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building pack unsure what is high internal resistance 18650 cells
#11
(05-14-2020, 11:56 AM)mikenr Wrote: Many thanks for the very useful info Wolf.

I noticed in the tests that you shared none of them were done with a yr1030 does it make any difference if one is testing with another instrument?

mikenr,
The use of the YR1030 is slightly obscured on the sheet with the sorting pulldown.
Sorry for the confusion but ALL my cells where checked with the YR1030 family of testers.
 
So yes all my IR tests are done with either a YR1030, YR1030+ YR1035+ or as of late a RC3563 all of which are
within μV and μΩ  tolerances of each other so no deviation there. Short of spending $5000.00 on a Keithley you have a very accurate mΩ tester with the YR1030 family of testers.
Yes I have all these testers and have checked them with my reference block for V accuracy and R accuracy.


Here is my V refboard and 10mΩ reference 

And I have 3 Fluke DMMs To collaborate with each other. If all 3 read the same its got to be right. Tongue




Wolf
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#12
Oh my god!!! haha I was just wondering and now I know Smile Many thanks again!
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#13
(05-13-2020, 08:46 PM)daromer Wrote: I did post a rather large paper on FB the other week. Like 250 pages testing this and its quite interesting. In their tests the cells did level out a bit after some decent amount of cycling Smile

Something for you to test Wolf Big Grin

daromer,
Could you give me the link to that post please?
Ha more testing OK I'll bite.
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#14
Wolf, I know this will be blatantly obvious to you and please excuse my ignorance....

So the majority of my cells tested with an IR of around 80-85 milliohms with the yr1030, the seller had written the capacity and IR on the side of each cell having tested them with a Liito Kala Lii-500

Sometimes the results were similar and more often than not way way different, either higher or lower. I know you know why this happens Smile can you explain for me?

I contacted the seller about the high IR on the majority of the cells, he asked if I had discharged the cells to 3.6volts before doing the resistance testing (which I had not) most were 4.15 or more, does the voltage of the cell make much difference when testing? Again please excuse my ignorance, I'm on a steep learning curve here Smile
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#15
(05-20-2020, 10:32 AM)mikenr Wrote: I'm on a steep learning curve here Smile

Ha Ha dont spin out or fall of it will only get better...............
mikenr,

I can go with what I have for results on the Moli-Energy cells that I have tested and say that voltage has very little effect on the IR of these cells.
Most of them measure a little less or a little more in mΩ after a full charge.
If the seller tested the IR with the Liito Ks then that IR is way off. The Liito Ks dont test the cells with a 1KHz 4 wire test they run a simple V drop test and calculate the DC IR which in its own right is OK but not the accurate way. Additionally the charger contacts themselves add a considerable amount of mΩs to the mix.

Here is a chart of all the Moli-Energy cells That I have tested with the Liito Kala Lii-500 These are the slightly higher capacity cells 2300mAh and 2600mAh ones.
 
The fact remains the same, the IR doesn't change that much from before the test and charge, to after the 30+ days recheck. That goes for all cells I have checked from all manufactures except the SONY GR series. (That's a strange cell) Huh
The Manufacture of the Moly-Energy cells claims that an IR of ≤80mΩ is acceptable for their J and K series I was not able to find the spec. for the H series but I would imagene it is about the same.
I did find a Moli B that is close to the Moli H at 2250mAh that says 75mΩ max.

Do your own experiment with them. Discharge 4 cells with your Liito K and measure the IR and then charge them and repeat the IR check.
Slap the data into a spreadsheet and slowly you will find a correlation. 

Also since this is a 2200mAh cell what are you getting for results? 

Link to molicel product info http://www.molicel.com/products-applicat...y-product/

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#16
Amazing! Many thanks Wolf, I knew you would know Smile

When I started out on this project I only had in mind to buy cells and build a battery for my house. Thinking I would buy cells tested and sorted by someone else, so I don't own a Liito K.... Undecided After reading around the forum I realised that testing the cells with a yr1030 makes a lot of sense, so I bought one - now I realise that in the future I will start harvesting cells so my next purchase is a Liito K (by the way, is there any particular one you would recommend?)

Do you think there's much possibility that my yr1030 is calibrated badly? is there any simple way of checking it? (I imagine 'no' is that answer to that)

Many many thanks for all your help and for sharing your immense knowledge! :-)
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#17
Mikenr: Put cells with similar resistance into parallel, it will give less heat when charging or discharging powerwall.
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#18
(05-21-2020, 07:02 AM)mikenr Wrote: ............. now I realise that in the future I will start harvesting cells so my next purchase is a Liito K (by the way, is there any particular one you would recommend?)

Do you think there's much possibility that my yr1030 is calibrated badly? is there any simple way of checking it? (I imagine 'no' is that answer to that)


mikenr,

The Lito K would not be my first choice.
If you can afford it and have some time to learn the SKYRC MC3000 menu and its capabilities I would get that one. But at ~$130.00 it is expensive but well worth it. It can graph the process on your PC and also on your phone.


My second choice would be the OPUS because it does 1A/1A/1A CDC(Charge/Discharge/Charge) and relatively simple to use. I also believe that is what you should go with. (If you don't have the means to go with the SKYRC) It is a standard that is liked here and I have grown to accept it even if it is around 3% to 5% high in its results.

One thing you want to remember if you are going to purchase a charger/tester stick with one make and model not like me and have them all. LOL

It will make it easier for you in the long run and not have to second guess the results.



My third choice is the Foxnovo S4 only because it is simple and easy doesn't have a lot of bang and whistle, the only downside is it does a CDC at 1A/.5A/1A but it seems to be relatively accurate.



Test results of these charger/testers with the same battery in all 4 slots.





I highly doubt your YR 1030 is miscalibrated and as you know I have several of them and they all read the same values. (at least so close that it is negligible) The best way to test the YR1030 is get a reference resistor https://www.rhopointcomponents.com/isabe...pbv-series (I have 1 for 10mΩ) or some nickel strips with a known mΩ value for a certain distance. Even a 1Ω resistor from anybody will give you an idea if your YR1030 is off. But I highly doubt it. I believe your cells are just high IR.



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#19
As always Wolf I appreciate your advice very much indeed. I'm crazy busy at the moment, but when I have time I will check out the SKYRC MC3000 and if I think it's too much for me go for the Opus Wink

Have a great weekend!

(05-21-2020, 10:04 AM)Lithiumseller Wrote: Mikenr: Put cells with similar resistance into parallel, it will give less heat when charging or discharging powerwall.

I wish I had known that 4 days ago when I was building the now built battery pack... But thank you for the advice Smile

BTW from where do you source your cells?
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#20
(05-22-2020, 07:21 AM)mikenr Wrote: As always Wolf I appreciate your advice very much indeed. I'm crazy busy at the moment, but when I have time I will check out the SKYRC MC3000 and if I think it's too much for me go for the Opus Wink

Have a great weekend!

(05-21-2020, 10:04 AM)Lithiumseller Wrote: Mikenr: Put cells with similar resistance into parallel, it will give less heat when charging or discharging powerwall.

I wish I had known that 4 days ago when I was building the now built battery pack... But thank you for the advice Smile

BTW from where do you source your cells?

https://ma.linkedin.com/in/aneta-jaskula-228b6933/de
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