Anyone know of any solar cell vendors that sell
solar cell modules that put out 6-9volt @ 100mA?


TIA,









Remove "HeadFromButt", before replying by email.

I think Harbor Freight had something.
Lots of stuff from places like Electronic Goldmine,
and others, real cheap.

Anyone know of any solar cell vendors that sell
solar cell modules that put out 6-9volt @ 100mA?
TIA,

maxfoo wrote:

Anyone know of any solar cell vendors that sell
solar cell modules that put out 6-9volt @ 100mA?

TIA,

Remove "HeadFromButt", before replying by email.

JC Whitney sells 12 volt panels competitively. These are not as
efficient when loaded to 6-9 volts, but they put out at least as much
current as when run with a 12 volt load.
http://www.jcwhitney.com/webapp/wcs/...X&appId=385939
--
John Popelish

Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run
the cells at their optimum load.

Regards, Joerg.

Joerg wrote:

Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run
the cells at their optimum load.

Regards, Joerg.

Seems foolhardy to me, to use a boost circuit, and waste a lot of power.
Just put more PV cells in series to increase the voltage.

On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the
Dark Remover\"" wrote:

Joerg wrote:

Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run
the cells at their optimum load.

Regards, Joerg.

Seems foolhardy to me, to use a boost circuit, and waste a lot of power.
Just put more PV cells in series to increase the voltage.

The solar cell operates as a (badly) regulated power supply with
current limiting. At low load currents, the cell operates nearly as a
constant voltage source, but after a specific current (for a given
illumination) it operates nearly as a constant current source and
deliver approximately that current even into a short circuit.

The largest power from the cell (for a specific illumination) is
obtained at the point it switches from constant voltage to constant
current mode, in which both the voltage is quite close (within 30 %)
of both the maximum voltage (as measured at open circuit) and maximum
current (as measured at short circuit).

This maximum power point varies with illumination, but if the switcher
always loads the cell at this maximum power point, the largest
available energy at a specific time is extracted from the cell
independent of illumination.

Even if the losses in the maximum power point tracker is 10-20 %,
usually more energy can be obtained than running the module in some
non-optimal constant voltage or constant current mode.

Paul

"Paul Keinanen" wrote in message
...
On Mon, 12 Apr 2004 13:02:38 -0700, "Watson A.Name \"Watt Sun - the
Dark Remover\"" wrote:

Joerg wrote:

Another option might be to use a different voltage panel,
whatever has a good price, and then use a small switcher to run
the cells at their optimum load.

Regards, Joerg.

Seems foolhardy to me, to use a boost circuit, and waste a lot of
power.
Just put more PV cells in series to increase the voltage.

The solar cell operates as a (badly) regulated power supply with
current limiting. At low load currents, the cell operates nearly as a
constant voltage source, but after a specific current (for a given
illumination) it operates nearly as a constant current source and
deliver approximately that current even into a short circuit.

The largest power from the cell (for a specific illumination) is
obtained at the point it switches from constant voltage to constant
current mode, in which both the voltage is quite close (within 30 %)
of both the maximum voltage (as measured at open circuit) and maximum
current (as measured at short circuit).

This maximum power point varies with illumination, but if the switcher
always loads the cell at this maximum power point, the largest
available energy at a specific time is extracted from the cell
independent of illumination.

Even if the losses in the maximum power point tracker is 10-20 %,
usually more energy can be obtained than running the module in some
non-optimal constant voltage or constant current mode.

Paul

Yeah, I see what you mean, sort of like an impedance match, but at DC.
But at the beginning or end of the day, or cloudy day, you can't pull
any more energy out of the cells than there is there. What it looks to
me is that you're adding circuitry to give a better match at the ends of
the day or a cloudy day, and in return sacrificing a few percent
overall.

My attitude is that rather than try to do this (and in the process lose
reliability), it's better to go supersize on the cells, add more area
and overall capacity to get you thru the cloudy days, and have a higher
capacity overall.

Watson A.Name - "Watt Sun, the Dark Remover" wrote:
My attitude is that rather than try to do this (and in the process lose
reliability), it's better to go supersize on the cells, add more area
and overall capacity to get you thru the cloudy days, and have a higher
capacity overall.

The argument usually goes that getting, say, 10-20% more power from a better
charge controller (one of these so-called 'maximum power point controllers')
can be cheaper (in additional expenditures) than getting 10-20% larger
panels. It's sometimes difficult to show, though, particularly on small
systems -- but MPPT controllers have been getting cheaper for awhile, now,
and I expect that eventually all but the cheapest/smallest will have this
functionality.


---Joel Kolstad

Watson A.Name - "Watt Sun, the Dark Remover" wrote:
My attitude is that rather than try to do this (and in the process lose
reliability), it's better to go supersize on the cells, add more area
and overall capacity to get you thru the cloudy days, and have a higher
capacity overall.

The argument usually goes that getting, say, 10-20% more power from a better
charge controller (one of these so-called 'maximum power point controllers')
can be cheaper (in additional expenditures) than getting 10-20% larger
panels. It's sometimes difficult to show, though, particularly on small
systems -- but MPPT controllers have been getting cheaper for awhile, now,
and I expect that eventually all but the cheapest/smallest will have this
functionality.


---Joel Kolstad

On Tue, 13 Apr 2004 09:18:00 +0300, Paul Keinanen
wrote:


The solar cell operates as a (badly) regulated power supply with
current limiting. At low load currents, the cell operates nearly as a
constant voltage source, but after a specific current (for a given
illumination) it operates nearly as a constant current source and
deliver approximately that current even into a short circuit.

The largest power from the cell (for a specific illumination) is
obtained at the point it switches from constant voltage to constant
current mode, in which both the voltage is quite close (within 30 %)
of both the maximum voltage (as measured at open circuit) and maximum
current (as measured at short circuit).

This maximum power point varies with illumination, but if the switcher
always loads the cell at this maximum power point, the largest
available energy at a specific time is extracted from the cell
independent of illumination.

Even if the losses in the maximum power point tracker is 10-20 %,
usually more energy can be obtained than running the module in some
non-optimal constant voltage or constant current mode.

Paul

I have seen elegant ckts where a simple switcher was used, regulating
the *input* voltage coming from the solar cell, keeping it in max
efficiency mode at all loads. This obviously only works with flexible
loads such as slow chargers or such.

--
- René