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hour avatar image

Load output - Enable only when charging

I'm going to be putting a spare 75/15 MPPT charge controller in a small pelican case with some small circular vents. I'll extend the PV input and battery connections to be panel mount jacks on the outside of the box, so that I can charge up two portable battery packs (separately, of course).

I'd like to run a tiny DC fan in the pelican case to draw air through the vents, and I really only need this to occur when charging is occurring. The fan will draw extremely low power but I still don't want it to operate continuously in case I forget to unplug things when night rolls around. I'd prefer this to some temperature controller... is it possible? Not sure basic load output nor streetlight function would give me the ability.

Thanks!

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3 Answers
Paul B avatar image
Paul B answered ·

Maybe just connect it to the PV output and let the fan run when the sun shines.

it will need to be able to run at the MAX pv voltage without damage so pick the correct voltage.

I suspect that as the voltage reduces the fan will just slow down.

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adev avatar image
adev answered ·

I would think you could make this work by connecting your fan to the load outputs, and setting the load disconnect to say 13.2v or so (depending on battery charge settings). That should allow the load to come on whenever there is float charge voltage or higher present, and shut it off at night.

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xmd avatar image
xmd answered ·

I have the same question, but for a different use case - I want to use the load output to charge my RV's starting battery. I've tried doing this using voltage on/voltage off rules for the Load relay, and it works sortof, but I'm not finding a perfect voltage range to make it work (the house battery is LFP, the starting battery is Lead Acid). Anyone get this to work?

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