question

joerg-eichenau avatar image
joerg-eichenau asked

Smart Solar MPPT 100/20: Connect 48 battery instead of PV solar panel; possible?

I happen do have a large 48V boat battery and wonder if that could be used to load/extend the capacity of my 12V Battery through the Smart Solar MPPT 100/20 by connecting the 48V battery to the Smart Smart Solar MPPT 100/20’s PV input.

Obviously the 48 battery is capable of delivering more than the rated 240W.

The handbook states, that the Smart Solar MPPT 100/20 may be destroyed if the connected solar panel delivers more power than the Smart Solar MPPT 100/20 can handle. Would it also be true in this configuration? What could I do about it?

From what I read in other posts it should not be a problem as long as the voltage limits are kept.

Firmware has been updated 1 Month ago.

AC PV Coupling
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wkirby avatar image
wkirby answered ·

Yes, that is possible.

The controller will limit its output current to 20A, or lower if you alter this is the settings. Ensure the you have adquate cooling when doing this because the MPPT will be running at maximum power all of the time, something it doesn't normally do in realistic solar applications.

The controller will be damaged if you exceed 100V at the input.

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JohnC avatar image JohnC ♦ commented ·

Hi @WKirby

What's the difference here compared to the short circuit current of a solar array? Like that 100/20 has a 20A Isc limit, and here there may be >500A potential applied, depending on the wire size.

Maybe it's to do with the mpp tracker, and I appreciate that it shouldn't track in this scenario. But what if it did, just the once?


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wkirby avatar image wkirby ♦♦ JohnC ♦ commented ·

It will always perform scans for the best power point. It has no idea it is connected to a battery.
Charging at 280W, it wouldn't see more than 6A at the input.
The hydro turbine boys often have large capacitor banks ahead of their charge controllers and I have not known them to have any issues.

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