Vapcell K31 18650 3150mAh 18A/35A batteries

Another set of 18650 batteries. They don't really stand out among the dozens I've tested, except for their slightly higher rated capacity and lower current rating than the well-known VTC6, HG2, and 30Q, which I'll compare them with at the end of the review.


Although these batteries have a higher rated capacity than the competitors mentioned above, their current rating is a little lower. And overall, they're kind of boring—there's no special feature that makes them stand out. But let's take a closer look in the review.

As usual, they come in a branded case.



Specifications from the Vapcell page
Model: K31
Size: 18.4*65.2mm
Typical Capacity: 3150mAh (0.2C discharge)
Min capacity: 3050mAh (0.2C discharge)
Nominal voltage: 3.60V
Max Continuous Discharge Current: 18A
Max Discharge Current: 35A
End-of-charge voltage: 4.20V
End-of-discharge Voltage: 2.5V
Weight: 48g ( Appr)
Internal resistance: 16mΩ ( Appr) （AC 1kHz）
Standard Charge: 1500mA,CCCV 100mA cut-off
Quick Charge Current: 4000mA

The exterior is classic, as usual. The only difference is the gold color; I haven't seen that in a while.


The dimensions and weight are all familiar, too.


They arrived at about 60% charge. In the “normalization” cycle, they measured 3111 and 3198mAh, so their actual capacity seems close to the rated value.


Like many other batteries, these support two main charging modes: 1.5A and 4A, for standard and fast charging, respectively.
In standard mode, charging takes 2 hours and 20 minutes, which is perfectly reasonable.


At 4A, though, charging seemed to take a little too long in the CV phase. Total charging time was 1 hour and 10 minutes.


Vapcell tested these batteries at 2, 10, 15, 18, and 20A, as shown in the graph captured using an EBC-A40L.


I tested them at more standard rates: 0.2, 0.5, 1, and 2C, as well as 10, 15, and 18A.
The first sample measured slightly below the stated capacity at 3101mAh, though it was still above the specified minimum of 3050mAh.


Temperatures at 10, 15, and 18A were quite acceptable.


The second sample did better, although that was already apparent in the preliminary run: 3174mAh, or 11.63Wh.


However, its temperature at the maximum test rate was a couple of degrees higher than the first sample's.


The comparison results show a noticeable spread in performance. The comparison was made at 0.2C, 1C, 10A, and 18A.


The impedance results aren't entirely consistent either: it was initially below 15mΩ, but after all the tests it had risen above 16mΩ.
Below are the results as received, after “normalization,” and at the end.


And, of course, a comparison. Vapcell has a graph comparing these batteries with the well-known HG2 and VTC6 at 20A.


I'll compare them with those same batteries and add the equally well-known 30Q. The comparison covers two modes: 1C and 20A (18A for the battery under review).

Yes, the graphs show the batteries under review outperforming the competition, but I wouldn't say by much. The difference shows up at high current, since at 1C they're roughly on par with the others.


Conclusion.
Pretty much as I expected: these are ordinary batteries, with slightly higher capacity and a slightly lower maximum current. They'd be perfectly fine if not for the noticeable variation between samples and the increase in resistance. How long will they last? I have no idea. I'd probably choose something from a well-known brand.
And given all of the above, I think the price is way too high. Not a good option.

That's all for today. As usual, I'd be glad to hear your comments.