IBM researchers say 70 percent of discarded laptop batteries could be used to power lighting in locations without reliable electricity supplies. They say it could make LED lighting far more affordable than with either solar panels or rechargable batteries.

The researchers are based in Bangalore and recently carried out tests using UrJar. That’s a gadget they developed that powers low energy devices using Lithium Ion cells from laptop batteries that no longer have enough power to run a computer.

The key is that a laptop battery is made up of multiple cells. The researchers discovered that many of the batteries they tested still had some working cells, even though they had been rejected as “dead.” In a few cases, all the cells were still working, and the only problem was with a conditioning circuit that, for example, is used to reduce voltage if a battery is in danger of overheating.

As part of the research, 25 people from Bangalore without mains power in their home were interviewed about how they powered lighting with rechargeable batteries. Most reported their set-up worked but didn’t give power for long enough, with a consensus that people needed at least four hours of continuous and reliable lighting to allow them to have a good home life or to keep shops open after dark.

UrJar is a play on words for urja (Hindi for energy) and “jar” as a synonym for the box-form of the gadget. The prototypes tested by the researchers used refurbished battery packs to power three built-in devices: a LED light made up of three 1W bulbs; a 5V/1A mobile device charger; and a small table fan.

Several locals were each given an UrJar to use at home or in their shop. All reported getting four to six hours daily use without problems, and most managed to go to or three days without having to recharge the device. While most testers only had the device for a week at a time, one tester was asked to use the device for three months and reported no problems. The researchers believe that a commercial version would be durable enough that it would be viable to offer a one-year warranty.

The report concludes that it could be commercially viable to set up dedicated charging stations in villages without an existing electricity supply, using solar panels, diesel generators or wind turbines. The researchers estimate that if UrJar users were willing to pay 6.5 rupees a day (at the lower end of current household spends on kerosene for lighting), the cost of setting up the charging station could be recouped in three years.