You've asked for a module that puts out 6-9 volts @ 100 mA. A more
accurate description of a solar panel would be that it puts out 100 mA
at 6-9 volts. Solar cells act a lot more like a current source than a
voltage source. So a panel that's rated at 100 mA at 12 volts will also
put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA,
but not a whole lot more.) The open circuit voltage of a "12 volt" solar
panel (one intended to deliver current to a 12-14 volt load) will be
somewhere around 18 or 20 volts, and one specifically designed to work
at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 -
9 volt device that you want to power with solar cells, you'll have to
float the panel across a battery, or use a voltage regulator to limit
the voltage. (A properly sized zener diode would be adequate for the
power level you're dealing with.) A 12 volt panel will be physically
larger than you need, but it might be easier to find and less expensive.

If you're looking for a module that includes a built in voltage
regulator to limit the voltage to 6 - 9 volts, you need to make it
clear. Most of the responses seem to be referring to 12 volt panels,
which will be fine if you limit the voltage, but won't be suitable if
you need voltage regulation to be included in the external module.

Roy Lewallen, W7EL

Bill Bowden wrote:

maxfoo wrote in message . ..

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


TIA,



Lots of solar panels for sale on ebay. Here's a 12 volt 200mA
unit for 11 dollars.

Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1


-Bill

Hi;
I must say that this last responce was well writen and informitive, it
was a pleasure to read.

Thank you Mr. Lewallen


On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen
wrote:

You've asked for a module that puts out 6-9 volts @ 100 mA. A more
accurate description of a solar panel would be that it puts out 100 mA
at 6-9 volts. Solar cells act a lot more like a current source than a
voltage source. So a panel that's rated at 100 mA at 12 volts will also
put out about 100 mA at 6 or 9 volts. (It'll be a bit more than 100 mA,
but not a whole lot more.) The open circuit voltage of a "12 volt" solar
panel (one intended to deliver current to a 12-14 volt load) will be
somewhere around 18 or 20 volts, and one specifically designed to work
at 6 volts will be about half that, 9 or 10 volts. So if you have a 6 -
9 volt device that you want to power with solar cells, you'll have to
float the panel across a battery, or use a voltage regulator to limit
the voltage. (A properly sized zener diode would be adequate for the
power level you're dealing with.) A 12 volt panel will be physically
larger than you need, but it might be easier to find and less expensive.

If you're looking for a module that includes a built in voltage
regulator to limit the voltage to 6 - 9 volts, you need to make it
clear. Most of the responses seem to be referring to 12 volt panels,
which will be fine if you limit the voltage, but won't be suitable if
you need voltage regulation to be included in the external module.

Roy Lewallen, W7EL

Bill Bowden wrote:

maxfoo wrote in message . ..

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


TIA,



Lots of solar panels for sale on ebay. Here's a 12 volt 200mA
unit for 11 dollars.

Http://cgi.ebay.com/ws/eBayISAPI.dll...7173 830&rd=1


-Bill

On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote:

If you're looking for a module that includes a built in voltage
regulator to limit the voltage to 6 - 9 volts, you need to make it
clear. Most of the responses seem to be referring to 12 volt panels,
which will be fine if you limit the voltage, but won't be suitable if
you need voltage regulation to be included in the external module.

my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with
a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a
battery pack with a 9v type clip. Wanted to be able to charge the batteries with
solar cells basically.

But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No?

thanks,







Remove "HeadFromButt", before replying by email.

maxfoo wrote:
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote:


If you're looking for a module that includes a built in voltage
regulator to limit the voltage to 6 - 9 volts, you need to make it
clear. Most of the responses seem to be referring to 12 volt panels,
which will be fine if you limit the voltage, but won't be suitable if
you need voltage regulation to be included in the external module.


my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with
a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a
battery pack with a 9v type clip. Wanted to be able to charge the batteries with
solar cells basically.

But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No?

For 6V, I would put two of these in series, along with a 1N5817 schottky
diode to prevent reverse current. Each cell is encapsulated with epoxy
and the wires can be soldered to the pads on the back. Each puts out an
honest 30 mA, or more in bright sunlight. Price is reasonable too.

http://www.allelectronics.com/cgi-bi...-60&type=store

You can also put two pairs in parallel to get a faster charge.

thanks,

But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No?

thanks,



My experience with tying together solar cells is that you'll probably
destroy a few along the way (the pads lift very easily when heated
with soldering iron), so either get extras or go with a solution which
does not require you to solder cells together (or be more careful than
I was, I guess).

maxfoo wrote:
On Mon, 12 Apr 2004 00:11:36 -0700, Roy Lewallen wrote:


If you're looking for a module that includes a built in voltage
regulator to limit the voltage to 6 - 9 volts, you need to make it
clear. Most of the responses seem to be referring to 12 volt panels,
which will be fine if you limit the voltage, but won't be suitable if
you need voltage regulation to be included in the external module.


my pcb has a Linear Tech LT1117-5 LDO regulator on board, regulates 5volts with
a min input Voltage of 6 volts, so I'm currently using 4 AA batteries in a
battery pack with a 9v type clip. Wanted to be able to charge the batteries with
solar cells basically.

But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No?

For 6V, I would put two of these in series, along with a 1N5817 schottky
diode to prevent reverse current. Each cell is encapsulated with epoxy
and the wires can be soldered to the pads on the back. Each puts out an
honest 30 mA, or more in bright sunlight. Price is reasonable too.

http://www.allelectronics.com/cgi-bi...-60&type=store

You can also put two pairs in parallel to get a faster charge.

thanks,

But after searching the web a bit it seems cheapest to buy individual cells
then tie them in series...No?

thanks,



My experience with tying together solar cells is that you'll probably
destroy a few along the way (the pads lift very easily when heated
with soldering iron), so either get extras or go with a solution which
does not require you to solder cells together (or be more careful than
I was, I guess).

Roy Lewallen wrote:

You've asked for a module that puts out 6-9 volts @ 100 mA. A more
accurate description of a solar panel would be that it puts out 100 mA
at 6-9 volts.

Also the currewnt outputdepends somewhat on the latitude you're at. You
won't get all that current at the arctic circle.

Watson A.Name "Watt Sun - the Dark Remover" wrote:
Also the currewnt outputdepends somewhat on the latitude you're at. You
won't get all that current at the arctic circle.

He might actually have a better chance there during the periods when the sun
never sets than at, e.g., the equator... solar cells are noticably more
efficient when they're keep cold, which is typically a lot earier to do in
the arctic than at the equator!

In article , "Joel Kolstad"
writes:

Watson A.Name "Watt Sun - the Dark Remover" wrote:
Also the currewnt outputdepends somewhat on the latitude you're at. You
won't get all that current at the arctic circle.

He might actually have a better chance there during the periods when the sun
never sets than at, e.g., the equator... solar cells are noticably more
efficient when they're keep cold, which is typically a lot earier to do in
the arctic than at the equator!

Ahem, Joel, consider the location of "the land of the midnight sun..."

:-)

Ackshully, based on a little bit of experience on Solar One, the
first (of two) experimental 50 MWe solar plant in Barstow, CA,
(in the middle desert of California with not much else), sunlight
has a considerable variance in energy over the course of a day.
A combined buck-boost switching power supply would be a
consideration for reliable solar cell charging of a secondary
battery during daylight. There are several different ICs just for
the purpose of wide-voltage-range inputs from National, Linear,
and Maxim along with application notes from all three.

Roy Lewallen hit the subject nail on the head in saying, correctly,
that solar cells behave more as constant-current sources than
constant-voltage (as batteries are) sources. Those who care to
test that will find out from connecting a fixed resistor to solar cell
outputs and measuring the voltage during the course of daylight,
especially the differences between clear and cloudy skies.

Solar One was a boiler system, over 500 independent mirrors were
used as a giant reflector array to focus sunlight on a central boiler
made from the same stainless-steel-like tubing used in rocket engine
bell structures. Rocketdyne Division of Rockwell International was
the subcontractor to MacDonnell-Douglas that made the boiler and
the underground steam-heat storage system of Solar One. The peak
daylight energy was in excess of 100 MWe equivalent but the extra
heat had to be stored overnight for the steam-turbine-powered
generators to run 24/7. Rocketdyne, now purchased by Boeing,
made the Space Shuttle Main Engines. Rocket engine bells
are made from tubing to circulate fuel before entering combustion.
That pre-warms the fuel as well as cooling down the tail of the
engine's output.

Not exactly what a QRP operator would need... :-)

Len Anderson
retired (from regular hours) electronic engineer person