Hand Crank can only charge the laptop 21 times

[arjs]

(With reference to the the green hand crank) On the page http://wiki.laptop.org/go/Product_News

there is a link to the Freeplay Hand crank spec sheet http://wiki.laptop.org/go/Image:OLPC_clamp_charger_detailed_spec.doc

Page 1 of the spec sheet (under the section of Benefits) mentions that the Crank can work upto 500,000 revolutions.

Cranking at the rated rpm(130rom), it means that it can do 500000/130 = 3846 minutes = 64 hours.

One session of cranking takes about 3 hours, which means that the laptop can only be charged 64/3 = 21 times.

[jg]

Seems like the specs v.s. reality needs testing... Certainly that spec is insufficient....

[vmb]

Replying to arjs:

Page 1 of the spec sheet (under the section of Benefits) mentions that the Crank can work upto 500,000 revolutions.

Actually, no -- it says it's been tested out to 500,000 revolutions, not that it's rated to a lifetime of 500,000. But we do need to get Freeplay to give us a more firm estimated lifetime.

[erikg]

Has anyone ever actually cranked a laptop to full charge from 0?

It seems like an extremely painful process, especially as the freeplay device appears to lack any kind of differential gearing.

[wad]

Closing, since we never approved the Freeplay hand cranks for use with the laptop due to the "extremely painful process" involved.

It is clear that 500K revolutions is insufficient for such a hand crank.