LG INR21700-M50T, high-capacity 21700 batteries

More 21700-format batteries, this time focused on fitting the maximum capacity possible into this size.
I’ve already reviewed similar batteries, but from Samsung. They’ll be taking part in today’s comparison.


Apparently, these batteries are Samsung’s answer to its INR21700-50E. The Samsung datasheet I found was dated late 2017 and was version 0.2, while LG’s version 0 description is dated July 2018—a difference of more than six months.
So the question is: which one is better? Especially since the Samsung INR21700-50E costs 4.45 euros, while LG’s competitor costs 4.25, putting them in the same price range.


They’re dark gray, and their size immediately stands out. Even at a glance, it’s clear they’re larger than the familiar 18650 cells.


A closer look at the specifications immediately reveals that the 0.2C current is listed as 970 mA, not 1 A as you’d expect for a 5 Ah capacity. In other words, the specs already formally indicate that the batteries have a capacity of 970 × 5 = 4850 mAh, not 5000 mAh.
This is another case of misleading labeling: both the 50E and the 50T have the number 50 in their names, which seems to hint at their capacity rating. But neither battery actually reaches that stated capacity: Samsung’s is 4900 mAh, and LG’s is 4850 mAh.


According to the S029 marking, the batteries were made in late January 2019. But since this model itself is new, it’s no surprise there aren’t any old ones yet.
The positive terminal is almost flush with the front edge of the casing. It also has small notches whose purpose is unclear. There’s also a matrix code, which provides additional protection against counterfeits.


The manufacturer also includes a photo in the description, along with the specifications and dimensions.


The dimensions and weight are well within the values specified in the datasheet, but during testing I noticed an interesting feature of these batteries: their center of gravity is offset. This made photographing them extremely difficult, because each battery kept rolling into the position it preferred rather than the one I wanted. To be honest, I’ve seen this with other batteries too, but never to such an extent. Both batteries had this quirk, so it’s quite possible the others will as well.


The batteries initially had about 40–50% charge, but the discharge... It took a long time: my charger discharges at 500 mA, so the full cycle—charge, discharge, charge—took almost 20 hours in total.


The store page lists a maximum continuous current of 7.3 A, so I used an EBC-A10H load for the test. Later, I decided to run an additional test at 3C, using an EBC-A20.


Two charging modes are specified: 0.3C (1.45 A) and 0.7C (3.39 A). I used the first mode.
The maximum continuous discharge current is also specified as 3C (14.55 A), but only at temperatures of 10–25 degrees. Above 25 degrees, the current is limited to 7.27 A.


As I mentioned above, I charged at 0.3C, but wow, it takes a long time... almost 4 hours for a single charge, and I ran 6 cycles on each battery.


I tested the battery in six modes, with discharge currents of 0.2C (970 mA), 0.5C (2.43 A), 1C (4.85 A), 7.3 A, 10 A, and 14.55 A.
At 0.2C, the battery delivered 4969 mAh or 18.12 Wh. The first figure is slightly above the stated 4850 mAh, while the second is slightly below the nominal 18.2 Wh.


Temperature at 7.3 A, 10 A, and 14.55 A. At the maximum current, the temperature climbed to almost 90 degrees—way too high.


As is usually the case with branded batteries, the second sample produced almost identical results.


The temperature was a little lower here, though: 87 degrees at the maximum current, compared with 89 for the first sample.


The initial, post-“conditioning,” and final resistance values are almost identical. The batteries were nearly identical in this respect, too.


I compared the battery under review with the Samsung INR21700-50E at four points: 0.2C, 1C, 10 A (9.8 A for the Samsung), and 14.55 A.
The graph clearly shows that LG has a slight edge over its competitor at low currents, but falls noticeably behind at higher currents. After all, its maximum really is around 7.3 A.


To sum up, the batteries themselves are pretty good, and I was pleased with how consistent the test results were. But compared with the closest competitor, I think Samsung is a little more appealing: it is rated for a slightly higher continuous current right out of the box (9.8 A versus 7.3 A for LG).
In short, LG is the better choice at currents up to 1–1.5C; at higher currents, Samsung wins.

That’s all for today. Thanks for reading, and as always, I’d be glad to hear your comments.