Liitokala Lii-51S battery, 26650, 20 A, 5100 mAh

This is the second battery from Liitokala. It’s the same size, but has a slightly higher capacity and a claimed continuous current of 20 A. You could even say it looks like a pretty good capacity-to-size ratio.
Inspection, tests, graphs, conclusions.

As a reminder, to stay up to date with new posts on the blog, I recommend following me on Instagram. I’ll post notifications about all new posts there, and might also write about something interesting from time to time: link to my account

As I mentioned earlier, one of the readers sent me several batteries, for which I’m grateful. In return, as usual, I’m putting them through their paces. Today we’ll look at the second of the four.

The packaging is the same as the previous one, but this time it isn’t dented :)
Interestingly, the batteries were ordered from two different stores, but arrived at the same time.


The specifications table is laid out much more neatly this time.
Two key points: the charging current is only 1–2 A, and the minimum voltage is 2.7 V, not 2.5 V as usual.


You could call this an ordinary battery: flat positive terminal, markings showing capacity in Ah and Wh, and maximum continuous current. But the manufacturer used not only unusual yellow heat-shrink tubing, but also gave it some kind of pattern. All in all, it’s a battery that stands out visually.


Dimensions and weight—nothing unusual.


The first charge cycle took 1700 mAh, which means it was initially charged to more than 65%.
During the “conditioning” run, I got 5641 mAh, which is quite respectable, especially considering the claimed 5100 mAh.


The specifications say the charging current is 1–2 A. To test charging speed, I used 1.5 A as a middle value; that current is also about 0.3C.
Charging took 4 hours and 13 minutes, which is quite a while. I also tried charging at 0.5C; that took 2 hours and 50 minutes, roughly matching the previous Lii-50A.


But let’s move on to the tests. I used almost the same set of discharge rates: 0.2C, 0.5C, 1C, and currents of 10, 15, and 20 A. At 10 A and above, I used a load set in 5 A increments rather than in multiples of the capacity, for convenience.
A continuous discharge current of 20 A is within spec, as the marking on the battery itself confirms. In every test mode, the battery delivered noticeably more than the claimed 5100 mAh. Interestingly, capacity was lower at 0.5C and 1C than in all the other tests. At 0.2C it was higher because of the low current; at 10–20 A it increased because the battery warmed up.


Temperature readings at 10, 15, and 20 A.
The battery runs cooler than the Lii-50A, but given its claimed continuous current of 20 A, I expected lower temperatures. At the maximum current, it was only 6 degrees cooler.


The residual capacity test gave 154 mAh, twice as much as the Lii-50A. That’s also strange, since the Lii-51S is clearly positioned as a higher-current battery.


The impedance remained almost unchanged in its initial state, after “conditioning,” and after the tests. It was slightly lower than the Lii-50A’s, which is consistent with the reviewed battery running a little cooler.


Conclusions.
This is a somewhat odd battery, primarily because of how it behaves at different discharge rates.
Sure, getting 5400 mAh at 0.2C is great and makes a good impression, but at higher discharge currents I expected a substantial difference in temperature and behavior compared with the Lii-50A. In practice, the difference turned out to be quite small, even though the Lii-50A is rated for just 5 A, while this one is rated for 20 A.

I’m no chemist, but my impression is that this battery is slightly “overclocked” and is actually more of a high-capacity cell than one designed for high load currents. The low recommended charging current and the 2.7 V end-of-discharge voltage also point to that.
Based on the test results, I wouldn’t recommend exceeding a continuous discharge current of 10 A, even though it can easily deliver 15–20 A.

That’s the second one done. I hope this was useful, and as always, I’m looking forward to your questions and comments.