A California company says its patented battery life extender will stop people from tossing still-usable alkaline batteries in the trash even though they still have plenty of charge left.

The Batteriser from San Jose-based Batteroo — a thin stainless steel sleeve that can be placed on a new or used battery — can provide an extra 80 percent of battery life, the company claims.

That's because most electronic devices only tap around 20 percent of a battery's usable energy before the device regards it as having insufficient juice, leading a user to toss the battery out, Batteroo says.

The company was co-founded by Bob Roohparvar, who is also a computer science professor at California State University, East Bay.

Batteroo says their Batterisers will be available to fit D, C, AA and AAA batteries and will sell in packs of four for less than $10.

Voltage boosters like the Batteriser are nothing new, experts note; the main feature of the Batteriser is that the technology has been incorporated in a sleeve less than 0.1 mm thick, which means batteries fitted with them will still fit in the battery compartments of most devices.

The sleeve makes contact with the positive and negative ends of a common alkaline battery to extract untapped remaining energy at a steady state system voltage, Batteroo says.

The company says it has tested the product in TV remotes, digital scales, flashlights, wireless keyboards and a number of other devices.

The product has been tested in a laboratory environment.

"When we get a new battery it is 1.5 volts, when we use it in a device it goes down to 1.3 volts under load condition, at that point we consider it to be dead and throw it away," says Kiumars Parvin, a physics professor at San Jose State University. "We tested the Batteriser sleeve in our lab and we confirmed that the Batteriser taps into the 80 percent of energy that is usually thrown away."

A battery's potential energy is like the toothpaste in a tube, Roohparvar says.

"If you just squeeze from the top, you're only going to get so much out of the tube," he says.

An estimated 5.4 billion battery-using devices drive a $14 billion disposable battery market.

Of the estimated 15 billion batteries used up globally each year, only about two percent are disposed of properly, leading to "soil contamination and a laundry list of negative environmental impacts," Batteroo says, suggesting its device could cut the number of batteries ending up in landfill each year by half.