Hi - wonder if anyone could advise me please - my inverter is set to Sbu - providing power to the loads with solar first, battery when insufficient and then utility, battery charging is set to SnU (Solar and utility). On a beautiful sunshine day, the PV drives the loads and charges the battery to about 88%, then it starts to switch the load to battery for a few minutes, then back to solar and so on until the sun sets and then it is battery only (as expected) until the battery reaches the low voltage or the next morning and PV starts powering the load again. The battery therefore do not load any further in the afternoon.  On the graph (attached) it looks as if PV input falls to 0W (starting at abut 13h35) when this happens (green is PV watts, purple is the battery watts (below zero when it is discharging to power the loads, cyan line is the load), but it cannot be as the sun still shines just as brightly as before. Up to 88% charge is works perfectly, solar powering the load, battery only used to supplement when solar is not sufficient for the load). 

Any advice would be greatly appreciated?

On 2021/12/30 at 10:29 PM, djza said:

the PV drives the loads and charges the battery to about 88%

Where does the 88% figure come from? If from the inverter, it's highly suspect.

What battery do you have?

Does the battery last about the expected time at night?

What are your back to utility and back to battery voltage settings?

What does the charge light do when the PV power goes to zero? I assume it was flashing (hence bulk/absorb stage) up to the point where the PV goes off, then it would go off for a minute or so. But what does it do after that?

Finally, there are many Axpert 5 kVA models. What model do you have? The 145 V max PV models behave differently to the 450-500 V max PV models.

Assuming you use LiFePh batteries, it looks to me as you should verify your bulk charge (26) and floating (27) voltage settings. Where are they? If they are set too low, it could behave that way when batteries are (partly) full. Also disable battery equalization (33). My 2 Axpert/Synerji MKS 5K work fine with settings (26) 54V, (27) 52.5 to 53V.

Happy new Year!

On 2022/01/01 at 4:35 AM, Coulomb said:

Where does the 88% figure come from? If from the inverter, it's highly suspect.

What battery do you have?

Does the battery last about the expected time at night?

What are your back to utility and back to battery voltage settings?

What does the charge light do when the PV power goes to zero? I assume it was flashing (hence bulk/absorb stage) up to the point where the PV goes off, then it would go off for a minute or so. But what does it do after that?

Finally, there are many Axpert 5 kVA models. What model do you have? The 145 V max PV models behave differently to the 450-500 V max PV models.

On 2022/01/01 at 4:35 AM, Coulomb said:

Where does the 88% figure come from? If from the inverter, it's highly suspect.

What battery do you have?

Does the battery last about the expected time at night?

What are your back to utility and back to battery voltage settings?

What does the charge light do when the PV power goes to zero? I assume it was flashing (hence bulk/absorb stage) up to the point where the PV goes off, then it would go off for a minute or so. But what does it do after that?

Finally, there are many Axpert 5 kVA models. What model do you have? The 145 V max PV models behave differently to the 450-500 V max PV models.

The 88% is reported by the Raspberry Pi monitoring software (SMH mobile app) - I have 4 x Pylontechs US3000 - I have recently upgraded to add another one, and it does seem to have extended the duration and load I can run off the battery. This is the Axpert model info I have Axpert RCT 5000MKS/4200.   I'll have to go look for the charge light, have not yet checked that.  Back to utility is set at 47V and back to battery at 52V.

On 2022/01/01 at 11:50 AM, Beat said:

Assuming you use LiFePh batteries, it looks to me as you should verify your bulk charge (26) and floating (27) voltage settings. Where are they? If they are set too low, it could behave that way when batteries are (partly) full. Also disable battery equalization (33). My 2 Axpert/Synerji MKS 5K work fine with settings (26) 54V, (27) 52.5 to 53V.

Happy new Year!

Thank you - will have a look at those.  The battery equalisation (33) is definitely enabled at the moment, I'll disable it as a trial.  The last few days I have not had enough sunlight to get back to the same level of charge again, so I have not observed it again since I asked the question.

4 hours ago, djza said:

I have 4 x Pylontechs US3000 - I have recently upgraded to add another one,

That sounds quite sufficient, and rules out some theories.

4 hours ago, djza said:

Back to utility is set at 47V and back to battery at 52V.

That certainly seems wide enough of a gap.

4 hours ago, djza said:

The battery equalisation (33) is definitely enabled at the moment, I'll disable it as a trial.

If it's actually trying to equalise now, and the equalisation voltage is higher than about 52.5 V, that could cause it. But it depends in how the monitoring software works; I have no experience with these.

Thank you for your input and advice, I suppose as long as the battery seems to handle the load I throw at it, I needn't worry.

2 hours ago, Coulomb said:

That sounds quite sufficient, and rules out some theories.

That certainly seems wide enough of a gap.

If it's actually trying to equalise now, and the equalisation voltage is higher than about 52.5 V, that could cause it. But it depends in how the monitoring software works; I have no experience with these.

Thank you very much - I think it is the monitoring s/w that is flaky - I checked the LEDs on the inverter as you suggested and the Charge one is solid indicating the battery is fully charged (it is at 54V).    Today it did that switching (on the monitoring s/w) for about 30 minutes, then it changed to PV supplying load only (constantly as one would expect when there is enough sunlight).