Saturday, September 22, 2012

Solar Cell Characteristics

So, a certain unnamed project that I am working on requires the use of a solar cell to charge some batteries. I got these solar cells from an "over-supply" store in Santa Clara for $4 a piece. As seen in Figure 1, its one of those typical solar cells from a garden lamp that charges batteries during the day and turns some LEDs on at night.

Figure 1: Typical Solar Cell from a Garden Lamp

Solar Data

Unfortunately, when I purchased it, I never wrote down its part-number, so I couldn't look up a datasheet. Since I will be using it in some low-power electronics, I had to do my own measurements and plot an approximation of its power characteristics. Table 1 shows the data points I collected with a simple multi-meter.
Table 1: Power Characteristics of a Solar Cell Loaded with a 1kΩ Potentiometer
And below is the graph produced by plotting the power as a function of the load resistance (measured using a 1kΩ potentiometer).
Figure 2: Rough Graph of the Power Characteristics of the Solar Cell as a Function of Load Resistance
Hopefully this data will be useful to me when I'm constructing the DC-DC Boosting Regulator circuit with the MAX756 I purchased a while back.

Since the MAX756 boasts of at least 87% efficiency, and the max power I measured was around 80 mW, I believe that means I can expect a maximum output power of around 68 mW (at either 3.3V or 5V, depending on which setting I used on the MAX756 IC).

2 comments:

  1. So how is that "project" coming along? I want to see the end result ok.

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    Replies
    1. Is that so? And who might this anonymous individual be that demands a completed result? Hmm?

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