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Solis inverter upgrade, performance decreased?

DrPhil

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Mar 23, 2021
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I may be losing my mind, but I'm convinced that since changing from a Solis 5kW inverter to a 5g 6kW one, my system performance has gone to crap.

Generation is lower on average, particularly at low times like early morning and late evening.

Mid morning on a poor day I'd normally be pulling 7-800w but these days I might only get half that. On a good day I'd still be generating 5-600w at 9pm, yesterday was the hottest day of the year and I was basically flat lined from 8pm.

I know that hotter weather affects panel efficiency but this was not normal.

Is there any possible explanation for this? Even today, its overcast and raining intermittently. Based on the past few year's experience I'd expect to be generating about 700w even in the rain. Instead it's about 300w.
 
2:30pm today and I'm generating 180w on a 7.4kWp system.

79w on the south facing 4kW string, 101w on the west facing 3.4kW string.
 
Can you link the two inverters datasheets? There are different country models of the 5G, in the US there is the HVES 5G and in EU is the 48ES

Either 5G has storage modes and need to be configured for the operation mode you desire, it won't grid-tie sell out of the box from the factory. It's a bit complex and a full reading of the modes and deciding where and when the energy should go is up to the owner / installer.
 
Thanks @Solar Guppy

I'm in Ireland so it'll be the EU model, I'll try to get the exact spec when I get home.

To clarify, this was put in by an installer and is functioning as it should, but the generation numbers are just way below what I'd expect.

I'm awaiting a reply from the installer but I expect that he'll say its working (because it kinda is) and it's very difficult to state a clear issue when it's just my subjective opinion of what it should be generating vs what it is.
 
First thing to check is differences in MPPT operating voltage range of new vs. old inverter. Compare to PV panel Vmp x number in series. That will be quoted under nominal conditions, so varies with light and temperature.

Check PV voltage reported by inverter.

Possibly, it wants one more panel in series (but never exceed max Voc spec, calculating increased voltage of panels with freezing weather.)

Sunlight varies, so unless you can measure it, no way to compare one overcast day against another.
Some times of light clouds, my system puts out 10%. Heavy clouds, 2%.
 
First thing to check is differences in MPPT operating voltage range of new vs. old inverter. Compare to PV panel Vmp x number in series. That will be quoted under nominal conditions, so varies with light and temperature.

Check PV voltage reported by inverter.

Possibly, it wants one more panel in series (but never exceed max Voc spec, calculating increased voltage of panels with freezing weather.)

Sunlight varies, so unless you can measure it, no way to compare one overcast day against another.
Some times of light clouds, my system puts out 10%. Heavy clouds, 2%.
I know that the max voltage is the same for both, as this was something the installer checked before install.

I'll find the exact spec of the new one when I get home.

The old one was Solis RHI-5K-48ES.

I know you can't directly compare days, so I agree it's very difficult to objectively measure which is why I don't expect much joy from my installer.


But generation on the new inverter has been consistently below what I would have expected from the old one in similar conditions.
 
The 5G's are storage inverters and by default with do self-consumption, if your battery is full, only the loads in the home are offset using the external CT's. monitoring the feed to the mains.

You need to read the manual and the work through the menus' to set-up for selling energy to the grid, it is highly possible your installer didn't setup for selling energy to the grid and from reading there is limits in the EU to how much can be sold back. If this isn't for you, you need to discuss with your installer what provided for.

So I doubt there is anything "wrong" with the inverter, it is working as it is configured.
 
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The old one was Solis RHI-5K-48ES.

Your 6K is just a different maximum power output difference, otherwise they are the same unit, it is definitely the storage mode and sell modes ( or mis configured CT's ) where one should be looking

Read the manual on storage modes, then look at the menus to see how your unit was configured.

I take it the installer isn't the one whom did the initial installation of the 5K unit?

On great thing on these inverters is they are highly configurable for just about any possible operational parameters, but one needs to know what everything does, it is NOT a rip and replace, everything has to be setup again.

If you still have the 5K unit, one could power it up and go through the storage menus to see how the old one was provisioned. This can be done by using one of the solar arrays, nothing else, just be sure to remove from the installed 6K unit, don't parallel the array wire to both units at the same time.
 
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The 5G's are storage inverters and by default with do self-consumption, if your battery is full, only the loads in the home are offset using the external CT's. monitoring the feed to the mains.

You need to read the manual and the work through the menus' to set-up for selling energy to the grid, it is highly possible your installer didn't setup for selling energy to the grid and from reading there is limits in the EU to how much can be sold back. If this isn't for you, you need to discuss with your installer what provided for.

So I doubt there is anything "wrong" with the inverter, it is working as it is configured.

GT inverters, like what you replaced, just sell all available energy to the grid.

To test, if @DrPhil initiated a heavy load when PV output is low, but solar potential is high, then the array should increase output to power the load?
 
To test, if @DrPhil initiated a heavy load when PV output is low, but solar potential is high, then the array should increase output to power the load?

Depends on if the unit is configured to support more than the battery via SOC, for example backup or self consumption mode with no selling, a load that isn't on the backup port wouldn't do anything to the 5G, solar just keeps the battery and backup port powered.

There is no guessing here for the OP, the Solis has more configurations supported that any other inverter I have worked with, one of the reasons I have a pair, but I am an engineer :)

Read the manual
Check installed units storage modes, TOU settings, power limits, export limits and CT settings
Compare to the old unit if possible

There are also a special settings, the mppt can be turned off and configured to fixed constant voltage specified in the menu, this isn't in the manual and you need the special code to enter these menus.
 
The 5G's are storage inverters and by default with do self-consumption, if your battery is full, only the loads in the home are offset using the external CT's. monitoring the feed to the mains.

You need to read the manual and the work through the menus' to set-up for selling energy to the grid, it is highly possible your installer didn't setup for selling energy to the grid and from reading there is limits in the EU to how much can be sold back. If this isn't for you, you need to discuss with your installer what provided for.

So I doubt there is anything "wrong" with the inverter, it is working as it is configured.
I think maybe I'm not explaining myself properly, apologies.

The inverter is working fine. It draws from the battery when it's available and it draws from the grid when the battery is empty. It fills the battery when there is space and it exports to the grid when the battery is full. The grid-tie aspect of the inverter isn't what I'm questioning.

What is potentially at fault (and maybe not) is that the generation from the solar panels seems much lower now than with the old 5kW inverter. Obviously the panels are the same, and it doesn't make logical sense that I'd get worse generation from a different inverter, but that's how it seems.

2 weeks ago I'd be generating north of 100w from about 6:30am. Now I'll be lucky to break that level by 8am. Previously I'd be generating 2-300w well past 9pm, yesterday on a beautiful clear day it was flatlined by 7:30pm.

Previously even on a horrible wet day I'd rarely drop below 500w generation through the day. Today its been constantly around 150w.


This is a good day in early June on the 5kW.
Screenshot_20220719-154231_Solis Home.jpg

This was a good day yesterday (admittedly very hot which would reduce panel efficiency):
Screenshot_20220718-204901_Solis Home.jpg

This is a crap day last July:
Screenshot_20220719-162156_Solis Home.jpg

This is a crap day (today):
Screenshot_20220719-162211_Solis Home.jpg
 
In most storage modes that battey would just sit fully charged, with an occasional short top off, what your describing sounds like some type of TOU is configured, they battery would only be discharged if sell to grid for the battery is enabled, which isn't typically used expect for situations where you get different credits based on time of day.

When the inverter is "filling the battery" the amount sent to the grid is reduced and I suspect that is what you are seeing.

If you look at the 7/13 graph, at 15:00 the output is reduced by @ 800 watts and not following isonolation changes, the inverter looks to be programmed to do this.

As I wrote before, there are MANY configuration options, the old and new unit are likely not configured in the same manor, this is the first place to look.
 
When the inverter is "filling the battery" the amount sent to the grid is reduced and I suspect that is what you are seeing.
Sorry I still don't think we're on the same wavelength.

All I'm looking at is this:
Screenshot_20220719-164633_SolisCloud.jpg

I'm only currently generating 223w when I should be generating twice that figure based on the current weather.

I'm not questioning the feed to the grid, from the grid, to the battery or from the battery. That is all working perfectly.

All I'm saying is that the amount of generation coming from solar panels to inverter seems much too low.
 
It does appear old and new inverters have same MPPT specs.


Inverter efficiency also varies with how much voltage conversion takes place. But, MPPT voltage doesn't vary all that much with sun exposure.

Are you able to access PV string voltage and current (or calculate missing figure from watts)?
South and West facing strings of course have different light angles most of the time. Maybe you can track relative production, see when power output per panel is identical and check if angle of light is also same or not.

I have observed differences between PV strings, then disconnected panels to test them individually and found some degraded.
 
5:15pm, cloudy but not raining.
Screenshot_20220719-171141_Solis Home.jpg

7w on a 7.44kWp system. I don't see how this is possible without some kind of fault.
 
360V is open circuit, 75V is the default start voltage for the mppt tracking, If near sunrise or sunset, this would be expected, I believe the inverter brings one array online at a time, so I would swap array 1 and 2 to see if it makes a difference as in the above the 360V would have more energy.

Since your inverter on the 7/13 image is putting out over 6kw, the arrays look fine, not an array or wiring issue.
 
To understand the issue, I would suggest you understand the mode the inverter is configured. From your image, the home loads are pulling power from the battery, not the grid, which also may means that power isn't being allowed to exported, when the battery is full, you have to sell to the grid to pull energy from the Solar.

Also heat lowers the voltage of the Array and will affect the morning startup and evening shutdown.

It may take some time reading the manual and understanding the modes and seeing how the inverter is configured, but in general TOU grid shifting will affect what your seeing vs what was seen before. Heat is another big factor in production and I see from the news the EU is in record temps lately?
 
To understand the issue, I would suggest you understand the mode the inverter is configured. From your image, the home loads are pulling power from the battery, not the grid, which also may means that power isn't being allowed to exported, when the battery is full, you have to sell to the grid to pull energy from the Solar.
Yes the system is pulling battery from the battery, as they should. That's what the battery is for.

If there is excess power over the home load, it goes to the battery. If the battery is full, it goes to the grid.
 
Interesting look at the string voltages.

20220719_235309.jpg

Monday which was a scorching hot clear day, each string voltage was quite stable, only dropping off late in the evening.

Tuesday, voltage drops started around 3pm with one string usually staying in the 350 range while the other dropped to 75v.
 
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