150/35 MPPT Not Allowing Charge

DIY
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Hello,

I’m currently having issues with the MPPTs mentioned above. I recently purchased three units to connect one string of 460W Amerisolar panels in a 2S2P configuration, and two additional strings of Canadian Solar 580W-T panels, also in 2S2P configuration, on the remaining two MPPTs.

All three MPPTs are connected to my Color Control via a high-quality powered USB hub, and the system detects them with no issues.

However, the two 580W strings are not producing any power. When I check the MPPT directly, it shows the state as “off” and lists things to check—all of which have been verified as correct, yet there is still no power generation.

I measured the voltage of the two 580W strings with a multimeter, and both are reading 96V as expected. The strange part is that when I close the DC isolators/fuses to supply power to the MPPT, the voltage immediately drops to around 2V. We’ve checked continuity in all the PV cables and verified the connections, but everything seems fine.

Any advice would be greatly appreciated, as I’m starting to get frustrated.:melting_face:

Thank you.

2

Since the 460 String is working, I would verify functionality of each mppt with that string.

Then, you at least can tell, if it’s a Panel/Connection related issue, or if the mppts are causing this.

3

I’ve been troubleshooting all week without success.

All three MPPTs are functioning properly; I tested them with old strings, and they’re producing power without issue. This rules out communication problems or faults with the MPPTs themselves. The PV fuse box and surge arrestors also appear to be working fine.

Here’s what I’ve tried:

  1. I ruled out wiring issues by laying new cables from the panels to the MPPTs, but that didn’t fix the problem.
  2. I tested different configurations of the 580W panels without any improvement.
  3. I redid the MC4 connections to ensure solid connections, but the issue remains unresolved.

I’m starting to suspect either all 8 panels are faulty (which seems unlikely) or the MPPTs might not be compatible with n-type panels.

4

Panel polarity? Never assume, test them…

1 Like
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In the original post you said the voltage drops to 2V when you close the breaker. Is that 2V or a typo for 12V dropping to the battery voltage. Tje usual cause is a panel or wiring problem with a high resistance joint. You measure the open circuit voltage, which due to very low current for the multimeter reads OK but as soon as you apply a load, the current causes high voltage drop. Have you done a short circuit current test on the panels as that tells you more than just Voc.
Testing solar panels

6

i would check for a polarity problem, as the panels are shorted in that case and your voltage drops nearly to zero.

Jens

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but having a 2s2p String connected wrongly wouldn’t yield regular voltage when beeing open-circuit, would it?

Seems more that - as soon as under load - for whatever reason all of the panels bypasses are kicking in.

=> I would also test them as only 2s1p arrays. And if that is working for all 8 panels, work the way up, seeing if bad (cheap) Y-Connectors, faulty mc4 conenctors, different angles, shading, different cable lengths and/or diameters etc. are causing the bypasses to be triggered.

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I would even go a step further and test each panel individually. More time I realize…

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I’ve tested several stringing configurations with no success. The only thing left is to check the polarity of each panel. I’ll do that this weekend and share the results.

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I realized that my stupidity overcomplicated the panel polarities, but it’s sorted now. And we producing.

From what I understand, the MPPTs should indicate reverse polarity—does that apply only to the battery connection?

Thank you all for your help, it’s much appreciated.

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reverse polarity will not be indicated in either way. Reverse battery polarity will destroy your device.

Jens

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