Moning Everyone,

Did a lock-down DIY solar project over the past 3 weeks. Managed to buy 10x360w Solar Panels, Mecer Axpert 5KW Mkii Inverter and 1xPolyntech 2.4Kw battery the last few days before the lock-down. Have installed everything and used most of the default settings for the Axpert found on this forum. Most of the time everything is running fine.

From time-to-time I get a Code 11 Failure (Main Relay Failed) error. This primarily occurs early mornings, and more on cloudy days. I have tried running with and without the battery, but I still get this error which cause the Axpert to shut down completely. There is nothing in the manual on this failure or what can cause it.

I have connected the 10 Solar Panels in series and have observed that I constantly peak at 425V which is not that far from the 450V limit of the Mkii.

I have a few questions, but the priority is to solve the Code 11 Failure. Any suggestions, or reasoning what can trigger the Code 11 Failure?

5 hours ago, Rulf said:

From time-to-time I get a Code 11 Failure (Main Relay Failed) error.

Actually, "main relay failed" is the meaning for an MKS model. For an Axpert MKS II, it means PV over voltage. It goes on at 450 V, off at 440 V.

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I have connected the 10 Solar Panels in series and have observed that I constantly peak at 425V which is not that far from the 450V limit of the Mkii.

It's even closer to the upper end of the MPPT range, which is 430 V. [ Edit: so what might be happening is that when it gets even briefly to 430 V, the MPPT gives up, the panel current goes to zero, and the panel voltage goes up even higher, exceeding 450 V even though if the MPPT was capable of converting at 430 V, it could stay well below the 450 V absolute maximum voltage. ]

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I have a few questions, but the priority is to solve the Code 11 Failure. Any suggestions, or reasoning what can trigger the Code 11 Failure?

I'd say it's your PV voltage. When you read 425 V, it may be spiking to 450 V or above between readings. I assume that the 425 V figure is from monitoring software. If it's from a multimeter, it may be that the PV voltage is reading high by the SCC.

I think your first experiment should be to drop back to 9 panels temporarily, to see if the problem goes away.

Edited April 17, 20206 yr by Coulomb

37 minutes ago, Coulomb said:

Actually, "main relay failed" is the meaning for an MKS model. For an Axpert MKS II, it means PV over voltage. It goes on at 450 V, off at 440 V.

It's even closer to the upper end of the MPPT range, which is 430 V. [ Edit: so what might be happening is that when it gets even briefly to 430 V, the MPPT gives up, the panel current goes to zero, and the panel voltage goes up even higher, exceeding 450 V even though if the MPPT was capable of converting at 430 V, it could stay well below the 450 V absolute maximum voltage. ]

I'd say it's your PV voltage. When you read 425 V, it may be spiking to 450 V or above between readings. I assume that the 425 V figure is from monitoring software. If it's from a multimeter, it may be that the PV voltage is reading high by the SCC.

I think your first experiment should be to drop back to 9 panels temporarily, to see if the problem goes away.

Thanks, you confirm what I was suspecting. I will reconfigure the panels tomorrow.