INR21700M52V: batteries even Google hadn't heard of

As I wrote in my previous review, almost all the batteries I received have some feature that caught my interest. Here’s the second one I’m testing, and what caught my interest wasn’t so much its specs as the fact that there’s no information about it anywhere.

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Like the previous batteries, these also come packed in cardboard boxes.


When I received the batteries, I naturally tried to find information about them—ideally a datasheet, though often even a brief list of specs is enough. But this time, the system failed: when I entered the model number INR21700M52V into Google, I got nothing in return. Absolutely nothing. Zero.
While preparing this review today, I tried again, and Google finally managed to come up with some results. That’s why the review is called “even Google hadn’t heard of them,” although I originally wanted to call it “even Google doesn’t know about them.” And after this review is published, it’ll definitely know about these batteries.


I followed the link and landed on a website that publishes information about battery certifications. It listed the model number INR21700M52V, along with a document number.


I clicked the link to the list and found the corresponding number. It says the battery belongs to LG. Well, that’s something, at least—the model number did look like an LG cell model number in the first place.


I followed the link and landed on an almost identical page, but this time there were no batteries with this model number listed. It feels like these batteries are so new that the safety certification application has been submitted, but they haven’t been certified yet.
Honestly, this is the first time I’ve tested batteries that there’s no information about anywhere yet.


Well, let’s give them a try. Judging by the model number, they should have a capacity of around 5200 mAh. But knowing that LG (like Samsung) usually rounds up, the actual capacity is more likely to be around 5100 mAh. The maximum discharge current for cells like these is usually around 3C, or 15 A, so that's the current I'll use.

They look unusual, packaged in clear heat-shrink tubing. I've seen this at the Nkon store, so I think this is already the "local" packaging for industrial cells, which are originally manufactured and supplied without any wrapping at all.


My theory is also supported by the fact that the matrix code is printed directly on the cell, while the text on the right is laser-engraved on the casing.
By the way, the matrix code here is the kind LG cells are supposed to have, and the codes are different, too.


As for the dimensions and weight, the cells are just a little longer than usual. I noticed this mostly during testing: they had to be pushed into the holder, catching on the measurement contact.


They were initially charged to about 25%. The normalization cycle measured a capacity of 5100 mAh.


As always, I checked the charging time in two modes, at 0.5C and around 1C. In fact, 1C is 5.2 A, but I couldn't be bothered to hook up a high-power charger, and my main charger only goes up to 5 A.
At a charging current of 0.5C, charging took 2.5 hours, which seems like a lot to me.


Increasing the charging current to 1C did speed things up, of course, but the CV phase dragged on quite a bit. I suspect they should be charged at closer to 0.3–0.35C, since these are high-capacity cells.


I measured capacity in five modes: 0.2C, 0.5C, 1C, 10 A, and 15 A. For the last two, I didn't bother tying the results to a capacity rating and rounded them to whole numbers.
As I expected, capacity came out to 5100 mAh—less than the "Rated capacity," but more than I've ever seen from 21700 cells.
But I have to say, even at 15 A, the batteries performed quite respectably.


I measured the temperature at 10 A and 15 A, and the results were excellent here too: the first cell didn't even heat up past 80 degrees.
By the way, the marker made from black matte electrical tape clearly helped here, because the thermal camera started under-reading on the shiny casing under the clear heat-shrink tubing.


The second sample produced almost identical results.


The temperature here was a couple of degrees higher, but I think that's more likely due to the measurement method not being perfect.


Measuring the remaining charge after the 15 A test gave an excellent result: 88 and 91 mAh.


The heat-shrink tubing stayed in place, though the temperatures weren't particularly high here.


The cells match each other very well. Here are the results at 0.2C, 1C, and 15 A.


The impedance measurement surprised me almost as much as the lack of information about these cells. The thing is, there's a big difference between the results right after receiving them and after "normalization"—the final results.
I do suspect some kind of instrument glitch, but it has never let me down before, even though I've tested a lot of batteries.

All in all, a very curious result...


For comparison, I picked six cell types with similar specs. I also have LG 50LT and BAK 5000 mAh cells at home, but I never seem to have time to run proper tests on them.
So, here we go:
1. The cells under review (red)
2. Samsung INR21700-50E (orange) - review
3. LG INR21700-M50T (yellow) - review
4. Samsung INR21700-50G (green) - review
5. Vapcell 21700 T50 (light blue) - review
6. Vapcell G50 21700 (blue) - review
7. Vapcell P50 21700 (purple) - review

At 0.2C, the cells under review comfortably outperform all the competition.


At 1C, the picture barely changes. The only cells that come close are the Vapcell 21700 T50.


At 15 A, the difference narrowed, but the cells under review still came out on top. The only ones that can keep up in this test are, once again, the Vapcell 21700 T50. One thing to note: although the Vapcell 21700 T50 cells have a lower capacity, their rated continuous discharge current is 20 A, so they manage to pull through the last test thanks to that.


I was about to wrap up the review here, but at the last moment I remembered that I already had some 21700 batteries with a capacity of 5200 mAh. How did I forget about those...?
They were Vapcell F52 21700 5200mAh batteries; the review is here. So I’ll compare these with them too, but on a separate graph—I can’t be bothered to redo the previous ones.

While putting the graph together, I thought I’d get the same results, but it turned out that the INR21700M52V cells under review perform better, which is certainly a nice surprise.


In principle, INR21700M52V cells could be used in Vapcell M52 21700 5200MAH 15A batteries Vapcell M52 21700 5200MAH 15A; the specs match.


And the published test results look similar too.


A few hours have passed since publication, and now everything’s in order :)



So, what can I say in conclusion?
I liked these batteries. In this case, I’m practically certain they really are genuine LG INR21700M52V cells, not some unknown cells like the ones in my previous review.
No, I wouldn’t call them high-drain: 15 A is genuinely their maximum, and it’s better not to run them continuously at currents above 10 A. I’d also limit the charging current to around 0.3C. But their specs and consistency are excellent, so I can confidently recommend buying them.

I’ll link to the Vapcell M52, since I think these are the same batteries as the ones in this review, just with a different wrap.

That’s all from me for today—but only for today. I think there’s plenty more interesting stuff coming your way :)