Zinc-Air Batteries Last All Day

In portable computing, no technology seems to be changing more rapidly than that of batteries. Today, nicad batteries are being eclipsed by nickel-metal-hydride (NiMH) and lithium-ion cells. On the horizon, however, are zinc-air batteries that can power a laptop for between 10 and 15 hours.

AER Energy Resources ((404) 433-2127) has developed zinc-air batteries (priced at $399) for portable systems from Toshiba, Hewlett-Packard, and Zenith that can last an entire workday. Zinc-air cells, which store 150 watt-hours of energy, have two to three times more gravimetric energy than nicad and NiMH batteries, but the batteries are boxy and bulky at about 4 pounds. These batteries use oxygen from the air to support reactions that generate electricity, and they need more airflow than other batteri es.

Besides the benefit of longer running time, zinc-air batteries lack the memory effect found in nicad batteries, so you can recharge them anytime rather than waiting until the battery is totally drained. The batteries, however, endure only 25 to 50 recharge cycles, but according to AER representatives, you get 200 to 400 hours of total run time from a zinc-air battery, which is about the same as with nicad and NiMH batteries that have 200 to 300 recharge cycles.