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Behaviour of cells in parallel.
#11
You get the nulls because you arent sending the data the database expects Smile The series you have there is set up to have data every second and since it doesnt it show nulls in between. Its not a problem persue.
Note that if you push data faster than 1 second the data will be interpolated to 1 second values since thats how its created.

I guess the "GUI" that you use creates the nulls because of that. If you do a normal select they wont really show up unless the "time" have any data in it.

https://docs.influxdata.com/influxdb/v1....amp-matter

So in your example you only have a resolution of +-1 Second at most. If you want it coarser you need to make sure to save with such. I hope you get it. There is like tons of documentation of it.
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#12
Glad to see I'm not the only amateur battery scientist here. I did a similar experiment a while back which you can find here: https://secondlifestorage.com/t-Differen...Experiment I did another more specific test paralleling a Leaf cell (LMO chemistry which has a higher average voltage) with standard Li-Ion (NMC or similar chemistry). Results showed what you might expect, the Leaf cells provided most of the power for the top majority of the SoC, then the lower (average) voltage Li-Ion cells kicked in in the last 30% or so of SoC. This is problematic since they will be taking a majority of the current drawn from the overall pack during the lower 30% or so of pack capacity.
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#13
(08-15-2019, 03:25 PM)rev0 Wrote: Glad to see I'm not the only amateur battery scientist here. I did a similar experiment a while back which you can find here: https://secondlifestorage.com/t-Differen...Experiment ........................

Welcome to the club or should I say I'm glad to be joining the club.

Wow completlycharged put out a commission on 06-17-2018 for a cells in parallel study
and you (rev0) on 02-19-2018, started a very similar experiment.
That will teach me too dig some deeper into the archives Cool
If I can ever figure out the search function. Big Grin

That being said here are the latest results on a discharge on 4 batteries. 
These batteries where parallel charged on a CC/CV board to 4.2V and sat for about 30 min before being inserted into the testing board.
Here are the parameters of the cells.


Notice in the beginning of the chart there is very little balance interaction of the cells as they are practically identical in voltage.
At 6:08 AM I hit the discharge switch at 2.5A and the reaction of 1 of the 13Qs in the beginning and the other 13Q at the end is interesting.
The 20Cs just more or less lumber along and at the end 2.8V cut off at ~8:00 AM are now charging the 13Qs as the 4p pack is slowly coming to equilibrium. That basically shows me that the 13Qs (understandably so) ran out of gas first and brought the bus voltage to 2.8V which caused the discharge to stop. The 20Cs still had plenty of gas to go as they were initially filling up their brethren after the 2.8V cut off with ~400mA and as of noon 4 hours later are still supplying them with ~60mA.
So that test begs for a different test, only 13Qs and only 20Cs with the same 2.5A discharge and we will see how they do on time. Also it will be interesting to see how their interaction is after the discharge cutoff.  Theoretically the 13Qs should last ~ 2 hrs and the 20C ~3.2 hrs. I will run those tests in the next couple of days. Before I do that I will run a charge curve on this pack. One thing I have noticed that even though I am charging these packs at 4A, 1A each the do not warm up in the slightest. I will see if I can find a "heater" and mix it in and see what transpires.
Man this has opened up a can of worms so many different variable to consider testing for. 
Here is the discharge chart

And here are all the parameters.

BTW I have updated Grafana to 6.2.3 so some of the menu items have changed but not by much if you visit the site and notice a difference.
Wolf

(08-15-2019, 02:22 PM)daromer Wrote: You get the nulls because you arent sending the data the database expects Smile  The series you have there is set up to have data every second and since it doesnt it show nulls in between. Its not a problem persue.................
....................... I hope you get it. There is like tons of documentation of it.

@daromer
No I get it and it is not a huge problem as you can see from my grafana graphs the data is good and represents itself accordingly.
I will take out the 2 second delay at the end of my loop to speed it up a bit. All in all I am very satisfied with the resolution that I am getting from all of this.
I will read up more on influx and such as I have time but for now I think we are doing quite well.

Thanks

Wolf
Korishan likes this post
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
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#14
(08-15-2019, 04:59 PM)Wolf Wrote: That will teach me too dig some deeper into the archives Cool
If I can ever figure out the search function. Big Grin

Just use this search: https://secondlifestorage.com/search.php Wink Most people miss the Advanced Search function.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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#15
Grafana reads the values. Your GUI to show the data does not. It reads all positions Wink On your current setup i guess you have "second" resolution in the series.
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#16
(08-15-2019, 08:16 PM)daromer Wrote: Grafana reads the values. Your GUI to show the data does not. It reads all positions Wink On your current setup i guess you have "second" resolution in the series.
Not sure what you mean by my GUI the picture is of the import into Excel and yes the series was set to 1 second.
I have played with that and have changed to 10s, 15s, 30s, 1m, and so on. Just to experiment.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
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#17
Brilliant,

P - personal
H - help with
D - data

:-)

Ah, I see how the data is being written. needs to be time syncronised to make the analysis easier, otherwise it's a bit of fliddling to get the numbers consistent. With the tollerances on the values it should be ok to start off with though.

+1 for the cache setting

Awesome..

I missed the rev0 post, interesting.

The analysis needs to be done in relation to Wh (or scale for mWh) because the mA is hard to correlate against other cells without a volt context as it removes or aligns the time variable by using Wh.

It's all about the net energy in / out, i.e. Wh...

Separate thought for another type of test, during the discharge process maybe run the discharge for 5 minutes, rest for 2 minutes and then start the discharge again for 5 minutes and repeat. This should show how well the internal chemistry recoveres from a discharge by way of the cell voltage recovering.. But.... the +ve and -ve bus is comon so this test would need to be done one cell at a time.

Quick calc...
This is the Wh difference between the cells for the discharge cycle (first cell is the baseline)



Notice the separation half way through.... cell 2 and cell 4 following the same path.

Cell 1 discharges 4.61Wh with the red cell only 3.76Wh

But, this variation is due to the IR differences or cell contact difference.... i think...

This is where you want to be..... this is for cell 1.
 
Discharge Wh delta vs Voltage as a scatter

Explanation...
Work out the mWh per time interval the cell has discharged
Create a running total of the cumulative mWh through the discharge period
The take two points, say 60 seconds appart and calculate the difference in the discharge
Then.... plot the value as a series in the first instance

End of the curve..... collapse in discharge rate.

Each cell has a different fingerprint due to the chemistry distribution, age, etc...

Will let the chart do the talking....
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#18
completlycharged,

Interesting. I'm going to have to read that post about 10 times to figure out what you are saying. Angel

Meanwhile at 6 AM EST another round is discharging.
This time it's all 18650-20C cells discharge at 2.5A for the pack.


You can already tell the even discharge between the cells.

These initial tests are to get a baseline and understand how cells interact with each other. The more "fun" ones with different chemistries ,and all kinds of variations of IR, and mAh ratings  voltage ranges etc will be in the wings.

I hope those who are following this have bookmarked the site where all the data is being displayed.

Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply
#19
Wolf: Upload issue being fixed Smile Thanks
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#20
(08-16-2019, 11:54 AM)daromer Wrote: Wolf: Upload issue being fixed Smile Thanks

Great I will edit my post.
Thanks
Wolf
If 18 X 650 = 2200+mAh then we have power! 
May all your Cells have an IR of 75mΩ or less Smile
Last count as of 8/7/2019
Total Number of Cells Recorded and processed                 6149
Total Cells required for PowIRwall                                   2856
Total Cells ≥2200mAh, ≥80%, ≥35mΩ, ≤75mΩ, ≥4.12V   2760
For Info Google Drive
Not your average Wolf       
            Cool
Reply


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