Posted by *Eeyore* on November 2, 2008, 10:28 am

fabtraninbox@gmail.com wrote:

*> Eeyore wrote:*

*> > fabtranin...@gmail.com wrote:*

*> > > i brought a solar panel from my friend. it is manufactured in 1993it*

*> > > is 4 x 1.5 feet in size with 36 cells.i am not sure about the watts.*

*> > > it is written 64 series probably i think it may be 64*

*> > > watt.but when i checked in sunshine with out any load it is giving*

*> > > 19 volts, but when i check for amps i am getting only 0.2 amps.*

*> >*

*> > Short circuit amps ?*

*> >*

*> > > does this panel work to charge a battery.*

*> >*

*> > 19 volts in full sunshine is fairly typical-ish.*

*> >*

*> > Are the cells circular ? Measure their diameter and that will give the*

*> > effective panel size. And where do you live ? Insolation (the amount of*

*> > sun) varies with location. From all of this one might be able to tell if*

*> > your panel has aged.*

*> >*

*> > If you connect it to a battery directly the voltage will drop due to*

*> > loading. Unless it has inherent reverse diode characteritics the battery*

*> > may lose power into the cells when it's dark.*

*> >*

*> > Charging a battery this way is not clever. It's primitive and may not do*

*> > that battery any good. You really need a proper charge controller and*

*> > preferably a 'maximum power point' type.*

*> Short circuit amps is 0.2*

Try it with a load of ~ 120-150 ohms. You'll need a resistor of several watts

dissipation. say a 120 ohm resistor of serval watts and 33 ohms 1/2 W to put

in series.

*> the cells are circular and 4 inches dia.*

*> i live in india ( visakhapatnam) we have a goodshine with min day temp*

*> 22 to max day temp 45 deg.*

OK

*> basically i want to know if this solar panel is in working condition,*

Will have to calculate.

*> later i will proceed for next step (charging)*

*> i came to know that 14 volts is required to charge a battery.*

*> what is the minimum amps required.*

There is no minimum amps. What is the battery capacity in Ah ? And what

technology e.g. lead-acid ?

Graham

Posted by *Ron Rosenfeld* on November 2, 2008, 1:23 pm

On Sat, 1 Nov 2008 20:28:24 -0700 (PDT), fabtraninbox@gmail.com wrote:

*>Short circuit amps is 0.2*

*>the cells are circular and 4 inches dia.*

*>i live in india ( visakhapatnam) we have a goodshine with min day temp*

*>22 to max day temp 45 deg.*

*>basically i want to know if this solar panel is in working condition,*

*>later i will proceed for next step (charging)*

*>i came to know that 14 volts is required to charge a battery.*

*> what is the minimum amps required.*

*>thanks for your valuable response*

*>ABDUL RAHEEM*

We have to make a number of assumptions to see if the panel is in working

condition; and you need to provide more information to assess whether it

can charge your battery.

Assuming you exposed the panel to the sun at noon, and the angle of the

panel was perpendicular to the "sun angle", at a time when there should

have been an irradiance of 1kW/M^2, it seems to be underperforming.

If my calculations are correct, 36 4" diam cells occupy an area of about

0.29 M^2.

I don't know what efficiencies were being obtained in 1993. But with a 5%

efficiency, the power output should be about 14W.

You have provided Voc and Isc (oc=open circuit; sc = short circuit).

On the few lower powered panels I just looked at, these values would be

higher than Vmp and Imp (mp=max power which is how panels are usually

rated). And the calculated output using Vmp and Imp is less than that

calculated using Voc and Isc.

Therefore, I believe we can assume that, for your panel, it's output will

be less than your measured Voc * Isc.

In your case: 19V x 0.2A = 3.8W. So, under load, this panel might put out

3W or less. And it will be even less efficient in your relatively hot

climate, assuming your temperatures provided are in the Celsius scale.

Clearly the panel is underperforming. Whether this is something as simple

as connections that can be repaired, or internal degradation of the actual

PV cells, is something you might be able to determine by inspection, and by

measuring the output of the individual cells.

As to whether this will be sufficient to charge a battery, that depends

critically on the charging parameters for the battery under discussion. For

some batteries, that output would be insufficient to even make up for the

normal self-discharge; and for others it might be excessive.

You'll need to provide more data.

It would be helpful to assess the output of your panel under a load.

--ron

Posted by *Eeyore* on November 2, 2008, 6:50 pm

Ron Rosenfeld wrote:

*> On Sat, 1 Nov 2008 20:28:24 -0700 (PDT), fabtraninbox@gmail.com wrote:*

*> >Short circuit amps is 0.2*

*> >the cells are circular and 4 inches dia.*

*> >i live in india ( visakhapatnam) we have a goodshine with min day temp*

*> >22 to max day temp 45 deg.*

*> >basically i want to know if this solar panel is in working condition,*

*> >later i will proceed for next step (charging)*

*> >i came to know that 14 volts is required to charge a battery.*

*> > what is the minimum amps required.*

*> >thanks for your valuable response*

*> >ABDUL RAHEEM*

*> We have to make a number of assumptions to see if the panel is in working*

*> condition; and you need to provide more information to assess whether it*

*> can charge your battery.*

*> Assuming you exposed the panel to the sun at noon, and the angle of the*

*> panel was perpendicular to the "sun angle", at a time when there should*

*> have been an irradiance of 1kW/M^2, it seems to be underperforming.*

*> If my calculations are correct, 36 4" diam cells occupy an area of about*

*> 0.29 M^2.*

*> I don't know what efficiencies were being obtained in 1993. But with a 5%*

*> efficiency, the power output should be about 14W.*

*> You have provided Voc and Isc (oc=open circuit; sc = short circuit).*

*> On the few lower powered panels I just looked at, these values would be*

*> higher than Vmp and Imp (mp=max power which is how panels are usually*

*> rated). And the calculated output using Vmp and Imp is less than that*

*> calculated using Voc and Isc.*

*> Therefore, I believe we can assume that, for your panel, it's output will*

*> be less than your measured Voc * Isc.*

*> In your case: 19V x 0.2A = 3.8W. So, under load, this panel might put out*

*> 3W or less. And it will be even less efficient in your relatively hot*

*> climate, assuming your temperatures provided are in the Celsius scale.*

*> Clearly the panel is underperforming. Whether this is something as simple*

*> as connections that can be repaired, or internal degradation of the actual*

*> PV cells, is something you might be able to determine by inspection, and by*

*> measuring the output of the individual cells.*

*> As to whether this will be sufficient to charge a battery, that depends*

*> critically on the charging parameters for the battery under discussion. For*

*> some batteries, that output would be insufficient to even make up for the*

*> normal self-discharge; and for others it might be excessive.*

*> You'll need to provide more data.*

*> It would be helpful to assess the output of your panel under a load.*

I agree totally.

Graham

Posted by *spaco* on November 2, 2008, 5:23 pm

Why did your friend sell the panel to you? Had he already determined

that it didn't work well? What was he using it for?

Pete Stanaitis

--------------------

fabtraninbox@gmail.com wrote:

*> i brought a solar panel from my friend. it is manufactured in 1993it*

*> is 4 x 1.5 feet in size with 36 cells.i am not sure about the watts.*

*> it is written 64 series probably i think it may be 64*

*> watt.but when i checked in sunshine with out any load it is giving*

*> 19 volts, but when i check for amps i am getting only 0.2 amps. does*

*> this panel work to charge a battery.*

*> *

*> ABDUL RAHEEM*

*> *

Posted by *Bill Kaszeta / Photovoltaic Re* on November 3, 2008, 4:35 am

On Sat, 1 Nov 2008 11:00:33 -0700 (PDT), fabtraninbox@gmail.com wrote:

*>i brought a solar panel from my friend. it is manufactured in 1993it*

*>is 4 x 1.5 feet in size with 36 cells.i am not sure about the watts.*

*>it is written 64 series probably i think it may be 64*

*> watt.but when i checked in sunshine with out any load it is giving*

*>19 volts, but when i check for amps i am getting only 0.2 amps. does*

*>this panel work to charge a battery.*

*>ABDUL RAHEEM*

I suggest you connect it to a 12-volt battery of any sort and measure the

resulting charging current with full sun on the PV module.

A good 64-watt module would charge at about 3.5 to 3.8 amps.

Bill Kaszeta

Photovoltaic Resources Int'l

Tempe Arizona USA

bill@pvri-removethis.biz

> Eeyore wrote:> > fabtranin...@gmail.com wrote:> > > i brought a solar panel from my friend. it is manufactured in 1993it> > > is 4 x 1.5 feet in size with 36 cells.i am not sure about the watts.> > > it is written 64 series probably i think it may be 64> > > watt.but when i checked in sunshine with out any load it is giving> > > 19 volts, but when i check for amps i am getting only 0.2 amps.> >> > Short circuit amps ?> >> > > does this panel work to charge a battery.> >> > 19 volts in full sunshine is fairly typical-ish.> >> > Are the cells circular ? Measure their diameter and that will give the> > effective panel size. And where do you live ? Insolation (the amount of> > sun) varies with location. From all of this one might be able to tell if> > your panel has aged.> >> > If you connect it to a battery directly the voltage will drop due to> > loading. Unless it has inherent reverse diode characteritics the battery> > may lose power into the cells when it's dark.> >> > Charging a battery this way is not clever. It's primitive and may not do> > that battery any good. You really need a proper charge controller and> > preferably a 'maximum power point' type.> Short circuit amps is 0.2