LiitoKala Lii-40E 26700 4000 mAh battery

This is the fourth battery from LiitoKala, but this time it’s not a 26650, and it’s not 3.7 V either. As always, find out more in the review.

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I got this battery from the same person who sent the previous three 26650 cells, so once again, many thanks. This battery was more of a bonus, though, since it’s a 26700, not a 26650; it’s rated for 3.2 V, not 3.7 V; and it’s a LiFePO4 battery, so it wasn’t included in the previous comparison.
It’s also rated for a current of 20 A, although it’s not quite that simple.

It was ordered from the liitokala Official Store, but came in the same basic packaging as the previous battery from another store.


The product page listed fairly detailed specifications. It also noted that the model—pay attention, this is neither an 18650 nor a 26650. I’ll add that it’s not a 20700 or even a 21700, let alone a 32700.


The batteries have a rather cheerful orange color. At least they’re different from the gloomy Lii-50A and the tolerant 55A, and probably closest to the neutral Lii-51S.


Dimensions and weight: the weight is fine, but the form factor really is strange. I’m even willing to guess that these batteries are intended for some niche application, but somehow found their way to LiitoKala by a roundabout route.


Neither of my chargers, which I use for “break-in” cycles, can handle LiFePO4, so I had to run the first cycle on the same battery tester I used for the other tests.
By the way, the battery was almost completely discharged—there was only about 3% charge left. In my experience, though, this is fairly common with LiFePO4.


The recommended charging current is 2 A, or 0.5C, which is what I used.
Charging took a little over two hours at that rate, which is pretty good.


I tested the discharge at 0.2, 0.5, 1, 2, 3, 4, and 5C, where C = 4000 mA.

Well, what can I say? The maximum current for these batteries is 8 A. You can already feel the strain at 12 A, and at the claimed 20 A the battery simply dies.


Temperature at 12, 16, and 20 A. At the maximum current, the battery simply didn’t have time to heat up because its voltage had already sagged.


The remaining capacity of 650 mAh didn’t surprise me at all. It was clear that at a 20 A discharge, the test stopped because the voltage sagged, not because the battery was actually discharged.


As always, the battery impedance is fine—after receiving it, after “break-in,” and at the end.
But there’s something odd here: the battery impedance is around 13 mΩ, noticeably lower than that of the 26650 cells shown earlier, and yet this battery just can’t handle the load.
It might have delivered more if discharged down to 2 V, but the graph clearly shows a significant voltage sag.


Conclusions.
Well, in my opinion, LiitoKala’s managers clearly overestimated this battery’s capabilities by at least a factor of two, maybe even two and a half. As I wrote, it just can’t deliver 20 A; 8 A is the maximum. These batteries might be considered high-capacity, but they’re not particularly small for 4000 mAh. The 32700 cells can easily deliver 20 A, aren’t much larger, and have a capacity of 6000 mAh.

All in all, I wouldn’t buy these batteries—or I’d use them at currents of 4–8 A.

That’s all from me. Thanks again for sending the “test subjects.” I hope I’ve “covered the topic” :)