Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Behaviour of cells in parallel take 2
#21
OK here is the charging curve of this test.
Again the same batteries in the same slots.


One thing to note this is a charge at 4A.
The thing that stands out of course is the low IR cells soak up the juice very early and once happy fade away.
Cell 1 which was depleted pretty badly during the discharge as it took the biggest hit for the duration was also right up there in the feeding troth.
Remind me to move the ambient temp sensor away from the charger................ Cool


Full chart of D/C cycle



Quote:Can you make a test with low Cap & high IR and high Cap cell with low IR?
I will see what I can find in my plethora of cells to run this test.


Also I think I will go with the icharger I have, to increase the discharge to 4A as the ZH-YU limits me to 2.6A.

Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply
#22
So this weekend I got busy with some more charting.
Hooked my icharger to the test board and went to town.
I can now easily do a discharge and charge trace. Smile
Don't know why I didn't think of using the icharger for this sooner but I think Iwas using it to build and analyse my packs. Well nevertheless i have 2 of them now an icharger x6 and x8

All tests below where done with the icharger x6 C/D/C at 1A, 4.2V to 2.75V

Just for a baseline I decided to  run 4 cells of the same kind through the tester.
Here are the results.
Very smooth and even discharge all the way to the end. The same with the charge cycle.
These are Panasonic NCR18650B which I believe is the cell of cells. If I had a bunch of these I would be very happy.
All tested ≈ 2800mAh a while back so I didn't retest. I did record the IR though and you can see they are pretty close.



So then after a long search I found some low capacity high IR cells. You have to remember that if anything is out of the IR range at my house it goes away to the recycler. So I was lucky to hang onto some Sony US18650S cells. Why I had these I have no idea I guess I was curious and kept them.
As you can see the difference is quite remarkable. The Panasonics from the getgo carried most of the load and there was no crossover at all.
Temperature also got right to the 30° C on the heavy lifters.
 


I ran the test twice just for the fun of it. The second time the Panasonics got a little warmer but so did the ambient.


Then lastly I ran a test with 4 cells with similar mAh results but different IR.
Relatively even results with some crossover action happening.



So there you have it.
I know what my conclusions are.

What are yours?

Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply
#23
Everyone assumes that if you have 4 cells at 4 Amps, that each cell has a 1 Amp load on it. Thanks for proving otherwise!

Without looking back, did you test two 3.7V cells in parallel with two 3.6V cells, all with equal capacities and IR? Just curious to see if the 3.6/3.7V makes a difference or not, as they have radically different discharge curves.
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
Reply
#24
(06-19-2020, 05:00 AM)Generic Wrote: Without looking back, did you test two 3.7V cells in parallel with two 3.6V cells, all with equal capacities and IR? 
If 4 cells are in parallel, they can't be different voltages as in 2 @ 3.7v and 2 @ 3.6v  (as I know you know Smile ).  I'm not sure I'm understanding this question/though - could you clarify?
Reply
#25
Nominal voltages. Like the Panasonic CGR18650E is a 3.6V nominal cell vs. a Samsung ICR18650-26D is a 3.7V cell. Chemistry could be the same, but the 3.6V cell has the bulk of its energy at 3.5-3.6V and the 3.7V cell has the bulk of its energy at 3.7-3.8V. I always theorized that at 3.5V, the 3.6V cell would be doing most of the work, while the 3.7V cell would be pretty depleted and not contributing much energy.
OffGridInTheCity likes this post
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
Reply
#26
18650's come in two basic nominal voltage 3.7 and 3.6 , I think Generic was seeing if anyone has done a parallel test with a mix of the two cells.

Later floyd
OffGridInTheCity likes this post
Reply
#27
Generic,

Those cells I do believe I have in stock I will find some with reasonable parameters and charge according to spec and run a parallel test.
I am on the hunt for CGR18650E and Samsung ICR18650-26D cells.

Till then

Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply
#28
Different nominal cells Will look like above where they deliver different current att different voltages
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#29
(06-19-2020, 05:00 AM)Generic Wrote: Everyone assumes that if you have 4 cells at 4 Amps, that each cell has a 1 Amp load on it. Thanks for proving otherwise!

Generic,

The other thing to consider is also the charging of the cells, as it is also influenced the same way. Just because you are charging cells in parallel does not mean they all absorb the same amount of energy at the same rate.
Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply
#30
(06-19-2020, 05:59 AM)Generic Wrote: Nominal voltages. Like the Panasonic CGR18650E is a 3.6V nominal cell vs. a Samsung ICR18650-26D is a 3.7V cell. Chemistry could be the same, but the 3.6V cell has the bulk of its energy at 3.5-3.6V and the 3.7V cell has the bulk of its energy at 3.7-3.8V. I always theorized that at 3.5V, the 3.6V cell would be doing most of the work, while the 3.7V cell would be pretty depleted and not contributing much energy.

Looky-Looky I found some. I was some surprised. Not!



I will get the 4 lowest IR and test them in my new Vapecell S4 fast charger 3A  
Just another off the shelf mediocre charger/tester. IR is slightly better. Cant trust it at low V though.
I can't wait to get my 2 MegaCellChargers and see what they will be like.


Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply


Forum Jump:


Users browsing this thread: 2 Guest(s)