Growatt SPF 3000 24v issues

[unkyjoe]

Greetings, I want to share my experience with this unit in the hopes that someone can explain to me what is going on.

I run a YT chan called Unkyjoe's Playhouse, I am getting into solar and starting small with the goal of powering my studio racks and office with Solar and Battery backup.

The Growatt unit was a donation from a supporter of the channel. It is working, however it has some quirks I am trying to wrap my head around, I have tried these settings both through the front panel of the unit and through the Solar Assistant program as well.

I want the unit to switch to grid power when the battery voltage drops to 25v or less, I have 2 12v LIFEPO4 batteries, that were charged fully and separate from one another, then connected parallel for 24hrs to balance one another, they are working fine. Below are my settings for each item on the Growatt menu.
1-sbu, 2-30amps, 5-us2, 10-2, 11-50amp, 12-25v if I try and set this higher it jumps back to 25v, 13-28.5v, 14-snu, 19-28.8v, 20-28.8v, 21-23v, 22-sbe

When testing I set 12 to 26v to see if it would switch to grid and start charging the battery from the grid, it simply defaults back to 25v, this is with USE and US2 setting.

When switching to grid, and charging the battery I want it to charge the batt to 28.8 before switching back to battery, but I am confused if I need to set 13 to 28.8v as well as 19-20, the documentation is not clear on this and I wonder why this setting is there at all.

I reached out to Growatt directly and they had me update the firmware on the unit, but the instructions they sent are not clear and there is a language barrier with their support staff, I think the firmware was updated, however in the Solar Assistant software I see Firmware version 097.00 and a Secondary firmware of 2.07 which appears to be the version number they had me upgrade to.

I can change the above mentioned settings in the Solar Assistant program as well, however setting 12 which is "To grid battery voltage" wont go above 25v, it drops back down if you set it higher.

Settings 19-20 are float and absorption, but how does one trigger the battery charger to manually kick on, or is that even possible.

Any help or insight would be greatly appreciated.
Unkyjoe

 

[octal_ip]

The manual for the SPF 3000 indicates that a range between 20v and 24v can be set for 21 (Low DC cutoff voltage). It's surprising you can set it to 25v, but any higher than that simply isn't supported.

It's important to remember that the battery charging algorithm works independently of the AC transfer options. It's pretty well documented on these forums that setting 5 (battery type) US2 behaves strangely for lithium batteries, so try setting it to USE instead. Even then, you'll also have to ensure your voltages are just right. Have a read of this thread: https://diysolarforum.com/threads/growatt-odd-behavior.22696/

Do you know if your system is always operating in line mode?
Are you using the LVM or HVM variant of the SPF 3000?

 

[Mattb4]

Low DC cut off voltage is a different setting than Battery to utility setting. How Growatt has these I do not know. In my 3kw EAsun unit the setting range is 22v to 26v with 23.0v as default, when in SOL or SBU modes. The default utility to battery setting is 28v setting range of 24-30v.

My personal setup is a setting of 25v (B to U) and a (U to B) of 26.6v. This is because when PV becomes available I want my unit to switch out of utility as a preference.

Charging happens anytime the battery drops to 26.6v after being fully charged. The default setting was 26v

 

[unkyjoe]

21 is set to 23v and not 25v, option 12 is set to 25v but I want to set it to 26 for some testing and it wont let me do this.

This is where the confusion comes in, setting 12 to 25 triggers the system to transfer to grid, in addition it charges my battery when this happens, so then what the heck are setting 19&20 for? if setting13 is set like I have it to 28.5v

Mine is the LVM-24P model.

I will go back and read the thread you mention and see if I can wrap my head around this. Thanks for your help.

 

[Mattb4]

Battery absorption on lithium batteries is different than lead acid. Battle born has this handy explanation.

 

[unkyjoe]

21 is set to 23v and not 25v, option 12 is set to 25v but I want to set it to 26 for some testing and it wont let me do this.

This is where the confusion comes in, setting 12 to 25 triggers the system to transfer to grid, in addition it charges my battery when this happens, so then what the heck are setting 19&20 for? if setting13 is set like I have it to 28.5v

Mine is the LVM-24P model.

I will go back and read the thread you mention and see if I can wrap my head around this. Thanks for your help.

Battery absorption on lithium batteries is different than lead acid. Battle born has this handy explanation.

I set float and absorption to the same level after watching Andy at "the off grid garage" run his tests.

So I guess I am going to set the batt to use and then set my voltages there and see how things go, nice thing is I can set them through the Solar Assistant app as well. Still cant change that "To Grid battery voltage higher than 25v" but I can live with that for now, anyone have any ideas about the firmware question I posed?

 

[octal_ip]

21 is set to 23v and not 25v, option 12 is set to 25v but I want to set it to 26 for some testing and it wont let me do this.

Yep, my mistake. All these numbers are meaningless out of context, so let's tabulate them:

Setting #	Name	Range	Your configuration
12	Back to utility voltage	22.0V~25.6V	25v
13	Back to battery voltage	24.0V~29.0V	28.5v
19	C.V. charging voltage	24.0V~29.2V	28.8v
20	Floating charging voltage	24.0V~29.2V	28.8v
21	Low DC cut-off voltage	20.0V~24.0V	23v

option 12 is set to 25v but I want to set it to 26 for some testing and it wont let me do this.

That's right, the highest you can set this to is 25.6V. I'm not sure why you would want it at 26V? With this setting your cells are at 3.25V, which means the system will switch back to grid without really having used any of the battery capacity. A typical configuration would have this at about 24V which is when the batteries are at 3V and just about empty.

This is where the confusion comes in, setting 12 to 25 triggers the system to transfer to grid, in addition it charges my battery when this happens, so then what the heck are setting 19&20 for? if setting13 is set like I have it to 28.5v

Put simply, 19 and 20 specify the maximum voltage the system will charge your batteries to as it goes through the constant voltage and float charge modes. At 28.8V you'd have 3.6V per cell, which is fine. The float charging should stop after about 2 hours of the batteries being held at 28.8V, assuming enough (or an excess) of input power is available.
What you need to remember is that these units have two power inputs - utility and solar. Using only utility power, your batteries will cycle between the "back to utility" and "back to battery" voltages. When solar is introduced, you have the potential to spend a lot more time above the "back to battery" voltage (up to 28.8V) as solar is providing for the load and charging whenever it can. At night your batteries will discharge to the "back to utility" voltage and start the "back to utility" and "back to battery" cycle until solar is available again.

The low DC cut-off voltage at 23V will mean your cells will discharge to no less than 2.875V when powering the load and both utility and solar aren't available to maintain charge. Probably a bit on the low side, but also within reasonable limits.

 

[unkyjoe]

Put simply, 19 and 20 specify the maximum voltage the system will charge your batteries to as it goes through the constant voltage and float charge modes.

Can you define what this means and when these modes occur?

What you need to remember is that these units have two power inputs - utility and solar.

Under battery settings I have it set to charge with Solar and Utility at the same time, however I noticed this morning that while the battery was charging with utility power, the solar kicked in and at about 25.7v on the battery the grid charging turned off and is still off, only using the solar 38-50 watts at this time "cloudy" to power a 374w load and charge the battery, which it can't do as the load is so high, I thought the grid charge would stay on until it reached the settings on 19-20 and not switch back to solar powering the load, it is like it is ignoring the configuration, and this is where my confusion is coming in. The 26v setting was just to run a test by the way.

Just now the battery reached 25.07v and the util charger kicked back in?

One more thing, I have NEVER seen the batteries charge up to the settings I have in 19-20, which is why I question setting 13 which I currently have set to 27v as a test to see if it even gets to this voltage.

 

[unkyjoe]

Update:
I changed setting # 13 to 28v and setting #12 to 24.8v.

Once it reached 24.6v even though I had a bit of solar it switched to the grid and charged it to the setting on #13 which was 28v. But again, I have no idea why it is not charging to the float or absorption rate of 28.8v that I have it set for.

I am wondering if perhaps it detects there is solar coming in and only charges to the rate set on #13 unless there is no solar, then it will charge to the float-absorption rate set on # 19-20.

I don't mind experimenting to find this out, but as long as this unit has been out, you think there would be some clear answers to these questions, so thank you to everyone who has tried to help, I will keep experimenting and posting my results.

 

[octal_ip]

Once it reached 24.6v even though I had a bit of solar it switched to the grid and charged it to the setting on #13 which was 28v. But again, I have no idea why it is not charging to the float or absorption rate of 28.8v that I have it set for.

This is because setting 13 "Back to battery voltage" always takes precedence over 19 and 20. In your setup, 19 and 20 will only be reached through solar charging, and only if sufficient solar power is available to supply the inverter (about 60w), your loads and the battery charging demand.

but as long as this unit has been out, you think there would be some clear answers to these questions,

Yeah, the logic is a tangled web and Growatt does an awful job of documenting how it works. There's a lot of interacting processes (multiple inputs and outputs) so figuring out how this "black box" operates can be difficult, particularly when you have changing external variables like solar conditions. There's whole threads on this forum just trying to figure out how the float and CV charging process works, something that should be quite straight-forward.
Maybe consider it a challenge and produce a flow chart to help others in your situation understand as your experimentation proceeds?

 

[unkyjoe]

19 and 20 will only be reached through solar charging, and only if sufficient solar power is available to supply the inverter

I find that hard to fathom, since I have the unit set to charge from both solar-util simultaneously, my observation last night was that after solar was gone, the charger on the unit came on and charged up to the setting on #13 and then switched the loads back to battery.

I am going to reach out to Ian at watts247 and see if he can answer the question, and sig solar as well, as I am sure people would like to know the answer to this question, does Ian hang out on this forum? Let me know if he does.

Also anyone have any ideas about the firmware question I asked?

 

[Mattb4]

I find that hard to fathom, since I have the unit set to charge from both solar-util simultaneously, my observation last night was that after solar was gone, the charger on the unit came on and charged up to the setting on #13 and then switched the loads back to battery.

I am going to reach out to Ian at watts247 and see if he can answer the question, and sig solar as well, as I am sure people would like to know the answer to this question, does Ian hang out on this forum? Let me know if he does.

Also anyone have any ideas about the firmware question I asked?

You can not charge from utility when the inverter is operating. Only when in AC bypass.

Need to understand the various operation Modes.
SBU
SOL
UTI

Battery charging preference Modes.
OSO
SNU
CSU
CUB

Consult your manual.

 

[unkyjoe]

You can not charge from utility when the inverter is operating

See picture above solar3.jpg, it clearly states that it can with that setting?

and per the user manual. and of course if I had read the line below it, only SOLAR when in battery mode!
Line-Standby-Fault are the conditions that allow it to charge at the same time.

So setting 19-20 are ignored when charging from UTIL, and I would have to set #13 to the same as 19-20 to get the UTIL charger to chg battery to this level if I am understanding this correctly?

 

[Mattb4]

Charging both from PV and Util can only happen when in AC bypass. The inverters circuitry can only work one direction at a time.

19 and 20 are not ignored when charging from Utility. In fact if you choose UTI Mode they will come into play. It is just when in SBU and SOL you have voltage settings to transfer to utility and back that take precedence.

 

[unkyjoe]

So when using SBU mode I would want to set #13 to my max charging voltage, because in the SBU mode setting 19-20 will never occur unless I have more solar and less load?

 

[Mattb4]

About all I can tell you is you will have to adjust Modes and voltages to meet your preferences for operation.

My setting for my EAsun 3kw with 24v lithium batteries are:
SBU unless low solar production and than I manually change to UTI to preserve battery.
OSO unless the battery voltage is getting close or below low voltage alarm point than it goes to SNU to charge from Utility.
Bat to util: 25v
Uti to bat: 26.6v
Boost: 28.4v
Float 28.2v

Battery fully charged recovery at 26.6v This setting not all inverters have but what it does is it sets when the battery has reached a low enough voltage to begin a new charge cycle.