10 hours ago, Shadders said:

I've seen it happen in the other direction though. The battery is full and needs to go from bulk to float. What I saw and recorded today is that the load decreases, panel voltage and battery voltage rises and the dip starts. It definitely happens when there is a regular switching of a load and what I suspect is that the SCC can't handle the sudden change in power either up or down and overshoots then needing to dump power which triggers a reset of the algorithm which starts again from zero.

Interesting, I'd not noticed that. Unfortunately, I don't have any King SCC firmware to read. They have different code, perhaps with new bugs.

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If this happens often enough the SCC freezes at 0 and needs to be reset.

Wow. That's even more interesting, because freezes are quite serious.

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I attach data recorded by ICC every 5s of a dip and freeze that happened today. Unit is a Axpert king.

Thanks for that. Data is building.

Thank you all for puzzling over my "Inverter problem" - I have approached the manufactures, Mustek in Durban, and they don't hesitate to tell me that it is operating voltage that is the cause of the problem. Please see quote from their technical department: "

"I have spoken to our Head Office and as per manufacturer specifications, your 5P inverter will only work with a solar output

of between 60-115volts. If it detects higher voltage, like the 125volts your solar panels are providing, then it will cut out to

prevent surge damage to solar charger.

 

Your installation is incorrect if it is outputting 125v to inverter MPPT and you will need to have it checked by your installer."

 

Could it be that my inverter settings are incorrect? The settings I have that are not default are as follows:

01  SOL - Solar power to loads as first priority

02  Max charging current  AC 30A  Solar 30A

05  Battery type  User Defined  USE

12  Point back to Utility 47 V

13  Point back to battery  52V

16 Charger source priority SNU Solar and utility - Default

26  Bulk charging voltage  57 V

27  Floating charging voltage  54.4 V

29  Low DC cut off voltage  44 V

Setting 01 above uses the utility during the night and the batteries are fully charged, and remain so until dawn when the inverter changes over to battery mode.

 

NB:

There has been another occurrence as I have been writing this reply on the forum.

See attached. Similar story to all previous except in this case the solar was definitely battling a bit to keep up with the load and the batteries were discharging more than we normally allow.

 

On 2021/04/14 at 11:55 AM, Coulomb said:

Your dips seem to be short duration; by the next set of data (30 seconds afterwards), it's all back to normal. So I'd guess what is happening is that the inverter is in the float stage, and your PV input is just barely able to cover your geyser load on a good day. Remember that there are other loads, there is a ~7% loss through the inverter, perhaps 10% from PV to load, and some 70 W (wild guess for a 7200 W model) of self consumption. So a sudden load, such as a fridge switching on, will cause a dip in battery voltage, as the battery goes from perhaps a slight charge to a ≈1000W discharge for several seconds. My guess is that it's enough to trigger the switch from float to bulk charge.

When using the Solar energy for non essential appliances - kettles and geyser 1400 and 1500 W respectively we keep a close look at the battery monitor and the WatchPower display to check the incoming power and we normally allow a battery discharge of about 5 amp and by midday it is often 0 discharge or charging at that stage, sometimes get caught out with clouds !!

Thank you all again

 

54 minutes ago, Bushtracker said:

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...Your installation is incorrect if it is outputting 125v to inverter MPPT and you will need to have it checked by your installer."

It's just not true. Even though the manual does imply that.

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Could it be that my inverter settings are incorrect?

No, settings can't affect how the solar charge controller operates.

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29  Low DC cut off voltage  44 V

Just in passing, I would increase that to about 48 or 47 V, to increase the life of your (presumed lead acid) battery. I would also raise the back to utility voltage, and probably the back to battery voltage as well, as you seem to want/need to keep your battery as full as possible.

But none of this will affect the solar dips.

59 minutes ago, Bushtracker said:

I have approached the manufactures, Mustek in Durban, and they don't hesitate to tell me that it is operating voltage that is the cause of the problem. Please see quote from their technical department: "

"I have spoken to our Head Office and as per manufacturer specifications, your 5P inverter will only work with a solar output of between 60-115volts. If it detects higher voltage, like the 125volts your solar panels are providing, then it will cut out to prevent surge damage to solar charger.

Your installation is incorrect if it is outputting 125v to inverter MPPT and you will need to have it checked by your installer."

Sadly very indicative of the quality of technical support we get for all Voltronic inverters.  It reminds me of another post Axpert King MPPT blown and Voltronic response - Inverters - Power Forum - Renewable Energy Discussion where the "technical support" essentially gave exactly the opposite advice.

It appears that their modus operandi is to always blame you installation - if you put in 2P they will say it should have been 3P, and vice versa.🤮

2 hours ago, ThatGuy said:

Hahaha, ah... No. No no, no, I don't think so, no

I don't want to say your supplier is a liar who's trousers should be at least smoldering a bit... But at the very least they should explain to you why the inverter datasheet says 60-145V, before they tell you to spend more money to "fix" this issue. The 125V you've reported is because the SCC shut down (open circuit), it's not the other way around. Your normal operating voltage seems to be 95-105V, which is great.

You could ask them if they'll give you a guarantee that changing to 2S will fix it though... bet them another inverter if it doesn't

 

I'm going to do just that thank you.

OK I can't get my head around the function of the Inverter/charger immediately prior and after the "dip"?

My inverter data sheet on the Solar Charger & AC Charger indicates :

• Max PV array Open Circuit Voltage  - 145 VDC    My panel array voltage is 3 X 47.6 V = 142 VDC

• MPPT @ Operating Voltage   60 VDC - 115 VDC   My normal operating voltage appears to be less than 115 VDC except when there is a "DIP"
• So it appears that my panels are configured correctly as both the above parameters are within the specs?

What I don't understand is what is the SCC doing while the inverter is under load and the panels are not quite coping and the batteries are supplying the shortfall of the load? The SCC is not charging at this stage,(or is it?) so how does one know that the batteries are in bulk or float stage of charging at this time? Then the voltage increases to beyond MPPT operating voltage because of the load and the SCC changes mode from float to bulk or vice versa and that's when it resets the algorithm, and that is when the "dip" occurs. AND on all accounts this is not uncommon and is not a big issue.?

OR have I got it horribly wrong?

 

 

18 hours ago, Bushtracker said:

My inverter data sheet on the Solar Charger & AC Charger indicates :

• Max PV array Open Circuit Voltage  - 145 VDC    My panel array voltage is 3 X 47.6 V = 142 VDC

Wow. That's really close. In Winter before the panels warm up you can expect about a 7% increase in voltage, which would be 152 V, well over spec.

• Quote

   

  • MPPT @ Operating Voltage   60 VDC - 115 VDC   My normal operating voltage appears to be less than 115 VDC except when there is a "DIP"
  • So it appears that my panels are configured correctly as both the above parameters are within the specs?

   

 

I would not run them like that; I'd run them 2S. But you seem to get away with it most of the time, so far.

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What I don't understand is what is the SCC doing while the inverter is under load and the panels are not quite coping and the batteries are supplying the shortfall of the load? The SCC is not charging at this stage,(or is it?)

 

Yes, it is. It's sending as much as it can to the "battery bus", it's just that none of it is making it to the battery. 

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so how does one know that the batteries are in bulk or float stage of charging at this time?

The DSP in the inverter is controlling the charge. It is aware of the net current into the battery, even though as you say the SCC can't. It's telling the SCC every second what current to output. When the DSP sees the net current into the battery is below a threshold and the battery voltage is above a threshold, it decides that the charge is over and it goes to float mode. When the battery is discharging, it will be below the voltage threshold. Or it should be. The dreaded premature charge bug is that it uses the wrong threshold; it uses the float voltage setting instead of the absorb/bulk setting.

So it might be going to float mode, then if the load continues and the battery voltage sags enough, it could decide to go back to bulk mode, via a dip.

If you are asking how can the user tell what stage the charger is in, the charge LED on the front goes from flashing to solid when the charger goes from absorb to float. Monitoring software can also tell, I forget the exact command, but my Node Red tells me what stage the charge is at.

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Then the voltage increases to beyond MPPT operating voltage because of the load and the SCC changes mode from float to bulk or vice versa

I don't think that's quite right. It may be that in your case with your PV voltage so close to the limit, anything that causes a PV power to decrease (e.g. a load comes off) may cause the SCC to freak out and reset itself.

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AND on all accounts this is not uncommon and is not a big issue.?

I only get about 1 or 2 dips per day. It sounds like you get a lot more. It's hard to say whether reconfiguring your panels might reduce the occurrence of dips or not.

 

@CoulombThank you so much for your time I understand a lot more of the workings of the SCC now. As mentioned previously my electrician/installer is going to add a further 6 panels to the system with the view that eventually I will acquire a bi-directional inverter which will be more automated and efficient!