Quote:
Originally Posted by Ken Maltby
The adapter can handle the output of two of these panels, I think.
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What method did you use to calculate this?
The adapter output is rated 5V at maximum 1A, which means it can provide a maximum output of 5V x 1A = 5W. (If the Libre follows USB rules, it will only draw a maximum of 2.5W, which lowers requirements even more, but we'll ignore this.) If the adapter is 100% efficient in converting the input power, the most it would pull from the panel is 5W. Therefore, a single 10W panel would be capable of providing twice the power required.
However, the adapter won't be 100% efficient in converting from 12V to 5V. I'm guessing it's more like 75%. With a 75% efficiency the maximum input required would be 6.67W. This is still less than the panel's 10W rating.
Then, I'd bet that under normal sunlight and alignment situations, this panel will probably only provide about 8W. Still, this is more than the maximum that the adapter can handle, so under bright sunlight a second panel would not provide any benefit.
But, as long as the "no load" voltage of the panels never exceeds the 24V maximum specified by the adapter, then two panels in parallel can do no harm. The extra panel would allow the system to continue to charge under lower light or poorer panel alignment.
So I say go for it. It can't hurt.
P.S. I wouldn't recommend leaving your Libre in direct sunlight. It could possibly overheat and be damaged. I'd put it in some shade. Maybe behind the panel?