Need help with new Growatt SPF 3000TL LVM...

[acdoctor]

Follow-up...

I received another reply from a fellow user, in which he stated my charging voltages were way too low. He then suddenly, before I even had the chance to finish replying, deleted the post. But it led me to believe I really don't know what I'm doing and now I'm even more confused. Oh well, such is life.

But anyway... I'm following up because, as I feared, I believe things are not going well. The SoC reached 100% and the Growatt just kept charging, to the point where I now think the cell balances are getting out of whack! But again, the previous dude said I wasn't charging enough, so now I'm questioning everything again. There are four cells that are being reported as 'iffy', or whatever.

So now I ask, importantly... "What constitutes a LiFePo cell being out of balance?" I mean, how much of a voltage difference constitutes being out of balance. Usually, as stated before, the difference is usually only in the thousandths. But with the continual charge it dropped into the hundredths, and now it's in the tenths - at about 0.15V.

At least however, the Growatt finally decided it's at full SoC and quit charging, only supplying enough to current to run the appliances I have running (overhead lighting, laptops, fridge). But this time I decided just to let everything run its course and just see what happens.

It also occurs to me that what I'm basing everything on is the BMS-Test app that is a companion the the S2 EG4 battery and you're probably not familiar with, so here's a screen shot of this.
View attachment 119340

Here's hoping the insert of the screenshot worked as I am hoping... and I let it go as this. Thanks!

So the growatt charges to a aggregate or total voltage of the battery.
If you have cells that are excessively low then you will need some excessively high to balance out.
Another way to look at it is add all of the individual cells together to get to 28 volts. If all are exactly the same then all are 3.5 volts. If some are 3 volts then some will need to be 3.6 or 3.7 or 3.8 volts so 8 cells add up to 28 and the growatt stops charging. But on the other hand the BMS should stop the charging before any of the cells are allowed to exceed a safe voltage, usually 3.65 volts.

So cells being out of balance is only problematic in the sense that you will need to stop charging at a lower battery voltage than you would if they were well balanced. This stopping charge at a lower voltage is only necessary to avoid tripping the BMS on cell over voltage. Which in turn is a small loss in capacity.

Cells usually stay very close together from 3.0 volts to 3.4 volt. That of course is where most of the capacity is.

 

[DesertDude]

So I don’t have the EG4 batteries but I have a 7.2 kw DIY LFP battery conned to the same growatt.

First let’s talk about the battery. Many people have been on here discussing their EG4s being out of balance near the top, so much so that they were loosing a little capacity and having issues with the BMS shutting down. Or in the cases where the com wires worked the BMS’s throttling the inverter back. So it may be necessary for you to change to the point where the cells start to go rogue and stop charging. Then over time increase to a suitable voltage. I don’t recall what the EG4 recommended charging parameter’s are. But the cell chemistry is considered fully charged at 3.65 VPC and empty at 2.5 VPC. So theirs nothing wrong with 3.4. VPC you mentioned earlier. In fact most BMSs don’t start cell balancing until 3.4 to 3.45 VPC. As long as the BMS isn’t disconnecting from individual cell over voltage I would continue to charge preferably at a slower rate ( like as the sun gets low) to allow the balance circuit time to work it’s magic.

I have a discrepancy between the voltage meter in my growatt and everything else in my system including 2 hand held meters. Mine is about 0.4 volts off. That doesn’t sound like much but with LFPs it is.

I charge to 28.0 volts at the battery or 3.5 volts per cell and a cell differential of 0.015 to 0.010 volts. I float at 27 volts at the battery or 3.375 VPC.
I have mine set to grid as first priority. With it set that way as soon as the generator is going it starts charging from it. With out fiddling with the settings.

My settings:
01. UEI
02. 80
03. APL
04. SdS
05. USE
06. Lfd
07. Lfd
08. 120
09. 60
10. 2
11. 40
12. 25
13. 26
14. SNU
15. bON
16. LON
17. AON
18. bYd
19. 27.6
20. 26.6
21. 23.6
22. SbE
23. SiG
28. 1
43. dIS

I too thank you more than I can say... and all your info seems most excellent. But with now so much coming in I'm baffled as to what to do or maybe even more so how to do it. Just let me say at this very moment, as I've got so much to contemplate and things to answer to in several different threads, that I'm kinda freaking out when one of my cells is now producing a overcharge condition at 3.63V. All the rest are at 3.5 or 3.4 volts and all over the place.

You are giving wonderful and pertinent data, and I'm gonna go over all your settings listed above and compare and make necessary changes.

Okay... the sun is now far enough to the west that I am no longer drawing enough current (I'm guessing) to continue charging, and the system is now discharging. In doing so, the overvoltage alarm has now disappeared and the cells now appear to be in much better balance and those warning too have now gone. Cell differential is now in the hundredths instead of the tenths, so I guess that something.

Pardon me for now, I've got a other replies and stuff I think I'd better take a gander at. Thank you so much!!!

 

[Mattb4]

To everyone that has now replied... I THANK YOU IMMENSELY!!!
But as all this new info comes in, and so much of it I barely understand, much less what to do to correct what might the the problem(s), it seems now my feeble little brain has turned to oatmeal. I apologize to all for my lack of knowledge and increasingly amount of confusion that seems to have taken over. I'll try and respond to each in as short a response as I can. I know I can be so verbose, which isn't helping matters I'm guessing. Please bear with me...

Most of all: Don't panic!

Give yourself sometime to absorb what you need to know. Your system has protection built into it.

 

[DesertDude]

Most of all: Don't panic!

Give yourself sometime to absorb what you need to know. Your system has protection built into it.

Too late!!! I've been panicking all afternoon! I can get really stressed out when things start piling up, and this afternoon has been just that. I know I'm know I'm getting very good advice, but so much of it has come in today alone and I'm having great difficulty concentrating on what's most important, and I'm very afraid that I'm not sure what that even is at this point. All I can say is thanks again so very much.

 

[acdoctor]

I too thank you more than I can say... and all your info seems most excellent. But with now so much coming in I'm baffled as to what to do or maybe even more so how to do it. Just let me say at this very moment, as I've got so much to contemplate and things to answer to in several different threads, that I'm kinda freaking out when one of my cells is now producing a overcharge condition at 3.63V. All the rest are at 3.5 or 3.4 volts and all over the place.

You are giving wonderful and pertinent data, and I'm gonna go over all your settings listed above and compare and make necessary changes.

Okay... the sun is now far enough to the west that I am no longer drawing enough current (I'm guessing) to continue charging, and the system is now discharging. In doing so, the overvoltage alarm has now disappeared and the cells now appear to be in much better balance and those warning too have now gone. Cell differential is now in the hundredths instead of the tenths, so I guess that something.

Pardon me for now, I've got a other replies and stuff I think I'd better take a gander at. Thank you so much!!!

I would lower setting #19 one tenth of a volt at a time until ( 1/10 per day) until cell over voltage goes away. Leave it at that setting for a couple of weeks. Then increase it 1/10 per week until you get to where you want if things look ok.

I think your only problem is the cells being a bit out of balance. The above should fix it.

 

[DesertDude]

I would lower setting #19 one tenth of a volt at a time until ( 1/10 per day) until cell over voltage goes away. Leave it at that setting for a couple of weeks. Then increase it 1/10 per week until you get to where you want if things look ok.

I think your only problem is the cells being a bit out of balance. The above should fix it.

Okay... I think I've caught up and having been trying desperately to calm myself down, as I get so stressed out as I've done all afternoon.
I'm gonna concentrate now on all you've said, especially this last response. Please, please bear with me, and I hope you don't mind, but a few questions have come to mind... that is if I can even remember them!

Now, moments ago as I stated, the battery has begun to discharge and it took very little time for the cells to all fall within 0.007Volts of one another. That I believe is where they should be, as they are 99.9% of the time. Q#1 - Did my battery suffer (or maybe that one cell) any damage for being overcharged - and that was to a cell voltage of about 3.65V?
As of today I set #19 to 27.4V per my very first respondent, and still the battery went to SoC of 100% and still kept charging. I just had to check, but it was you in a previous reply that stated the cell voltages need to add up to 28 volts. I'm now thinking I've been paying too much attention to SoC instead of total battery voltage.
Anyway, your advice on reducing setting #19 down a tenth a day sounds like excellent advice. I'll go from 27.4V down to 27.3V. Okay... done, as well as adjusting a few other settings as well to match yours. (#19, 20, & 21 mostly).

While I was finally trying to settle down and think about things, it finally dawned on me that the only thing the Growatt knows about my EG4 LiFePower4 battery is it's voltage. All the info I'm looking at, from the jpeg image I posted above in another thread, is the BMS-Test app and the cell voltage data, cell differential, etc. Everything there is being controlled by the internal BMS, so this brings me to Q#2 - As far as I know, I have no way to talk to or do anything with the BMS and let it just do it's own thing... right? It seems to be doing an amazing job all through the charging process, with cell differential voltages of being only a few thousandths volts off. That is until, and I've only noticed the SoC rather than the battery voltage, it reaches 100% charge and keeps going, at which point up to four cells become out of balance. And again, from the jpeg image above, Q#3 - those cells are indeed out of balance???... or only approaching being out... or ??? Same line of thought, or Q#4 - How much voltage is considered for a cell to be out of balance with the rest - thousandths, hundredths, or tenths of a volt???

Okay, I've rambled on enough I can't thank you enough for already the time you've spent to help me out. Hugely appreciated indeed...

 

[acdoctor]

Okay... I think I've caught up and having been trying desperately to calm myself down, as I get so stressed out as I've done all afternoon.
I'm gonna concentrate now on all you've said, especially this last response. Please, please bear with me, and I hope you don't mind, but a few questions have come to mind... that is if I can even remember them!

Now, moments ago as I stated, the battery has begun to discharge and it took very little time for the cells to all fall within 0.007Volts of one another. That I believe is where they should be, as they are 99.9% of the time. Q#1 - Did my battery suffer (or maybe that one cell) any damage for being overcharged - and that was to a cell voltage of about 3.65V?
As of today I set #19 to 27.4V per my very first respondent, and still the battery went to SoC of 100% and still kept charging. I just had to check, but it was you in a previous reply that stated the cell voltages need to add up to 28 volts. I'm now thinking I've been paying too much attention to SoC instead of total battery voltage.
Anyway, your advice on reducing setting #19 down a tenth a day sounds like excellent advice. I'll go from 27.4V down to 27.3V. Okay... done, as well as adjusting a few other settings as well to match yours. (#19, 20, & 21 mostly).

While I was finally trying to settle down and think about things, it finally dawned on me that the only thing the Growatt knows about my EG4 LiFePower4 battery is it's voltage. All the info I'm looking at, from the jpeg image I posted above in another thread, is the BMS-Test app and the cell voltage data, cell differential, etc. Everything there is being controlled by the internal BMS, so this brings me to Q#2 - As far as I know, I have no way to talk to or do anything with the BMS and let it just do it's own thing... right? It seems to be doing an amazing job all through the charging process, with cell differential voltages of being only a few thousandths volts off. That is until, and I've only noticed the SoC rather than the battery voltage, it reaches 100% charge and keeps going, at which point up to four cells become out of balance. And again, from the jpeg image above, Q#3 - those cells are indeed out of balance???... or only approaching being out... or ??? Same line of thought, or Q#4 - How much voltage is considered for a cell to be out of balance with the rest - thousandths, hundredths, or tenths of a volt???

Okay, I've rambled on enough I can't thank you enough for already the time you've spent to help me out. Hugely appreciated indeed...

Q#1 No you didn’t damage it. However you don’t want any cell reaching 3.65 volts on a regular basis. 3.65 volts is the industry accepted full cell “charge” voltage. If a cell reaches 4.2 volts it should be removed from service because it will fail at some point according to a university study I read.

On SOC, if all cells were not at 3.65 volts per cell so 29.2 battery volts, technically you went at 100% SOC. You were close enough for the BMS to reset to 100% nothing more.

You are correct the growatt only knows the total battery voltage. That’s why the battery has a BMS. The battery doesn’t care where the charge goes. It can all go to 1 cell for all its concerned.

Q#2 The BMS in your battery is set at the factory to the cellular tolerances they are comfortable with warranting. My understanding is that you can’t change them. You can monitor them through a computer via a RJ45 cable. The BMS is not doing anything in the middle 90 % of charge but monitoring.
It only balances during charge and on cells above 3.4 volts and 0.010 higher than the lowest cell. Cells below 3.4 volts usually have no trouble staying within 0.009 volts of each other. It just in the top about 8 % SOC and the bottom 5% that they may have a little help from the BMS balance circuits.

Your cells are indeed out of balance in my opinion. I have never heard a industry standard for balance tolerance. I do know many factory assembled batteries are sold with cells with more balance discrepancy than the customer expected. Just like yours. It usually results in the BMS disconnecting even though the charger voltage was set within the proper range.
There are a few ways to balance them. The only one I know of without opening and some requires disassembling is the one we have discussed above. Reducing charge voltage to barley prevent highest cell from tripping the bms. Over time the balance circuits will balance them. As they become more balanced the charge voltage can be increased to a higher ( normal) voltage.

Q#4 If your charge voltage is 28 battery volts or 3.5 volts and you have a cell running 0.150 volts over the rest that would be a problem at 3.65. Most people end charging at somewhere from 3.4 to 3.5 volts. Ideally you don’t want any cell going over your max charge voltage.
I watched mine top out today I have attached a picture of my BMS in the last minute before float.

 

[DesertDude]

Q#1 No you didn’t damage it. However you don’t want any cell reaching 3.65 volts on a regular basis. 3.65 volts is the industry accepted full cell “charge” voltage. If a cell reaches 4.2 volts it should be removed from service because it will fail at some point according to a university study I read.

On SOC, if all cells were not at 3.65 volts per cell so 29.2 battery volts, technically you went at 100% SOC. You were close enough for the BMS to reset to 100% nothing more.

You are correct the growatt only knows the total battery voltage. That’s why the battery has a BMS. The battery doesn’t care where the charge goes. It can all go to 1 cell for all its concerned.

Q#2 The BMS in your battery is set at the factory to the cellular tolerances they are comfortable with warranting. My understanding is that you can’t change them. You can monitor them through a computer via a RJ45 cable. The BMS is not doing anything in the middle 90 % of charge but monitoring.
It only balances during charge and on cells above 3.4 volts and 0.010 higher than the lowest cell. Cells below 3.4 volts usually have no trouble staying within 0.009 volts of each other. It just in the top about 8 % SOC and the bottom 5% that they may have a little help from the BMS balance circuits.

Your cells are indeed out of balance in my opinion. I have never heard a industry standard for balance tolerance. I do know many factory assembled batteries are sold with cells with more balance discrepancy than the customer expected. Just like yours. It usually results in the BMS disconnecting even though the charger voltage was set within the proper range.
There are a few ways to balance them. The only one I know of without opening and some requires disassembling is the one we have discussed above. Reducing charge voltage to barley prevent highest cell from tripping the bms. Over time the balance circuits will balance them. As they become more balanced the charge voltage can be increased to a higher ( normal) voltage.

Q#4 If your charge voltage is 28 battery volts or 3.5 volts and you have a cell running 0.150 volts over the rest that would be a problem at 3.65. Most people end charging at somewhere from 3.4 to 3.5 volts. Ideally you don’t want any cell going over your max charge voltage.
I watched mine top out today I have attached a picture of my BMS in the last minute before float.

I don't even know where to begin... but I took a break, watched some football, and normally I would have been done today sitting here at the laptop. But I just had a feeling...
Your reply... again most excellent and I send kudos and am more grateful than you can imagine that you so fully answered each and every question. I wish of some way I could repay you for all your time.
I've learned a lot, and I'm now to the point that I think I understand enough to actually realize that I'm so very close to solving this dilemma. I think the one comment you made to reduce the voltage (#19) one tenth a day is going to solve everything. I started out today with 27.4V and ran into trouble. I've since knocked it down a peg to 27.3V, and that may very well take care of it. If not, I'm confident the next day or so will take care of it. I say that because the system basically runs flawlessly and does exactly what it needs to do, with a voltage difference of about 0.003V, +/- a couple... It's only the few times that it's reached full charge and then goes over a bit, when everything goes haywire and I freak out. But since I'm so new I didn't know if I hurt anything or not... now I know better.
I don't think I've ever seen the battery reach 28 volts. Just an observation...
And if memory serves, the cell voltages towards the end are in the 3.35 range usually, but my memory (at my age) I've begun to question as of late!
So I'm kinda thinkin' all will be well in a day or so. I've learned from you to watch the battery and cell voltages above all and not so much just the state of charge. I just checked my battery monitoring software and all my cells are currently at 3.317 and within 0.002V of each other. Perfect. And that gives me a battery voltage of 26.536V, which is exactly right. That's what the voltage monitoring software is giving me, and also doing the math (3.317 x 8 = 26.53V). I know they will stay that way when I get the Growatt to stop charging at the appropriate voltage, and I'm thinking the new 27.3 volts I just set earlier should do it. Ya know, after having just typed that, I'm gonna go an extra step and go down another tenth. You, or someone, said it's best to start low and increase as the days go by. So I just now stepped setting #19 to 27.2V. Maybe things will shut down charging before a full charge, but as I understand it, that'll be a good thing and help the battery to have a longer life. I hear a range of about 15% to 80% is prime, give or take, so I am feeling much better and a bit more confident I'm making headway.

Again, I have you today to thank for that, and I'm so very appreciative of your kindness to spend so much of your day to help me out. Have a good one...

 

[acdoctor]

I believe in other threads it has been said that the BMS’s balance starts at 3.40 volts per cell. So be sure most are getting a little high than that or the balance will not get any better. You are quite welcome ?