Sorry… banggood unbranded:)
I’m wondering if anyone is following the .6C charge rate advise? A 650mAh 18350 should be charged at 390mA, according to data out there. Charging at 500mA or 1000mA will shorten the life of the cells dramatically. As will discharging at rates beyond the recommended for the particular cell.
I have a LOT of Efest 18350’s that I’ve used in some seriously high output small lights and in tandem in MT-G2 lights. Hard hitting lights. And I see reduced capacity over time due to the overwork nature of the hot rods I build. I haven’t lost any of my 18350’s, nor have I lost any of my 10440’s that I do 3A and over on. I have only recently lost a few 18650’s that are 3 and 4 years old.
A good example of this is my recent experience with a highly modified Ti X6. The pair of light purple 18350’s I first tested it with and are almost 3 years old (having been hammered many times before) gave 15.87A through 3 XHP-50.2 emitters for 10,315.5 lumens. A new pair of dark purple Efest 18350’s allowed 17.22A and made 10,661 lumens. So in this one case of an older pair of 18350’s from Efest they remain viable even after hard use and several years of being stored at full charge condition.
my current understanding, as a LiIon newbie, is
how hot matters: storing fully charged in a hot car will permanently deplete capacity more than storing in a cool place
how full matters: storing fully charged will permanently deplete capacity, more than storing at half charge.
how empty matters: draining below 50% will permanently deplete capacity, more than draining to less than 50%
here is where I got that info
Interestingly, I have some laptop cells (Samsung 2500ma IIRC, forgot exact model) in a SRK in my truck for over a year now. It has sat through all of last Texas summer and this one so far.
When I checked the voltage on those cells a few months ago they were still holding ~4.15V even under those conditions.
Some chemistries simply hold a charge better. Sony cells I have noticed tend to discharge faster then others and don’t like staying above 4.1V much at all.
Unprotected cells should self discharge very slowly !
But if you test you will find variance .
A lot of batteries will find a voltage level they like and maintain it …
I have some 16340 that stop around 4.04 volt and others that go down to 3.8v ish … This is after 12 months
I think a very long time ago I did a 16340 self discharge test for a period over 12 months , must be over half a decade ago now …
I totally missed his post before :person_facepalming: , but CRX is assembling a great summary table of all people’s data in post #27.
Thanks for doing that! 
Updatwd the OP with the test in progress
Did you measure them right off the charger?
Immediately after charging lithium batteries have a voltage drop after a few minutes or hours.
If you didn’t let them rest for a while then you will probably see a bigger drop than other people that didn’t measure right after charging.
Definitely want to wait an hour or more to test for normalized voltage …
Due to Variables the battery voltage off the charger may be artificially raised …
And those same variables will dictate how far the voltage will drop after allowing the battery to normalize .
A bit off topic:
djozz, congratulations on your 10k :partying_face:
Oops, missed that, thanks! It is a dubious achievement, I like to say that I have a real life too, but who will believe me with 10kPosts? :person_facepalming:
I will think about a giveaway then, probably another bag-o-lights. My girlfriend will love to see them go 
No plans on proposing to celebrate the 10000 posts?
Hmm, on my knees and give her an engagement flashlight I assume? :nerd_face: , that may just be the end of my hobby 
That answers that question. I guess you plan to stay happy for a lot longer yet. 
Finally remembered to check my stored cells(ones not seeing regular use or charging) all of these have been sitting for at least two years without charging.
5- 10440’s all at 3.8V+
8- 14650’s all at 3.8V+
2- 14500’s both at 3.75V
2- 18350’s one at 3.6V+ and the other at 3.7V+(bought at the same time as the first Reylight Ti)
As far as I’m concerned this is a non issue unless there is some climatic effect mine aren’t subjected to.
Checking in 2 months later for my efest imr 16340. Now voltage is 3.99V.
EDIT: to follow djozz format below:
t=0 t=2months type
4.12V 3.99V Efest imr16340 V2
The cell is 2yrs 9months old and has been used a lot.
t=0 t=2months capacity type
1 4.02 4.03 360 mAh Nitecore 16340 (NL166)
2 4.16 4.11 547 mAh Efest dark purple 14500
3 dead Nitecore 16340 (NL166)
4 4.09 4.06 456 mAh Efest red 14500 V2
5 4.11 4.06 472 mAh Efest red 14500 V2
6 4.13 4.12 493 mAh Efest red 16340 V1 flat top
7 4.17 4.13 870 mAh Efest red 18350 V2
8 4.15 4.13 875 mAh Efest red 18350 V2
9 4.16 4.13 638 mAh Efest lila 18350
10 4.17 4.13 713 mAh Efest dark purple 18350
11 4.19 4.17 704 mAh Keeppower black IMR 18350
12 4.16 4.10 1160 mAh Aspire 15A 1300mAh 18350
13 4.18 4.17 2313 mAh Panasonic CGR18650CG protected
14 4.20 4.19 2225 mAh Panasonic CGR18650CH (IMR)
15 4.18 4.14 1210 mAh Efest lila 18500
16 4.17 4.16 1771 mAh Sanyo red 18500 1700mAh
17 4.17 4.14 2003 mAh Panasonic NCR18500A
18 4.16 4.08 1198 mAh Efest metallic purple 18500
19 4.16 4.13 3472 mAh Enerpower protected NCR18650GA
20 4.21 4.17 2960 mAh Samsung INR18650-30Q
21 4.08 4.02 542 mAh Efest red 16340 V2 550mAh
22 4.14 4.13 617 mAh Efest red 16340 V2 700mAh
23 4.17 4.14 576 mAh AW red 16340 IMR 550mAh
24 4.13 4.05 812 mAh Kinoko IMR 18350 850mAh
25 4.16 4.13 1189 mAh Aspire 15A 1300mAh 18350
General trend: smaller batteries drop more voltage, it looks correct that after a year they appear half-drained, but there are exceptions, i.e. the Keeppower 18350 is still at 4.17 V, and one Aspire cell is down to 4.10 V while the other is still at 4.13 V.
I noticed that all small Efest batteries show a few hundreds of a Volt increase after 20 seconds under the small load of the voltmeter, sort of waking up effect.
Next is checking all capacities. This will take a while with only 4 slots in my Opus.
Update with the “before” voltages shown by my OPUS set on 0.5A after charging up until “FULL”
and the “after” voltages on august 16th when my OPUS starts re-charging with 0.5A plus energy recharged:
Keeppower IMR 18350 750 mAh = 4.17V > 4.12V = 42mAh
Efest IMR 18350 700 mAh = 4.17V > 4.13V = 40mAh
Trustfire TR14500 900 mAh = 4.19V > 4.16V = 0mAh (FULL)
Nitecore 14500 750 mAh (NL147) prot = 4.15V > 4.07 = 75 mAh
Windyfire IMR 14500 600 mAh = 4.19V > 4.14V = 34mAh
Keeppower 18650 3400 mAh prot = 4.18V > 4.13V = 2mAh
Olight 18650 3400 mAh (ORB 186P34) prot = 4.21V > 4.15V = 0mAh (FULL)
Samsung INR18650-30Q 3000 mAh = 4.20V > 4.14V = 40mAh
Samsung ICR18650-28A 2800 mAh = 4.20V > 4.14V = 0mAh (FULL)
Thorfire 18650 3000 mAh (BRC18650) prot = 4.20V > 4.10V = 0mAh (see remarks below)
Lumintop 18650 3400 mAh with USB charging prot = 4.20V > 4.16V = 0mAh
Klarus 18650 3600mAh (18GT-36) prot = 4.21V > 4.15V = 72mAh
Apparently all can be charged in my OPUS.
The Klarus 18GT-36 was recharged on august 4th, because it left the scene in a present to a dear friend.
The Thorfire initially showed “FULL” when I put it in the charger the first time.
Did not trust that, and started to recharge without ending when I put it in for the second time.
Nice to see how many mAh can de added to fill them back up Henk, that would have been a good idea to measure for my batteries too (too late now).
But I guess there’s enough data to see a general trend: the small batteries vary per individual battery, but on average hold their charge better than I feared, and even the capacity of small old batteries has not decreased that much.