What triggers Growatt 3000 to exit float and resume bulk charging (via solar)

[Librelec]

I may have found a way to know the actual voltage that the Growatt will resume charging after it has stopped charging. However, this is only for the ultra adventurous types as it requires you to read the internal Growatt registers via the MODBUS protocol/interface. The document that describes this can be found at https://www.photovoltaicsolar.in/Growatt_Manual/MAX Series Modbus RTU Protocol.pdf. If you look under Register 1007 in that pdf file you will see something called Vbat start for charge. The description says "should charge when lower than this voltage". The units are in 0.01V with a default of 5300 (probably 53V).

While I have not yet tried reading the Growatt registers using MODBUS, I have been totally successful doing this exact same thing for the Midnite Classic and reading its internal registers using an existing Arduino library. I seem to remember seeing an Arduino library for reading the Growatt registers using MODBUS, but to not remember where I saw it. If you are interested, you will probably be able to find this Arduino library or something similar by searching the web for something like "Growatt modbus registers" or something similar.

If you don't want to go to all that trouble, you may want to assume that the default of 53V in the Growatt MODBUS pdf is the actual voltage threshold the Growatt uses to restart the charging cycle. If you make this assumption, then this could/should impact your Float Voltage value in the Growatt Setting #20. The default Float voltage for Setting #20 is 54V as stated in the Growatt SPF 5000 ES manual. So with all these assumptions, as long as you set your Float voltage at or above 53V then the Growatt should trigger a new charge cycle when the voltage drops to 53V.

The main problem with assuming that the 53V is the actual trigger for starting a new charge cycle is that this internal register can be written to. This means that the internal Growatt software can potentially modify this register any time it wants to during run time based on unknown criteria. For instance, at least one forum user speculated that the trigger "to resume charging is when battery voltage drops a set percent below float" (see https://diysolarforum.com/threads/growatt-odd-behavior.22696/). While I do not see anything in the Growatt MODBUS pdf to support this theory, he may be right. So to be more sure of where this trigger is actually set during run time would require you to read the Growatt registers as discussed above (yes that is a pain).

This is all a guess at this point so do not take this information as truth! (everyone likes a disclaimer).

Hi,

Just wanted to revisit this as I'm having issues with my LFP batteries in the Growatt SPF5000ES.

When in the Growatt monitoring (app or web portal) all the settings are able to be set, including the Float, Bulk, etc etc.

I've now set my setting as per the pic, and we'll see how they go over the next few days.

I just wanted to chime in, because accessing those settings that you've found, are actually easily accessible.

I should add, I *think* "vBatt start for charge" is actually the voltage that the system charges from AC bypass? That's how it seems for me, anyway.

 

[apctjb]

I should add, I *think* "vBatt start for charge" is actually the voltage that the system charges from AC bypass? That's how it seems for me, anyway.

Will be very interested to hear how it goes for you and if VBatt start for Charge is the same as AC Bypass voltage. Having watched my system for close to a year now it appears that mine resumes the cycle somewhere around 52.5V, +/- .5V

 

[derekisastro]

Will be very interested to hear how it goes for you and if VBatt start for Charge is the same as AC Bypass voltage. Having watched my system for close to a year now it appears that mine resumes the cycle somewhere around 52.5V, +/- .5V

If you change your float voltage does this change this behavior... I recall reading a theory that it would start a charge cycle at "float voltage - 1V" or something similar.

I need to test this too ...

 

[derekisastro]

Hi,

Just wanted to revisit this as I'm having issues with my LFP batteries in the Growatt SPF5000ES.

When in the Growatt monitoring (app or web portal) all the settings are able to be set, including the Float, Bulk, etc etc.

I've now set my setting as per the pic, and we'll see how they go over the next few days.

I just wanted to chime in, because accessing those settings that you've found, are actually easily accessible.

I should add, I *think* "vBatt start for charge" is actually the voltage that the system charges from AC bypass? That's how it seems for me, anyway.

What program is this screenshot of settings from?

 

[Librelec]

What program is this screenshot of settings from?

The online portal server.growatt.com

After setting up the wifi usb dongle

 

[coolbz]

If you change your float voltage does this change this behavior... I recall reading a theory that it would start a charge cycle at "float voltage - 1V" or something similar.

I need to test this too ...

Have you found what parameter triggers resume solar bulk charging? I’m seeing same issue on my Growatt as reported in this thread.

I never had this issue in winter because my solar was never able to fully charge battery before it deplete. The grid charging parameters are more intuitive and predictable compared to solar Bulk/float settings.

 

[mtngun]

This thread may be covering or confusing 2 separate issues.

With 1 set to "SBU" and 19 = 20, my Growatt will bulk up to about 0.5V below 19/20, then kick into float mode. It actually never reaches 19/20 but stays about 0.5V below. I dunno why it stays 0.5V below the setpoint but since that is the case I have compensated by tweaking 19/20 up. I.e., I have 19/20 set to 57.7V and it actually charges to about 57.2V, occasionally hitting 57.3V. As long as enough solar power is available, it'll maintain 57.2 or close to it, with the charge automatically increasing if the load increases.

Note that with 1 set to "SOL" charging works differently. I prefer "SBU," though it depends on your goals.

BUT ..... as described in post #6, occasionally first thing in the morning, after the battery has partially discharged during the night, the Growatt will not recognize the solar power as the sun comes up. The Growatt will say 0 volts solar and 0 amps solar even though the sun is hitting the panels and I verify there is PV voltage with a multimeter. It's as if the solar side of the Growatt has "gone to sleep." So far the only way I have found to "wake up" the Growatt is to power it down, then power it back up. Then it immediately recognizes the solar side and starts charging normally.

I suspect this problem of the Growatt's solar side sometimes "going to sleep" in the morning is a software bug. So far it has happened to me twice in the one month that my system has been running.

 

[derekisastro]

Have you found what parameter triggers resume solar bulk charging? I’m seeing same issue on my Growatt as reported in this thread.

I never had this issue in winter because my solar was never able to fully charge battery before it deplete. The grid charging parameters are more intuitive and predictable compared to solar Bulk/float settings.

I've never had that experience so I cannot offer a sugestion. Every time I get any solar energy, it seems to go into my battery. The fact that it doesn't, and with what you've described in other threads (and without knowing ALL your settings) it seems like your inverter is faulty.

 

[WindWizard]

Thanks; I could not find mention of it in the manual, (the manual leaves lots to the imagination.)

As I have a fairly large array relative to my current loads, I quickly move through bulk charge, to absorption and then float. But after a while in float, it goes into a "fully charged" mode (charging light goes from flashing to solid on) and solar no longer supplies any loads that are applied (during the charging mode solar immediately picks up additional loads, plus keeps charging). I need more time to observe but it almost seems like it is stuck in charged mode even thought battery voltage drops below float and absorption setpoints and this is impacting energy harvest.

I have the Outback FM80 and was experiencing the same thing. The batteries would be in Bulk until the Absorb voltage was reached and then they went to float and then I would see charged on the display and all of the Solar was not used until something triggered the batteries back to bulk again. I could not get it to stop by changing the rebulk voltage. The only thing that helped was to set a time for the Absorb voltage which I set for 55.5 volts for a 48 volt pack. The charge controller then would continue to use the solar and then keep the pack at 55.5 volts which all of the cells in the battery pack were happy and none were trying to go to 3.65 volts.

I am not familiar with the growatt software but looking at the manual it seems very vague and difficult to interpret, but maybe it has some time that you could set for the absorb voltage to keep using the PV panels while the sun shines. It seemed to be the answer for me.

 

[Gerg]

This thread may be covering or confusing 2 separate issues.

With 1 set to "SBU" and 19 = 20, my Growatt will bulk up to about 0.5V below 19/20, then kick into float mode. It actually never reaches 19/20 but stays about 0.5V below. I dunno why it stays 0.5V below the setpoint but since that is the case I have compensated by tweaking 19/20 up. I.e., I have 19/20 set to 57.7V and it actually charges to about 57.2V, occasionally hitting 57.3V. As long as enough solar power is available, it'll maintain 57.2 or close to it, with the charge automatically increasing if the load increases.

Note that with 1 set to "SOL" charging works differently. I prefer "SBU," though it depends on your goals.

BUT ..... as described in post #6, occasionally first thing in the morning, after the battery has partially discharged during the night, the Growatt will not recognize the solar power as the sun comes up. The Growatt will say 0 volts solar and 0 amps solar even though the sun is hitting the panels and I verify there is PV voltage with a multimeter. It's as if the solar side of the Growatt has "gone to sleep." So far the only way I have found to "wake up" the Growatt is to power it down, then power it back up. Then it immediately recognizes the solar side and starts charging normally.

I suspect this problem of the Growatt's solar side sometimes "going to sleep" in the morning is a software bug. So far it has happened to me twice in the one month that my system has been running.

Just installed a 12kW LF unit, exact same issue. Running 15.6kWh lifepo4 server batteries and 5000W+ of panels. Used manufacture recommended bulk of 56V and float of 54.4V
Can’t communicate with Growatt so using USE2.
I have never had a full charge, 3 of 4 lights on the batteries is the best I have done. So far the battery manufacturer says it’s on the Growatt side of things and the Growatt rep I bought from does not have a solution except to use the manufacturer specs. Usually the panels charge in the morning 4000W and quickly stop charging for the rest of the day as the batteries deplete ending the day basically where it started in the morning.

 

[apctjb]

Usually the panels charge in the morning 4000W and quickly stop charging for the rest of the day as the batteries deplete ending the day basically where it started in the morning.

It is frustrating , I know. I have yet to find a setting that fully resolves the issue. If there are loads mine typically will resume charging, it is only when loads are very light that it will not charge at all during the day. Of course light loads means the battery is not being discharged much, especially with as large a battery bank as you have.

 

[derekisastro]

To add to my experiences over the last few days, with my battery not powering any loads for some of the time (I just had the battery disconnected from the load side of the system) when going through its daily cycle, with my absorption set to 28.4 and float at 27.8, it would charge daily, with only solar, to 28.1 - 28.3, according to the Growatt inverter readings (interestingly my 2 Growatts seem to show a 0.1v difference consistently, with the 'slave' unit being 0.1v lower than the master unit) before dropping to float settings for a time (though seems to hit 27.7 not 27.8 at float), which would then require the solar to 'kick back on' for a bit. See images below for a better idea of what's going on.

 

[apctjb]

I have 2 Growatts operating in parallel. Interesting that while the Growatts share the load (1/2 of total load on each inverter) that is not the case for PV charging. One of the Growatts MPPT charger will shut down allowing the other to follow load once bulk charging voltage has been hit. In the graph below it appears that the battery is being discharged to meet load, but as you can see in the second graph the MPPT charger is covering the load for both inverters.

 

[lakehead7]

Thanks; I could not find mention of it in the manual, (the manual leaves lots to the imagination.)

As I have a fairly large array relative to my current loads, I quickly move through bulk charge, to absorption and then float. But after a while in float, it goes into a "fully charged" mode (charging light goes from flashing to solid on) and solar no longer supplies any loads that are applied (during the charging mode solar immediately picks up additional loads, plus keeps charging). I need more time to observe but it almost seems like it is stuck in charged mode even thought battery voltage drops below float and absorption setpoints and this is impacting energy harvest.

I have the same problem my batteries get charged up by noon or so and then by the time the sun's going down in the sky they're low enough to need more juice and I go into darkness with low batteries I have even spoken to a tech support guy at grow out and nothing he suggested helped it may not be possible I guess