On 02-Oct-05 Randall R Schulz wrote:
Mike,
On Sunday 02 October 2005 06:45, Mike wrote:
...
I wish they were available here. I've been wanting a hand crank laptop since I saw the wind up radio, wondering when or if they'd produce a wind up power supply for other devices..
Old meets new, eh?
I've heard that the Eton Grundig FR200 can charge a cell phone, but I can't see mention of that capability on their Web site catalog. Even if it's true, it's pretty clear it could not power a laptop. They say 180 rotations of the crank over 90 seconds charges the internal lithium-ion battery enough for 40 to 60 minutes of operation. You'd probably have to operate the dynamo constantly to power a device like a laptop.
I think one would need to look at the real power specs for these
things, to see what's really implied. It has been difficult to guess
at these from the press reports.
An example which may help folk to get a feel. Recently I've been
experimenting with my own mobile power supply for an ancient laptop
(Daewoo CPC-7400S) whose internal battery is totally dead.
On the laptop battery it states that it delivers 11 volts, so I had
the idea of buying a 12-volt battery for small motorcycles (YT4L).
The m/c battery weighs about 1.6Kg (3.5lb), and it's compact (about
4in x 2.5in x 4in), so it's easily portable. Rig up a lead with the
right size of insert plug at one end, and you've got a power supply!
The battery has a nominal capacity of 4Ah. With a few tests I've
found that I can run this laptop (which by modern standards is a
very low-power machine) for upwards of 4 hours. One test, in console
mode, involved doing a "du -s /" every five minutes, to exercise
the hard drive reasonably. This one lasted nearly 5 hours before
the battery became insufficient (seems to happen when the battery
voltage drope to about 10v). Running X at the same time cuts the
time by 10-20 per cent. The OS is a straightforward Debian, with
fvwm as X-window manager.
So it seems that weak machine draws about 0.8-1.0 amps at 12 volts,
so 10-12 watts, in a simulation of normal use.
That being the case, it would be interesting to know what wattage
or capacity can be delivered by these human-powered mechanical
devices. A typical bicycle dynamo, for instance, delivers 0.5A
at 6V or 12V (depending on model), i.e. 3W or 6W. When you've
tested your bike-lamp circuit by turning the pedals by hand,
you'll have a feel for the effort required.
Any recent laptop would presumably have greater power requirements.
In any case, to run a computer the power delivered would have to
be kept pretty steady.
Comments welcome!
Best wishes to all,
Ted.
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E-Mail: (Ted Harding)