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High and low drain cells mixed
#31
Just to add context and a comparison to the working voltage range of a different chemistry, this is what my LTO pack looks like regarding volt drop vs Wh.

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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#32
(08-23-2019, 03:33 PM)OffGridInTheCity Wrote: So let's say 4.1 to 3.4?  as aged but not yet at the limit.    (i.e. don't want you to have to run multiple tests etc - appreciate the effort here Smile )
First off I apologize for not getting all this done on Saturday. 
That done let's get to the results!
OK So I had to do a bait and switch on one of the batteries.The ICR18650-28As at 50mΩ are at their marginal end. Which means they barely hit 80% SOH.

What I did do is replace it with an LGABB41865 that tested at 2770 on my Foxnovo so it was a very good cell.
These cells where charged to 4.1 V and rested for at least 4 hrs before measurements were taken.
The initial discharge was at 1A for the pack  Sorry OffGridInTheCity goofed Blush on the 2Amp discharge but I recharged the pack to 4.1 again and did the test again
Cell#1 NCR18650A  35.9  4.0797
Cell#2 NCR18650A  34.2  4.0775
Cell#3 LGABB41865  54.4  4.0782
Cell#4 NCR18650A  34.2  4.0794
1A Discharge  for pack
3.4 Volt Cut Off 
Here is that chart Looks like all cells liked each other around 3.68 V


OK here is the chart with the same cells at 2 Amp Discharge for the pack.
Completely different discharge curve for the pack.


So I ran the NCR18650As through my Foxnovos and had a few LGABC41865s that tested very well so I decided to run another test with these.
The IR on the LGABC41865 is only 10mΩ higher but let see what happens.
Cell#1 7195  NCR18650A  34.6  4.1820  3049
Cell#2 7196  NCR18650A  33.2  4.1968  3020 
Cell#3 7190  LGABC41865 43.0 4.2164  2944
Cell#4 7197  NCR18650A  33.7  4.1874  3045
Discharge 1.2A to 3.0V
Preliminary chart any guesses where this will go?

Wolf
completelycharged 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
Not your average Wolf       
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#33
Dude this Data is utterly Amazing. Wild how much the LGA puts out during that last chart. Just goes to show that parallel does not mean equal current from each cell
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#34
(08-26-2019, 11:28 AM)Wolf Wrote:
(08-23-2019, 03:33 PM)OffGridInTheCity Wrote: So let's say 4.1 to 3.4?  as aged but not yet at the limit.    (i.e. don't want you to have to run multiple tests etc - appreciate the effort here Smile )
First off I apologize for not getting all this done on Saturday. 
That done let's get to the results!
OK So I had to do a bait and switch on one of the batteries.The ICR18650-28As at 50mΩ are at their marginal end. Which means they barely hit 80% SOH.

What I did do is replace it with an LGABB41865 that tested at 2770 on my Foxnovo so it was a very good cell.
These cells where charged to 4.1 V and rested for at least 4 hrs before measurements were taken.
The initial discharge was at 1A for the pack  Sorry OffGridInTheCity goofed Blush on the 2Amp discharge but I recharged the pack to 4.1 again and did the test again
Cell#1 NCR18650A  35.9  4.0797
Cell#2 NCR18650A  34.2  4.0775
Cell#3 LGABB41865  54.4  4.0782
Cell#4 NCR18650A  34.2  4.0794
1A Discharge  for pack
3.4 Volt Cut Off 
Here is that chart Looks like all cells liked each other around 3.68 V

First - thank you for these tests.

One of my batteries (14s120p) is 50/50 NCR18650A and LGABB41865 and these 14packs run / stay in balance with no problem at least as shown by Batrium stats.
My OPUS shows that my LGABB41865 cells are in the 80mOhm range as apposed to 60mOhm range of NCR18650A -  so the IR is not that different AND I suspect the discharge curve does not seem that different.

I would conclude from this experiment/info + my operating battery that these cells are pretty compatible.    But interested in what you think as I see the data but you are much better at interpreting and I could be missing some key element!

However, back to MOLI's with much higher IR and I suspect (just visually watching the OPUS charge/discharge tests) a different charge/discharge curve.   I guess I'm still unsure if I should mix with NCR18650As.       Any comments appreciated.
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#35
(08-26-2019, 02:44 PM)OffGridInTheCity Wrote: ......But interested in what you think as I see the data but you are much better at interpreting and I could be missing some key element!
However, back to MOLI's with much higher IR and I suspect (just visually watching the OPUS charge/discharge tests) a different charge/discharge curve.   I guess I'm still unsure if I should mix with NCR18650As.       Any comments appreciated.

OffGridInTheCity,

I don't think you are missing any key elements. Big Grin
Here is the chart of the same 4 cells from ~4.1V to ~3.4V discharge at 1 Amp for the pack and 2 Amp for the pack
Cell#1 NCR18650A  35.9  4.0797
Cell#2 NCR18650A  34.2  4.0775
Cell#3 LGABB41865  54.4  4.0782
Cell#4 NCR18650A  34.2  4.0794
On the first discharge curve you can see the deviation of the "blue line" cell#3 from the rest of the pack by a bit ~30mA to ~80mA at the 1Amp discharge not bad I think. Also  the "green line" (cell#1) follows cells 2 and 4 albeit just a little less of a discharge. It has 1.7mΩ higher IR.

At a higher 2Amp discharge the separation is a bit more pronounced as more demand is put on the cells and it looks like the "blue line" Cell#3 again  has a ~120mA deviation and Cells 1,2 and 4 are working in unison with the "green line" Cell#1 mirroring  Cells 2 and 4 but slightly above.
So as daromer has stated at a lower mA draw it is not much of a difference but as the mA draw increases so does the mA contribution of a different IR cell. So +1 for daromer. Now this is for a low drain cell combination only though.

On another note,
If these cells were left to go to 3.0 V cut off or possibly to 2.8V for complete DOD there would surely be a much harder swing at the end. Test to be conducted as these experiments are far from over Big Grin .

OffGridInTheCity,
I have the NCR18650A batteries if you so feel inclined to send me one of the MOLI's so I can throw it into the mix or if they are new MOLIs where I can buy one let me know. I am just as curious as you are and more than happy to carry out the test. Till I do a NCR to MOLI comparison with this board at the voltages and amperages you are looking at I cant say whether to mix them or not. Probably won't hurt the pack as long as there are enough of them to balance each other out so there isn't a lone "wolf" (pun intended) in the pack that will absorb all of the stress.

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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#36
(08-26-2019, 11:28 AM)Wolf Wrote: Here is that chart Looks like all cells liked each other around 3.68 V

Brilliand trace,

The cell temperature would be curious in this case. Thought is the initila discharge warms the cell up, which increases IR, drops the output voltage slightly as a result and therefore the current drops back. The initial peak is where the curiosity is....

Thought would be to run the same test, one with no airflow and then again with a high forced airflow over the cells.
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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#37
(08-26-2019, 05:38 PM)completelycharged Wrote:
Thought would be to run the same test, one with no airflow and then again with a high forced airflow over the cells.

LOL I knew I left some room on my board for a reason. And now it has become clear. A FAN.
I can also at some time get some temp sensors embedded into the holders and monitor that.
What's that sensor some TI sensors that work on i2c I think? I think they can be daisy chained.

Although random checks by hand (I know not very accurate) does not indicate any cell temp as the resistive load is far away.
I can always take some temp readings with my thermal camera.

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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#38
If you got 1 digital pin free use ds18b20 if you got some. They are cheap and works well.
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#39
(08-26-2019, 06:24 PM)daromer Wrote: If you got 1 digital pin free use ds18b20 if you got some. They are cheap and works well.

Ordered now to incorporate into the sketch. Big Grin
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
#40
(08-26-2019, 11:28 AM)Wolf Wrote: So I ran the NCR18650As through my Foxnovos and had a few LGABC41865s that tested very well so I decided to run another test with these.
The IR on the LGABC41865 is only 10mΩ higher but let see what happens.
Cell#1 7195  NCR18650A  34.6  4.1820  3049
Cell#2 7196  NCR18650A  33.2  4.1968  3020 
Cell#3 7190  LGABC41865 43.0 4.2164  2944
Cell#4 7197  NCR18650A  33.7  4.1874  3045
Discharge 1.2A to 3.0V
Preliminary chart any guesses where this will go?

Wolf
Due to a technical difficulty this test was aborted. (The ESP32 decided to stop communicating with the database)
So I recharged the batteries and started the test again.
Slightly new numbers on the 4 cells.
Cell#1 7195 NCR18650A 34.6 4.1963 3049
Cell#2 7196 NCR18650A 33.2 4.2011 3020
Cell#3 7190 LGABC41865 43.3 4.2195 2944
Cell#4 7197 NCR18650A 33.7 4.1976 3045
Discharge 1.2A  Cutoff 3.0V

So far so good hope to have the results tonight.
Wolf
jdeadman 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
Not your average Wolf       
            Cool
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