Vapcell K15 18500 1500mAh 15A Batteries

Batteries in this size aren't particularly rare, but these caught my attention because they're rated for a continuous discharge current of 15 A.
As usual: a look at the cells, tests, graphs, and conclusions.


The packaging is very basic: a plastic case, with the batteries wrapped in film inside like little candies :)


Specifications from the Vapcell page.
Model: K15
Size: 18.2*50.0mm
Typical Capacity: 1500mAh (0.2C discharge)
Min capacity: 1400mAh (0.2C discharge)
Nominal voltage: 3.60V
Max Continuous Discharge Current: 15A
Max Discharge Current: 25A
End-of-charge voltage: 4.20V
End-of-discharge Voltage: 2.5V
Weight: 37g ( Appr)
Internal resistance: 20mΩ ( Appr) （AC 1kHz）
Standard Charge: 500mA,CCCV 100mA cut-off
Quick Charge Current: 2000mA

As you can see, these batteries don't have a particularly high capacity. For example, I've come across Panasonic NCR18500A cells rated at 2000mAh and Vapcell INR18500 cells rated at 2200mAh in this size. The key difference here is the maximum continuous discharge current, which is 15A.

The red heat-shrink sleeve has the capacity in Ah and Wh printed on it, along with the maximum current. The positive terminal is flat.


Dimensions and weight.


The batteries arrived at roughly 70–75% charge. In the initial “conditioning” cycle, they delivered 1616 and 1598mAh, somewhat more than the rated 1500mAh.


Two charging modes are specified: standard at 500mA and fast at 2A.
In standard mode, charging took about 3 hours and 15 minutes. The CV phase was relatively short, but that's due to the low charging current of just 0.3C.


At 2A, charging took just under an hour, which also seems reasonable to me.


Capacity was measured in eight modes: 0.2, 0.5, 1, 2, 3, and 5C, plus 10 and 15A, where C = 1500mAh.
Up to 3C, delivered capacity decreases as the current increases, but then it starts to rise. The battery heating up and the characteristics of its chemistry are factors here.
I'd also note the sharp voltage drop at the end of discharge, similar to what we saw in the review of the 14650 batteries.
In any case, the battery delivered its rated capacity in every discharge mode.


Temperature rise at discharge currents of 7.5, 10, and 15A. In my opinion, the heating at 15A is a little excessive, though of course it's all relative.


As expected, the second sample performed a little worse. That was already clear after the “conditioning” cycle.
Still, even in the worst case, capacity was 1442mAh. As with the first sample, delivered capacity also increased at currents of 7.5A and above.


The temperature is a little lower here.


I found a test graph from Vapcell. The results, including the increase in capacity as the battery heats up noticeably, match my own.


The usual consistency test—and unfortunately, the difference is clearly visible here. The graph shows results at 0.2C, 1C, and 10 and 15A.
I wouldn't call it bad, but I would have liked to see a little better.


Battery impedance and voltage upon arrival, after “conditioning,” and after the tests. This partly explains why the second sample ran a little cooler.


Conclusions.
In my opinion, although the batteries delivered their rated specs, they're still in the “mid-range” quality class.
Vapcell often puts branded cells in its own heat-shrink sleeves, but for less common sizes it uses less well-known options. I think these are better than no-name cells, but not as good as name-brand ones. If you don't push them to their limits, they'll work just fine.

That's all for now. I hope you found this useful.