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building pack unsure what is high internal resistance 18650 cells
#1
hello
im building a 12s9p 18650 pack for a skateboard i have teted all my cells but unsure what is high internal resistance ? 
have lots of 18650s and want to reduce the likleyhood of building a bad battery using high internal resistance cells, my highest so far is 80 ohms
thankwe
Battery is li iron using 18650s, 14s, 0p, and growing cell so far 1000ish, untesteded.
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No solar yet, very soon, looking to buy panels if anyone has any?
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#2
(05-10-2020, 11:59 PM)Jonisingt35r Wrote: hello
im building a 12s9p 18650 pack for a skateboard i have teted all my cells but unsure what is high internal resistance ? 
have lots of 18650s and want to reduce the likleyhood of building a bad battery using high internal resistance cells, my highest so far is 80 ohms
thankwe
@Wolf has done extensive data gathering on battery types and their IR and what's good.   See this thread, 3rd post, "Harvest.xlsm" for a spreadsheet download with much info.   https://secondlifestorage.com/showthread.php?tid=9006&highlight=wolf   

A
nd search "wolf" for other discussions and info and downloads on IR.
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#3
I been playing around with my yr1030 IR tester, I tested hundreds of cells, I would say anything under 65 milliohms is ok for a pack, that is my cutoff for me. But I don't use in a high drain device. Batteries at 80 milliohm or higher got hot during testing and were taking longer to reach 4.20 volts and had lower capacity.

But for a high drain application I would go even lower. Some of the high drain sony's (powertool batteries) are less then 30 milliohms, I seen the panasonic at about 34 milliohms, the red sanyo's in the 45 milliohms for the ones with 2500 capacity. I seen some blue samsung cells less then 20 milliohms. In your situation i would stay under 50 milliohms.

But with laptop batteries its rare to get under 40 milliohms, I was lucky to get the panasonic in just one pack total 9 cells, those are definitely premier batteries all testing at minimum 2900 mah.

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#4
thanks
Battery is li iron using 18650s, 14s, 0p, and growing cell so far 1000ish, untesteded.
Bms chinese bluetooth
No solar yet, very soon, looking to buy panels if anyone has any?
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#5
Hi there,

I just got my yr1030 yesterday and started testing the 500 18650s that I bought, they are Moli ICR-18650H cells - none have an internal resistance of less than 73 milliohms, and the average would be just over 80... A few are over 100.

They were sold to me as tested cells, the capacity has been written on each cell and the marks from spot welding ground off both ends. The seller has great ratings and they were sold as second hand but unused.

Does anyone have any idea what is a typical IR for these cells? I have checked Wolf's database and unfortunately no info there.

Any help very much appreciated, along with any advice as to what I should do with the 100+ milliohm cells.

Smile

Many thanks!
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#6
(05-13-2020, 05:49 PM)mikenr Wrote: Hi there,

I just got my yr1030 yesterday ..............t, they are Moli ICR-18650H cells - none have an internal resistance of less than 73 milliohms, and the average would be just over 80... A few are over 100.
............ I have checked Wolf's database and unfortunately no info there.................
mikenr,

First off congratulations on a giant leap into proper battery testing with the purchase of the YR1030.
I do have some information on the Moli ICR cells. They are Lithium cobalt oxide cells  generally low drain high capacity.
The ICR-18650H is a 2100mAh cell. I probably haven't come across any so that may be why they aren’t in my analysis sheet.
But have no fear I have plenty of ICR-18650J and ICR-18650K cells to go by.
I find that most manufactures like Moli do not change their cell chemistry for mAh results they just add more product to each cell.
In essence it is just a heavier battery. 
I have been fortunate enough to test 101 of these gems. Tongue

Results with lowest IR.


Results with highest IR.


My database info on them.


My best guess at proper IR values.


That's what I have.

As far as a cell (actually any cell) with > than 100mΩ I'm not to fond of. What do they test out at?
Best guess with the data that I have is that anything >80mΩ is marginal at best with ≤80% SOH.
Any cell <80mΩ down to my lowest at 56.1mΩ seem to perform OK with obviously the lower the mΩ the better the chances.


Wolf
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#7
The IR is HIGHLY dependant on the application. On RC cells you dont want IR above 5mOhm... Meanwhile a laptop is generally below 60mOhm and for many of us we can go up to 100 or so without noticing it.

The internal resistance affects voltage drop and we all know voltage drop = heat = wasted energy.
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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
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#8
(05-13-2020, 08:19 PM)daromer Wrote: ........... Meanwhile a laptop is generally below 60mOhm and for many of us we can go up to 100 or so without noticing it.

The internal resistance affects voltage drop and we all know voltage drop = heat = wasted energy.

Correct daromer.

It took my quite a while to find 4 cells with close mAh results and very different IR readings.
I just did this experiment a couple of days ago.

4 cells

1  INR18650PHH  1782mAh    39.89mΩ
2  LGDAS31865   2004mAh    71.02mΩ
3  UR18650E       1871mAh    36.29mΩ
4  UR18650FJ      1853mAh    62.55mΩ

I couldn't find any >80mΩ cells as they are all gone to the recycler. OOPS.
We may not notice the 100mΩ cells but the other cell certainly do Tongue

All in all if you stay in the 4V to 3.5V range there is not much going on between the cells but when you get outside of those parameters then things start to happen.



Also the charging profile is very different between these cells.



Wolf
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Great prices and superb service.
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#9
What many doesnt see is that they are uneven now in beginning. The cells that is capable with higher current have lower ir and will be stressed more. But that is not really a bad thing since they are often in better condition than the ones with slightly higher IR.

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
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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
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#10
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?

Unfortunately I would say the average IR of my cells is just over 80 millohms Undecided Few are in the sixties and the majority low to mid eighties.... The average voltage of each cell would be 4.15v I would say, some are even at 4.2v !
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