PV Gap

Nicholas Said:

need to test a solar cell before stringing them to make panel?

We Answered:

Luis, testing of solar panels, and cells is done with the use of a digital multimeter today, even by the professionals. Virtuallly all photovoltiac panels have two ratings on them, the open circuit voltage, and the short circuit current. Use a voltmeter to sample the voltage in direct sunlight, no shading should be present, find an open space to work in on a sunny day. The voltage for a single cell will be right around .5 volts if it is operating properly. The current will be a function of the size, and its efficiency. A one square foot panel should be putting out .5 volts and close to 20 amps. Silicone based cells produce about 10 watts per square foot, so at one half volt, you would need 20 amps to make 10 watts, volts X amps = watts. The variations in sunlight on a clear day are negligible if you test all your panels at the same time of day, or your cells in your case. If this is not possible, a better technique is to make up a test stand with a heat lamp over the cells on a work bench, then put one at a time on the bench and attach a meter. This way, each one will be getting the exact same solar insolation during the test.

Most cells are much smaller than this. My Kyocera panels put out 7.4 amps, each cell is still .5 volts, and they have 36 of them in series, for an open circuit voltage of 18 volts. But each cell is about 7 inches square, so they put out about 7 amps, or one third of 20, since they are about 1/3 sqaure foot each. Your cells should all be the same size to work together, so they are putting out nearly identical amperage, or the big ones will try to over heat the little ones. Just make sure the multimeter you're using is fairly accurate, don't get the one at the discount tool place for $3.99, go with somthing that has a tighter tolerance.

In case you're wondering, I'm not an engineer, I just live in a solar powered home, so most of this I picked up the hard way. I'll list some places below where you might find other info. Good luck Luis, and take care, Rudydoo

Pauline Said:

im trying to power up a cell phone and laptop with a solar panel.?

We Answered:

They are powered from internal batteries, so what you really want to do is to charge the batteries.

Take them one at a time, as they have different power and voltage requirements. Don't try to do them both together, unless you use an inverter.

To directly charge a battery from a solar panel, you need to find out the voltage and current requirements for the charge operation. Then find a solar panel with a voltage somewhat higher. the current can be lower, it will just take longer for the charge. You will have to monitor manually the state of charge of the battery(s) to avoid overcharging and damage.

Another alternative is to get a solar panel that will supply 12 volts and use that to operate an inverter that will output 120 VAC with AC sockets on it. then you can plug in the battery chargers that you have, and they will handle the batteries correctly.

Or you can buy solar panels with built in circuitry to handle the charge control.

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Lillie Said:

What solar panel should I use to charge a deep cell?

We Answered:

That's an engineering question, based on the details of the battery or cell, as well as the charge controller and the solar insolation properties of the location, as well as your constraints (e.g. on average 80% of days at this location).