New battery technology promises quarter-hour charge

Rechargeable batteries that charge in minutes and last up to four times longer than current cells are coming soon, according to American battery giant Rayovac.

The new technology is based on existing nickel metal hydride (NiMH) chemistry -- the most widespread in general use -- but adds in-battery monitoring and a new basic design. Batteries based on the technology will be included in products from next year, with retail rechargeables in standard sizes available in shops by the end of 2003.

The batteries will recharge in quarter of an hour, says the company, and can be charged to 90 percent of their capacity in ten minutes. Ordinary rechargeables would dramatically overheat and be damaged by such treatment: an in-battery pressure sensor in the new design monitors the precise state of the chemical reaction that takes place during charging. The system, called in-cell charge control (I-C3), is currently going through patenting and has not been fully disclosed.

"Charging so quickly makes a huge difference to portable devices like cellphones, portable games and music players," Jim Pilarzyk, manager of OEM Engineering at Rayovac, told ZDNet UK. "You can just top your charge off in minutes, whenever's convenient." He added that because the batteries did their own monitoring, the charger could be a lot simpler than existing fast chargers. "The cells are a lot more resistant to abuse (than existing rechargeables)," he said.

The new batteries also have a much lower internal resistance, so they can deliver a lot more power in short bursts -- giving up to four times more pictures in digital cameras, says the company. In other applications such as PDAs and mobile phones, they have a more conservative 20 percent advantage over existing batteries, with AA cells having a capacity of 2000 milliamp-hours (mAH) compared to the normal 1600 mAH. They do have one drawback, Pilarzyk said. "Like all rechargeables, they self-discharge when not in use -- around 5 to 6 percent loss of charge per day, compared to existing NiMH batteries at 3 to 4 percent." The new batteries will work perfectly well with old chargers, he said, but without the fast charge advantage. Pilarzyk declined to discuss safety issues, although some form of short-circuit protection will be required to prevent catastrophic overheating in fault conditions given the batteries' ability to produce very high currents.

When launched, the batteries will be available world-wide under the Rayovac name.

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