Discharge four 18350 at 0.5a. Got 888, 892, 893 and 909mah.
Also did a ceiling bounce test with a cheap UNI-T luxmeter and Emisar D4 XPL. Pkcell got 240 and Keeppower got 284.
I got four Pkcell for $10aud. So they are a bargain. The same seller on ebay even sells 12 for $23aud.
First test on one cell, charged to 4.2V@300mA (4.19V after 5 minutes), shows 831mAh at 500mA discharge current. Cut off voltage 3.0V (as specified in the data sheet).
Nice numbers for the moment.
2nd cell shows the same numbers and as I am pretty shure all the other cells will do the same, I will not continue testing.
snakebite did the test @1A. I´m sure my cells would just confirm his numbers.
It would be interesting to see some discharge diagrams in near future.
I got a few of the PKCell ICR18350, IMR18350 and ICR14500 batteries from AliExpress (fortunate to have ordered them last month, when they had free shipping via Turkey Post; just checked right now, and they’re only offering expedited shipping options US$40+ Fedex — seems like Turkey Post is not shipping batteries anymore).
What current should I charge them with? Standard charge current? Rapid charge current? There doesn’t seem to be a spec sheet. The seller’s page in AliExpress only indicates max continuous discharge current (2C for the ICR type, and 10C for the IMR type). How about discharge current (when testing discharge capacity), is 1C too high or still OK (for the ICR types).
based on the seller item page description:
PKCell ICR14500 750mAh max continuous discharge current = 2C = 1.5A, cut-off voltage = 3.00v
PKCell ICR18350 900mAh max continuous discharge current = 2C = 1.8A, cut-off voltage = 3.00v
PKCell IMR18350 700mAh max continuous discharge current = 10C = 7A, cut-off voltage = 2.75v
So far I did discharging of the above batteries at 0.25A discharge current and also getting around 800-900mAh (the ICR18350 900mAh and IMR18350 700mAh seem to have similar capacity?)
keep in mind my ir testing was impedance at 1khz.
thats the most common method in most datasheets.
and testing at 3.5v is testing a discharged cell.
ir goes up as cell is discharged.
quote.
Okay, i calculated the internal resistance of one of my PKcells, i think i did it right.
The Voltage of the cell was 3.5 V without load.
I put on a load with a 1.35 Ω resistor, giving a Voltage of 3.2 Volts over the resistor, I=U:R so the current was 3.2 V : 1.35 Ω = 2.37 A
Now i can calculate the total resistance. R=U:I so R = 3.5 V : 2.37 A = 1.47 Ω
Subtract the 1.35 Ω from that, so 1.47 – 1.35 = 0.12 Ohm or 120mΩ
When I (current) is 2.3 A (M3 turbo mode) P (power) wasted as heat in the battery is P=I²×R —> I² = 5.29 —> 5.29 × 0.12 Ω = 0.63 Watt heating up the battery, which is nothing to worry about i.m.o.
Anyway, with Ri=120mΩ this is not a high drain cell at all…
PS: The numbers could be off by 15% (or something) due to my equipment.
3.5 Volts is not discharged, 3.0 Volts is discharged.
But thanks for the point you make, i will test it again with a fully charged cell and one ‘half full’ at 3.7 Volts.
I didn’t know it depends on the charge.
I wouldn’t know why i should test at 1kHz, and i’m not sure of you mean a PWM-ed load with 50% duty cycle at 1 kHz or what.
I was testing with a similar load as the turbo mode of a OTR M3 flashlight, which is a constant load of 2.3 Amperes.