question

samooore avatar image
samooore asked

Parallel PV Input Does Not Total What it Should

I'm doing my first install for a customer on what should be a pretty straight forward install.

I have a VE 100/30 mppt controller attached to two SunPower 170w cells.

From each, I've measured 33v/1.5A above the parallel junction.

When I connect one panel (renogy y) to the system, the VE Connect App measures ~75 watts "low sun angle" and the appropriate volts/amps. When I complete the connection the watts/amps don't change. I expected it to double since the cells are pretty closely aligned.

I disconnected the panel1 and connected panel2 and got the expected ~75w/33v/1.5A in the VE connect app.

With both panels connected in parallel I expected to see about ~150w and about 3A coming into the system.

Can anyone help me understand what might be going wrong?

Thanks!

MPPT ControllersSolar Panel
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4 Answers
ejrossouw avatar image
ejrossouw answered ·

Hello @samooore. Just a couple of things I'd check over. What was the voltage measured after the splitters with both panels? Could one of the splitter inputs be faulty? Secondly, MPPTs do not always react immediately as it is seeking the maximum power point so maybe with full sun things be sorted. Finally, have you set the correct battery voltage?

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Justin Cook avatar image
Justin Cook answered ·

@samooore, I concur with @ejrossouw; if you've tested each panel individually with the expected results then the fault must be in the "Y" connector. I will add one consideration, which is just to make sure to independently verify the polarity of both panels; theoretically you've already done this while you were testing the individual panels, but it's worth a triple-check.

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svtti123 avatar image
svtti123 answered ·

you don't mention your soc if your batteries are near fully charged nearing the end of absorption or in float I would expect the controller to do exactly what you describe . if the current with both panels hooked is the same or close to the current with a single panel I would suspect your very close to a full charge. if the controller only requires 75 watts because of the above and you hookup a second panel it would still only need 75 watts that would now be divided between two panels or 37.5 watts each panel

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samooore avatar image
samooore answered ·

This is a learning experience for me.

After checking the connections I believe the system is working normally. Yesterday I stressed the system by turning off the battery charger and engaging the freshwater pump, inverter, refrigerator, and microwave.

While I did this, I had the VEconnect app going and to my surprise, while the system was under load the watts went down to 4-5. The system recovered in some time as the load was eased.

If you look at the data from the CVS export you will see where what's been going on.

Thanks for the input.


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