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GETTING STARTED Solar Array Modules (A/B/X Class) | ||
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A "module" is a unit of solar cells that have been connected so the unit has a voltage suited to an application (such as charging a battery or powering a motor). Custom-made modules, like their commercially-available counterparts, consist of individual solar cells wired in series. In this configuration, the front of each cell is electrically connected to the back of the next, and each cell adds its voltage to the total of the string. Thirty-six cells (plus or minus a couple) are needed to effectively charge a 12-volt battery. Any fewer, and the module may not develop enough voltage to fully charge the battery; any more, and the module will operate less efficiently and may overcharge and damage the battery.
We are going to look at a few examples of how many modules to use for 12 volt and 24 volt systems. Please note that these are just examples. You may have a different system voltage to consider or different modules. Please also note that manufacturers are constantly updating their technology. The specific examples here may no longer match the current production information. Use this information as a guide for how to think about your system, but be sure to check your own numbers! Understanding some basic electricity will help you understand how to connect your panels. If you are not familiar with electricity, you should find a teacher or mentor and also a good reference book. Be sure you know how to work with electricity safely! Two quick points to understand with this section are:
One example of a light weight manufactured panel is the BP Solar/Solarex MSX-30 Lite module. This module is wired to charge a 12 V battery. But one module is much smaller than the 1.6 m² maximum array area allowed. How many modules can you use for your array (on your bike and in the pits) and still be within the allowable size? Find the cell area of the module in m² and divide that area by 1.6 m² (in this case, it should work out to be about 6 modules). You can connect the modules in parallel. This will keep the voltage at 12 volts (voltage stays the same in parallel). Your array power will be about 30 watts times the number of modules (6 modules x 30 watts/module = 180 watts).
But what if you plan on using a 24 volt electric drive system? With a 24 V system, you need to use at least two MSX-30 modules connected in series to be able to charge your 24 V battery pack (voltage adds in series). You may connect additional modules by paralleling pairs (connected in series) up to your maximum size (6 modules in this example). This keeps your voltage at 24 V.
4" x 4" SOLAR CELLS First, you need to find the area in SI units so you can compare it with the 1.6 m² maximum array area. At 2.54 cm/inch, this works out to 155 cells. If you are running a 12 V drive system, you need 36 cells per module wired in parallel. How many modules can you connect? You can fit four complete modules with about 11 cells to spare. For a 24 V system, you will need an even number of modules (two modules connected in series and then the pair wired in parallel with the other pairs). This still works out to four complete modules with 11 cells to spare. If you are concerned with maximizing your solar array area, you may want to research what solar cell sizes are available. A smaller cell size may allow you to use more of the available area.
ARRAY WIRING
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