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The dreaded Growatt algorithm and LFP dumb batteries


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Posted

I'll get straight to the point. If you are thinking of using a Growatt SPF series inverter with stand alone Lithium batteries, DONT! 

Growatt, for reasons known only to themselves have a charging algorithm that abandons the battery after charge, leaving it to supply a load (solar) or just invisibly feed its internal circuits (about 1A), slowly discharging to some mysteriously defined threshold where the charger kicks in again and tops up. This is purported to be 95% SOC or 2V drop below -?? float apparently. The 95% SOC (State Of Charge) threshold seems to be linked to a Lithium battery with comms to the inverter. Otherwise it's the 2V drop. 

Now.. enter a lithium battery with no comms. These are all the rage now and selling like hotcakes. The Hubble S120 being a good example - internal BMS with external balancing unit when connected in series. Lithium batteries have a very flat discharge curve so a small drop in voltage represents a big drop in SOC. This is quite different to lead acid batteries which have a relatively bigger drop in voltage with drop in SOC. 

Enter the Growatt dreaded algorithm: Without comms to the battery the inverter seems to estimate SOC by means of voltage drop. The magical 2V drop translates to a big drop in SOC for a lithium battery. The upshot of this is the "clever" Growatt algorithm essentially lets the battery discharge to around 30% or less before re-engaging the charger. That said I have yet to see this in action. Perhaps I have been too impatient. Its more like a 2V-ish drop. What this means in this case is that the poor Lithium batteries, in grid bypass mode are left invisibly feed the inverter at about 1V for three days or more before they are topped up. The result: constant relatively deep cycling of the the batteries for no good reason. A similar scenario would play out with solar as the charging source.

Growatt claim that the logic behind this algorithm is to save the "charging relay" from wearing out. Seriously??? 

IFFF the battery were left completely to its own devices to rest with no load at all after charging this might make sense but to subject a battery to perpetual cycles (deep in the case of LFP) for no good reason makes no sense to me. The friendly Growatt "international engineer" has spent three weeks of confused exchanges trying to convince me this is normal and nothing to worry about. Nothing to worry about is also the Invest Solar guy's response. 

So there is my observation. I wonder how many others have unwittingly hit on what they thought was a cost effective long(ish) life setup.

Wow - can't anybody make a decent reasonably priced inverter?  

Posted (edited)

@RobMI have the exact same gripe. With the AM2 Battery it discharges to power the Inverter after being fully charged. And the exact same lame excuse was given to me by the Growatt China International support.
Now if there wasn't any solar input I could still understand, but the logic applied by the algorithm, or rather lack thereof, is just astounding.
I cannot for the life of me understand why they wish to use battery power to power the inverter whilst there is excess solar available.
In my case it shows anywhere between 0,4 and 1 A discharge as soon as the battery is at 100% SOC. It takes about 6 hours to reach the 95% SOC and then starts charging again. 
Today was a good sunny day so my geyser was hot and the battery fully charged just after 10:00. My usage never exceeded the available solar power today and you can see the steady battery usage as soon as it was at 100%. At around 16:00 it started the charge again.  image.thumb.png.dcbcb89f50e6ff9d7e78865c3fddfb04.png

Edited by zsde
Posted

With a battery with comms at least it only goes down to 95%. As much as this wastes solar power and cycles the battery unnecessarily at least it's still fairly viable. With dumb lithium batteries its a much bigger mess because the battery discharges deeply even when there is power available. 

Posted
25 minutes ago, RobM said:

With a battery with comms at least it only goes down to 95%. As much as this wastes solar power and cycles the battery unnecessarily at least it's still fairly viable. With dumb lithium batteries its a much bigger mess because the battery discharges deeply even when there is power available. 

@RobM Have you done the settings according to this Hubble recommended page?

Also, what Firmware do you currently have on your Inverter. Perhaps a later firmware addresses the issue? 
image.thumb.png.0be534445023ea9f56d46abcf5adb4db.png

Posted (edited)
49 minutes ago, zsde said:

 


Also, what Firmware do you currently have on your Inverter. Perhaps a later firmware addresses the issue? 

 

Hi @zsde - yes I have indeed used recommended settings and the Growatt "International engineer" has confirmed firmware is latest. (sigh). I am now using USE2 for battery type as recommended by Growatt guy. This looks like a design issue which is particularly dysfunctional when using lithium batteries with no comms. 

Edited by RobM
Posted (edited)

If I had the choice again, I would rather have opted for the Luxpower Inverter with the dual MPPT.

 

Edited by zsde
Posted (edited)

Running batteries without comms is indeed a thing. I'm not sure it's a good thing, but you can see how it happens. 

BobPower pty Ltd unleashes their batteries on the world, but they have to get a BMS from somewhere, and then have to get all the inverter manufacturers to support their batteries, which may involve a firmware upgrade. 

My Goodwe comes pre-programmed for a number of battery brands, most of which are unavailable or hellish expensive in this country. Hubble, Revov, Bull, Freedom Won... Forget it. You have to use Goodwe's self define mode, or hope their comms mimics those of one of the supported brands. 

For Growatt you can try Solar Assist. 

Edited by Bobster
Posted
15 hours ago, RobM said:

I'll get straight to the point. If you are thinking of using a Growatt SPF series inverter with stand alone Lithium batteries, DONT! 

Growatt, for reasons known only to themselves have a charging algorithm that abandons the battery after charge, leaving it to supply a load (solar) or just invisibly feed its internal circuits (about 1A), slowly discharging to some mysteriously defined threshold where the charger kicks in again and tops up. This is purported to be 95% SOC or 2V drop below -?? float apparently. The 95% SOC (State Of Charge) threshold seems to be linked to a Lithium battery with comms to the inverter. Otherwise it's the 2V drop. 

Now.. enter a lithium battery with no comms. These are all the rage now and selling like hotcakes. The Hubble S120 being a good example - internal BMS with external balancing unit when connected in series. Lithium batteries have a very flat discharge curve so a small drop in voltage represents a big drop in SOC. This is quite different to lead acid batteries which have a relatively bigger drop in voltage with drop in SOC. 

Enter the Growatt dreaded algorithm: Without comms to the battery the inverter seems to estimate SOC by means of voltage drop. The magical 2V drop translates to a big drop in SOC for a lithium battery. The upshot of this is the "clever" Growatt algorithm essentially lets the battery discharge to around 30% or less before re-engaging the charger. That said I have yet to see this in action. Perhaps I have been too impatient. Its more like a 2V-ish drop. What this means in this case is that the poor Lithium batteries, in grid bypass mode are left invisibly feed the inverter at about 1V for three days or more before they are topped up. The result: constant relatively deep cycling of the the batteries for no good reason. A similar scenario would play out with solar as the charging source.

Growatt claim that the logic behind this algorithm is to save the "charging relay" from wearing out. Seriously??? 

IFFF the battery were left completely to its own devices to rest with no load at all after charging this might make sense but to subject a battery to perpetual cycles (deep in the case of LFP) for no good reason makes no sense to me. The friendly Growatt "international engineer" has spent three weeks of confused exchanges trying to convince me this is normal and nothing to worry about. Nothing to worry about is also the Invest Solar guy's response. 

So there is my observation. I wonder how many others have unwittingly hit on what they thought was a cost effective long(ish) life setup.

Wow - can't anybody make a decent reasonably priced inverter?  

@RobM Mine works differently from what you say. Two Growatt 5000 ES + 1 X 100 A/h 5.1 KW/h LBSA battery. working without coms, usually it charges the battery to about 95% SOC than goes in to float mode, after about 1 hour battery reaches 100% SOC and inverter keeps floating while there is enough PV see attached 

image.thumb.png.dd000ceffa800fefdc716436e8fd8246.png

Posted
2 hours ago, Bobster said:

For Growatt you can try Solar Assist. 

Would solar assist tell the inverter how to charge and overcome the deep discharge problem? 

Posted
47 minutes ago, RobM said:

Would solar assist tell the inverter how to charge and overcome the deep discharge problem? 

I use Solar Assistant as a monitoring tool. It has a power Management Tab which I am not using, but you can read here what it it's functionality is.

Whether it will override your current predicament I cannot say. But maybe write them a mail and see if it might help you.

https://solar-assistant.io/help/power-management/voltronic


The ability to use this functionality was implemented for Growatt inverters as well now. 

image.png.acf207045d3116b5ec1a0dde55036ca5.png

Posted
54 minutes ago, RobM said:

Would solar assist tell the inverter how to charge and overcome the deep discharge problem? 

My understanding is that with a Growatt and compatible (with Solar Assist) batteries, it will provide accurate SOC information to the inverter, and thus there will be better management of the batteries. But as @zsde suggests, first check out the web site and maybe the drop them a line.

Posted
21 hours ago, Antonio de Sa said:

Mine works differently from what you say. Two Growatt 5000 ES + 1 X 100 A/h 5.1 KW/h LBSA battery. working without coms, usually it charges the battery to about 95% SOC than goes in to float mode, after about 1 hour battery reaches 100% SOC and inverter keeps floating while there is enough PV see attached 

Hmm, yes this seems to be a more intelligent beast, different model to TL-HVM. 

Posted
18 minutes ago, RobM said:

Where did you get it? Online through web site? 

The link in the post will take you to the website. The developer is based in Pretoria.

It is of course an extra expense as you need a Raspberry Pi. He supplies the configured package with the Pi or if you already have one then you will need to purchase the cable and you can then download the bootloader and software to be loaded onto an SD card.

Posted

@RobMJust something you may want to try to see if the Inverter acts any differently if you use the Default AGM Battery Type setup.
Set all voltages manually as per the Hubble recommendations but also ensure that the Battery Equalisation in Program code 43 is set to disabled.
Then we also had the change in the Firmware from Voltages to Percentages. If you look at Program 12 and 13 you will see the Manual refers to voltage settings. This was changed to Percentages in the later Firmwares. 54 V as an example is something completely different than 54% of a Voltage. 
So have a look on your Inverter whether yours shows V or %.
And I have tried to communicate this to both Hubble and Growatt and to date none of them have responded. 
So lets assume your back to battery is set at 54, then it would be 54% of a Voltage. The question is what Voltage? Perhaps the float voltage? If it is float voltage then that should be 100%. 
It may well be that your batteries are discharging so low because of the percentage values.
On my installation I picked it up when my system shut down due to low Battery Voltage although my SOC was at 42%. Thats when I looked at code 21 which was set at 42 as the Hubble low Voltage setting is 42V which is around 20%. So after changing that to 20% my issue was resolved. 

Posted

Thanks @zsde, I'll take another look although I am pretty sure its all voltages. The inverter in question is the SPF 3000TL HVM which is a somewhat lesser beast than the 5000ES which I assume you have. This is used as a backup system so no PV, just grid power. It spends most of its time in grid bypass mode (slowly wasting away battery capacity). I am not aware of a firmware upgrade and the Growatt people confirm it has the latest firmware. 

I found the Hubble support line very helpful. I logged a query through their web site and someone called me and answered my questions directly. The local Growatt support guy seems to be little more than a postbox with scant product knowledge. The Growatt "international engineer", Amos is responsive but frequently gets the wrong end of the stick and also has to refer queries to "Research". 

I am now thinking Kodak is your best bet for Axpert type inverters. They are distributed by Segen Solar who carry spares locally, have knowledgeable tech support locally and seem to be a well run outfit.  

  • 1 year later...
Posted

Hi, 

 

I recently installed a Growatt SPF5000ES, with a Hubble AM-5 with comms. No solar, so using it as pure backup.

When the utility supply is present the battery also charges to 100%, drops down to 95% over time then charges to 100% again.

Is there a solid workaround for this ?

Posted

Hi

I have a grid fed backup system consisting of a Growatt SPF 5000 ES and single Hubble AM-2 configured in the Growatt as:

Battery  = Lithium

Protocol = 52

Comms cable connected on Inveter BMS to Battery CAN port (trust that is right) and am experiencing the same issue with battery discharge once it reaches 100% after recharging from either loadshedding or inverter load. Once it reaches 95% the inverter charges the battery again. The main concern here for me is,

1 - why is the inverter drawing current from the battery when the utility available and inverter is set to Utility Primary

2 - this means my battery is losing cycles for no good reason, this reducing its lifespan.

Please advise if my understanding is correct and it there is anything I could do to correct it.

Posted
8 hours ago, kjza said:

why is the inverter drawing current from the battery

This is an algorithm that Growatt applies. Nothing you can do to change it. Their engineering department is convinced it's better for battery and inverter.
Whether you apply the Li Protocol or use the US2 mode, once the battery hits 100% the Inverter will use the battery to power itself.
I have changed to USE mode with no comms and apply the voltages as per the battery specs. The BMS manages the charge of the battery cells.
 

  • 2 weeks later...
Posted

Wish i found this thread before i installed. Im on my installers case almost everyday because of this. I think if he explained to me this would happen i would have gone with another inverter. I did try the setting back to utility on 25.5v which is the highest it can go on my inverter and still it would discharge to what i would assume around 50% or less of the battery before charging back. Also now the battery dont charge to 27v anymore, it gets to about 26v and battery would switch off and on, as to maybe tell me its overcharging or heat. 

Posted
On 2023/06/19 at 7:17 AM, jcs said:

Wish i found this thread before i installed. Im on my installers case almost everyday because of this. I think if he explained to me this would happen i would have gone with another inverter. I did try the setting back to utility on 25.5v which is the highest it can go on my inverter and still it would discharge to what i would assume around 50% or less of the battery before charging back. Also now the battery dont charge to 27v anymore, it gets to about 26v and battery would switch off and on, as to maybe tell me its overcharging or heat. 

change your battery type to USE. 

set the bulk and float voltage yourself. 

Posted
On 2023/06/22 at 5:15 PM, Flouw said:

change your battery type to USE. 

set the bulk and float voltage yourself. 

I did, its at its max. I set the setting that supose to kick over to utility again to 25.5v. At the moment battery is at 25.8v but battery show 50% depleted. And charger not kicked in yet.

Posted
2 hours ago, jcs said:

I did, its at its max. I set the setting that supose to kick over to utility again to 25.5v. At the moment battery is at 25.8v but battery show 50% depleted. And charger not kicked in yet.

What is your output priority. And charge priority set to? 

Im not sure what you have set to max. 

 

You will have to list all settings. 

 

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