Vapcell N40 batteries: 4000 mAh in an 18650 size—who knew that was possible?

A small package arrived recently with four batteries inside. To be honest, I wasn't expecting it, but the batteries inside were an even bigger surprise.

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Just a few days ago, I would have been pretty skeptical about a 4000 mAh capacity in an 18650 cell. Six months ago, I would have said it was impossible, but these batteries managed to surprise me.
Actually, there's nothing unusual about this at all. You might ask, then why aren't batteries with this capacity available for sale? Because capacity, discharge current, cycle life, and safety are four factors that have to be balanced to find a reasonable compromise. In other words, increasing one means reducing the other three—assuming the volume stays the same, of course.

When I got these batteries, I first looked at the capacity: 4000 mAh. Then I checked the maximum discharge current: just 10 A. I thought they must be something really budget-oriented, like the Samsung INR21700-33J, but I'd overlooked one thing: these were 18650s, not 21700s. That made it clear they were something out of the ordinary.

Sure, it's easy to find 18650s with this capacity for sale, and they're really cheap too: link. But I have my doubts about those.

Anyway, let's get straight to the review.
There are four batteries, packed in branded cases, and each one has a protective film on it.


Specifications from the Vapcell website.
Model: N40
Size: 18.3±0.2*65.0±0.3mm
Typical Capacity: 4000mAh (0.2C discharge)
Min capacity: 3850mAh (0.2C discharge)
Nominal voltage: 3.60V
Max Continuous Discharge Current: 10A
Max Discharge Current: 12.5A （with 60 °C temperature cut）
End-of-charge voltage: 4.20V
End-of-discharge Voltage: 2.50V
Weight: 48g ( Appr)
Internal resistance: 17mΩ ( Appr) （AC 1kHz）
Standard Charge: 1500mA,CCCV 100mA cut-off
Quick Charge Current: 2500mA
Cycle Life : 1C discharge，70% capacity，>1000 times

The manufacturer of the cells themselves is unknown. There's no marking on the battery casing; the heat-shrink sleeve just lists a few basic specifications.


Dimensions and weight. I picked this pair completely at random; the other pair is very similar.


As always, I started with a “normalization” cycle, and it was already clear at this stage that the capacity really is around 4000 mAh.


Two charging modes are specified: standard at 1.5 A and fast at 2.5 A.
The results at 1.5 A are pretty good, and considering the capacity, they're actually very good.


At 2.5 A, the graph does run on for quite a while during the CV phase, but that's perfectly normal for high-capacity cells. Overall, I'd recommend charging at 1.5–2 A, or even less.


The Vapcell website has discharge graphs at 1, 2, 5, 10, 12.5, and 15 A. The maximum continuous current is specified as 10 A, but they have plenty of batteries, so they can afford to push them hard :)


I tested at 0.2, 0.5, 1, 1.5, 2, and 2.5C, or 0.8, 2, 4, 6, 8, and 10 A, respectively.
Well, the capacity turned out to be even higher than specified. It's summer now, though, and the room temperature is a little higher than the standard measurement temperature, so I'd say the actual capacity is simply around 4000 mAh.
I'd also point out that the graph shows no obvious voltage sag at high currents, as you'd see if a battery were overloaded. That's a good sign.


The temperature was also reassuring. The specified cutoff is 60 degrees; below are the results at 6, 8, and 10 A.
Yes, at 10 A the temperature went a little over 60 degrees, but tests are usually run at 23 degrees, not 28. At 23 degrees, I would have measured 61 degrees. Overall, the temperature performance is excellent.


The second sample is almost a carbon copy.



I expanded the test of how closely the cells match by adding the results for the second pair as well. There were too many results to fit on one chart, so I split them across two charts.
First, at 0.2C and 1C, the spread is around 1%—you could say it's within the measurement error.


At 2C and 2.5C, the spread is still just 1%. Excellent, in my opinion.


The cells' impedance as received and after testing. The spec says no more than 17 mΩ; in reality, it's probably around 15 mΩ, which is also an excellent result. In this respect, they're more like versatile, medium-current cells than high-capacity ones.


Vapcell's website also has comparison charts where they tested these cells at 10 A against the Sanyo GA first, and then against the popular VTC6. The first comparison makes sense to me: the cells are in roughly the same class. But the second one seemed odd.
Still, looking at the second chart, you can see that the voltage sag at 10 A is comparable to the VTC6, which is rated for a continuous discharge current of 20 A.


I compared them with other cells, including the Sanyo NCR18650GA:
1. Vapcell N40
2. Vapcell N36
3. Samsung INR18650-35E
4. LG INR18650-MJ1
5. LG INR18650-M36
6. Murata VC7
7. Panasonic NCR18650G
8. Sanyo NCR18650GA
9. Vapcell F34
10. Vapcell F35

First, at 0.2C—and there was no contest at all. The Vapcell N40 simply blew all the competition away.


And at around 2C, or close to it.
Its capacity lead was already expected, but I was more interested in the voltage during discharge. The charts show that it's roughly on par with the LG INR18650-M36 and Vapcell F35, while the other competitors clearly lag behind.


Conclusion.
Honestly, I really liked these cells. Their capacity isn't just genuine and high; all four samples are also within 1% of each other, which is an excellent result. Their current delivery is excellent too, though I still wouldn't recommend using them at high currents.
In my opinion, cells like these are for applications where you need maximum capacity in a compact, standard form factor and won't be drawing high discharge currents—for example, power banks and medium-power flashlights.

The question of cycle life remains open. I suspect they probably won't last as many cycles as ordinary cells—high capacity doesn't come for free. On the other hand, in power banks and flashlights, the battery is more likely to die of old age than from being cycled, at least for most users.

The downside is the price: they're expensive. I did find them on Alibaba for about half the price, though. If you're interested, try buying them there—but keep in mind that shipping will cost extra, and they probably won't sell just a couple of cells.

That's all from me for today. What do you think of cells like these?