CATL LiNiCoMnO2 3.7 V 50 Ah Batteries

Continuing the discussion of multi-cell batteries, today I'm reviewing another model in a different form factor and with noticeably higher capacity.


I've reviewed batteries in a similar form factor before, but all of those were 3.2 V LiFePO4 cells. Today's review is about 3.6 V cells with LiNiCoMnO2 chemistry.

There are no major visual differences from the others: the same rectangular "books" wrapped in blue film.


The store page has a table listing the specifications, and those are the figures I used as a reference when running the tests.


But while writing this review, I came across what appear to be the same cells, but with slightly different claimed specifications.


Everything looks very neat. The contacts are aluminum with nickel strips welded on, and the welds are good. There's a matrix code and a serial number in "digital" form. The negative contact has a protective plastic insert, since the positive contact on these batteries is connected to the case. There's no complete electrical connection, but the case is definitely at a potential.

While looking for more information, I came across three terminal configurations: the one shown in the photo, one with a larger nickel strip on the negative contact, and one with a nickel strip plus a threaded hole.


1–3. The battery measures 148 × 92 (97) × 26 mm.
4. One of the samples had some "scratches"; the film is slightly damaged.
5, 6. The batteries weigh just under the claimed 850 g.


Along with the electrical specifications, I also found a drawing online with all the dimensions. It differs very little from my measurements.


Both batteries arrived completely discharged. I assume the store tested them too, but didn't recharge them before shipping them to me.
In any case, as usual, I ran a "conditioning" cycle consisting of charging, discharging, and charging again, and the capacity was already a pleasant surprise at this stage.


The description listed just one charging current—25 A—and also gave it as the maximum.
For more consistent test results, I charged at 20 A to 4.2 V, with cutoff at 0.5 A. I also ran a test at 25 A (0.5C).

I'd say that's pretty good, especially considering that these batteries are actually high-capacity cells, which typically have a charging current in the 0.3–0.5C range.


Unfortunately, I can only plot graphs for currents up to 40 A, so I tested at 0.2C, 0.5C, and 40 A. I ran the 40 A test twice, but the results were practically identical.
What's more, the battery delivered practically the same capacity at every current from 10 to 40 A, and it was over 52 Ah in every case.


The second sample did even slightly better. The average discharge voltage for both batteries is 3.67 V, midway between the figures on the store page (3.70) and those I found online (3.65).


For comparison, here's a graph of the first sample (blue) and the second (red) at 10 and 40 A.
Yes, there's a small difference in the results, but since both samples have a capacity above the claimed figure, we can overlook it.


But as always, I wanted more, so I put together another "test rig" consisting of three electronic loads rated for 20, 30, and 40 A, for a total of 90 A.

The connections are, of course, very awkward, especially when you have a lot of wires to hook up. That's exactly why I didn't test the battery in the freezer—I didn't want to accidentally short a battery with 200 Wh of stored energy.



The result was 23.27 + 11.48 + 17.243 = 51.993 Ah.


Case temperature at 40 and 90 A.


The discharge graph recorded by the EBC-A40L tester. The capacity doesn't match the total, of course, but it's perfectly fine for seeing the voltage curve.


The second sample delivered 23.66 + 11.68 + 17.608 = 52.948 Ah in the same test.


Temperature at 40 and 90 A.


And the discharge curve. At the very beginning, the voltage sagged. It seemed that the alligator clips were getting hotter than the first time. I rubbed them in a little, and the measurement contact shifted (it is connected separately).


Both batteries were checked for self-discharge. After a full charge, they were left for about three days, then charged again while measuring the capacity delivered. Of course, this isn't a pure self-discharge test, but it does give us some idea.
Strangely, the second unit behaved quite differently: the charging current stayed around 1 A for a long time, and in the end it took twice as much energy to restore it.


Also, after all the tests and a subsequent full charge, the batteries seemed to have gotten thicker. Unfortunately, I only have one photo from the initial measurements, so I can't be completely sure, but in my opinion their thickness increased by about 1–2 mm.
If you squeeze the case a little (gently, of course), you can hear a slight hissing sound, so I probably wouldn't clamp them tightly against each other when assembling a battery pack.


Since I didn't run many tests and didn't push them to their limits, I measured the impedance only when they arrived and after the "normalization" cycle.


Conclusions.
Overall, I can say pretty much the same thing here as in my conclusions to the review of 26800-size batteries. These are interesting batteries, with a very respectable capacity for their size. They are clearly new, not used.
I liked that I got almost 200 Wh of energy in this size; a 3S battery pack would therefore deliver around 550–570 Wh.
I'd also point out that the results were almost identical at 10 A, 40 A, and even 90 A.
The only thing that slightly dampened my overall impression was that the batteries got a little "fatter."

In short, I liked them, though they do have some drawbacks. For example, a screw-terminal connection would still be more convenient.

As before, the store offers a 5% discount on any batteries if you provide the code "kirich" when ordering, by any convenient method. I don't think anyone would turn down a little extra savings.
I was also told that although the store is Ukrainian, you can ask about the possibility of shipping to Russia. Check with them for details.

That's all for now. As usual, I'll be glad to answer any questions or read your comments.