“They are measuring current and voltage at the same time”
Yes, I think what is being done is that AC is used and they are calculating the delta V and delta I at each sample point of the Sine Wave
No, the peak current will not change from cycle to cycle, but it would all along each cycle.
It could be that they are calculating the instantaneous change in voltage with respect to the instantaneous change in current along that sine wave. Dividing the 2 will give the internal resistance.
Now, who am I to say how they are actually doing it. All I am saying is that they are calculating the internal resistance based on the principles of my circuit and equations.
As long as you circuit can measure AC only need to divide voltage with current, no need to use the DC formulas.
You can find it all in my article about resistance/impedance: Internal impedance of a battery
Wow, that Samsung 21700 30T looks like it could deliver the highest current of any cell I’ve seen. I see articles saying it’s a Panny/Tesla 21700 competetor cell. Looking at the reviews, very impressive.
Will the difference be significant for that same battery? (eg. measuring the same battery at 3.0v vs 3.6v vs 4.2v)
or will there be a big variance depending on the type/chemistry/age of the battery?
For flashlight use the relevant measurement for battery resistance is the DC IR. As mentioned this meter measures something different which might or might not be useful.
All these measurements seem very close. Some batteries listed I would have thought to have higher resistance. So these are very accurate numbers? Shows perception does not mean much.
This is a multimeter test method of battery internal resistance, but the battery's internal resistance is very small, the error is relatively large
There is also a great resistance between the conductor and the conductor, and it is easy to change
HKJ has an comment of this instrument
This YR1030 instrument measures the same cell and test many times ，almostly the same data
Some chager have function of tested the internal resistance , but the error is large, each test data is not the same, each slot data is not the same
I just got a YR1030 to go through some older cells to decide if they should go into the recycling bin. Also, I’m interested to see how well old and new cells match each other. After collecting some info about how resistance changes with time, I might sell it on. At least that’s how I justified spending $50. I used a battery holder for the cells and clamp for the switches and tested at room temperature. Here are a few newer cells that weren’t already listed.
Molicel 21700 P42A 3.54v (they come discharged from Liion Wholesale) (9.31 mΩ) I like how these have a slight button top allowing 2s in some 26650 lights.
Molicel 21700 P42A (9.57 mΩ)
Molicel 18650 P26A 4.19v (11.44 mΩ)
Samsung 30T 3.57v (6.97 mΩ) slightly higher than Trisky’s cells from 2017. I never tried to calibrate my meter. They did match each other well though
” ” (7.08 mΩ)
Older but barely used
Efest 18350 700mAh 3.99v (32.4 mΩ)
Efest 18350 700mAh 4.02v (37.1 mΩ)
Liion Wholesales protected cells. Re-wrapped PANASONIC/SANYO NCR18650GA 3500MAH 10A 18650
3.66v (37.4 mΩ) compared to Trisky’s unprotectected GA cells, with a measurement of (24.5 mΩ). Not sure if this is a well designed protection circuit or not.
Switches from Mountain Electronics
Tested a few Bare Omten 1288 with the clamp right next to the plastic i.e. would increase to over 4 when tested on the thinner part of the tabs closer to the ends.
3.24-3.61 mΩ
Inkidu, 1KHz AC resistance or impedance figures can be accurate and useful for ideal resistors like switches, but not so for batteries in this league of ours.
For comparison purposes, cold DC internal resistance for a Shockli 18350 1150mAh is close to 60mΩ (discharge curve inferred value, check its review at lygte-info.dk).
This is not to discourage anyone doing what he/she thinks it is good though. Thanks for providing information.
This A123 15 Ah pouch has been in storage for years. Not something you handle with a watch on. Got a few more to test. I’ll be curious how they have held up through the years of storage.
