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tony-bennett avatar image
tony-bennett asked

MPPT100/15 not working

Installed correctly only have the green light on, app shows solar no watts, 21.11v battery 18.70v battery state off. what is wrong?

MPPT Controllers
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klim8skeptic avatar image klim8skeptic ♦ commented ·

2 things to check. The battery fuse in the bottom of the mppt. And in the Mppt's battery settings, make sure the battery voltage is set to 12v.

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tony-bennett avatar image tony-bennett klim8skeptic ♦ commented ·

its 24v and fuse is fine

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2 Answers
Murray van Graan avatar image
Murray van Graan answered ·

Hi @Tony Bennett. Is it the PV panel voltage which is 21.1v? You need the PV voltage to be a minimum of 5V higher than the battery voltage just for the MPPT to start, ideally it should be more than that. It sounds like you have a panel suited to charge a 12V battery

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tony-bennett avatar image tony-bennett commented ·

yes its the PV voltage is 21.1v i think this is too low. A panel for 12v battery I asked for 24v, how can I tell if the panel is for 12 or 24v? Many thanks for your help

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ tony-bennett commented ·

Most "12V panels" have 17-22Voc, a "24V panel" will have around the double.

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ejrossouw avatar image
ejrossouw answered ·

@Tony Bennett What does your system comprise of? For a 24V batttery the battery voltage is far to low at 18.7V, I assume it is a lead acid or similar) and your panel voltage has to be vbat +5v to start charging meaning if all was in order, your panel must be at about 30V min to get things going. If the battery has not failed, an external charger may still recover it to some degree. That is what I see in the very limited information you provided.

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tony-bennett avatar image tony-bennett commented ·

Thanks for your help

I have a 24v lead acid system that is normally charged by a big industrial charger and lasts for weeks for lights and water pumps before the voltage drops to below 24v. When I first installed the 175 watt panel and controller the battery was 26+ volts so no charge came from the panel as the max output on the app was just over 21v. I put all the lights on and water pumps and when it dropped to 5 v lest than the panel outlet the controller started working but only until the battery volts went up then it stopped and will only cut back when the battery voltage drops again. Im pretty sure the batteries are Ok due to how long they can last with no charger. From what I can see the solar panel outlet of 21 odd volts is too low. Any advise greatly appreciated. Tony

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ tony-bennett commented ·

You need to add at least one more panel in series to double the PV voltage.
The MPPT needs a PV voltage 5V higher than the battery voltage to start charging, after that it needs 1V more.

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