Using Discarded Laptop Batteries To Power Lights

mrspoonsi sends news of an IBM study (PDF) which found that discarded laptop batteries could be used to power lights in areas where there's little or no electrical grid. Of the sample IBM tested, 70% of the used batteries were able to power an LED light for more than four hours every day throughout an entire year. The concept was trialed in the Indian city of Bangalore this year. The adapted power packs are expected to prove popular with street vendors, who are not on the electric grid, as well as poor families living in slums. The IBM team created what they called an UrJar — a device that uses lithium-ion cells from the old batteries to power low-energy DC devices, such as a light. The researchers are aiming to help the approximately 400 million people in India who are off grid.

Comments

Re:sorry, all my laptop batteries are dead

[mysidia]

If you're discarding laptop batteries while they can still hold a charge

You are likely to discard the battery as soon as it can no longer hold a satisfactory capacity for your application. The battery is no longer effective for your use at that point, and you're wasting electricity time and $$$ and not getting the portability you want.

Based on the IBM study:

Fig. 2 shows the charge capacity as a percentage of designed capacity for the investigated laptop battery packs. We found that although there was a significant variation in the residual capacities, the mean value was 64% while the median was 73%.

The mean value corresponds to more than 50 Wh of capacity for the batteries tested, which is sufficient to power a 3 W LED light bulb, a 6 W DC fan and a 3.5 W mobile phone charger simultaneously, for around 4 hours

Therefore, discarded laptop batteries appear to have satisfactory potential for reuse as backup energy sources to power low energy DC devices

40 watt PC battery vs. 3 watt LED

[billstewart]

Sure, your laptop battery may not hold enough charge to power your laptop any more, but an LED needs a lot less power than your laptop, depending on what it's being used for. Most of the lightbulb-replacement LED bulbs I've seen want 9-23 watts, but the flashlights are more like 3w, and nightlights are more like 0.5 watts.

Also, that laptop battery is a battery of cells, and they usually don't all die at once. They may not be in good enough shape to remanufacture into new laptop batteries, but still have enough of them good enough to disassemble at third-world labor costs to recover cells for off-grid LED lighting.

Re:sorry, all my laptop batteries are dead

[dgatwood]

If you're discarding laptop batteries while they can still hold a charge, not only are you doing it wrong, there is something very seriously wrong with you.

The problem with Lithium ion batteries is that their failure mode is often really obnoxious. When one cell in a pack fails, the battery ceases to be usable as a laptop battery, because as soon as you discharge down below some arbitrary fraction of its capacity, the voltage suddenly plummets below the operating threshold for your hardware, and the machine shuts itself off unceremoniously, with no opportunity to save your work or shut down cleanly. If the failure percentage is 5%, a few people will put up with it, and make a mental note not to let it get too low. If the battery drops dead at 60%, or if the failure point is a bit more variable, then you have to be pretty seriously hardcore to keep using the battery, because you risk losing all your data if you do.

However, under a lighter current draw, those same batteries will behave much better. The voltage probably won't sag at all, because (if I understand the problem correctly) there's enough time for the charge to properly redistribute itself across the entire pack even with a single, high-resistance (bad) cell. And even if it does sag, a voltage sag on an LED light would just make it put out less light, which isn't a big deal. For that matter, if they're cracking open the packs, they could probably fully utilize most of the cells for years before they would fail, so long as they toss the cells that have failed.