You can see the archived poll results on the Wayback Machine:
https://web.archive.org/web/20221220093741/https://budgetlightforum.com/t/-/72713
Which will be brighter when fully charged and direct driving a Cree XM-L2? This unprotected 18650 or this protected 26650 ?
18650:
26650:
45 reads and 1 vote? It’s anonymous guys, take a stab 
We basically have a tie with 7 votes and 97 views. Lets make it more interesting.
IN NO PARTICULAR ORDER, here are the test results. The hint is that there is a big difference! Guess which battery made the brighter image!
Both images were of a professional camera in full manual mode, and the same flashlight at the same exact position each time. Yes, the flashlight was on 100% both times.
Very cool picture!
I’d guess the 18650 is the brighter of the two.
I think the 18650 unprotected has a lower internal resistance…
Edit, After seeing the links I think the 26650 might have the upper hand…
Keep voting. I will post the results when we get over 50 votes!
If I know you guys, some of you will lose sleep over this tonight! :evil:
ive done similar tests before and the 26650 cell always wins. but it has been with some very power hungry lights.
i have used the best 18650 and 26650 cells, and when put in series for a 3x cell light that has 9x or 12x emitters, the 26650’s gave more lumens.
but your test is slightly different,
but i will still choose the 26650 cell.
i have a feeling im wrong though, or you wouldnt have created this thread.
the underdog prolly won…18650
Looking at the discharge graph of the NCR18650PF, it can do 10A, but voltage will drop quickly. The 26650 will only do 8A, so for a short period the NCR18650PF might be brighter?
I'm certainly one!
Come on! Can't wait!
My guess is the 18650 during the first ten minutes
Bump, Bump 
I guess I didn’t post a pic of the flashlight, but it runs off of one battery, not pairs. fyi.
So yea the question is did the battery with lower internal resistance and high discharge rate win, or did the battery with a lower discharge rating but just simply bigger win.
It seems like you need to better define ‘win’.
I am completely new to this, but the engineer in me looks at the graphs and numbers posted and says:
“When both cells are freshly charged, at time 0, the 18650 should win since it should be able to supply 10 amps (from memory when I looked at them last night) versus the protected 26650 which should only be able to supply 8 amps. BUT after a fairly short time, (I think) that fresh charge aint so fresh and the current drops below what the 26650 can supply, moving it into the lead.”
Interesting experiment, and makes me want to know more about how the protection circuits work.
The 26650 5200's are not low resistance, like a KK 4000. Add to that protection circuitry and I'd find it hard to believe it could beat a ~10A PF, certainly not from the get go.
Sometimes the protected cells compress the springs so much better than a shorter unprotected cell, it cuts down the spring resistance dramatically - I've seen this before. Who knows though - dunno for sure bout the 5200 cells. I got the lower capacity EVVA 26650's but no 5200's.
Actually use the HKJ comparator here: http://lygte-info.dk/review/batteries2012/Common18650comparator.php
and choose the Orbtronic PD 2900 and the KeepPower 26650 5200mAh 2014 w/protection circuit and look at 5A or 7A.
Internal resistance # is lower on the PD, and I think the KP 5200 is bout equal to the EVVA, but not sure. Could be the EVVA has a more efficient protection circuit.
Alright, we have 44 votes and it’s been 24 hours. No need to keep everyone in suspense
Voting results:
59% said the unprotected 18650
25% said the protected 26650
16% said no difference
All guesses were good, the answer is not obvious.
The answer is the protected 26650 performed better than the unprotected 18650!
Both are brand new quality batteries that I had charged to the exact same voltage. The 18650 has slightly better specs, but in this direct-drive situation the 18650 just did not dump watts as fast as the 26650.
So next time you’re building or buying a flashlight you will know the sexier 18650 leaves some lumens on the table. The fatter 26650 can quench your appetite for lumens a bit better
Does closing the poll close the comments?
EDIT: Guess not. huh.
I had a feeling it was going to be this way, I had voted for the 26650. In my experience in a 1 cell direct drive light on almost any decent 26650 outperforms a 18650 for discharge capability. I was betting on a decent protection circuit, so minimal loss from its addition to the 26650.
Official/Unofficial Shoot-Out
I didn't realize I had a couple of EVVA 5200's here. I just did my own tests, measuring lumens output on a fully modded FET based SupFire L5 with a T4 5B1 XM-L2. The two #'s are measured @start and at 30 secs:
- Sam 25R @4.17v: 1173 - 1139 (Samsung 25R 18650)
- Pana PD @4.17v: 1125 - 1098 (Panasonic PD 18650)
- EVVA 5200 @4.18v: 1204 - 1176 (26650)
- KK26700 @4.21v: 1319 - 1261 (26700)
- SAM 30Q @4.22v: 1292 - 1227 (Samsung 30Q 18650)
- EFEST 26650 @4.19v: 1258 - 1217 (26650)
I voted for the PD - should have known better, but lately haven't done much with 26650 single cell lights. I believe this shows how really good the EVVA protection circuitry is - most others can kill a cell in resistance. I totally forgot how good the 26650's can perform, even against our supposed leading 30Q.
Interesting Notes:
- I did this mod to the L5 one year ago, and at the time I measured on a KK 26700 @4.21v 1346 lumens @30 secs, so that's a 6.3% drop. Could be because of the battery variation and age, or could be the LED's output drop over time, or some combo thereof.
- The 26700 beat a 30Q? HHmmmm
- The EFEST 26650 is an IMR 3500 mAh cell, but was my 2nd pair purchased. The first pair definitely performed better, consistently. Dunno why, but thought it was either a worse batch or possibly they were changed in design for the worse.
Neat test. What size are those batteries?