Mate3 showing battery voltage 1.1v higher than every sensor reading

[Slug]

My problem appears on its surface to be similar to the one described in this post from 2017: viewtopic.php?t=9235

The main display on my Mate3 always shows a battery voltage 1.1v higher than my readings everywhere else. Here are some recent example readings:

• Battery bus plates, measured with DVM: 52.5v

• Battery BMS: 52.5v

• FNDC (which I'm assuming is where the settings>inverter>calibration reading comes from): 52.5v

• Charge controller (similarly read from the calibration settings): 52.5v

• Main display on the home screen: 53.6v

The last reading on the main display is always 1.1v higher than everything else--i.e. if I'm reading 52.3v everywhere else, the main screen then says 53.4v. I'm not sure where this number comes from. Adjusting the calibrations on the inverter and charge controller settings has no impact upon it.

Is there anything I can do about this? Someone in the 2017 post described installing a potentiometer in the negative lead to their FNDC, but wouldn't this just change the reading on the inverter calibration screen, rather than the main screen?

I think this 1.1v-miscalibrated number is impacting the SOC readout as well, which is makes monitoring difficult.

[raysun]

The Mate has no internal voltmeter, and the battery voltage displayed by the Mate will be from one of the connected devices in this order:
• FNDC
• Inverter (Master in multi-inverter configurations)
• FlexMax Charge Controller

If there is an active FNDC in the system, the voltage reading on the Mate is from its internal voltmeter. The voltmeter can be calibrated per this guide: FN-DC Field Calibration - Outback Power https://www.outbackpower.com/downloads/ ... p_note.pdf

FYI:
The inverter's internal voltmeter is independent of the FNDC. For the 48V inverters, the voltmeter's precision is +/-0.4V. Calibration offset is via the Mate.

[intellact]

Very helpful information, Ray, as always!

The interesting part of Slug's problem is that he has already stated that the FnDC voltage was 52.5, so the MATE3 does NOT appear to be using the FnDC voltage (unless I'm missing something).

It would be interesting to use the diagnostic power of a tool like WattPlot ACKcess to directly access the MATE3 settings (using Modbus) to see what values are *actually* in there, versus what it's displaying. A trial activation costs nothing.

[raysun]

the FnDC voltage was 52.5,

I assumed this to mean the measured voltage at the FNDC's Bat +/- wiring terminals, not the voltage it reports via its internal voltmeter. My supposition is the FNDC's internal voltmeter is off by +1.1V

It would be interesting to use the diagnostic power of a tool like WattPlot ACKcess to directly access the MATE3 settings (using Modbus) to see what values are *actually* in there, versus what it's displaying. A trial activation costs nothing.

Everyone should have ACKcess in their operations toolbox, if not their "daily driver" for managing their Outback system.

[Slug]

Very helpful information, Ray, as always!

The interesting part of Slug's problem is that he has already stated that the FnDC voltage was 52.5, so the MATE3 does NOT appear to be using the FnDC voltage (unless I'm missing something).

It would be interesting to use the diagnostic power of a tool like WattPlot ACKcess to directly access the MATE3 settings (using Modbus) to see what values are *actually* in there, versus what it's displaying. A trial activation costs nothing.

Possible misunderstanding on my part! I'm struggling to find the source now, but at some point I read that the "inverter" voltage was actually the FNDC's reading, which is why I referred to it that way. If the voltage I see when I go into settings>inverter>calibration is not measured at the FNDC, then the FNDC may be the culprit, as I have not measured it directly!

Thank you Raysun for the FNDC calibration document! I will try walking through this, as it seems very likely to be what I need!

[Slug]

The Mate has no internal voltmeter, and the battery voltage displayed by the Mate will be from one of the connected devices in this order:
• FNDC
• Inverter (Master in multi-inverter configurations)
• FlexMax Charge Controller

If there is an active FNDC in the system, the voltage reading on the Mate is from its internal voltmeter. The voltmeter can be calibrated per this guide: FN-DC Field Calibration - Outback Power https://www.outbackpower.com/downloads/ ... p_note.pdf

FYI:
The inverter's internal voltmeter is independent of the FNDC. For the 48V inverters, the voltmeter's precision is +/-0.4V. Calibration offset is via the Mate.

Finally got around to calibrating the FNDC's trim pot. This 100% fixed the issue, thank you!