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Axpert pf1 5kW troubleshooting


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Hi I am trying to help a forumite with his install and have hit a blank.

He has two pf(1) Axpert inverters in parallel and Pylontech batteries. The installers have disappeared into thin air (like Aladin's genie).

I have set the following settings according to the SOP published by Pylontech SOP values in bold

  1. Program 1 set to SBU
  2. Program 2 = 50A (there are two inverters so they share the permissible 100A charging rate)
  3. Program 5 = USE
  4. Program 11 = AC charging 30A on the one inverter and 20A on the other my thinking was that if one was to charge from grid 2.5kW was a significant load and one would not want to go higher. I think there are solar geysers but one might  have other high draw items in the house. It never hurts to imagine the man is off-grid as you won't make silly mistakes. You may be conservative but you won't mess anything up.
  5. Program 12 = 48V
  6. Program 13 = 51V
  7. Program 16 OSO. You want to discharge the batteries - reach a predetermined cutoff return to grid if need be and wait for the morning to recharge the batteries with solar.
  8. Program 26 53.2V (Bulk/absorb voltage) 
  9. Program 29 47.5V (Battery low cut off voltage)

The problem is that in spite of good solar and full batteries the inverter remains in bypass (grid) mode.

Since Program1 is set to SBU and Program 12 is set to 48V the inverter should be powered by solar then battery and once the batteries have hit 48V it should then go to grid wait for the sun and charge the batteries and then operate of solar again.

This evening I tested my own setup (4kW pf0.8 inverters) on SBU and it functioned exactly as I expected.

The firmware of the troublesome inverters is 74.10.

I think the 47.5V Battery low cutoff has an unseen hand in this. I know that if the inverter shuts down the inverter will not restart until battery voltage is 4V higher than the battery cut-off voltage.

Could Program 29's setting cause the inverter to go to grid prematurely?

Tomorrow I might just sequentially lower program 29 and see if it makes a difference.

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On 2018/08/25 at 6:44 AM, Chris Hobson said:

Could Program 29's setting cause the inverter to go to grid prematurely?

Yes. The low battery cutoff setting is used to determine other battery voltage thresholds.

Also, setting 13 (Back to discharge) seems a little high. Perhaps take it down one volt, at least temporarily. Maybe two to get things happening. But try setting 29 first.

74.10 is a PF1 firmware; not to be confused with 72.40 and higher which are for PF0.8. [ I believe that there is a 72.20 firmware available, which might fix a bug, possibly to do with equalising. But that's not likely to be your present problem.] [ Edit: 72.20 is not relevant here; I was confusing 72.X and 74.X, after warning others not to do just that. Sigh.] 

Edited by Coulomb
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OK so we lowered Program 29 to 46V and the inverter switched to batteries at the end of the day as it should. Tim when he went to bed raised Program 29 all the way to 48V and nothing happened. Batteries discharged to 48V and then inverters went over to grid as they should. There must be a spike at sunset that lowers battery voltage momentarily below 47.5V.

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