question

pierre-tavares avatar image
pierre-tavares asked

Controller limits PV voltage below batteri voltage

Hi guys,
I have the Smartsolar mppt 75/15 controller and it has been working as expected for almost 2 month without any problem. I have updated to latest firmware.
A couple of days ago I introduced a second panel and have an input about 36-38 volts. It worked a couple of days but suddenly the controller stopped charging and indicates the input voltage below my batteri voltage even thoug I have lots of power from my panels. I have tried to reset to factory settings, disconnected everything, removed the fuse for a while as well and nothing happens making it impossible to charge my batteries. Any suggestions on how to fix this ?

MPPT Controllers
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klim8skeptic avatar image
klim8skeptic answered ·

Sounds like you have a bad connection between the mppt and solar panels.

Worth a look.

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pierre-tavares avatar image pierre-tavares commented ·
Thanks, thats also what I thougt and I have used several hours to check for that, also tried other cables, it seems to relate to something internal in the controller.
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Paul B avatar image
Paul B answered ·

so whats the voltage at the PV connection at the solar controller when you measure at the connections -

also check that the system voltage is set correctly in the controller. ie it may have been changed accidentally to say 48 volt or 24v and these maybe above the panel voltage.

also when you added the new panel did you add it in series or add it as parralled to the other panel, also what are the panels specs ie OCv and max amps for each panel

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klim8skeptic avatar image
klim8skeptic answered ·
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pierre-tavares avatar image
pierre-tavares answered ·

Currently I can measure about 37 volts on the panel output. The moment I connect to the controller it drops to 12.4 v. I connected two identical panels in series with these specs:

Maximum peak power (Pmpp) 100 W. Voltage at max. Power point (Vmpp) 18.0 V. Current at max. Socket (Impp) 5.55 A. Open circuit voltage (Voc) 21.6 V. Short circuit current (Isc) 6.11 A. Module efficiency 21.7 %. Maximum system voltage 700 VDC (IEC). Solar cell type monocrystalline.

I have a 12 v battery and the settings is also correct on the controller. I did not change any setting and the setup worked fine for a couple of days showing correct voltage and charged very well.

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klim8skeptic avatar image klim8skeptic ♦ commented ·
You could always beg, borrow or buy another charge controller. You know just to test.
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pierre-tavares avatar image pierre-tavares klim8skeptic ♦ commented ·
Yes, I bougt it on Amazon and wrote to the seller if they can help with a replacement. Will also buy another one and see what happens. Very strange experience overall.
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kevgermany avatar image
kevgermany answered ·

Maybe post screen shots of the controller output screen and battery settings.

Does it still work with a single panel?

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pierre-tavares avatar image pierre-tavares commented ·
Just tried each panel separately and it does not work. Current output is about 18 v each, but the controller only let 12,4 volt in.
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