Growatt - Odd behavior

debron55

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Thanks to anyone that can provide some input. I have a Growatt 24v SPF 3000TL LVM in service. I built 2 24 v batteries from CALB 100AH cells and 24v overkillsolar bms. I have a single critical circuit in my home I am wanting to power from this unit. (Computers, WIFI etc.) I also have 4 renogy 320 Watt panels 2p2s. I top balanced the cells and batteries as per will's video. I monitor the BMS' using an apple IPAD. I have the relevant parameters on the Growatt set as follows:
Option: 19 (CV) - 27.3, 20 (Float) - 27.3 21 (Batt Undervoltage) 22.9

here is a video of the BMS on the ipad and the screen of the growatt. There is also a renogy guage on the unit - ignore the AH 100%. I have yet to actually set it up with full and empty settings but the power and volt measurement is accurate. Just the AH guage part is not dialed in

here is the relevent entries from the pvmonitor program from ian.
1620970700194.png


Here's the issue... early in the morning the the sun comes up and 80% of the time the charger starts creeping up naturally. But twice now I have came out at 9 am ish or so and no solar charging going on... if I reboot the growatt it powers up and will quickly start charging the batteries and powering the load. It continues powering and charging through the day... then about 1 pm generally the unit stops charging the batteries (IE it reaches the CV amount) and the solar charge controller seems to full on stop. The load is transferred to the batteries. Though there is many hours of sunlight left the unit does not use that solar power at all. I can see the line from the panels disappear and the amps and watts go to zero. IF I manually power cycle the unit it will power on and start charging the batteries and carry the load again for a while.

The video shows this happening at 30 second into the short video. You can see from the growatt screen that the battery voltage the unit sees has hit 27.3. at that moment the unit stops using solar power for anything. My understanding is that it should continue to use solar to power the load until solar alone was not sufficient and that it would then augment the solar with battery power... but it appears that the solar just gets completely dropped...

I can provide additional detail if needed... thoughts? ideas? hints or tips?
 

debron55

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that user is having more difficulty in the morning with his system starting... I only had an issue twice in the am. My bigger issue is at / around 1 - 2 pm in the afternoon the batteries are fully charged. When they hit full charge the mppt controller turn off and the entire unit goes into battery consumption even when there is a nominal load on the system that the solar can easily handle... it's infuriating to see this happen . if I power cycle the unit it goes right back to using the panels, charging the batteries a bit more and carrying the nominal load
 

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Zwy

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that user is having more difficulty in the morning with his system starting... I only had an issue twice in the am. My bigger issue is at / around 1 - 2 pm in the afternoon the batteries are fully charged. When they hit full charge the mppt controller turn off and the entire unit goes into battery consumption even when there is a nominal load on the system that the solar can easily handle... it's infuriating to see this happen . if I power cycle the unit it goes right back to using the panels, charging the batteries a bit more and carrying the nominal load
What is setting number #1?
 

apctjb

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Yes, 1 of my 2 inverters will typically stop MPPT charging (usually by 10-11am) after having reached absorption setpoint and having been in float for a while. On some days both inverters will stop.

I suspect because Growatt's can charge from utility or solar that there is timeout on the length of time the inverter will stay in float before stopping the charge cycle. That makes sense for a utility charger (reduces standby losses), not so typical for a PV MPPT charger. If loads are sufficient to drop battery voltage charging will resume later in the afternoon. If loads are small it may take a day or two before solar charging resumes. Graph below is for my system yesterday. Batteries were fully charged by 11am, charging stops.

Not a big deal as this only occurs when loads are small relative to battery capacity and PV input and I have power to burn. Hoping a future firmware update will disable the float timeout when setting 14 (charging source) is set to (OSO) solar only, or better yet make length of time in float a user adjustable setting.

1621432723389.png
 

apctjb

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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.


1621433565128.png
 

debron55

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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
thats interesting. I have 2 of the growatts. but have only put one of them into service. I'm surprised I am not seeing more posts regarding this behavior... I see so few posts that I can't determine if it's a product failure, me misunderstanding how it should act or if it's user error as I am pretty new to all of this... a bit frustrating if I'm to be honest
 

TomC4306

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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 don't understand why you think this is bad behavoir. They both charge and when the battery is full there is only enough work for one of them. As far as going back to battery for a period of time...voltage level is the instructional signal that these devices use to know what to do.... therefore....YOU have told them through settings what to do and when to do it. I suggest you rethink the relationship between bulk, float. Maybe make them closer and see what effect that has on your perceived problem.
I think they are working correctly.
 
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apctjb

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I think they are working correctly

Working as designed; no doubt. All in ones perform many functions; inverter, AC charger, MPPT PV charger, solid state transfer switch. That's a lot of different functions to manage via firmware and settings and for the most part Growatt does a brilliant job. It makes sense for AC charger to turn off after batteries are fully charged as this reduces standby loss. For a solar MPPT charger it makes sense to stay in float after batteries are fully charged, as it increases potential energy harvest, albeit not significantly. When setting 14 is set to solar only (OSO), it would be nice if Growatts operated purely as a MPPT charger; ie stay in float rather than turning off after being in float for the programed time. No doubt staying on must create some other control problem so Growatt did not program it that way.

relationship between bulk, float. Maybe make them closer and see what effect that has on your perceived problem.

The closer you set bulk to float, the sooner the charger turns off. It appears that the trigger to resume charging is when battery voltage drops a set percent below float (the percent drop not user settable as far as I can tell).
 

Zwy

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I don't understand why you think this is bad behavoir. They both charge and when the battery is full there is only enough work for one of them. As far as going back to battery for a period of time...voltage level is the instructional signal that these devices use to know what to do.... therefore....YOU have told them through settings what to do and when to do it. I suggest you rethink the relationship between bulk, float. Maybe make them closer and see what effect that has on your perceived problem.

Yes, I think that is why we are seeing the current behavior many experience. When the GW began to be adopted more mainstream, everyone wanted the float set way low as the thought was float would shorten cycle life of LFP. It appears the lower settings can create the condition of no charging occurring once bulk was achieved and many mistakenly believe the GW is somehow at fault but the bottom line is the settings are the problem.
I think they are working correctly.
I agree.
 

debron55

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I would like to ask for input on the original post. IE why, once the charge controller has charged the batteries does it turn off the solar panels and consume battery power ONLY when there is plenty of sun. While it is charging the batteries it will divert some of the solar power to the load but the rest of the power goes to the batteries. But once my system hits the voltage set in 19 the solar to inverter process is stopped and the system goes 100% to load from batteries. I would expect the system to consume solar power as much as possible for as long as possible and augment with battery as needed / if needed and until solar was no longer sufficient or available. But my system does not do that as it stands today.
 

Zwy

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I would like to ask for input on the original post. IE why, once the charge controller has charged the batteries does it turn off the solar panels and consume battery power ONLY when there is plenty of sun. While it is charging the batteries it will divert some of the solar power to the load but the rest of the power goes to the batteries. But once my system hits the voltage set in 19 the solar to inverter process is stopped and the system goes 100% to load from batteries. I would expect the system to consume solar power as much as possible for as long as possible and augment with battery as needed / if needed and until solar was no longer sufficient or available. But my system does not do that as it stands today.
Move float closer or equal to the bulk charge setting. SBU should work but SOL might be better.
 

debron55

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Move float closer or equal to the bulk charge setting. SBU should work but SOL might be better.
Growatt set as follows:
Option: 19 (CV) - 27.3, 20 (Float) - 27.3 21 (Batt Undervoltage) 22.9

in user2 mode on the growatt the two items appear to be hardwired together.
 

Zwy

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Growatt set as follows:
Option: 19 (CV) - 27.3, 20 (Float) - 27.3 21 (Batt Undervoltage) 22.9

in user2 mode on the growatt the two items appear to be hardwired together.
I would change to USE and not USE2.

What is your setting for #22?
 

debron55

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as an aside - this morning I popped into the growatt server and realized the unit was not charging (8:30 am nice full sun) so went out to inspect and basically since there was a low load last night the unit had not depleted the batteries enough to trigger what ever it needs to trigger to start the charge controller and use the solar panels. so from yesterday at around 4:40 pm when the batteries got full and the unit turned off solar until my manual intervention this morning at 8:30 am the panels were off. Had I not power cycled the unit they would have stayed off until some point was hit.. may have been hours and I lost 3 hours of charging time yesterday and 2 hours this morning.

this was yesterdays and todays chart of production / usage left one is yesterday and you can see it clip out at 4:40 pm... and never start back up. then the right chart shows today ... not turning on until 8:30 when I manually intervened... Capture.png is the settings as pulled using PVKeeper2
 

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apctjb

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What voltage have you observed MPPT charging stopping and what voltage is it resuming? How many watt-hrs of load are then supplied by battery in the time between stop and resumption of charge and what percentage of your total energy storage does this represent?

The charging behavior you are observing appears normal for Growatt, what is unclear is if the trigger for resuming charge is simply a voltage drop below setting 19 or 20, or drop in SOC , or some combination of factors.

Yes it would be nice if when setting 14 is set to OSO, (solar charging only), MPPT charging remained active as long as solar was available, but this behavior does not result in a material reduction in energy harvest or overall system performance, at least not on my system. Not suggesting that is the case for everyone, but on most days my system has to curtail charging as PV input far exceeds load demand so its not like I am loosing significant energy harvest..
 

debron55

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What voltage have you observed MPPT charging stopping and what voltage is it resuming? How many watt-hrs of load are then supplied by battery in the time between stop and resumption of charge and what percentage of your total energy storage does this represent?

The charging behavior you are observing appears normal for Growatt, what is unclear is if the trigger for resuming charge is simply a voltage drop below setting 19 or 20, or drop in SOC , or some combination of factors.

Yes it would be nice if when setting 14 is set to OSO, (solar charging only), MPPT charging remained active as long as solar was available, but this behavior does not result in a material reduction in energy harvest or overall system performance, at least not on my system. Not suggesting that is the case for everyone, but on most days my system has to curtail charging as PV input far exceeds load demand so its not like I am loosing significant energy harvest..
MPPT Charging stops at the voltage set in 19 (27.3) or within a tenth of a volt so 27.4 etc... But to be clear the issue isn't the charging. It should stop "Charging" at that voltage. the issue is it stops using solar for powering a load. While it is working as expected. say with battery at 60% soc currently the pannels are on and their power is split between charging the batteries and powering the load (in my case the load is around 250 watts) as inidcated by pvkeeper etc. But when the batteries fill or at least growatt sees them hit the setting 19 value. Growatt turns off - not only the charging - but also completely stops using solar for the inverter (Load)... so once the batteries are charged (usually around 1:30 - 3 according to cloud cover etc. the solar panels may as well not even be hooked up to the inverter. it completely shut them down for powering the load...
 

apctjb

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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.
 
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