low power consumption laptops

[Denny Moore]

Well, we haven't tested the netbooks to see if 
they operate on 12 V DC, but we did test a light 
Vaio notebook, a VGN-SZ450N, which uses input 
voltage of 19,5 V.  It would not run on 
15V.  With an adapter to fit the input plug it 
would take solar energy of 18-20 V directly and 
function.  However, for some reason, only about 
1/3 of the watt-hours delivered to the input are 
saved in the battery (our measurements), and that 
is independent of whether the notebook is 
switched on or not.  This is quite bad for use 
with solar energy.  For charging laptops from 12 
V DC current there are DC adapters, for example 
those made by Kensington, that increase the 
voltage till it is appropriate for a particular 
model of a laptop.  These have worked well for us 
and are probably more efficient than using an 
inverter to produce AC current and then the 
transformer of the laptop to convert the AC 
current back to DC.  Another laptop, whose brand 
I don't recall, would accept 18V solar energy 
directly into its input but would not run below a 
certain number of watts.  When the wattage was 
too low the laptop thought that the transformer 
was defective and an amber light would come on 
and the machine would not run.

The general point is that one would want to test 
the particular netbook model to confirm that it 
works with lower voltage, since this is not the 
case with at least some notebooks.

One device that is useful for storing solar or 
other energy and supplying it to devices such as 
notebooks is the Tekkeon MP3450 rechargeable 
lithium battery with adjustable voltage 
output.  It holds about 50-60 watt-hours and can 
supply any laptop (or camcorder) if the right tip 
is used.  There is an optional attachable second 
battery, a mate to the first, which doubles the 
storage capacity.  The only problem we have had 
with these is that when 85-90% full they become 
harder to charge, though that effect  seems to 
disappear by the next day.  That is, the other 
10-15% enters normally the next day.

Hope this is useful.

Denny Moore
Belém, Brazil


At 02:49 PM 4/15/2011, Matthew Dryer wrote:
>I am looking for advice re netbooks that have 
>low power consumption, for use where the only 
>source of power is solar.  Since I am normally a 
>Mac user, I don't know much about 
>netbooks.  Some of the discussion I've seen on 
>this list talks about number of hours the 
>battery lasts, but that's not necessarily the 
>same as low consumption, since one can imagine a 
>laptop whose battery lasts longer than another 
>laptop (because it's a good battery), but which 
>still consumes more energy.  However, I don't 
>know if this difference is in practice real; 
>maybe it turns out in practice that number of 
>hours a battery lasts is a good measure of 
>energy consumption.  Does anyone know the answer to that?
>
>Someone said a few months ago "The best bit 
>about the netbook is that 19V models, as i've 
>said, will run happily in a 12V DC environment 
>without the need for inversion".  Does this mean 
>one doesn't need an adaptor?  I find this 
>attractive since with my Macs I have had a lot 
>of bad luck with adaptors for use with 12V DC 
>failing.  And I can't find any information 
>online about 19V netbooks.  Can anyone recommend a specific model like this?
>
>Thanks,
>
>Matthew