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Axpert not switching back to solar on SOL/SBU


Jack007
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Hi All!

I have a problem with my Axpert inverters not switching back to solar or battery as primary output source for loads when it is set to SOL or SBU.

I have a off-grid system (no Eskom):

2x Axpert 5000-48, v74.10

24x 320W panels

14.8kWh LiFePO4 bank

I have recently purchaced a 5kva honda generator to supplement the load on rainy days if i want to use woodwork machinery or weld ect.

If i set them to SOL and disconnect the pv from the inverters (open the fuses) the generator (gridside) takes over the load if it is running. That is good, but as soon as i connect the pv again the system does not swich back to Solar/battery as priority. It doesnt want to let go of the generator and keeps it as the only primary source for the loads (like Uti). This causes problems because 5kva is easily overloaded on our system. I would ideally like the generator to supplement the solar/battery on cloudy/rainy days and still have access to all of the 10kw that the inverters can supply.

I have the following settings set:

1: SOL

2: 10A (in order to rule this out as the problem)

11: 2A (in order to rule this out as the problem)

12: 44v (logic: swich to utility source as late as possible)

13: 48v (logic: swich back to battery mode as soon as possible)

16: SNU

23: bYE

26: 54.6v

27: 53.8v

29: 47.0v

31: SbE

Q2) Also is there no way to limit the Amp draw from the grid/generator side in order not to overload the generator?

If any one can help/guide me i will really appreciate it.

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12 hours ago, Jack007 said:

I have a problem with my Axpert inverters not switching back to solar or battery as primary output source for loads when it is set to SOL or SBU.

29: 47.0v

Once the battery is declared weak, with factory firmware it will have to rise to 4.0 V higher than setting the voltage in setting 29 (low DC cutoff voltage). That's 51 V, or 3.4 VPC, which is over 90% SOC. If you update to the LFP flavour of patched firmware version 74.40e, that 4.0 V value shrinks to 1.0 V, much more suitable value for LFP.

Or you could just reduce the value of setting 29.

But I'm not sure that your problem is due to the battery being declared weak. Is the low battery warning showing?

Quote

Q2) Also is there no way to limit the Amp draw from the grid/generator side in order not to overload the generator?

I'm not aware of any method. The manufacturer recommends a generator whose capacity is at least 150% of the inverter's rated capacity. Sadly, it seems to be assumed that the AC-in power source is stronger than the battery.

When the generator overloads, I assume that its speed decreases dramatically. Presumably, that should make the inverter declare the AC-in as out of spec, and switch to battery mode. Does the AC-in icon start flashing when the generator overloads?

It's possible that this problem is fixed in factory firmware version 74.20 (and hence in factory firmware version 74.40 and patched firmware version 74.40e as well). I've heard of problems with factory firmware version 72.10, and I suspect that 72.10 and 74.10 come from the same source code base using different #defines.

Edited by Coulomb
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Hi @Coulomb

Thank you for your help and feedback.

2 hours ago, Coulomb said:

Once the battery is declared weak, with factory firmware it will have to rise to 4.0 V higher than setting the voltage in setting 29 (low DC cutoff voltage). That's 51 V, or 3.4 VPC, which is over 90% SOC.

Or you could just reduce the value of setting 29.

I do not think this is the problem because i tested this when the battery was above 90% SOC, but ill check that again today.

2 hours ago, Coulomb said:

If you update to the LFP flavour of patched firmware version 74.40e, that 4.0 V value shrinks to 1.0 V, much more suitable value for LFP.

It's possible that this problem is fixed in factory firmware version 74.20 (and hence in factory firmware version 74.40 and patched firmware version 74.40e as well). I've heard of problems with factory firmware version 72.10, and I suspect that 72.10 and 74.10 come from the same source code base using different #defines.

Im afraid to do a firmware update because the system is still under warranty (Installed 2018 with 5years warranty). Should i ask the supplier of the inverter (they where also the installers) for the latest factory version? Would that help or does it need to be the patched version?

2 hours ago, Coulomb said:

But I'm not sure that your problem is due to the battery being declared weak. Is the low battery warning showing?

Warning no 4? No not that i saw.

2 hours ago, Coulomb said:

When the generator overloads, I assume that its speed decreases dramatically. Presumably, that should make the inverter declare the AC-in as out of spec, and switch to battery mode.

What i did see happen is when the load goes from 4kW+ down to less than 1kW, the generators voltage output goes a bit mad. It fluctuates dramaticly and the lights flicker and computer ups kicks in. Inverters still accept the input prob because it is set to Apliance mode. It seems as though the gen cant handle the sudden drop in draw. That is one of the reasons i want it to only supplent the load and not let it be the main primary source when solar and battery is available.

2 hours ago, Coulomb said:

Does the AC-in icon start flashing when the generator overloads?

You mean the round icon with the sinewave? I did see it flash even before the unit switched over to grid. Does this the mean the power is too dirty? It is set to Apliance mode. Ill see to set it to UPS mode to see if there is any difference.

When i overloaded the generator the system kicks over to solar/battery mode but this cannot be good for the generator. I only want it to supplent not be the only source untill it overloads.

 

What settings do you reccomend i try in 12 an 13? Setting them to the lowest would be the best to test the switchover back to solar/battery is that correct?

Thank you again!

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Ok so ive done some more testing at 90%+ SOC.

 

These were all the setting:

1 SOL

2 10A

3 APL

4 SdS

5 USE

6 LFE

7 EFE

9 50Hz

11 2A

12 47v

13 48v

16 SNU

18 bON

19 FEP

20 LON

22 AOF

23 bYE

25 FEN

26 54.6v

27 53.8v

28 PAL

29 47.0v

30 ONE

31 SbE

32 AUt

33 EdS

34 58.4v

35 60

36 120

37 30d

38 dlS

39 AdS

 

The inverters do not accept the generator when set as UPS (no grid icon is displayed). On APL the grid icon (round sinewave icon) flashes before it connects but i did not see it flash when the generator is connected as primary source for load.

When i disconnect the pv the generator is accepted as the primary source for the load (bypass icon appears) and the generator also charges the batteries. There is a very slight flicker in the lights (most would prob not pick it up).

When i reconnect the pv the solar is only used to charge the system even though the battery voltage is more than 4v higher than setting 13 (battery voltage was at 54.xv). I want the solar to supplement the load draw.

large.IMG-20200723-WA0004.jpg.8ec37488ae2c44ea6041355d9928bf96.jpglarge.IMG-20200723-WA0003.jpg.2a768e44c3996ac9433b62bda316e795.jpg

The voltage seems constant (230 +-5v) and the Hz runs between 49.x - 52.x but mostly on 51.xHz.

Does the generator seem to have a poor AVR? Its a Honda Petrol 5kVa. We paid extra to have the 'Japanese' AVR. The installers did recommend a "Axpert filter box" inline between the genset and the inverter, but neither they or i seem to find what they are talking about. Do you know if anything like this is available that does not cost more than the generator itself @Coulomb?

When high loads are applied to the system the input Hz and Voltage from the generator falls to 47.xHz and 190v for a brief moment and the lights flicker badly after it stabilises again. The generator refs (hi/low/hi/low) for a short while whenever load is appied or taken away then sabilizes.

 

The inverter still does not want to switch back over to Solar/battery as main primary source for the loads. It also does not want to use the available Solar/battery power to supplement the load. It only switches back if the gen is overloaded (>5.5kw load) or if a sudden high draw mashine is turned on (like a table saw) and the Voltage and/or Hz drops below a certain threshold (prob defined by the appliance setting) and then it rejects the generator completely and fall back to Solar/battery mode only.

 

Ideally i want the generator as well as the solar/battery to supply the needed load together. eg. the generator should be seen as an extra power source not the only source. Is this possible?

Thank you very much

Edited by Jack007
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7 hours ago, Jack007 said:

I do not think this is the problem because i tested this when the battery was above 90% SOC, but ill check that again today.

But was the battery above 51.0 V (the 47.0 V of setting 29 plus 4.0 V) at that time?

7 hours ago, Jack007 said:

Should i ask the supplier of the inverter (they where also the installers) for the latest factory version? Would that help or does it need to be the patched version?

Depending on what the problem is, the patched firmware may be helpful. Unfortunately I don't know if the latest (74.40 or later) firmware will fix the problem. I think it's definitely worth asking them.

7 hours ago, Jack007 said:

What i did see happen is when the load goes from 4kW+ down to less than 1kW, the generators voltage output goes a bit mad. It fluctuates dramaticly and the lights flicker and computer ups kicks in. Inverters still accept the input prob because it is set to Appliance mode. It seems as though the gen cant handle the sudden drop in draw. That is one of the reasons i want it to only supplement the load and not let it be the main primary source when solar and battery is available.

Unfortunately, your generator isn't all that suitable for this application (despite paying extra), and the model of inverter isn't one that can blend AC-in and battery. There also isn't a model that will act as a bolt-in replacement; the ones that blend are all the ones with the high voltage SCC, so you'd have to rewire your PV panels as well.

7 hours ago, Jack007 said:

You mean the round icon with the sinewave?

Yes.

Quote

I did see it flash even before the unit switched over to grid. Does this the mean the power is too dirty?

Yes. I think it means its patience with this generator is running out (I actually thought it would switch to line/bypass mode immediately).

Quote

What settings do you recommend i try in 12 an 13? Setting them to the lowest would be the best to test the switchover back to solar/battery is that correct?

You want both setting 13 and setting 29 to be low (13 less than the battery voltage, and 29 at least 4.0 V less than the battery voltage) for it to switch back to battery. Be aware that once it has switched to line mode, it won't switch back to battery mode for at least 10 minutes (2 minutes for fully patched firmware), under any circumstances.

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1 hour ago, Jack007 said:

26 54.6v

27 53.8v

Is your battery 15S LFP or 16S? Setting 26 is a little low for 16S. I use 55.2 V for my 16S LFP battery.

1 hour ago, Jack007 said:

29 47.0v

I'd like to try with setting 29 lower.

1 hour ago, Jack007 said:

The inverters do not accept the generator when set as UPS (no grid icon is displayed).

This is quite common, except perhaps with generators that have an inverter built in.

Quote

When i reconnect the pv the solar is only used to charge the system even though the battery voltage is more than 4v higher than setting 13 (battery voltage was at 54.xv). I want the solar to supplement the load draw.

In your model, the solar charge controller connects directly to the battery. Also when in line/bypass mode, the loads are supplied solely from AC-in; there is no blending.

To do what you want, you really need an Axpert MKS II, although it's possible that an Axpert King might do it. An Axpert King has the same 145 V max SCC that you have now, so there would be no need to rewire your PV panels.

Quote

 

The voltage seems constant (230 +-5v) and the Hz runs between 49.x - 52.x but mostly on 51.xHz.

Does the generator seem to have a poor AVR?

 

For the demands of the Axperts, unfortunately yes. They are very picky.

Quote

The installers did recommend a "Axpert filter box" inline between the genset and the inverter, but neither they or i seem to find what they are talking about. Do you know if anything like this is available that does not cost more than the generator itself @Coulomb?

Sorry, I know nothing about these filters. But it doesn't sound like it would help with your problem.

Quote

The inverter still does not want to switch back over to Solar/battery as main primary source for the loads.

But did you wait the ten minutes?

Quote

It also does not want to use the available Solar/battery power to supplement the load.

That's because this model isn't capable of that.

Quote

Ideally i want the generator as well as the solar/battery to supply the needed load together. eg. the generator should be seen as an extra power source not the only source. Is this possible?

Unfortunately, no.

Are you and your supplier willing to consider swapping to a different model of Axpert? Perhaps for the difference in price, plus a "restocking fee" to cover the hassle for the supplier, having to repack the unit, can't sell it as brand new any more, etc.

IF an Axpert King equivalent can blend AC-in and battery/PV, then that would be your best solution. The manual isn't clear on this point. Are there other Axpert King owners who can rule this in or out? It all hinges on whether the Axpert King allows both relays to be on (the one that connects AC-in to AC-out, and the one that connects the output of the inverter full-bridge to AC-out). In that situation, power from the battery and/or PV can blend with AC-in power to drive the loads.

IF NOT, then you'd have to go to an Axpert MKS II equivalent, and rewire your panels for higher voltage and fewer strings in parallel (e.g. 6S2P for each inverter).

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@Coulomb Thank you so much for all the explanations. I really do appreciate it!

50 minutes ago, Coulomb said:

That's because this model isn't capable of that.

I understand now that i cant do "blending" with my inverters, thank you for pointing that out. I doubt they will take them back seeing its been 2 years since installation.

50 minutes ago, Coulomb said:

But did you wait the ten minutes?

I was not aware of the 10minute waiting time. Thank you for pointing that out.

1 hour ago, Coulomb said:

Unfortunately, your generator isn't all that suitable for this application (despite paying extra),

That is a bit disheartening after paying R18k for a 5kVa. Am i right by saying i sould of rather have gone with a diesel of at least the kW eq of the inverters combined?

50 minutes ago, Coulomb said:

Is your battery 15S LFP or 16S? Setting 26 is a little low for 16S.

16S =16cells? I think so yes.

 

This was on the quote from 2018:

7.4 kWh mypower24 advanced battery solution

1x 16s 110Ah TüV certified LiFePO4 cells /0.3C (+5% tolerance)

SMC - self-extinguished enclosure

Protection fuses 100A (2 x for positive and negative pole)

Protection mechanical relay

mypower24 advanced BMS - Battery monitoring and management system (CAN bus communication with mypower24 data logger)

IEC compliant design and safety

 

And then i also receintly installed another module. Both the modules connect to one busbar and then go to the inverters. They are CATL cells apparently.

New module specs:

Model: SS202

Rev: 5

Manf: SolarMD

Cap: 144Ah / 7372.8Wh

Nominal Voltage: 51.2V

Rated ch/disch current: 100A/100A

50 minutes ago, Coulomb said:

I use 55.2 V for my 16S LFP battery.

I'd like to try with setting 29 lower.

What would you recommend at setting 26, 27, 29 and 34?

 

Edited by Jack007
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So it seems with my current setup i have the following options:

Disable Uti charging and make sure load stays under 5kVa

Set the Uti charge current to 20A and only use the genset to charge the batteries when the load is going to be low (in order not to overload it).

Get a dedicated 20A charger to bypass the inverters and charge the batteries directly.

Disconnect the genset from the solarsystem and power highdraw devices directly from it.

Else:

Change out inverters (and prob rewire panels)

Get a larger (10-15kVa) diesel? genset (because as i understand they have cleaner outputs than the petrol gensets?)

Get another 7.4kWh module ;)

Edited by Jack007
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19 hours ago, Jack007 said:

I doubt they will take them back seeing its been 2 years since installation.

Ah.

19 hours ago, Jack007 said:

That is a bit disheartening after paying R18k for a 5kVa. Am i right by saying i sould of rather have gone with a diesel of at least the kW eq of the inverters combined?

That's possibly going a little far. I have no idea if diesels are actually better for inverters than petrol generators.

19 hours ago, Jack007 said:

16S =16cells? I think so yes.

Good. That quote confirms it.

19 hours ago, Jack007 said:

And then i also recently installed another module.

Different aged battery modules have their own issues.

19 hours ago, Jack007 said:

What would you recommend at setting 26, 27, 29 and 34?

26: 55.2 V

27: 53.7 V

29: Could stay at 47 V or 48 V, but I'd use setting 01 = UTI so that settings 12 and 13 definitely don't take effect. That might solve most of your problems, actually.

34: 55.2 V. It's irrelevant while setting 33 is EdS (disable equalisation), but you might need to use the equalisation facility (or timed absorb) to work around the premature float bugs.

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19 hours ago, Jack007 said:

Get a dedicated 20A charger to bypass the inverters and charge the batteries directly.

That's not a really bad option, if you can get a decent one for not too much money. Though you'd want one with PFC (power factor correction, some of the cheap and nasty ones are just rectifier-capacitor), and perhaps more than 20 A of battery-side charge current; whatever load brings you near the top end of generator comfort at higher battery voltages (say 54 V). Then you'd just stay in battery mode 24/7. It should be one where you can adjust the absorb and float settings, or at least one where the fixed voltages are near 55.2 and 53.7 V respectively. If you mainly use it for supplementation, then the voltage thresholds might not be so important.

The only problem is that during the day, you could exceed the maximum charge current for the battery (all modules), if you have enough PV and generator power. But presumably, you'd rarely run the generator when it was a good solar day.

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