I'm just geting into electonics and stuff. So I am trying to make a simple USB charger. I'm looking for at least 4 volts output. What I've got is two solar panels (detached) a 4 AA battery holder, and a circuit board with an led on it (took the solar panels out of old lawn lights. I need more charge out of my panels (I think) so I tried attaching them. I soldered the positive wire from one to the positive connection on the other and negative wire to negative connection. After doing so and checking the multimeter, it says I have no output at all. How do you connect them?
Huh? you should have got something, in full sun, you should have gotten 3 or 4 volts, but milliamps in current. By connecting them pos. to pos., neg to neg,(paralell) it increases the current output. If you connect pos, on one, to neg. on the other, and measure between the remaining pos, and neg. you should have twice the voltage (series). You need 4 volts, but 4 AA's in series is 6 volts. If your going to use the panels to charge the batteries, you'll need a diode in series to prevent discharge during dark conditions, which the LED will work for.
You will need to wire several cells in series to obtain the necessary voltage, and you may need to wire several sets in parallel to obtain the required current. Series: Connect the + lead of one cell to the - lead of the next. You may chain any number of these together this way, and the output voltage will be the sum of the output voltages of each cell. The output current will be the greatest current of each individual cell. Parallel: Connect the + leads of each cell together, and the minus leads of each cell together. The output current will be the sum of the output currents of each cell. The Output voltage will be the greatest voltage of each individual cell. Picture this: think of the series cells as a column, connected from top to bottom. Think of the parallel cells as a row, with all the tops connected together and all the bottoms connected together. To arrive at the required voltage *and* current, you will need an array of cells, in rows and columns. The voltage will be the sum of each column, while the current will be the sum of each row. Most solar panels are arrays of individual cells. The arrays are then connected in the same fashion to provide the necessary combination of voltage and current.
You have to look at the power output of the cell. The first consideration has to do with voltage. A single cell with no load might output one volt or less. Wiring cells in series would double that output, at least in theory. (Internal resistance will lower the actual voltage.) You've wired the cells in parallel, however. Try unsoldering one electrode and then measure voltage output of each cell. There is still the issue of current output. I don't know if there will be enough with your setup. How many cells are there and what kind of batteries were they charging?
Leave the two positive terminals connected together.Disconnect the negative leads from each other. Get two amp diodes from radio shack. Connect each diode in series with each negative lead. there is a band on one end of the diode. Connect each diode so that the end with the band is attached to the negative side of each solar panel. Tie the other ends of the diodes together. This will become the new negative end of your solar panel supply. With the sun shining on the panels , you will now measure the voltage from the plus side of the solar panels to the new negative junction. Connect your load leds in place of the voltmeter and enjoy. Without the diodes , each solar cell thinks the other solar cell is the load. In effect each solar panel is shorting out the other. Some solar panels that you buy already have a diode in their junction box connected for that purpose. You need the diodes to provide the necessary isolation between the two panels, then they can both act in parallel to provide current to the load.
Most solar lamps use a single .2V nicd or nimh battery as a back-up supply, so they should be able to generate at least .5V in full sun to allow charging of the battery (you can verify the voltage of a single panel with your DMM) If you have two of these panels, I wouldn't expect them to make more than approximately 3V. The proper connection would be a series connection where the negative of one panel connects to the positive of the other and the remaining positive and negative wires become the outputs. Try this connection and measure again with your multimeter set to DCV and the panels in full sun. If the voltage is not high enough, add a third panel wired with its positive lead to the remaining negative of the first two. This should bring your voltage up another 50 percent.When you wire the panels positive to positive, negative to negative as you already have, voltage will be that of one panel, but current output will double (more amps) If you have many of these panels, you could combine series and parallel wiring to increase voltage and current.
