18650 3400 mAh batteries

Today I have a very brief review—or rather, a quick photo showcase—of my latest batch of lithium batteries.
Inspection, tests, conclusions.


These batteries are listed as “genuine” on the product page, but since I can neither prove nor disprove that with complete certainty, I’ll assume they’re copies.
But I think the tests will tell us more.


I ordered four lots of six: 12 went to a friend and 12 came to me. As usual, they were packed neatly in a cardboard box, with the batteries themselves in soft bags of six.


They look neat, though the black part of the heat-shrink tubing is a bit scuffed. I don’t remember the genuine ones looking like that.


The markings are clear, but there’s a noticeable seam running the full length of the heat-shrink tubing. Again, it’s probably not the original wrap, but I can’t say that for sure. The date is marked 8103, which would mean January 3, 2018 for a genuine cell. Some time ago I showed similar batteries marked January 30, 2017, so even if the wrap isn’t original, they do update the date after all :)

Most of the batteries weighed about the same, but one was lighter and a pair noticeably heavier. For the tests below, I used that “mismatched” pair plus two regular ones.
Length and diameter are all within spec.


The positive terminal is flat and partly covered by the insulator, so it may not make contact in some devices. There’s no protection circuit, so it’s best not to use these in devices without over-discharge protection.


First, a test with a regular charger. Although it measures capacity correctly—that is, during discharge—I still use it only for a rough estimate.
The batteries were at about 50% charge and showed quite a wide spread during discharge. The lightest battery is first, the heaviest second, and the third and fourth were picked from somewhere in the middle.


For the remaining tests, we’ll use a more accurate measuring instrument: an electronic load that also works as a battery tester.


I decided to test the first and second batteries. To start, let’s measure their actual capacity; the product page claimed 3400 mAh.
Capacity is usually measured at a current of 0.2C. In this case, I set it to 3400/5 = 680 mA.

As usual, capacity was measured across three voltage ranges: from a full charge down to 3 V, then from 3 to 2.8 V, and finally from 2.8 to 2.5 V. I added the results together.

Battery No. 1.
Total capacity: 3125+129+90=3344 mAh. Close, but a little short. Although at a 680 mA charge current, I should have stopped charging at 68 mA, but my minimum was 100 mA, so it may have been slightly undercharged.
Capacity in Wh was 12.077


Battery No. 2.
Total capacity: 3130+144+90=3364 mAh, almost there. It came to 12.131 Wh.


Next, I decided to test the same batteries at 1C and 2C (their maximum rate).

Battery No. 1, discharge current 3400 mA (1C).
Capacity was 2897+191+156=3244 mAh, which is quite good, although new branded cells delivered a little more. The energy came to 11.094 Wh.


Battery No. 2, current 6.8 A (2C).
Capacity was 2486+416+319=3221 mAh, or 10.386 Wh.


At the same time, near the end of discharge at 1C and 2C, I measured the batteries’ temperatures. They reached 43.5 and 69.7 degrees, respectively. The genuine ones ran a little cooler, by just a few degrees, but their discharge currents were 3200 and 6400 mA.


After all the experiments, I measured the internal resistance. Of course, I should have measured the first pair before testing too, but I’m not going to repeat the experiments—it takes far too long.
The average is about 33–34 mΩ. The batteries I tested in the summer (also Litokala) were around 30–32 mΩ, and I think that difference is negligible.


In short, these batteries are a great fit for devices that don’t need high currents but do need maximum capacity. Suitable devices include power banks, especially since capacity variation isn’t critical there. They could also be used in laptop battery packs, but it’s best to sort them by capacity first.

That’s all for now. I hope you found the review useful.