Growatt - Odd behavior

debron55

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If you want to increase PV production/energy harvest you might try setting 5 to USE, 19 to 28.5 (3.55v/cell) and setting 20 to 27.5. I don't think this will prevent the Growatt from turning off at the end of the absorption charge but you will be pushing battery voltage higher and away from the flatter part of the charging curve so voltage will drop faster after charge termination and in theory charging will resume faster.
yeah I had moved it down to 27.3 because of a suggestion from IAN regarding his thought that the BMS was tripping out. so this lower setting was a "test" value while we give the unit some headroom to prove it wasn't tripping the bms and resetting the unit. (which I might add I use overkill solar bms's and monitor through an ipad and so no evidence of it tripping) but...well... trying anyhting to get this figured out


what's the difference between use2 and use? (and as an fyi I did change it from use2 to use last night... but been a cloudy day so haven't hit the magic 27.3 number yet. though I did not alter the 19 and 20 setting from 27.3
 

apctjb

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what's the difference between use2 and use

Good question; use2 appeared after a recent firmware updates I tried it; and it set 19-20 to same value but not sure what other impacts it has.

MPPT charger turning off after absorption charge, is frustrating no doubt, but on a daily basis does it really result in a material reduction in your system performance? At the end of the day is your energy output appreciable more than the energy input or is it just that for a period of time energy has to come from the battery which is then refilled a little later when charging resumes? ( From what you have described I gather your PV capacity at this time of year is greater than the loads so at some point during the day your batteries are fully charged and PV input has to be reduced.)

I can only guess why Growatt decided to turn off MPPT charging at the end of the absorption cycle but suspect its is because keeping the MPPT charger on causes other issues and increases tare losses so from a system standpoint better to turn it on and off than keep it on. I also suspect that control design predates widespread use of LiFePO4 batteries that have a much flatter voltage curve where battery voltage does not drop 1 or 2 volts soon after stopping charging. All guesses on my part, I wish I knew.
 

debron55

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Good question; use2 appeared after a recent firmware updates I tried it; and it set 19-20 to same value but not sure what other impacts it has.

MPPT charger turning off after absorption charge, is frustrating no doubt, but on a daily basis does it really result in a material reduction in your system performance? At the end of the day is your energy output appreciable more than the energy input or is it just that for a period of time energy has to come from the battery which is then refilled a little later when charging resumes? ( From what you have described I gather your PV capacity at this time of year is greater than the loads so at some point during the day your batteries are fully charged and PV input has to be reduced.)

I can only guess why Growatt decided to turn off MPPT charging at the end of the absorption cycle but suspect its is because keeping the MPPT charger on causes other issues and increases tare losses so from a system standpoint better to turn it on and off than keep it on. I also suspect that control design predates widespread use of LiFePO4 batteries that have a much flatter voltage curve where battery voltage does not drop 1 or 2 volts soon after stopping charging. All guesses on my part, I wish I knew.
I do appreciate your input. the issue is primarily this: I want the batteries to go into the evening with as much power as they can have before the sun goes down and they are needed. As it stands - the batteries are generally full by 1 - 2 pm. At that point the panels are being shut off by the growatt. The unit then starts using the batteries. and the batteries are sized to have enough capacity for an entire evening. But not if the evening starts at 1:30 in the afternoon. So the batteries are being depleted at around 4 am and then the unit switches to utility. and it powers the load from utility. When the battery would have chugged right along until the sun came up if the unit would have consumed the abundant solar power from 1:30 to 6 or 7 pm the day before when it shut the panels off. I mean it's so straight forward. Use all of the solar panels power for as long as possible. I mean 1:30 pm is like full on afternoon sun at this time of year. I prefer the battery power to be conserved for the nighttime or for a power outage. Not used when the sun is fully up. as it stands I am probably losing about 4 KWh a day or more because of this odd behavior.
 

apctjb

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I do appreciate your input. the issue is primarily this: I want the batteries to go into the evening with as much power as they can have before the sun goes down and they are needed. As it stands - the batteries are generally full by 1 - 2 pm. At that point the panels are being shut off by the growatt. The unit then starts using the batteries. and the batteries are sized to have enough capacity for an entire evening. But not if the evening starts at 1:30 in the afternoon. So the batteries are being depleted at around 4 am and then the unit switches to utility. and it powers the load from utility. When the battery would have chugged right along until the sun came up if the unit would have consumed the abundant solar power from 1:30 to 6 or 7 pm the day before when it shut the panels off. I mean it's so straight forward. Use all of the solar panels power for as long as possible. I mean 1:30 pm is like full on afternoon sun at this time of year. I prefer the battery power to be conserved for the nighttime or for a power outage. Not used when the sun is fully up. as it stands I am probably losing about 4 KWh a day or more because of this odd behavior.

Yes I understand and agree its not ideal, but it appears to be normal for Growatt (for now). My system behaves the same way, except charging resumes long before 4KWHrs is drawn from the battery but perhaps I have a much smaller battery. Can you share how many kwhrs of battery you have??

Raising setting 19 should help, as it will result in a higher SOC at the end of day, and you will be operating further up the charging curve so voltage should drop faster after charge termination, hopefully resulting in faster resumption of charge.
 

TomC4306

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The granularity you desire is not available using an all in one unit. You need separate devices with separate wires. All of this functionality you want is derived currently from one pair of dc wires going into a black box.
 

TomC4306

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You get what you pay for. There are reasons why Growatts are $700 and SMA are $4000
 

Lt.Dan

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The granularity you desire is not available using an all in one unit. You need separate devices with separate wires. All of this functionality you want is derived currently from one pair of dc wires going into a black box.
I disagree, the Growatt should be acting exactly like he wants it to.

I have an MPP LV6548, which I understand is a different brand, but they are very similar in so many ways. And it does exactly what he wants. If my batteries get to 100% by 2pm (which is everyday), then it dials back the MPPT output to exactly match the load, but it never turns it off and expects to use the battery power and waste free PV energy.
 

apctjb

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If my batteries get to 100% by 2pm (which is everyday), then it dials back the MPPT output to exactly match the load, but it never turns it off

Curious; does this occur if your load is very small relative to the PV capacity after reaching 100%? With my Growatt if loads are small (<100w) it stops charging after having completed absorption and hitting float voltage. If I have larger loads then it stays on and follows the load.
 

Lt.Dan

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I have seen it get down to 65w before (standby consumption of the unit), and I have never had to "force it" to keep charging. As soon as the load increases, so does the PV, and if the load exceeds the PV capability, then it supplements with battery power.
 

debron55

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The granularity you desire is not available using an all in one unit. You need separate devices with separate wires. All of this functionality you want is derived currently from one pair of dc wires going into a black box.
The batteries hit a certain voltage and the unit is capable enough to stop charging them. The unit is also smart enough to, while charging, siphon off some of that power from the Solar Panels to power the load. The unit's failure is that it does not scale back the power drawn from the Solar Panels to match the load when the batteries are charged. Or it doesn't actually try, it basically flips immediately from using the MPPT to charge and power the load OFF and only pulls from the Batteries. I mean who would buy an all in one unit if they would be curtailing a big portion of their solar panel output.
 

apctjb

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I have seen it get down to 65w before (standby consumption of the unit), and I have never had to "force it" to keep charging. As soon as the load increases, so does the PV, and if the load exceeds the PV capability, then it supplements with battery power.

Curious; are your batteries Lead Acid or LiFePO4. Just looking for useful data points. Thx
 

Zwy

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I disagree, the Growatt should be acting exactly like he wants it to.

I have an MPP LV6548, which I understand is a different brand, but they are very similar in so many ways. And it does exactly what he wants. If my batteries get to 100% by 2pm (which is everyday), then it dials back the MPPT output to exactly match the load, but it never turns it off and expects to use the battery power and waste free PV energy.
Put up your settings Dan, then maybe we all might learn what is occurring. My opinion is that a setting on the GW is causing the issue.
 

Lt.Dan

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Curious; are your batteries Lead Acid or LiFePO4. Just looking for useful data points. Thx
It is a homebrew 48v 272ah LiFePO4 battery

Put up your settings Dan, then maybe we all might learn what is occurring. My opinion is that a setting on the GW is causing the issue.
My inverter actually just pooped the bed a few days ago and is inop right now. I remember most of the settings, so I'll pull up the manual and post my settings here shortly.
 
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Mendo Home Power

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And this graph for my 2nd inverter (the are paralleled) and shows that the second inverter continues to MPPT charge following the load for the remainder of the day.


View attachment 49606
I have three different parallel Growatt installations and all of them are acting in the same manner. I believe it is a bios issue and look forward to updaing it as my clients call me regularly about the issue. I am awaiting results of a possible fix that I did on one install where I switched inverter roles, i.e. master slave. I'll have more complete info on that tomorrow.
 

snoobler

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Just helped someone configure two of these in parallel 120/240V operation, and he experienced something similar.

Prior to final configuration, the unit behaved as the OP described. After reconfiguration and the complete hard "reboot" necessitated by wiring changes that completely disconnected the units from all sources, proper operation has initiated:

Bulk to bulk
Hang out there awhile.
Drop to float.
Hold float and power loads with solar.

IMHO float should not be above 27.2 as floating them above 3.4V/cell is never recommended and can damage cells.

1622129006792.png
1622129096518.png
1622129129351.png
 

Lt.Dan

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I'm not as fancy as snoobler, but here is the link to the manual for mine. Keep in mind most of the Program Numbers do carry over to Growatts, and they are very similar, but not all of them. You will also notice that I do push my battery further into both knees and never have a problem either. I use the ol' saying "I bought the whole battery, i'm gonna use the whole battery!"
  1. SBU
  2. 100a
  3. APL
  4. USE
  5. N/A
  6. Enabled
  7. Enabled
  8. N/A
  9. 60hz
  10. 120v
  11. 2a
  12. 48v
  13. 51v
  14. N/A
  15. N/A
  16. Only Solar
  17. N/A
  18. Off
  19. Stay
  20. Off
  21. N/A
  22. On
  23. Disable
  24. N/A
  25. Record
  26. 57v
  27. 56v
  28. Single Phase
  29. 40v
  30. Disable
The rest are machine specific and dont change how the inverter acts.

Hope this helps.
 

apctjb

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Thanks Snoobler & LtDan for posting settings.

I have been trying to figure this one out for months!

On my system (2x3000LVM) there are days where one inverter keeps solar connected after reaching float (never both inverters, one always shuts down as the other is sufficient to maintain float), and then there are days where neither inverter with start charge after having hit float the day before. Today is one of those days. First graph is for yesterday and you can see near the end of the day MPPT charging stops... and so far this morning it has not resumed (clear skies). My battery voltage currently is 52.4 which is about the point where it will typically resume charging so I expect it to kick in soon.

Best I can tell what triggers MPPT charging to stop is reaching float when loads are very small (close to tare loss). What triggers resumption of charging appears to be battery voltage dropping about 1.5V below float.

My settings are same as Snooblers (48V system) except for 12 which I have set at 48V.

In my case I am not really loosing any appreciable "free PV energy" , because PV is my only energy source and my batteries will be recharged by the end of the day regardless of this odd behavior. I am cycling my batteries a little more than if the Growatts always followed the load so hoping there is a setting or firmware update that will change this.

1622138578140.png
1622138614317.png
 
Last edited:

snoobler

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Thanks Snoobler & LtDan for posting settings.

I have been trying to figure this one out for months!

On my system (2x3000LVM) there are days where one inverter keeps solar connected after reaching float (never both inverters, one always shuts down as the other is sufficient to maintain float), and then there are days where neither inverter with start charge after having hit float the day before. Today is one of those days. First graph is for yesterday and you can see near the end of the day MPPT charging stops... and so far this morning it has not resumed (clear skies). My battery voltage currently is 52.4 which is about the point where it will typically resume charging so I expect it to kick in soon.

Best I can tell what triggers MPPT charging to stop is reaching float when loads are very small (close to tare loss). What triggers resumption of charging appears to be battery voltage dropping about 1.5V below float.

My settings are same as Snooblers (48V system) except for 12 which I have set at 48V.

In my case I am not really loosing any appreciable "free PV energy" , because PV is my only energy source and my batteries will be recharged by the end of the day regardless of this odd behavior. I am cycling my batteries a little more than if the Growatts always followed the load so hoping there is a setting or firmware update that will change this.

1.5V - good to know. Hopefully that scales down to 0.75V @ 24V.

That's mostly normal behavior. It's configurable on other MPPT. Most have a "re-bulk" or similar options that specify when the MPPT should re-initiate a bulk charge.

When the Growatt resumes, does it just maintain float, or does it re-bulk?

What's not normal is not maintaining float. I mean a pair of the damn things will pull 70W+, and that should be enough to demand solar! :)
 

apctjb

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As predicted MPPT charging resumed once battery voltage dropped to 52.4V , so about 1.5V below float 54V.

1622140379866.png
 
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