By Steve Welker
We were talking last week about batteries and how long (or short) they are and they last.
The dual concerns about batteries' size and lifetime has grown in lockstep with the growth in shrinking consumer electronics. Engineers standardized the now-common AA size only 60 years ago. In the past 20 years the smallest commercially available batteries have shrunk to as little as about 1/16th of an inch thick and less than a quarter-inch wide.
As for improving battery life, the alkaline batteries appeared in the 1960s and, as their prices dropped, quickly began replacing the older, shorter-lived zinc-carbon batteries. Today the hot-selling nickel-metal hydride batteries can be recharged up to 1,000 times, theoretically extending their lives into years.
Just last Wednesday Panasonic introduced a new battery, the Evolta, with a 10-year shelf life. Plug it in and the Evolta will power your MP3 player or digital camera 1.2 to 1.5 times longer than conventional "long-life" alkalines.
How many years can a battery last? What better way to keep track of passing time than with a battery-powered wristwatch?
I’ve worn Pulsar wristwatches for at least 20 years, probably because my dad wore Hamiltons for much of his life. Hamilton Watch Co. of Harrisburg, Pa., maker of the first electric wristwatch (the Ventura in 1957) introduced the Pulsar in 1972.
Perhaps more than any other item in consumer electronics, wristwatches created the demand for today’s tiniest, highly efficient batteries. Hamilton Watch Co. started its development of an electric watch in 1946 or 1947, but couldn’t produce a small-enough, long-lasting battery to fit inside the case. Hamilton finally partnered with National Carbon Co. (later Union Carbide, maker of the Energizer) to create the first wristwatch battery in 1954.
Those early Hamilton Pulsars needed a new battery every three months.
My first Pulsar, a graduation gift in the 1970s, went more than a year on a single mercury button battery.
My current Pulsar has run for five years on a single silver-oxide battery.
Sometime late this year or in 2009 I'll probably replace that battery with a lithium iron disulphide battery. It will have a 10-year lifespan.
Size and lifetime aren't the only driving forces in battery technology.
Mercury batteries contained toxic compounds with long persistence in the environment.
Nickel-cadmium batteries hold toxic materials, too; that's one reason why nickel-netal hydride and lithium batteries are quickly replacing them. By the way, you should never throw away used NiCads; instead, take them to Lowe’s, Wal-Mart, Radio Shack and other stores that participate in a national recycling effort.
NiCads have remained on store shelves because they are rechargeable, produce near-constant voltage before becoming exhausted and supply high current (good for electric toys and cordless power tools) when you connect several batteries in series. Their downside is they supposedly suffer from a “memory effect” — I say supposedly, because some manufacturers dispute this — that prevents their being fully recharged unless they’re specially conditioned. Even so, manufacturers produced 1.5 billion a year as recently as 2000.
More recently, engineers have designed more consumer electronics to use nickel-metal hydride (NiMH) and lithium-ion (Li-Ion) batteries. Both are rechargeable. Nickel-metal hydrides cost more than NiCads and their shelf life is shorter. Left unused, NiMH batteries lose about 30 percent of their capacity per month, compared to 20 percent per month for NiCads, which is why you always should check the manufacturing date when you buy any battery. However, NiMHs can be recharged faster than NiCads, they have no “memory effect,” they are environmentally safe and you don’t have to worry about overcharging them.
At first I didn’t like lithium-ion batteries. I read too many stories about their overheating or exploding. I have changeed my mind since more advanced lithium polymer cells (also called “prismatics”) become common and less expensive. Li-Ions show up frequently in personal computers and cell phones, because they have high energy density and they produce electricity at a very steady rate. They also have a very slow discharge rate when not in use. Ford Motors says the keyless entry fob for my 1998 mini-van uses a Li-Ion battery and it’s still clicking away after nearly seven years’ use.
What’s ahead in battery technology? Recent developments have centered on the “e-squared” batteries with titanium technology that supposedly doubles their life. Panasonic's new Evolta also uses a new titanium compound (titanium oxyhydroxide), but gets most of its long life from manufacturing tweaks (slimming down the the sealing gasket and reducing the sidewalls' thickness by 17 percent) that let Panasonic pack in more graphite, manganese dioxide and a zinc corrosion inhibitor. Five or six years ago there was some buzz about “super-iron” batteries using a new, high-valent form of iron, but I haven’t heard much lately. I also remember reading about a flexible battery that could be applied to paper.
The real revolution in batteries may come from carbon nanotube technology being explored right here in North Carolina. Otto Zhou and his colleagues at UNC-Chapel Hill first showed that an array of carbon nanotubes (super-microscopic cylinders of pure carbon) could hold twice the energy of Li-O batteries. Since then, MIT researchers have demonstrated a carbon-nanotube array that can be recharged in 60 seconds.
Carbon nanotubes may drive many changes in tomorrow's technology, but I’ll save that topic for another day ... in the future.
Steve Welker is the editor of SurryBusiness.com. His e-mail address is firstname.lastname@example.org.