Noname 18650 batteries with a capacity of 2600 mAh

Some batteries I’d never seen before landed in my hands—or, to be more precise, they first landed with a friend of mine. He wanted to find out more about them, so he asked me to test them in different modes and give him my opinion.

There’s no link to a store, and I can already anticipate the obvious question: what’s the point of this review, then? The answer is simple: statistics, plus someone might come across these batteries by chance.

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I’ll say right away that the batteries are brand new. A search online turned up no information about them; the only thing I found was a search query for batteries with the same code.

Anyway, I got four specimens to test.


They look like ordinary, common 18650 batteries. The markings are a mystery to me, but one thing stands out: each battery has a clearly marked serial number, and all four have different numbers. That suggests they’re not some no-name basement product, but quite possibly from a proper manufacturer.
The positive and negative terminals are flat, and the positive terminal has four spokes, but I won’t draw any comparisons with batteries from other brands.


As for size and weight, there’s nothing unusual here—or so I’d say, except there is one oddity after all: two of the four specimens differed in weight by 0.75 g. That seems like a lot to me, so I chose the two batteries with the biggest weight difference for testing.


The conditioning cycle yielded about 2700 mAh. The first battery, which weighs more, also delivered more capacity.


Since there’s no datasheet, the charging current was a bit of a guess. In the end, all charging cycles were run at the “universal” rate of 0.5C, or 1.3 A based on the stated capacity of 2600 mAh.

There’s a difference in charging time and, accordingly, in the duration of the CV phase. It’s not huge, but it’s there.



Discharge tests were run at load currents of 0.2C, 0.5C, 1C, 2C, 3C, and 10 A. I chose the upper limit based on the results of the previous tests.

The first specimen delivered 2652 mAh, which is excellent for a stated capacity of 2600 mAh.


Temperatures at discharge rates of 2C, 3C, and 10 A. In my view, 3C is its limit, but to extend its service life, it’s better not to use a current above 2C.


The second specimen did a little worse, but 2575 mAh is still fine for a stated capacity of 2600 mAh—a difference of about 1%.


The temperature results are noticeably better, though: 66 degrees versus 75 for the first specimen. Unfortunately, for reasons beyond my control, the room temperature didn’t always match the conditions required for the tests. You can see this in the middle screenshot, where the minimum temperature on the tabletop is about 14 degrees. And yes, this is in an apartment—“thanks, liberators.”


The test comparing performance at 0.2C, 1C, 3C, and 10 A shows that the first specimen, which weighs slightly more, has higher capacity in every mode. But some of you may have noticed that at 3C and 10 A, the second specimen has a higher voltage during discharge.


The explanation for the voltage difference during high-current discharge is pretty simple: the second battery has noticeably lower impedance, so it performs better at high discharge currents. This also explains the temperature difference: the first specimen heated up more for that reason.
Results before testing are on the left, and after testing on the right. I actually ran more tests, and interestingly, I had to redo the high-load tests on the second specimen several times.
You can also see that before testing, the first specimen had noticeably lower impedance than it did afterward.


Mostly out of curiosity, I also tested the second pair at 0.2C, 0.5C, and 1C. Below are the results at 0.2C and 1C. Their results mostly fall somewhere between those of the first pair, although at 0.2C the fourth specimen delivered as much as the first one.


Above, I mentioned that I didn’t maintain the required temperature during the tests. In fact, during the first tests, the room temperature was about 19 degrees, which is acceptable, all things considered. Nevertheless, I measured the difference in capacity delivered by the second cell at 19 and 23–24 degrees. The blue graph is for the lower temperature, the red one for the higher temperature; discharge currents are 0.2, 0.5, and 1C.


But back to the second pair: measuring their impedance showed that it was almost identical to that of the second test cell. So, for some reason, the first test cell is the one with the unusually high impedance.


Conclusions.
These are pretty good batteries for discharge currents up to 2C. I’d say the same about how consistent their characteristics are, but the first test cell rather spoiled the picture. In any case, I liked these batteries. If you come across them, they should be fine for undemanding loads, especially since, as I understand it, they’ll probably be inexpensive.

That’s all for today. Hang in there, friends. Kharkiv Oblast has been liberated from the “liberators”; I hope the rest will be liberated too.