ESR? Acceptable rates

Juized

Juized

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After a little research I was able to determine that the ESR rating of a battery is essentially the internal resistance of the battery. But unfortunaley I dont seem to understand the signicficance of this number. Obviously batteries with low interal resistance will naturally outlive those with higher resistance, but I would like to know what are acceptable ESR levels that people have used in their batteries. The Megacell charger has default value of 250 mOhm MAX ESR rating for acceptable batteries. What would happen if i were to double it? is it temperature realted or something else?

Thanks for your time
 
Juized said:
After a little research I was able to determine that the ESR rating of a battery is essentially the internal resistance of the battery. ......... The Megacell charger has default value of 250 mOhm MAX ESR rating for acceptable batteries. What would happen if i were to double it? is it temperature realted or something else?
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ESR (or cell IR) is a good indicator for cell health & most people here look for numbers under I think about 80mOhms.
250mOhms is pretty high already.
Cells with have been abused or have less remaining useful life, this number usually rises.
"Wolf" in particular has done some great work tracking, measuring & understanding cell IR/ESR.
See some of these threads:
https://secondlifestorage.com/index.php?threads/one-handed-ir-jig-saves-my-sanity.10770/
& https://secondlifestorage.com/index.php?threads/dc-ir-vs-ac-1kh-ir-measurements.9471/ << long but good info
 
Juized said:
After a little research I was able to determine that the ESR rating of a battery is essentially the internal resistance of the battery. But unfortunaley I dont seem to understand the signicficance of this number
Click to expand...
@Juized
(ESR) Equivalent Series Resistance is really a misnomer when dealing with the (MCC) MegaCell Charger / (MCM) Mega Cell Monitor.
ESR is not measured by the MCC. The MCC measures "DC" (IR) Internal Resistance in its most rudimentary form which is a basic simple voltage drop measured across a known resistance value and software that calculates the IR. This IR reading is not nor can it be very accurate as for an IR reading at that low of an ohmage the system needs to be a 4 wire kelvin measuring device. Neither is it an actual ESR reading as ESR is always an AC resistance, which means it is measured at specified frequencies, in our case most of the manufacturer of Li-Ion cells measures the IR at 1kHz and publishes acceptable values.

ESR meters, essentially AC milliohm-meters such as the YR1035+ or the RC3563 are calibrated to be 1kHz 4 wire kelvin IR/Impedance meters designed to measure the AC Impedance of the cell giving us an accurate IR reading in mΩs.

The significance of this number is paramount when determining the (SOH) State of Health of a cell. But before we get into that we also need to discuss how battery chemistry comes into play. There are basically 2 types of chemistries ICR and INR, where ICR (Lithium Cobalt Oxide / LiCoO2) are your low drain cells and INR (Lithium Manganese Nickel / LiNiMnCoO2) are your high drain cells. The general rule of (my) thumb is cells above 40mΩ are ICR and those below 40mΩ are INR. There are hybrid chemistries that bridge some of these values depending on their application but your high performance high amp cells are generally INR with IR values as low as 10mΩ.

Determining the SOH of a given cell.
We already have concluded that the ESR 😒 / IR of the MCC is of no use to us as its measurements cannot be trusted and most certainly are not consistent, so by using a proper tester such as mentioned above, YR1035+ and my favorite the RC3563 we can consistently get a mΩ reading on the cell no matter what the (SOC) State of Charge is. I have a cheat sheet with most popular cells we see in the harvest process and a go and no go mΩ value. This sheet is by no means the golden authority but it is the result of testing over 6000 cells and determining the best mΩ value of each manufacturer and model # for good SOH results. The sheet can be downloaded here.
This is also a good thread https://secondlifestorage.com/index.php?threads/18650-harvesting-flow-charts.9714/#post-74868 regarding harvesting procedures.
I hope this explains some of your questions and welcome aboard!

Wolf



 
One major difference between ICR and INR cells, which I found in many (all?) cases, is that ICR also have PTC ring inside cell!
The PTC itself adds noticeable part of resistance!
For example 2 cells from laptops:
Sony US18650GR G3 (very crappy, had CID popped up too) - had PTC 25.7mR
Samsung ICR1865022F (was healthy bu wit ~55% SOH) - had PTC 9.6mR
Both measured by YR1035+

Even difference between these 2 is huge.

I never saw PTC rings in cells used in power tools, they all were INR (from Samsung) or probably INR from other manufacturers (Sony VTC2, VTC3, VTC4, VTC5)
20211024_001224.jpg
 
Pro tip for ESR on the MCC.
If a cell fails the workflow because of high ESR, take the cell out, clean the ends and re run the test.
After almost 6000 cells tested through my MCC's, cells with high internal resistance will fail twice on ESR, cells which simply have dirt, glue and crap on one or both ends will fail only once after being cleaned.
Remember the ESR measurement on the MCC is NOT at accurate internal resistance check but it does give you an indication of unhealthy cells.
Good luck :)
Darren
 
Oleksii said:
One major difference between ICR and INR cells, which I found in many (all?) cases, is that ICR also have PTC ring inside cell!
The PTC itself adds noticeable part of resistance!
For example 2 cells from laptops:
Sony US18650GR G3 (very crappy, had CID popped up too) - had PTC 25.7mR
Samsung ICR1865022F (was healthy bu wit ~55% SOH) - had PTC 9.6mR
Both measured by YR1035+

Even difference between these 2 is huge.

I never saw PTC rings in cells used in power tools, they all were INR (from Samsung) or probably INR from other manufacturers (Sony VTC2, VTC3, VTC4, VTC5)
View attachment 26349
Click to expand...
Thanks for sharing this interesting finding!
PTC-material is very temperature sensitive, so you have to take the measurement at a specific (hopefully low) temperature to give the reading a meaning :)
Also i guess the contact possibility of PTC may be poor - so do the test a few times (maybe at slightly different temp.) to get a feeling of the sensitivity.
 
paddy72 said:
Thanks for sharing this interesting finding!
PTC-material is very temperature sensitive, so you have to take the measurement at a specific (hopefully low) temperature to give the reading a meaning :)
Also i guess the contact possibility of PTC may be poor - so do the test a few times (maybe at slightly different temp.) to get a feeling of the sensitivity.
Click to expand...
Measurement made on room temperature. Yes, I measured at least 3-4 times to make sure it's consistent.
Note - these cells are old/used ones and I'm not sure what temperatures stress they may have in the past.
 
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