Possible causes of "#38 PV Input Shutdown"?

Q&A and troubleshooting
, , , , ,
1

My MPPT (250/70) shut down today with an “Error code: #38 - PV Input shutdown (no retry)”. This was 13:14 in the UK, on a variably-sunny day with a full battery, having reached 100% SOC at 12:44. This was just about peak irradiance for the day (666W/m2), but peak PV generation had been an hour earlier at 3.6kW.

It has never done this before so I had to look up the error. Everything seemed to be operating correctly and within spec (PV was 178V, battery 56.4V, house load ~200W.
Disconnecting PV and battery, then reconnecting battery and PV made everything go back to normal, but as this can only be reset manually locally, and I’m off on hols for 6 weeks soon, this is concerning. So I’d like to know why it might happen.

The system has been running happily since January, and nothing has changed in the last 2 weeks (before that I upgraded the original 35mm2 battery cabling to 70mm2 to be in-spec for the multiplus, and the wiring does now run cooler at peak discharge).

There is nothing obviously untoward in the graphs at the time of failure. PV was generating about 2.2kW, varying as clouds came in and out. Exporting 2-3kW. SOC 100%, battery voltage 56.37V.
Why would it suddenly turn itself off, shorting the PV contacts?
What criteria does it use?

Do I just have to wait and see if it does it again? Anything to check?
Is overheating a possibility - the unit gets quite hot, but then it’s passively cooled so that’s not too surprising (it is mounted with vertical airflow and a vent higher up).

2

@wookey

Possible causes of error #38 are described in the manual.
It is usually related to preventing battery overcharge protection.

If you click the link in the alarms logs it also takes you there.

So check that or settings. Check if the dC voltage overshot the battery CV

3

Yes. I read that. Where is this voltage limit specified? In the Multiplus ESS assistant numbers?
The battery BMS limits the voltage to 57.6V (3.6V per cell), and will turn off the charge FET if anything tries to drive it higher.
The peak voltages over the last 7 days have been:

   At MPPT     At BMS
Thu   57.3      56.25
Fri   57.1      56.31
Sat   54.9      54.93
Sun   56.9      56.27
Mon   57.3      56.34
Tue   57.2      56.34
Wed   56.8      56.23

Why would it fail today, but not Monday or Tuesday (or Friday or Thursday), all days with higher peak voltage, if high batt voltage was the reason?

So there is nothing in the logs to suggest an unusually high battery voltage.

4

What you have programmed. And also based on if it is can connected.

Ultimately you don’t want that happening on a regular basis.

It doesn’t have to be unusually high. Just higher than it should be based on programming or battery command.
Ripple can also cause issues where there doesnt seem to be readings to support the happening.