,000 milliamp-hours of capacity, it can deliver 1 milliamp for 1,000 hours

or 100 milliamps for 10 hours.

Disposable

Batteries generally come in two types, rechargeable and nonrechargeable (or

disposable). Both types are available in many different shapes, sizes, volt-

ages, current capacities, and performance characteristics. Let’s first look at

the ones you toss once their power is depleted.

Zinc carbon cells

One of the earliest types of nonrechargeable batteries was the “dry” cell, or

zinc carbon battery. Previous batteries were composed of solid electrodes

(metal rods) immersed in a liquid solution. The dry cell did not require a

liquid solution, hence the name. The invention of the zinc carbon cell is

attributed to Georges Leclanche, a Frenchman. This type of battery is avail-

able in a variety of sizes and is useful for circuits that draw low-to-medium

amounts of power. Table D-1 lists commonly available zinc carbon batter-

ies and their characteristics. The capacity of this type of battery decreases

when more than a few tens of milliamps are drawn. Ray-o-Vac (http://www.

rayovac.com/) and a number of other companies still make this type of bat-

tery. Check the manufacturer’s web site for details.

D. Power Sources

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Part III: Appendixes

Table D-1. Common zinc carbon battery types

Cell type Voltage Capacity Size

AAA 1.5 300–600 mAh 44 mm × 10 mm (diameter)

AA 1.5 600–1000 mAh 50 mm × 14 mm (diameter)

C 1.5 2200–2700 mAh 49 mm × 25 mm (diameter)

D 1.5 4500–6800 mAh 60 mm × 33 mm (diameter)

9V 9V 350–450 mAh 47.5 mm × 25.5 mm × 16.5 mm

Alkaline

Alkaline cells have begun to overtake zinc carbon cells in popularity, main-

ly due to their ability to hold more electrical power. These cells can also

supply a more instantaneous current than zinc carbon cells. Alkaline cells

are available in many sizes and capacities. Several companies are marketing

improved types of alkaline cells that allow a larger instantaneous current

draw, more capacity than their competition, and limited rechargeability.

Table D-2 lists the basic characteristics of popular alkaline batteries.

Table D-2. Common alkaline battery types

Cell type Voltage Capacity Size

AAA 1.5 800–1100 mAh 44mm × 10mm (diameter)

AA 1.5 1600–2500 mAh 50mm × 14mm (diameter)

C 1.5 5500–7200mAh 49mm × 25mm (diameter)

D 1.5 10,000–15,000 mAh 60mm × 33mm (diameter)

9V 1.5 550–650 mAh 47.5mm × 25.5mm x 16.5mm

Lithium (nonrechargeable)

Disposable lithium-type batteries have been a popular cell for cameras due

to their long shelf life and high capacity. The charge in these batteries can

last for many years without degrading. They also store more power unit

weight and unit volume than other nonrechargeable or rechargeable batter-

ies. Table D-3 lists a few of the commonly available disposable lithium cells

available. This list is not exhaustive, and you should search the web sites of

manufacturers such as Duracell, Sanyo, and Energizer.

Table D-3. Common lithium battery types

Cell type Voltage Capacity Size

AA 1.5 2900 mAh 44mm × 10mm (diameter)

CRV3 3 3000 mAh 52mm × 28mm × 14mm

EL2CR5 6 1500 mAh 45mm × 34mm × 17mm

CR2032 3 225 mAh 3.2mm × 20mm (diameter)

CR2450 3 575 mAh 5mm × 24.5mm (diameter)

Batteries

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