In Queen Battery's lineup QB18650-2500 stands very close to QB18650-2600 not only by capacity rating but also with max supported discharge current - the 2500mAh cell supports 5C or 12.5A and the 2600mAh one - 13A. So not only testing the 2500mAh cell is interesting but also comparison between them.
The battery was bought from Queen Battery which is my reliable supplier of genuine cells 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.
This is the first test done using my battery holder v.4.0. A detailed video about it is available on my channel.
I've followed all the prescriptions of the IEC61960-2003 standard concerning battery's capacity measurement. Before each discharging cycle the battery was charged at standard charge current mentioned in its datasheet to charge end voltage. Before each discharging or charging i've held a 1-1.5hr pause. The environment temperature was 25±2°C. To be sure in results i've done each test minimum twice (usually 3-7 times).
Queen Battery QB18650 2500mAh
The heat shrink tube doesn't have much information on it. There is only the model number, nominal capacity, max discharge current and nominal voltage mentioned.
Nominal capacity: 2500mAh
Minimum capacity: 2400mAh
Nominal voltage: 3.7V
Standard charge current: 1.25A / 0.5C
Max charge current:
2.5A / 1C at 15+°C
500mA / 0.2C at 0-15°C
Charge end voltage: 4.2V
Max continuous discharge current:
1.25A / 0.5C at -20°C - -10°C
2.5A / 1C at -10°C - 10°C
12.5A / 5C at 10+°C
Discharge cut-off voltage: 2.75V
AC impedance: ≤25mΩ
Max weight: 48g
Cycle life:
Using 1.25A (0.5C) charge and discharge current with 10 minute rest time after each charge or discharge session cell's capacity should be ≥80% after 500 full cycles.
DC IR at 2500mA in fully charged condition was 23.2±1.2mΩ (measured using EB Tester Software's Resistance test feature).
Measured dimensions: 18.3mm (diameter) × 65.3mm (length).
Measured weight: 45.66g
Queen Battery QB18650 2500mAh capacity test results:
At 0.2C (0.5A) discharge the capacity is much higher than declared - 2752mah, which is normal for Queen Battery - for some reason they always declare lower capacity than the cell actually has and i like that approach.
At all the other discharge rates the capacity goes around 2500mAh, even at 12.5A, and it's very good. The curves look nice, almost linear, which is good for SOC detection by voltage.
Comparison with QB18650 2600mAh
The 2600mAh cell's max discharge current is limited by 7A at 0°C≤t<20°C and by 13A at 20°C≤t<60°C. My tests are held at 23-25°C, so 13A is the case that's why i decided to compare the 2500mAh/12.5A cell with the 2600mAh/13A one though the latter was tested using version 3.0 of my battery holder.
Comparison in numbers:
QB18650 2500 is the clear winner and looks like it's the upgraded version of 2600mAh cell.
Verdict
QB18650-2500 appears to be an excellent cell for two reasons:
1. Its actual capacity (measured at 0.2C) is higher than declared by 10%!
2. All the way up to 5C discharge the capacity remained around 2500mAh and the curves without distortion.
QB18650-2600 looks pretty much outdated and even being labeled higher it lost the battle.
Here is the video version of this review:
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