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Dimensioning solar panel for CR300 - max current considerations to CHG terminals?


reinhu Aug 18, 2020 10:05 AM

I'm working on a setup with a CR300 where we'd like to use a solar panel to charge the onsite battery.

I'm planning on having the battery connected to the BAT terminals and the solar panel directly to the CHG terminals, and let the built in regulator on the CR300 take care of the charging.

In the manual I see that the "Current limited to 0.9 A maximum" on the CHG terminal. Does that mean that any current from the solar panel that is above 0.9 A is wasted/ignored, or does it mean that 0.9A is the max the terminal can handle?

For example, a 50W panel can output ~3A current at peak - but since our site is far north and will have very low solar input during winter I'm thinking about oversizing the panel to get sufficient charge during the darker months. I also see that Campbells own solar panels with 50W (SP50-L) is not listed as compatible with the CR300, while the smaller SP20 is listed as compatible. So is that due to the higher current output of SP50 or is there a different reason?

Thanks!


JDavis Aug 19, 2020 01:21 PM

Yes, you are correct in your assumptions. Connecting a higher current panel will just be able to source the 0.9A limit of the CR300, and won't damage anything. The larger 50W rated panel will overall provide more power through the CR300 than a 20W panel, when you receive reduced sunlight.

For a solar panel to output the rated power, it needs a full 1000W/m2 of sunlight coming in. When you have 500W/m2 of sunlight, expect half the rated power from the panel. Oversizing solar panels does have benefits in shaded areas, or far northern latitudes.


reinhu Aug 20, 2020 04:47 AM

Great, thanks @JDavis!

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