A model to recycle smartphone lithium ion batteries into solar power systems

April 19, 2016, American Institute of Physics
The prototype system consisting of a solar panel and 12V LED lamp wired to a battery pack containing three Samsung Galaxy Note 2 batteries. Credit: Diouf/Kyung Hee University

Despite their hefty price tag, smartphones have an average consumer lifetime of about three years. The lithium ion batteries that power them, however, can last for about five years—meaning that just about every discarded smartphone generates e-waste and squanders the battery's twilight years. To cut down on the environmental waste and provide storage for rural communities, researchers at Kyung Hee University in Seoul have proposed a model for recycling unspent lithium ion batteries into energy storage units for solar-powered LED lamps.

Boucar Diouf, a professor in the Department of Information Display at Kyung Hee University in Seoul, describes the logistics of his recycling and repurposing program this week in the Journal of Renewable and Sustainable Energy.

The proposed program consists of five general steps—battery collection, testing and selection, system manufacturing, commercialization, and installation. Each of these steps would provide opportunities for job creation, Diouf said.

The candle and kerosene lamps used to light the homes within many rural communities are harmful, inefficient and more expensive than a small solar home lighting system, provided the right approach is taken, explained Diouf. "Using the battery of mobile phones in small solar home systems becomes obvious in order to make access to electricity easier to those who live without."

Batteries are one of the more expensive components of a solar home system and contribute significantly to the cost barrier of decent lighting systems in . Old car batteries, which are lead-acid based, are commonly used storage units in improvised systems, but don't have a very good lifespan.

A standard phone battery of 1000 milliamp-hour capacity can power a one-watt LED lamp for about three hours, or a 0.5-watt lamp—bright enough for reading and writing—for about six hours. When wired to a small solar panel, this maintenance-free system can last for approximately three years.

The researchers also constructed a full 12-volt system made of three mobile phone batteries of 3100 millliamp-hour capacity each, with a 5-watt LED lamp and a small solar panel, for less than $25. These systems have the capability to light up a room for about five hours each day, and can last for approximately three years without any maintenance.

Future work for Diouf and his colleagues in the field involves setting up battery collection and e-waste recycling systems, as well as contributing to reducing the cost of solar systems for rural populations of developing countries. He plans to start pilot projects in Senegal and sub-Saharan African countries within the next year.

Explore further: So long lithium, hello bacteria batteries?

More information: "A second life for mobile phone batteries in LED solar home systems," DOI: 10.1063/1.4944967

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not rated yet Apr 19, 2016
The lithium ion batteries that power them, however, can last for about five years

That depends on how cheap the batteries are to begin with. The cheapest won't last more than 600 cycles, the typical standard is 700-800 cycles, which goes in about four years of typical use. Any better would be over-engineering and unnecessary cost becuse of the short lifecycle of the products, so they aren't used.

High end models will have high end batteries, but most phones have crappy batteries.
not rated yet Apr 19, 2016
I would just like to know where they manage to get 3 used phone batteries, a 5 watt led and a solar panel capable of charging the batteries for less than $25!

They need a charge controller too for those batteries.... just hooking them up to a solar panel is a recipe for a nasty fire.

not rated yet Apr 20, 2016
They need a charge controller too for those batteries.... just hooking them up to a solar panel is a recipe for a nasty fire.

A zener diode will do for crude cell balancing and overcharge prevention as long as the solar panels are small and cannot push excessive amounts of current.

The solar cells themselves can also be designed with a maximum open cell voltage at the lithium battery charge limits, because each cell of a silicon panel is producing only 0.6-0.7 Volts. You need one more diode to prevent discharge backwards into the cells, so 7 cells in series and a diode should yield a maximum output voltage between 3.6 - 4.3 Volts which is under the upper limit for a typical lithium cell.

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