Onto each panel a little shade must fall.

Pudsey Bear

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I was testing my new clamp meter on the output current of a spare 85w panel I have, and Liz arrived just in time to block the sun, I was truly amazed at the effect it had.

 
I had a fault on my solar regulator on the m/home. When in bright sunlight, the current fell. When a passing cloud covered the Sun, the current went up. The controller was about 8 years old and PWM, so I changed it for the one Trev had. Votronic MPPT.
 
Mione has been working well for years, never had a flat van or starter battery yet. :)
Thing I really like Trev is the size, its tiny compared to my Victron one. Can't hear the fan on it either and that's not bad seeing as it starts its 7th year later this year
 
The diodes help a bit with reducing the overall effect of partial shading but covering even one cell does have a considerable effect.

Worth googling the brief increase in output due to the cloud edge effect as well.
 
Didn't think they had a fan Neil?🤔
Yes sorry is the votronic b2b that has the small computer fan that I can't hear. 30A b2b and same size as the 250 duo. or is looks same by eye, not measured it
 
Because a solar panel is made up of several mini panels in series it means that if just one mini panels gets shaded it ruins the current flow for the entire string. Texas instruments developed an Ideal diode chip here:
Specifically for bypassing every mini panel enabling current to be maintained with minimum voltage drop across the diode. A great idea but with each diode costing about £5 it really bumps up the cost. Probably what Renogy are doing?
 
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