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Axpert and ICC - Not switching on SOC settings


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I have 2 x 5kVA (450 VOC) Axperts in parallel with 8 x US3000B Pylontechs and 24 x 380W PV panels, implemented with a Raspberry Pi running ICC software.

System worked perfectly for about a year with switching between Grid and Battery/Solar being controlled by the ICC. Been religiously keeping my ICC software up to date and downloading a new version the moment it becomes available. 

I recently developed a problem where the system does not switch based on the battery SOC anymore. My ICC settings for this are 20% SOC back to grid and 50% SOC to Battery/Solar but the system seems to switch at about 34% to grid and 77% to Battery/Solar.

This does not make sense to me as I was under the impression that the ICC overrules the Inverter as far as battery control is concerned.

The problem only developed after I downloaded version 4.2 of the software but the supplier is adamant that the software is not the problem.

Anybody else experiencing a similar problem or know where I can get an earlier version of ICC (below version 4.0)?

Any advice will be appreciated

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1 hour ago, Smirresa said:

This does not make sense to me as I was under the impression that the ICC overrules the Inverter as far as battery control is concerned.

I don't use ICC, but my understanding is that it can only override the settings in the Axpert as long as various settings are "out of the way". So setting 12 needs to be a very low value; otherwise it can take effect before the SOC threshold is reached.

The subtle setting is setting 29, battery low DC cutoff voltage. If it's not also quite low, then there can be an "effective" back-to-grid voltage setting (the inverter firmware only deals with voltage) of 2.0 V higher than the cutoff voltage. I explain it in FAQ #2.

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@Coulomb Originally set up the system with all the values and settings for Pylontechs as published on this forum - and it worked perfectly for a long time!

I will confirm later today that all is in line with the suggestions as per FAQ #2 and will also monitor the voltages when the switching occurs.

Is it possible that the battery voltages will change (after being used for a year) to such an extent that settings that used to work no longer do so?

Any idea why the switch from grid to batteries is now also higher? 

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1 hour ago, Smirresa said:

Any idea why the switch from grid to batteries is now also higher?

A thought: perhaps the BMS hasn't reset its coulomb counter in a long time, for whatever reason. Then it's possible that the BMS is giving unreliable SOC estimates, and the voltage based estimates from the inverter are actually more sensible 🤔

That could happen if the battery isn't getting fully charged lately. Check the battery voltages against reported SOC to see if the BMS reported SOC makes sense. Or perhaps one of your battery modules isn't connecting (thrown an error, cable loose), so the battery capacity is less than what the master thinks it is. Actually, if a module is in an error state, that would probably get communicated to the master, so a cable issue seems more likely.

Is it possible to revert to older version of ICC software? Despite Mannie's assertions, there may be an issue, perhaps only affecting a small number of users. It would be good to rule out that possibility, if nothing else.

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@Coulomb Got an earlier version of the software and testing it now. Had an erroneous switch to grid again this morning (at about 24% SOC instead of the 20% setting).

Looks like the battery voltage may have momentarily dipped below my Back to grid Voltage setting of 48V, coinciding with a increase in power draw - refer to attached graph. The graph shows a minimum of 48,5V but the switch happened at that time hence my suspicion as described above..

Any harm in reducing the back to grid voltage to 47V?

Battery volts.JPG

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1 hour ago, Smirresa said:

Any harm in reducing the back to grid voltage to 47V?

No, and in fact I think it needs to be even lower, 46 V comes to unreliable mind, so as to be "out of the way".

Also keep setting 29 (battery cut-off voltage) two volts below any likely switch point, because of the undocumented interaction with the back-to-grid voltage, as mentioned in FAQ #2.

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@Coulomb Made some changes to the inverter voltage settings in line with your suggestions and it seems to have solved the problem.

The inverter now switches on the SOC settings of the ICC.

What puzzles me is that the system worked perfectly fine with the old inverter settings for almost a year (approximately 200 battery cycles logged).

Is it possible for the Pylontechs' voltage profiles to change/deteriorate over time so that, after 200 cycles, the voltage at approximately 25% SOC is now lower than when installed?

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2 hours ago, Smirresa said:

Is it possible for the Pylontechs' voltage profiles to change/deteriorate over time so that, after 200 cycles, the voltage at approximately 25% SOC is now lower than when installed?

It could be, all batteries degrade, and usually more at the start of life than later. But I would not expect the difference to be noticeable, and in any case the BMS should be compensating for it (so you get 25% of a lower capacity before switching over). I have no idea how good Pylontechs are at tracking state of health.

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