Best High Capacity 21700

My pack of 5 came in a cardboard divider pack, looks like it was specially made for 21700 batteries (or at least other similar-sized cylindrical batteries). Probably the best battery packaging I’ve ever seen. Odd that yours were so poorly packed and mine so well.

Mine were wrapped up inside a pinkish red sheet of foam, then the foam sheet was held together with some sort of black cling wrap… inside a tyvek bag… Loose, just rolling around inside with nothing protecting the terminals. I was surprised when they weren’t in a case.

Sounds like packaging is all over the board. Hopefully they’ll respond to my message, or at the very least package future shipments in a safe manner.

My three came last saturday or so… packages in the grey plastic with no markings and inside a clear bubble wrap with packing tape. I do have testing equipment to easily test up to 3A. The higher current testers are a PITA to work with for these small tests and I don’t think these seem like they are going to be useful in high current lights by the sound of it. Won’t get around to it til next week but I can share some curves if people care to see them

Just finished grading the other 4 Tesla 21700s I received. All 4 came out in the 4400mah capacity range, well under rated minimum. So again, these seem to be salvage cells already in their middle age, already down 10%. They’ll be useful to me as backup and in my low-amp Convoys, but not for my top tier lights. Not unhappy with them for the price but they are what they are.

Mine just arrived and they have recessed tops… do not work in my charger without special treatment. Just an FYI

The tops on the 3 I got aren’t recessed and work just fine on my Opus 3100. I don’t have anything that discharge at more than 1A and these are the results. They were fully charged on my Accucell-6 last night and discharged this morning using my Opus 3100 (only charges to 4.15v).

Volts off charger / Volts this morning / Capacity
4.19 / 4.17 / 4655
4.19 / 4.17 / 4564
4.18 / 4.16 / 4664

Dug the old “Nitecore New i4” out of the closet and it charges the Epoch fine. I avoid that charger because it gets hot enough to fry an egg, but it is good enough for now and I watch it closely. The batteries do not heat up, just the power supply, so their are probably no real safety issues… I just am uncomfortable with it. The Epochs shipped fast and arrived early. Very happy with the purchase.

Charged mine up last night, and discharging two right now (my charger only has two 1A slots).

Fresh off the charge, all three were 4.22V, and in the morning 4.2V. All checked with my DMM.

I finished testing two cells earlier… the third one will be maybe tomorrow night.

My results are:

Cell #1: 4841mAh
Cell #2: 4833mAh

Testing was on my Vapcell S4 Plus at 1A from full charge 4.2V, down to 2.5V. I let them rest for an hour, and the voltage bounced back to 2.89V. Voltages were checked with a DMM.

I’m curious how many mah you gained from 2.9v to 2.5v —- got to be minimal — 90% of mine test 4700 - 4850 range 4.2v — 2.9 v —- the Opus goes to 2.9 then drops to 2.8 instantly

I have one more cell to test today. I’ll make sure to see how much is between 2.9V, and 2.5V.

Just finished the test, and it was 100mAh from 2.9V -> 2.5V.

This cell came in at 4893 at 1A.

Cell #1: 4841
Cell #2: 4833
Cell #3: 4893

I think I’ll order more.

I’d like to see what they can do.

In case everyone’s wondering, I heard from someone at Vapcell that T50s wil not be restocked :weary: if you want the best high capacity 21700, try to find some Samsung 50S.

Havok —— Thanks for that information —— for 100mah not really worth stressing the cells ——- I’ve been playing around with solar and EV (scooters) from what I’m learning it’s much better not to charge or discharge to the limits —- even 4.15 - 3.10 will add lots of cycles — Don’t get me wrong I still like to max voltage for my extreme light testing — but in my sphere and outside the difference in lumens is minimal

I usually don’t stress the cells like this under normal usage either. I only do it to see what their capacity is when I first get ’em.

I only let my cells go from 4.2V to 3.7V.

I charge to 4.20 V, but seldom discharge below 3.4-3.5 V. My MC3000 is calibrated to within 2-3 mV, so the max voltage (4.200 V) is not exceeded during charge. Unfortunately, not all chargers are that precise. I remember having a charger (don’t remember the brand, could have been Nitecore) years ago, that would charge to something like 4.22 V. Not terrible, and still within spec, but not ideal for cycle life.

The Nitecore I2 I bought many years ago charges my batteries to 4.22v.

That’s not ideal, especially if the end of charge current is low (1/10 of the CC current or less). You may expect a reduction of cycle life. It will not be huge, more like 15-20%, but still there. I’d rather prefer to have a charger that charges to 4.18 V (thus undercharging), than to exceed the 4.2 volts limit.

Edit: if you measure above 4.20 V after the end of the charge (even shortly after), this means that the end of charge voltage was even higher. That’s not good. A properly charged LiIon cell, right after the end of charge should read slightly below 4.20 V

Yeap that’s why I’ve only used the I2 less than 5 times since I got it around 2013 or so. After reading the off-the-charger voltage at 4.22v it went into my junk collection. These days I mostly use my Opus 3100 where the cells come off at 4.16 - 4.17v.