Growatt 24V SPF 3000TL LVM Settings Help

[CompMan2020]

Hi All,

I was wondering what settings is best for this inverter and battery combination. Growatt inverter with 2 24V batteries in parallel.

Inverter Manual
Battery Used

I did a search first and found a thread with some inverter info, but the batteries used on that thread were different. I'm a bit of a noob (some would say a boob) when it comes to Lithium batteries and their ratings/settings. I really want these batteries to last a while and don't want to ruin them with the wrong settings.

The website for the batteries has 3 ratings (Min, Max, Standard?) which is a bit confusing to me. There's also a link to Will's video but that video is for the New cells only and the one purchased already comes enclosed with a BMS.

Also, I hear that Lithium shouldn't be floated? But the inverter makes me have a value since I'm using the USER setting since the Lithium setting is for Watts 24/7 batteries.

I'm using this setup for my Garage/workshop. My intension is to have all loads powered by solar and the batteries when possible. My average load overnight is around 250WH (full size fridge). If I get good sunlight during the day I can power the loads overnight via the battery without having to tap into the grid. During the day I can pretty much run anything off solar and battery power.

I just want to make sure all the charging and discharging settings are optimized for this setup. Also, these are products that Will recommends so I'm sure this will help others down the line.

Thanks,
Rich.

 

[snoobler]

Can't comment on the bulk of your inquiry, but Lithium doesn't NEED to be floated. If you choose to, it should be at less than 3.4V/cell.

Additionally, the Growatts are light duty units with negligible surge capacity. If you're using power tools, particularly high surge items like a table or circular saw, you may find the Growatt overloads.

Not uncommon for electric motors to have a surge 3-6X their run currents, so a 1hp motor (750W) might need 4000W to start.

 

[CompMan2020]

Can't comment on the bulk of your inquiry, but Lithium doesn't NEED to be floated. If you choose to, it should be at less than 3.4V/cell.

Additionally, the Growatts are light duty units with negligible surge capacity. If you're using power tools, particularly high surge items like a table or circular saw, you may find the Growatt overloads.

Not uncommon for electric motors to have a surge 3-6X their run currents, so a 1hp motor (750W) might need 4000W to start.

I'm really not worried about that since the inverter should kick over to grid power for help if needed. I'm more concerned about my battery charge and discharge settings.

In Will's video he mentioned 28.8V absorption for those cells which I believe is the bulk charge? Also, Float is set to the default of 27V. But again I'm not entirely sure if this is correct. Especially for my use.

 

[apctjb]

But the inverter makes me have a value since I'm using the USER setting since the Lithium setting is for Watts 24/7 batteries.

I also have Growatt 3000. My understanding is that if you set program setting 5 to USER, you set bulk and float voltage set points (program settings 19, 20) to match you specific battery characteristics and application. My battery is large enough that I don't need to push it so have bulk set to 3.5 volts (56V for 48V battery) and Float at 3.35 (53.6) . This is what I am starting with, may adjust over time based on how my system operates.

Growatts are light duty units with negligible surge capacity. If you're using power tools, particularly high surge items like a table or circular saw, you may find the Growatt overloads.

Can you clarify what you mean by "light duty"? Growatts are high frequency inverters, which have their advantages (weight, efficiency, cost) but have lower surge capacity than low frequency inverters. I have 2 Growatt 3000 in parallel and they operate my table saw and tools without problem and they operate at +90% efficiency most of the time. That said if operating large motors is the primary load then a low frequency inverter might be a better choice.

 

[snoobler]

I'm really not worried about that since the inverter should kick over to grid power for help if needed. I'm more concerned about my battery charge and discharge settings.

Many have found the MPP Solar and Growatt units limited to their rated output even when fed by grid. The specifications don't state it explicitly, but the output power derating curve in Table 2 strongly implies rated power is the limit.

Can you clarify what you mean by "light duty"? Growatts are high frequency inverters, which have their advantages (weight, efficiency, cost) but have lower surge capacity than low frequency inverters. I have 2 Growatt 3000 in parallel and they operate my table saw and tools without problem and they operate at +90% efficiency most of the time. That said if operating large motors is the primary load then a low frequency inverter might be a better choice.

How does your table saw perform on only one unit?

I literally clarified it right after I used the words, "with negligible surge capacity." They claim a 2X surge capacity for 5 seconds, which is typically optimistic - more likely to be available for milliseconds. There is also no measurable difference in efficiency vs. a quality low frequency unit.

 

[CompMan2020]

Many have found the MPP Solar and Growatt units limited to their rated output even when fed by grid. The specifications don't state it explicitly, but the output power derating curve in Table 2 strongly implies rated power is the limit.

Yes, I get it... They're cheap, but for now this is what I have to work with. It fit the budget and Will recommended them so I pulled the trigger.

That being said, I'm still in need of the correct settings for this unit and batteries. I guess I will need to reach out to Big Battery and see what they say.

Thanks for your input.

 

[snoobler]

Yes, I get it... They're cheap, but for now this is what I have to work with. It fit the budget and Will recommended them so I pulled the trigger.

That being said, I'm still in need of the correct settings for this unit and batteries. I guess I will need to reach out to Big Battery and see what they say.

Thanks for your input.

I addressed that in my initial response (3.4V/cell), and I didn't think you needed me to do the arithmetic for you, but here you go:

3.4*8 = 27.2V

@apctjb use of 3.35/cell is just as good (3.35 * 8 = 26.8)

Your 27V is right in the middle of those.

 

[CompMan2020]

I addressed that in my initial response (3.4V/cell), and I didn't think you needed me to do the arithmetic for you, but here you go:

3.4*8 = 27.2V

@apctjb use of 3.35/cell is just as good (3.35 * 8 = 26.8)

Your 27V is right in the middle of those.

I didn't ask you to!

I mentioned that it was set to the default 27V which is under your 3.4 per cell recommendation. Thanks!

You did mention that you couldn't comment on the Bulk and that's what I'm trying to figure out as well. Also, would like to see what the other settings should be. Like #12 & 13. Again, all this I'm guessing will vary with my setup and usage.

Thanks for your input!

 

[snoobler]

Ah. You only directly mentioned float, and I didn't extrapolate.

28.8V (3.6V/cell) per the website. You may choose a more conservative 3.5V/cell at 28V

The min/max refer to the BMS voltage protection circuit, i.e., the BMS will prevent any cells from exceeding those values, and those values aren't perfect, they have a tolerance range, e.g., the BMS will protect the battery when any one cell exceeds 3.72-3.78V

 

[apctjb]

Also, would like to see what the other settings should be. Like #12 & 13

Might want to check with Ian , my understanding 12 & 13 are user settable low/high setpoints for controlling generator start/stop and when power will be supplied by the battery vs utility and do not impact battery charging.

 

[CompMan2020]

Might want to check with Ian , my understanding 12 & 13 are user settable low/high setpoints for controlling generator start/stop and when power will be supplied by the battery vs utility and do not impact battery charging.

Yes, he recommended I set them up to 23V and 24V.

My understanding is when back on utility (23V) and with no solar, utility will handle the load and battery chagrining up to the 24V, then the system will jump back onto battery power until the battery voltage is back down to 23V? And this will cycle on and off until I have solar energy to top off the batteries. At least that's what I understood it to mean.

I have setting #14 on CSO.

 

[apctjb]

My understanding is when back on utility (23V) and with no solar, utility will handle the load and battery chagrining up to the 24V, then the system will jump back onto battery power until the battery voltage is back down to 23V? And this will cycle on and off until I have solar energy to top off the batteries

Seems right based on reading the manual, but I have not tried it so curious to hear if that works in practice for you.

 

[CompMan2020]

Seems right based on reading the manual, but I have not tried it so curious to hear if that works in practice for you.

This only happened the night it rained all day and my batteries weren't topped off.

That night it looked like grid power cycled on and off every hour until the sun came out and started charging the bank fully.



Is charging this way via Grid more efficient? I would have thought that charging the batteries all the way once is better?

I'm sure Ian knows his stuff, but that was on the inverter side of it. My specific battery info never came into play.

 

[CompMan2020]

Here's the info Big Battery sent me for Inverter settings for these batteries.

Bulk Voltage: 28V - 29.2V
* Absorption Voltage *: 28V - 29.2V Absorption Time 0-15 min
* Float Voltage *: 26.6V - 27.6V
* Equalize *: OFF or as short time possible @ float voltage
* not necessary
VOLTAGE CUTOFFS Low Voltage: 22V High Voltage: 29.2V

 

[apctjb]

I am envious of your monitoring software, what program are you using?

Did you try to adjust the upper voltage setpoint to a higher setting and/or lower the lower setpoint so once you switch to utility power you stay there longer to reduce the cycling on/off? Also could adjust setting 11 down to minimum (10A) which would extend the duration of time on utility power.

If the goal is to reduce grid energy consumption then reducing utility charging current will give solar more opportunity to recharge batteries.

 

[snoobler]

Is charging this way via Grid more efficient? I would have thought that charging the batteries all the way once is better?

I'm sure Ian knows his stuff, but that was on the inverter side of it. My specific battery info never came into play.

Not more efficient, but it is less costly. If these were FLA/AGM, then yes, best to charge them to full in one shot, but since these are LFP, it doesn't matter. It is more economical for you to charge with solar rather than grid.

 

[CompMan2020]

I am envious of your monitoring software, what program are you using?

This is the online PC based software that you get when you set up the Growatt WIFI Dongle. You can also use the Shinephone app to get the same info.

Did you try to adjust the upper voltage setpoint to a higher setting and/or lower the lower setpoint so once you switch to utility power you stay there longer to reduce the cycling on/off? Also could adjust setting 11 down to minimum (10A) which would extend the duration of time on utility power

No not yet, still trying to figure things out.

If the goal is to reduce grid energy consumption then reducing utility charging current will give solar more opportunity to recharge batteries.


I'll try that. I've only been set up for about a week with these batteries, but since adding them I haven't been using the grid at all.
That day Ian was helping me out with some other software issues I had and for some reason I knocked the inverter offline by mistake and the settings went back to default. That's why it shows a load that night.

What sucks is that if the inverter doesn't see any batteries then it won't default to grid power, it will simply shut off. These batteries have circuit breakers built in and if tripped you will lose power to the loads. In my case, my back up fridge with all my beer and goodies in it!

 

[CompMan2020]

Not more efficient, but it is less costly. If these were FLA/AGM, then yes, best to charge them to full in one shot, but since these are LFP, it doesn't matter. It is more economical for you to charge with solar rather than grid.

Ah I see. Awesome! That's exactly what I'm looking to do.

Right now I have a lot of wasted power since my load is very small, but I plan to move my office in there amongst other things.

I have an AC unit I got for the space, but I need to get the ventilation issues straighten out first. I'm sure it will consume a lot of that extra power generated during the day. Plus keep me from melting away while in there.

Thanks again for the input!

 

[CompMan2020]

This is todays usage so far...

 

[BCS13]

This is todays usage so far...

View attachment 22185

Slightly off topic, but been messing with the various 'user defined' battery settings on the Growatt as well...

My question is: When trying to change/set parameters via the web or mobile app, it asks me for a 'key' or 'password' and I've tried everything but can't seem to guess it? Any idea?