dissipating solar panel power between the two wires. No voltage output implies a bad solar
panel, or cable. The magnitude of the voltage output depends on the incident solar radiation.
5. Power considerations
5.1 Solar panel and storage batteries
The solar panel converts light energy to electricity, or specifically to direct current. The direct
current produced is used to provide power to the system and to charge storage batteries.
The solar panel operates in both direct and diffuse light (cloudy days), but not at night.
The minimum battery size and solar panel output required depend on:
l
The average current drain of the system
l
The maximum time the battery must supply power to the system without being charged
l
The location of the site
NOTE:
When some batteries are discharged below a specified voltage, the battery becomes
damaged and cannot be recharged.
On average, the solar panel must be able to provide at least the amount of power necessary to
operate the system for 24 hours. This means that the solar panel should not only be able to
supply power to the system during the day, but it should also be able to provide power necessary
to charge the battery for the power lost during the night. In addition, the battery must have
enough capacity to power the system during times of no charging (night) and several days of low
charging (cloudy and stormy days).
Campbell Scientific has developed an Excel power budget spreadsheet that estimates the solar
panel size and battery required for a system based on the components in the system, scan
interval, communications interval, and location.
This Excel spreadsheet may be downloaded from
www.campbellsci.com/downloads/power-
.
A video demonstrating how to use the spreadsheet is also available. View it at
www.campbellsci.com/videos/power-budgeting
.
For additional help in computing the power budget for a specific system, please contact
Campbell Scientific.
SP50-L, SP90-L, and SP305-L Solar Panels
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