HP recalls 70,000 li-ion batteries

[needWheels]

http://www.cpsc.gov/cpscpub/prerel/prhtml09/09221.html

I wonder if they will ever switch to safer lifepo4 for consumer devices?

[swbluto]

The energy density of lifepo4 is nearly twice that of cobalt lithium (meaning consumer batteries would be nearly twice as heavy), its long life is a deterrent to programmed obsolescence that helps fuel a company's revenue stream and it has a higher market price for a given amount of energy capacity, so I doubt it'll happen anytime too soon in the consumer market. However, they've been using lifepo4 in the "$100 laptop program".

[nutsandvolts]

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[needWheels]

I hope we'll see another evolution of lifepo4 to reduce the weight in the next five years and maybe even the cost.

I did not know that li-ion has a shorter life than lifepo4.
I thought lifepo4 was only 10% larger in mass for the same capacity as lifepo4 but apparently I am very wrong.

But this brings up a concern I've had for awhile - what if these cheap lifepo4 cells from China are cutting corners somehow and are not "pure" lifepo4 - somehow introducing a safety risk, especially as they age? Is this possible? There are claims around here of cheap 18650 lifepo4 cells exploding as people solder them, etc.

[swbluto]

It's not about energy density, it's about volumetric size, LiFePO4 takes up way more space than LiPo.

Yes, that also matters, but I don't think size is the only consideration. I believe consumers do want their game boys and cell phones to be hand held if I'm not mistaken.

For volumetric energy density comparisons, see http://en.wikipedia.org/wiki/Lithium-io ... er_battery and http://en.wikipedia.org/wiki/Lifepo4 . 300/220 is only ~1.4 times as much volume per given capacity. Although, I do believe modern volatile lithium technology has a higher volumetric energy densities and those figures might be old.

[nutsandvolts]

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[needWheels]

I would suspect at your skill level you could rebuild that HP battery much more cheaply by replacing the cells?

From what I have learned it might even be just one bad cell in that pack while the rest could go on much longer?

[nutsandvolts]

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[needWheels]

If you are going to use it on your bike, can't the ac adapter on the laptop convert the 48v output from a lifepo4 pack into what the laptop needs? I get this idea from people using the 5v cellphone chargers to run bike lights, it should be the same concept with just higher wattage?