Used GP INR18650-26L batteries from OLX

I recently posted a review of LG HE2 batteries, but as I mentioned then, someone sent me a couple more batteries to test. Many thanks to him for that, since battery reviews are very useful.

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There won’t be a product link today, because for some reason I couldn’t find the listing anymore. They were being sold (quoting the person who sent them to me) as cells from used Ninebot 10s2p scooter batteries, which could be bought on OLX in August for 900–1100 UAH.
So there were 20 of these batteries in each pack, and even if the pack cost 1100 UAH, that works out to 55 UAH per cell, which is pretty good.

The same person was also selling eVE18650-26L cells, so we can assume these cells are roughly in the same class.


They look like ordinary batteries, except for the GP marking. Though as I understand it, they have nothing to do with GP, but I’m not certain :)


As you can see in the photo, these batteries have clearly been salvaged; there’s even a protective cardboard disc left on the positive terminal.
Note that the batteries have matrix codes, and the codes are different on the two cells.


Dimensions and weight—nothing new, except that the second one seems to be a little lighter.


The batteries arrived fully charged.
By the way, the person who sent them had first selected cells for a battery pack and sent me the ones with lower capacity. I actually find that more interesting, since the others had better specs.


I couldn’t find a datasheet, so I charged them at the “standard” rate of 0.5C.
Subjectively, charging took a very long time, and it’s clear that these batteries aren’t new. Yes, the charging cycle depends on the batteries’ impedance, which in turn increases with age. So a battery may have lost almost none of its capacity but still have higher impedance. You can still use it, but you’ll have to reduce the current load.


I initially planned to test them at 0.2, 0.5, 1, 2 and 3C, as well as at 10, 15 and 20 A, but the 15 A test showed that this is their limit.
In any case, the capacity matches the stated value, which is good news.


As it happened, I only took thermal images of the first cell at 10 and 15 A, but you can already see that at 15 A its temperature rose to almost 100 degrees.


The second cell performed about the same as the first; there isn’t much difference.


I measured the temperature of the second cell at 3C, 10 and 15 A, where C = 2550 mA.
This cell heated up even more, exceeding 100 degrees. That tells us the maximum continuous current for these batteries is 10 A, and it’s even better not to exceed 3C. Of course, I’m talking about these particular cells. I think they might have managed 20 A when they were new.


You can also see how “tired” the batteries are from their residual capacity after discharging at the maximum current: the first had 127 mAh left, and the second 167 mAh. At the same time, it was clear that the second cell got a little hotter.


Here’s a comparison of the results for the first and second cells. You can clearly see what I mentioned above: the relationship between delivered capacity and load current.
The second cell delivered more capacity than the first at 0.2C, but at 10 and 15 A its voltage sagged more and its delivered capacity was lower. In other words, this cell is more “tired.” That’s why it’s best to test used batteries at different currents, or at least measure their impedance. You can do this with a dedicated meter, such as the YR1035 - review



As it happened, I missed the end of the first cell’s test at 15 A, so I had to run it again. That also gave me capacity readings from two tests, and the capacity was lower on the second run. Aging or measurement error? In any case, it's best not to use them at currents above 10 A.


The impedance after delivery is shown at the top, and after testing at the bottom. You can see that it's higher for the second cell, which is what we saw in the test results.
After testing, though, the impedance values were almost the same. I think the extra run at 15 A and the resulting additional heating affected the first cell.
The seller's photo shows an impedance of 17.3 mΩ, which doesn't quite match my measurements, but the cells may have come from different batteries with different levels of wear.


There were some visible changes, too: the heat-shrink tubing on the first cell has come loose a little. This usually happens with Chinese-made wrapping.


Conclusions.
So, what do we have here? Used batteries in relatively good condition. Considering they cost about 50–55 UAH each, the results are pretty good. Also, the unique matrix code suggests these cells aren't completely anonymous. They could theoretically be GP, but I think they're from some Chinese factory, perhaps EVE.

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