Yezl 18650 2400mAh - has anyone tried it?

Who will be first?

I have recently received a couple of these batteries. Hopefully I'll get a chance to run some discharge tests over the weekend.

Here is a test at 1Ah discharge. They seem good quality, virtually identical to the Sanyo 2600mAh, but with the added PCB. Note the high voltage held under load, this point looks even better than Panasonic cells.

I had actually considered mentioning that Torchy for one already had discharge curves for this cell, but I thought that might be a conflict of interest..... after all, it was him from whom I purchased my Yezls!

Are Torchy's results to be trusted?

I just ordered four, I'll do a test at 1A when I get them (not for at least a month, I'm going on holidays next week


Well, I have no reason to disbelieve him (and hey, taking the trouble to publish any type of test results is better than the dealers peddling "4200mAh" batteries, and denying any knowledge of li-ion cell technology if you point out that those capacities are not even possible), but hopefully I'll be able to show my own results soon enough.

OK, I've got the raw data that I collected from the discharge tests, but having some issues getting Logview to produce discharge graphs in the format that I want them. My German isn't good enough to work out what I need to be doing.

I've posted a thread in the Logview forum to try and find out what I need to be doing.

Do you guys want the data in the meantime, or wait until I (hopefully) have the discharge graphs sorted out?

I'd like the data.

OK, fair enough.

With regards to the batteries themselves, they appear to have the thin, somewhat brittle, wrap style covers, rather than vinyl like heat shrink.

Charging was carried out on a 4Sevens single bay charger, version 2. This was basically to speed up the process, so that I could have one battery charging while another was discharging.

The discharge was carried out with a Junsi iCharger 106B+. The battery was connected via leads with crocodile clips, using three small nickel plated rare earth magnets at each end to attach the crocodile clips to the battery. Discharge was from fully charged (charge seemed to be terminating consistently at 4.21v), down to 3v.

The batteries themselves were taken straight out of the pack, discharged from their storage voltage down to 3v, fully charged, and then tested. No previous cycles have been carried out, so it is possible that the batteries may gain a little capacity after a few cycles have been carried out. Something to bear in mind when considering the capacities achieved.

Cell 1 came out of the pack with a voltage of 3.91v, cell 2 had 3.93v. A bit higher than I am used to a storage voltage being, but beats a very low voltage or a tripped protection circuit.

It had been my intention to carry out a discharge at 0.5A (roughly 0.2C - often quoted as the discharge rate used by manufacturers to measure the capacity of their cells), 1A (for comparison with other 1A discharge tests), 3A (representative of the current used by many flashlights using MC-E, P7, XM-L or underdriven SST-50 emitters) and 5A (roughly 2C as you would expect a quality li-ion battery to sustain, and representative of the current to a fully driven SST-50). As it happens, I decided not to proceed with the 5A discharge, more of which later.

Yezl 2400mAh 1

Yezl 2400mAh 2

0.5A 2224mAh 2339mAh
1.0A 2153mAh 2283mAh
3.0A 1098mAh 2063mAh

As you can see, the cells are not particularly well matched, with cell 1 having a little lower capacity than I had hoped. Cell 2 wasn't bad at all. Not meeting or exceeding their stated capacity at 0.2C, but no-where near as bad as some that I have seen (for instance, Ultrafire 3000mAh cells only having 1200mAh capacity).

The same pattern is repeated at 1A. Capacity has reduced a bit at the higher discharge rate, as is only natural, and cell 2's capacity remains about 100mAh higher than that of cell 1.

The big difference occurred at a 3A discharge rate. Cell 1 sagged horribly, with it's usable capacity halving in comparison to cell 2 as a result. It's at that point that I decided not to move on to a 5A discharge rate. Cell 2 might have coped, but cell 1 had obviously given all it had to give.

Having seen this big difference between the cells at 3A, I measured the internal resistance to see if there was any obvious disparity between the two. Would have been handy if I had checked this before and after testing, but it didn't occur to me at the time. Cell 1 recorded 226mOhm, while cell 2 (oddly) was even higher at 231mOhm, though testing a second time gave a reading of 226mOhm, same as cell 1. As such, that doesn't give me any insight as to the poor performance under load of cell 1, but does tell us that these cells have pretty high internal resistance compared to the best li-ion cells.

Obviously, with only three cells tested (including Torchy's) it's hard to really come to any solid conclusions - too small a sample. Maybe I'm really unlucky to have got a cell with a lower capacity than the other two, and to have it sag so badly under load. However, it does mean that you can't expect all these cells to be up to spec. If I had received two batteries that both performed like the second one, I would have been very happy - maybe with some cycles on them, they would even have achieved the stated 2400mAh at 0.2C. Unfortunately, cell 1 just isn't up to high discharge rates.

Thanks very much or the data Stephen.

Let's forget about Torchy, he's actually promoting his merchandise.