How good can batteries get?

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More years back than I care to count, when I was beginning to shave, the Gillette brand was synonymous with disposable blades. These lasted only for one or two shaves, even on my adolescent fluff, but they seemed sharp enough by the standards of the day.

Then everyone started talking about new Wilkinson Sword superblades that lasted for several shaves and made the old Gillettes feel like a rusty chisel. It sounded like an advertising spiel but it was absolutely true. Shops soon ran out of supplies and a black market sprang up. Shady characters would come up to you in the street and whisper in your ear: "Psst ... want to buy some Wilkinson Sword?"

Shortly afterwards Gillette too came out with a similar class of blade. I would be the last to suggest that it had had the technology all the time; but if it had, there would have been little incentive for it to release a product that was going to reduce sales.

There is a delicious twist to this story. In 1996 Gillette bought the battery manufacturer Duracell, whose products are similar to razor blades in that the better they get the fewer they are likely to sell.

It happened that I bumped into a former Duracell employee, consultant John Broadhead, at Comdex, where he was evangelising some interesting specialist microbatteries . He told me that at the time of the Gillette takeover Duracell had for some time had the technology for a longer-lasting battery. There are, of course, many reasons why a launch might be delayed: new products have to be tested for safety, for instance.

What is sure is that Gillette, perhaps fearing of replay of the Wilkinson story, quickly released the Duracell Ultra battery. Within months Duracell's US market share dropped 8percent as users switched the more expensive but longer-lasting product.

The manufacturer's problem is not limited to use-once primary batteries: cheap, powerful rechargeables could nigh-on kill the market for throwaways. But it would be unwise to conclude that battery makers are holding back better products. If they are they must have nerves of steel, with every man's uncle looking for better ways to deliver energy on the move.

A company called the Electric Fuel Corporation has announced a zinc-air micro fuel cell for small devices with an energy density of 400 watt-hours per kilogram(wH/Kg). That translates into a 3 x 3 x 0.25in (7.6 X 7.6 x 0.7cm) battery weighing 3ounces (90grams) with a life of some 16 hours, the company claims.

But it is cagey about prices, and the fact that the new cells are not rechargeable limits them to the market for back-up power sources. A spokesman for the company said: "We could make a rechargeable zinc-air micro cell but the energy density would be less than that of Lithium-ion [the leading rechargeable technology]."

Electrovaya, a Canadian company that makes auxiliary batteries for mobile devices, including notebooks, claims to have achieved the world's best Lithium-ion energy density. Its 0.9Kg PowerPad 160, which looks like a 9.5mm-thick mouse mat and is said to drive a notebook for up to 12 hours, has a claimed density of 470 watt-hours per litre(wH/l), or 195(wH/Kg).

"Our competitors are around 400 wH/l, or 165wH/Kg,' claimed Pat McCool, vp of sales. "We will be moving to 500wH/l very quickly and we expect 600wH/l within a couple of years." He says Electrovaya achieves its high density by its choice of materials, plus efficient packing and mixing.

Watch out for more on this subject shortly in PCW.
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See also:

Boffins show off miniature fuel cell

Prototype could soon replace rechargeable batteries  25 Feb 2002

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