42OhmsPA
What's in a title?
What are the highest cell voltages for the batteries?
Install and Operation of the SUNGOLD 10KW 48V SPLIT PHASE SOLAR INVERTER
- Thread starter Kenny_
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Kenny_
Solar Wizard
When, where? What do you think I should I be looking for?
Right now #5 is 3.316 High , 3.315 average, 3.314 low
I'm not sure what I should be looking/watching for.
As I was watching them approaching 100 % soc they were all close no discrepencies as with the "UV" error before (on #2)
I wasn't watching the cell voltages with the charging stopped. I was out on my walk...
Right now the inverter is drawing exclusively from #5 (formerly #3) ... I'm watching to see if the others come in as it reaches their same SOC.
(I know you don't care for SOC etc. but that's where I'm seeing the deviation/difference in these batteries/packs)
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Kenny_
Solar Wizard
See this is the thing that's bugging me...
It was drawing exclusively from #5 (the one I'm worried about) and then added the other four in but at much lower levels...pulling 48 W from each of them but 250 w from #5 ... all with 'similar SOC...
It was drawing exclusively from #5 (the one I'm worried about) and then added the other four in but at much lower levels...pulling 48 W from each of them but 250 w from #5 ... all with 'similar SOC...
Kenny_
Solar Wizard
Tell me why I'm wrong, but I'm thinking this is just a difference in the way each battery BMS is working and communicating with the others and possibly the inverter. The four all seem to be working/acting similarly while the other one (formerly #3, now #5) is working/acting differently.
I'm just shaking my head going WTF?
Nothing appears to be 'broken' just not all operating the same which could be a problem if one or more are operating _enough_ differently....
I'm just shaking my head going WTF?
Nothing appears to be 'broken' just not all operating the same which could be a problem if one or more are operating _enough_ differently....
Kenny_
Solar Wizard
....and if I turn #5 off then the others tend to even out to supply the power needed...
Hedges
I See Electromagnetic Fields!
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I doubt they are operating differently, except in response to different applied voltages. Probably just measuring parameters differently.
Parallel batteries?
The only thing BMS can do is open or close its "switch".
Division of current is determined by resistance, internal plus your external connections.
BMS has its voltage measurements and its current measurements, which have error and offset. So each could measure charge vs. discharge current differently and think SoC is walking up or down, until reset to 100% at some voltage.
A shunt is a resistor, maybe just copper PCB trace (which varies with temperature.) Op-amp sensing voltage has offset, although some are "chopper" and very low offset and drift. But errors accumulate.
Hopefully that has no actual impact on operation, and differences in SoC catch up to each other at the upper and lower knees.
Hence my bus bar comment
Kenny_
Solar Wizard
and now as the voltage drops...the seem to be adjusting so maybe it is the voltages of the batteries that is at work?
Kenny_
Solar Wizard
Thanks. Yeah I don't know that this is having any effect on overall operation.... I only noticed because I had that earlier Undervoltage Error on battery #2 which got my thinking that I really need to fully charge all five batteries and discharge and got through a few cycles to try and equalize/stabilize the operation. (this is still a relatively new system just over a month old and the batteries have never been fully cycled together).
Maybe I just need to stop obsessing over this (minor) thing and let 'er rip! LOL!
Kenny_
Solar Wizard
Understand. After I physically moved the 'suspect' battery the behavior followed it so I'm thinking there isn't a cable/resistance/connection issue.
Hedges
I See Electromagnetic Fields!
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Undervoltage of entire battery #2? Or undervoltage of one cell?
They're all going to be near the same battery voltage, unless high resistance to some (could be internal).
If a cell is actually low voltage (try to confirm with DMM), must be either unbalanced or near battery near empty and that cells is the "runner". Or high cell IR, or bad connections.
They're all going to be near the same battery voltage, unless high resistance to some (could be internal).
If a cell is actually low voltage (try to confirm with DMM), must be either unbalanced or near battery near empty and that cells is the "runner". Or high cell IR, or bad connections.
Kenny_
Solar Wizard
Apparently it was just one cell in battery #2 and once it was 'fully charged' it hasn't shown any signs of problems in/between the cells... And it did happen when the battery (all the batteries) were pretty low after several days of low/no sun.
42OhmsPA
What's in a title?
The soc is computed from the cell voltages, that's why I keep asking about them. Everything should stay close until they get above 3.4v.When, where? What do you think I should I be looking for?
Right now #5 is 3.316 High , 3.315 average, 3.314 low
I'm not sure what I should be looking/watching for.
As I was watching them approaching 100 % soc they were all close no discrepencies as with the "UV" error before (on #2)
I wasn't watching the cell voltages with the charging stopped. I was out on my walk...
Right now the inverter is drawing exclusively from #5 (formerly #3) ... I'm watching to see if the others come in as it reaches their same SOC.
(I know you don't care for SOC etc. but that's where I'm seeing the deviation/difference in these batteries/packs)
Hedges
I See Electromagnetic Fields!
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- Mar 28, 2020
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Can you get a reading of all the cell voltages?
Could be that one cell is at lower SoC, so limits total Ah you can draw from battery because it its lower voltage limit while others still have unused capacity.
If that is the case, holding battery within voltage range that allows balancing could fix it (after eternity, slow passive balancing by bleeding off all others. Active charging of one cell could fix. But don't know why low in the first place, if it actually is.)
Or, maybe you had drained all the batteries close to 0% SoC. There will always be one cell that is the weakest, no matter how close their capacity is.
Can you determine what DoD they were at?
Kenny_
Solar Wizard
Thank you I appreciate all the help....still trying to wrap my head around all this and understand why the difference in behavior of the one outlier battery which on recent inspection seems to be more in line since the "full" charge to 100%... Maybe that's what we need here is a few full cycles.
Kenny_
Solar Wizard
I can see all the cell voltages at once if I connect a computer to the battery string but have to disconnect the inverter communication when I do.
What I've been watching a bit is the SA battery info which provides High, Low, and Average Cell voltage and temp.
I know the first time I 'bottomed out' (this switch to Utility charging has only happened twice) the SOC hit 10% and that appears to be what triggered it but it could have been something else. This was also without all 5 batteries (not sure whether it was 2 or 3) and the inverter went to grid and charged all batteries with the exception of #3(at the time, now #5) to 100% SOC but #3 was 'stuck' at 94.6 (or so) % SOC and would/did not go above that for several hours. Now the problem is that I'm such a neophyte that I might have missed something and perhaps the system had simply stopped charging. I do know for certain that the inverter was in bypass mode. I believe I switched the battery #3 off and back on and the charging stopped. I then turned the AC off and that put the inverter back in normal operation running from batteries (before sun came up).
The second time the inverter 'went to grid' ... it was getting near the bottom again due to overcast/snow/etc and that is when I got an Under Voltage Alarm on Battery #2 I looked at the SA (or maybe computer PBMSapp) and definitely say Cell #7 was undervoltage. Oh Wait I LOOKED ON THE BATTERY READOUT to see cell #7 way under the other cells. The error was not only the inverter, but flashing red on the battery etc. so it definitely was an under-voltage cell. I did (something ??) to get it charging again and let it run til everything was back in the 90+ SOC ....and have not had any issues with #2 since then for a week or more....
but in the process I noticed that Battery #3 was acting different than the others... holding consistently 5-10% below the others (which were pretty equivalent...within a few % of each other) and that's what started all this.
I shot a message off to Sungold about both of the above but have not gone much further with them. I just wanted to lay down the ground work in case I need to make a case to return/exchange this battery.
Now I have to say (I'm watching things right now of course) and battery #5 (the former #3) is acting much more like the others ... currently at about 92% SOC with the others at 93.5 92.5 95.5 and 93.1 ....
... so I'm thinking that full charge I did on #5 this morning made a bit of difference and perhaps that all the system really needs is a few full cycles of all batteries...
In the mean time I think it's 'to school' time so that I better understand BMS and these batteries and inverters. Generally if I can understand the theory and the reasoning behind a system I can take that down to the details (at least in understanding and managing it)
So: https://www.einfochips.com/blog/und...s-how-it-works-building-blocks-and-functions/
and https://www.synopsys.com/glossary/what-is-a-battery-management-system.html
Kenny_
Solar Wizard
...and so I'm gonna cook some bacon in the microwave....that'll draw some current ... toaster toasting at same time.. and I get this...which I don't understand.... WHY IS Battery #5 Supplying most of the power? that's what's bothering me...
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Quattrohead
Solar Wizard
Something about that battery is different, no idea what but I would not obsess about it but keep an eye on it.
Kenny_
Solar Wizard
Ah! we're back! New server .. working out the bugs I presume
So after I stopped cooking / loading the system and back to normal operations I notice battery #5 is supplying all the power for my circuits
See below.
So I turn battery #5 off and all four of the remaining batteries SHARE the Load ... see the two images below. I also checked the cell voltages on #5 on the battery display and all 16 cells are in the 3.314- 3.316 volts range. ??
I'm still thinking ... maybe even moreso that there is a BMS problem:
So after I stopped cooking / loading the system and back to normal operations I notice battery #5 is supplying all the power for my circuits
See below.
So I turn battery #5 off and all four of the remaining batteries SHARE the Load ... see the two images below. I also checked the cell voltages on #5 on the battery display and all 16 cells are in the 3.314- 3.316 volts range. ??
I'm still thinking ... maybe even moreso that there is a BMS problem:
Kenny_
Solar Wizard
See my post just now with battery 5 breaker turned on and off...(all other batteries on in both images).
I sent these images to Sungold. We'll see what they say.
Kenny_
Solar Wizard
All your voltages are the same. It's fine
42OhmsPA
What's in a title?
I'd bet the 3.269V cell in pack 5 is what's dragging the soc down.
Kenny_
Solar Wizard
I 
dunno..... I mean it's only 0.001 off of other lows.... Now my 5 batteries are all supplying power (#5 a bit more than the others...but)
And SOC has dropped significantly on #5.... Maybe I just need to let 'er run, let 'er rip and see what happens... I mean hell the thing is working, right?
dunno..... I mean it's only 0.001 off of other lows.... Now my 5 batteries are all supplying power (#5 a bit more than the others...but)And SOC has dropped significantly on #5.... Maybe I just need to let 'er run, let 'er rip and see what happens... I mean hell the thing is working, right?
42OhmsPA
What's in a title?
I'd just run it and pay attention to cell deviation in pack 5.
I attached mine to make you feel better about it. Come summer when the batteries float before noon just about everyday cell balance will be much better, unless I go with active balancer BMS's before then...
I attached mine to make you feel better about it. Come summer when the batteries float before noon just about everyday cell balance will be much better, unless I go with active balancer BMS's before then...
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