# Direct photovoltaic connenction for a notebook

#### Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

•  Subject
• Author
• Posted on
Has any laptop a programable power input?

The power input is driven by demand.

This means the DC-DC converter takes
from the power input as much power as
the notebook needs.

This is not suitable for the direct usage
of photovoltaic.

http://laptop.pege.org/2007/foldable-photovoltaic.htm

When the photovoltaic can only deliver
15W, but the notebook takes 18W,
it will not happen, that the notebook
takes 15W from the input and 3W from
the battery.

The DC DC will pull down the PV to
short cut Ampere.

So it's necessary to use a buffer battery
http://laptop.pege.org/2005-photovoltaic/sealed-lead-acid.htm

In above case, the PV delivers 15W,
the laptop needs 18W, the buffer battery
will deliver 3W and the PV 15W.

But this requires a car adapter and makes it all very
heavy.

1,8 kg leight weigth notebook
0,8 kg foldable photovoltaic
_______________________
2,5 kg lead acid buffer battery
0,5 kg car adapter

So it would be very nice to eliminate
buffer battery and car adapter and to
use the notebooks internal battery
as the buffer.

This requires an intelligent power input circuit.

There are 2 approaches:

1.) Recognice that there is a photovoltaic attached
Take power at constant 12,5 V
That's not optimal, but will at most times have
more than 80% of the maximum, the PV can deliver

2.) Work with MPP tracking.

MPPT = Maximum Power Point Tracking

At a given amount of light and temperature,
the photovoltaic delivers for each voltage
a given rate of ampere.

The MPPT tries to find the best combination
of V and A to get most W out of it.

So I repeat here my question:

Has any laptop a programable power input?

--
Roland Mösl
http://car.pege.org cars and traffic
http://live.pege.org building and live
http://www.pege.org

## Re: Direct photovoltaic connenction for a notebook

I have a laptop that freezes when I connect external power, but works
ok with battery only, so I experimented a bit and found this:

disconnected battery positive (+) connection
connected multimeter to measure battery power
connected stabilized power supply unit (SPSU), measuring power output,
in parallel to battery
my battery output voltage is around 11.4V
started setting SPSU at 11.4V
switched laptop on, let windows 7 run
ampere readings are the same from both battery and SPSU
rising SPSU voltage output raduces ampere reading from battery, going
to 0A when output of SPSU is near 13.5V, at the same time the power
output from SPSU goes up proportionally

after these tests I am succesfully using the laptop connected to a
regular PC ATX power supply, using a 12V line, keeping the battery (+)
disconnected, and all other battery connections connected, so that
windows is showing the real battery level, 100% going down a bit for
self-discharge

hope this helps