18500 cells share the same 18mm diameter with 18650 cells but are 15mm shorter - their length is 50mm vs 65mm in case of 18650.
QB18500 is a 1600mAh low-drain cell which supports continuous discharge at 1.6A max.
The battery was bought from my reliable supplier (Queen Battery) and tested with ZKETECH EBC-A20 and a self-made battery holder. It's a PC-connected battery tester supporting 4-wire measuring and discharging at up to 20A.
I've used version 3.0 of my battery holder based on 0.5mm thick pure copper terminals
I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle each battery was charged at standard charge current mentioned in its datasheet to charge end voltage. Before each discharging or charging i've held a 1-1.5hrs pause. The environment temperature was 23.0-24.5°C. To be sure in results i've done each test minimum twice (usually 3-4 times).
Queen Battery QB18500 1600mAh
The cell's heat shrink tube shows brief specs but has no data about production date or batch number.
The main specifications from Queen Battery QB18500's datasheet:
Nominal capacity: 1600mAh
Nominal voltage: 3.7V
Standard charge current: 320mA (0.2C)
Max charge current: 800mA (0.5C)
Charge end voltage: 4.20V
Max continuous discharge current: 1.6A (1C)
Discharge cut-off voltage: 2.75V
AC impedance at 1KHz: ≤80mΩ
Measured initial DC IR at 1.6A in fully charged condition was 51±4mΩ
Measured weight of the tested cell was 33.7g
Queen Battery QB18500 1600mAh capacity test results:
At 0.2C or 0.32A QB18500's capacity was noticeably higher than the 1600mAh declared. Even at it's maximum allowed 1.6A it remained above 1600mAh which is a pretty good surprise. All three curves look beautiful, without any sags or peaks.
Though QB18500's results are excellent, there is a serious disadvantage which can't be ignored - the standard charge current. It's only 0.2C which means that you gonna charge it for long 5 hours. Of course nobody bans you from charging it at up to 0.5C but even that maximum allowed 0.5C looks too low for nowadays. For some people 2.75V discharge cut-off would also be a disadvantage but i think the most packs where 18500s are used the BMS cuts off at 3.0V.
Here is the video version of this review including size comparison:
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