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

apctjb

Solar Addict
Does anyone know what triggers the Growatt 3000 to exit float mode and resume bulk charging?

After powering on my system and connecting the array, bulk charging commences until absorption setpoint is reached and then charging goes to volt mode. But what triggers the resumption of bulk charging? Is that a set time, is it a percent drop in voltage or is there a resume charging setpoint that somehow I have missed.

Thanks
 

snoobler

Solar Honey Badger
I don't see it in options or otherwise discussed in the manual.

Most SCC either have a default or programmable re-bulk value. It is either a set voltage or an offset from float.

I suspect it has a default that is not published like their tail current.
 

apctjb

Solar Addict
Most SCC either have a default or programmable re-bulk value. It is either a set voltage or an offset from float.

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.
 

apctjb

Solar Addict
Based on observation; my Growatt 3000LVM (and I assume similar MPP inverter/chargers) appears to work as follows when charging battery from solar.
  1. After powering on the inverter and connecting the array bulk charging commences and continues until battery voltage reaches setting 19 Absorption Voltage Setpoint. ( Charging lights flashing/graphic display shows array connected to battery. )
  2. Once setpoint 19 is reached it goes into absorption mode. ( Charging lights flashing/graphic display shows array connected to battery. ) It stays in absorption mode until ???
  3. After absorption it goes into float. ( Charging lights flashing/graphic display shows array connected to battery. ) It stays in float mode until ??
  4. After float it goes into a “charged mode” (Charging light is solid on the graphic display no longer shows the array connected to the battery. ) It stays there until ???
Is this how it works for other folks??

Questions that I am hoping to answer but not covered in the manual.

1) Once it is in absorption mode what triggers it into float mode? Is this a preset time or something else

2) Once in float mode what triggers it into “Charged Mode”. Is this a preset time or something else

3) Once in “charged mode what triggers it to resume charging? (this is where mine appears to get stuck. Once it goes into Charged it stays there…

Would appreciate hearing from anyone that can answer these questions or shed further light onto how solar charging is supposed to work with Growatt/MPP inverter-chargers.
 

Darren Orange

Solar Enthusiast
Mine does not stop charging ever from my experience so far, however both my Bulk and Float are set to my target voltage of 57V. However I do notice during the day my peak pull rarely goes above 20 amps to the batteries regardless of settings it seems to act like I have max charging voltage set to 20 amps. LV5048 btw.

Later during peak times which is when testing is easier if I apply extra loads to the system the pull from solar will go up like from 1800watts to 2300watts, tested this using a bunch of older lights to slowly push it up. So I am finding that about 200-500 watts are not being pushed to the batteries. So about 1/4th to 1/3rd of my production is being lost during peak times. Also to be clear my solar panels can produce 4000W, currently I have some shading this time of year so it effects that peak but it should be even more obvious later this year.

I'm surprised no one has made a video yet I feel like Will should be able to test or figure out what is going on, he has a lot of the MPP solar units. It has to be a simple weird setting or something minor to tweak to fix this.
 

apctjb

Solar Addict
Most SCC either have a default or programmable re-bulk value. It is either a set voltage or an offset from float.
I suspect you are right. I increased the float and bulk voltage settings to see if this would trigger a resumption of charging but no luck.

I spoke with Ian (distributor for Growatt) who suggested a factory reset and then leave settings in factory default mode. I did this yesterday. I checked this morning and neither unit was charging from solar (charging light not on, no line on the graphic display showing array connected to battery. Overnight battery voltage had dropped below absorption and float voltage settings. At time of observation I was drawing ~30A from batteries to power loads. I observed for quite a while and it just sat there pulling power from the batteries despite solar being available. See photo 1 below. I then powered down both units, powered back up and both units started charging. Photo 2. This is the same problem I have observed every day since installing solar on these units. Obviously having to manually turn off the inverters to resume charging can’t be right.

Anyone else observing this type of behavior with their Growatts or suggestions on settings to adjust that could solve this problem???


Not charging; ample solar, drawing 30a from battery
1614872453764.png
Charging resumes after powering down and back up .
1614872515380.png
 

Darren Orange

Solar Enthusiast
So today after over night having set the float and bulk to my target of 57V for fully charged it now seems today that so far it has been working correctly as far as I can tell. I've never had it just not charge but that is interesting. At the moment I am happy with what I am seeing. It seems like it takes a good while for the Bulk mode to reset or whatever it is doing.
 

smoothJoey

SmooJo
What is your bulk/absorb voltage?
What is your float voltage?
Doe you battery ever get below float voltage?
How low does it get?
 

Darren Orange

Solar Enthusiast
What is your bulk/absorb voltage?
What is your float voltage?
Doe you battery ever get below float voltage?
How low does it get?
Actually I think that may be the problem, you want to make sure it goes well below those values for a while like over night.
 

smoothJoey

SmooJo
Actually I think that may be the problem, you want to make sure it goes well below those values for a while like over night.
You could try a profile without float and see what happens.
If there is no way for this thing to re-enter bulk then its not very useful.
I have a charger that doesn't automagically re-enter bulk so I just run it on an outlet timer.
But that is not a solution for an all_in_one.
 

stienman

Solar Addict
I would like to know the control flow as well. I have an SPF 6000T DVM and if it thinks the batteries are full then the MPP drops so much that the battery has to supply most of the load even though there's plenty of power available on the solar input!

I've started turning on a heater to draw more current, which causes it to use the full power of the array, and start charging the batteries again. Their app and graphs don't really shed any light on the issue, and I've started thinking about adding a dump load that's triggered whenever it looks like the MPP controller isn't drawing full power.

Either that or I should have purchased a separate charge controller and inverter rather than an all-in-one unit.

But I can't complain too much. It runs my 240v compressor and welder just fine. I just need to figure out how best to configure it so it's not throwing energy away.
 

Darren Orange

Solar Enthusiast
You could try a profile without float and see what happens.
If there is no way for this thing to re-enter bulk then its not very useful.
I have a charger that doesn't automagically re-enter bulk so I just run it on an outlet timer.
But that is not a solution for an all_in_one.
I'm not sure that I can disable it, but it set it to Bulk set to 57V and Float to 57V. I am pretty sure that the Float is the issue it is just not obvious and whatever timer it has running inside takes it while to shake out of it. Shutting the whole system down might work in theory to reset this for those that are testing. However over night seems to be enough..
 

smoothJoey

SmooJo
I'm not sure that I can disable it, but it set it to Bulk set to 57V and Float to 57V. I am pretty sure that the Float is the issue it is just not obvious and whatever timer it has running inside takes it while to shake out of it. Shutting the whole system down might work in theory to reset this for those that are testing. However over night seems to be enough..
Set the float lower than the bulk/absorb then draw hard enough on the battery to overcome the float see if that makes it rebulk.
 

apctjb

Solar Addict
I have Bulk set to 56 and Float to 54. Batteries at 52 after settling overnight. Not sure how low the batteries would have to go before it would resume charging but this does not seem optimal from the perspective of maximizing energy harvest.
 

Darren Orange

Solar Enthusiast
Set the float lower than the bulk/absorb then draw hard enough on the battery to overcome the float see if that makes it rebulk.
The Float does not seem to do much lowering it seems like it would trigger it to go into bulk mode. Right now I'm seeing near peak performance that I would expect honestly. Have to wait and see once I have no more shading on my panels to know for sure.
 

smoothJoey

SmooJo
The Float does not seem to do much lowering it seems like it would trigger it to go into bulk mode. Right now I'm seeing near peak performance that I would expect honestly. Have to wait and see once I have no more shading on my panels to know for sure.

Float can be considered "power assist" for lifepo4 batteries.
Usually float is set considerably lower than bulk/absorb.
This means that after the battery charges to between >3.4ish and <3.65 volts per cell the battery gets to carry the load and cycle down until the battery voltage and the float voltage are equal.
Then the charge source starts helping with the load.
If the load amperage is less than the charge source amperage the battery voltage won't go below float voltage.
If you don't go below float voltage then you won't hit a voltage based re-bulk trigger which is very likely less than float voltage.
Sometimes the re-bulk trigger is based on other factors though.
 
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Darren Orange

Solar Enthusiast
Float can be considered "power assist" for lifepo4 batteries.
Usually float is set considerably lower than bulk/absorb.
This means that after the battery charges to between >3.4ish and <3.65 volts per cell the battery gets to carry the load and cycle down until the battery voltage and the float voltage are equal.
Then the charge source starts helping with the load.
If the load amperage is less than the charge source amperage the battery voltage won't go below float voltage.
If you don't go below float voltage then you won't hit a voltage based re-bulk trigger which is very likely less than float voltage.
Sometimes the re-bulk trigger is based on other factors though.
I HAVE SOLVED MY PROBLEM!

I failed to read the instructions...so I think it solved it.

I failed to follow the instructions correctly. I plugged the solar into MPPT2 rather than 1. I only have one array it must be in 1 or it acts weird. Not sure if this matches up with others issues...but it says to do this in the instructions. I feel foolish...at least nothing exploded.
 

apctjb

Solar Addict
Float can be considered "power assist" for lifepo4 batteries.
Usually float is set considerably lower than bulk/absorb

Power assist is exactly is what I expected but not getting as after being in float for a while it stops charging altogether. At some point I assume that the voltage drops low enough to restart charging (I wish I knew that triggers reconnect, how low does the battery have to drop before it starts charging again)? With my 560AH LiFePO4 batteries once the battery hits 3.35 volts per cell it stays there along time......
 

Steve_G

New Member
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).
 

apctjb

Solar Addict
I may have found a way to know the actual voltage that the Growatt....

Wow; great great post! While above my skill set, it seems you have found the answer to my question. Observing my system the past 4 months it does appear that the charging cycle resumes somewhere around the 53V mark (52.5 is as low as I have seen my batteries go). Thank you
 
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