question

bobcat1000 avatar image
bobcat1000 asked

SmartSolar 75/10 controller in existing system vs panel output voltage

I replaced the old PWM controller with this one. It's a simple system on a small sailboat. The last time I used the panel I wasn't getting any charging to the battery. The no load voltage on the 100w panel is around 17.8 v which is close to what the label says at 19v, so I think the panel is working ok. Thinking the 5 year old controller must be bad I purchased this new one. However on a clear sunny day in FL the app shows the connected panel voltage about 12.5v which was less than the battery (12v AGM) which was about 12.6v at the time. Manual says the voltage has to be 5v above the battery voltage! That's about the maximum output with perfect conditions which isn't going to happen very often. Is this controller not going to work with my panel?

MPPT Controllers
2 |3000
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JohnC answered ·

@bobcat1000

A faulty panel may still be capable of developing a healthy Voc. But when called upon to deliver any Amps will simply drop to a 'short-circuit' V, in your case the battery V. I suspect a faulty panel.

Ideally an mppt would have a higher V rated panel, or 2 in series, so it won't be so easily affected in the same way by poor light. Just don't go too close to that 75/ hard limit.

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bobcat1000 avatar image bobcat1000 commented ·
Alright. Thank you, I will check out the panel more.
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