26650's that are 65mm long

lampeDépêche

Flashlight Enthusiast
Joined
May 15, 2012
Messages
1,241
Hi Team!
Can you help me to find a brand of 26650 cell that is not much longer than 65mm?
I foolishly thought that all 26650 cells would be about 65mm long, or not much longer, as 18650s generally are.
But the one I got (an XTAR) is labeled on the cell as 69.3mm in length.
And sure enough, it will not fit into the light (or rather, the tailcap will not screw down all the way).

Any other brands that are closer to the official length?
Thanks!
 

lampeDépêche

Flashlight Enthusiast
Joined
May 15, 2012
Messages
1,241
Orbtronic does not have any of their unprotected 26650 cells available. Most are 66-67mm but the Sony (not much capacity) is 65mm. Maybe you can find unprotected somewhere else.

Thanks, KITROBASKIN!
So you figure the extra length on the XTAR comes from a protection circuit?
How dangerous would it be to remove that circuit? I.e., both how dangerous is the resulting unprotected cell (in a 1-cell flashlight), and how dangerous is the process?
 

KITROBASKIN

Flashlight Enthusiast
Joined
Mar 28, 2013
Messages
5,435
Location
New Mexico, USA
Your XTAR is protected I bet. What flashlight needs this shorter length? One would think the flashlight circuitry has safeguards if the battery compartment is ~65mm.

I trust illumn:

67.55mm 5.2Ah

65.8mm 4.2Ah

65.4mm 6.2Ah
 

lampeDépêche

Flashlight Enthusiast
Joined
May 15, 2012
Messages
1,241
Thanks again, Kit!
(I assume "Kit" is part of your name??)
The flashlight is this one:
It takes 18650s or D-cells or 3xAA in a carrier.
Since it takes 18650s, and the diameter is big enough for a D-cell (=33mm), I thought it would be easy to drop in a 26650 and get more capacity. But not when they are too long....
 

aznsx

Flashlight Enthusiast
Joined
Apr 24, 2015
Messages
1,677
Location
Phoenix, AZ USA
Hi Team!
Can you help me to find a brand of 26650 cell that is not much longer than 65mm?
I foolishly thought that all 26650 cells would be about 65mm long, or not much longer, as 18650s generally are.
But the one I got (an XTAR) is labeled on the cell as 69.3mm in length.
And sure enough, it will not fit into the light (or rather, the tailcap will not screw down all the way).

Any other brands that are closer to the official length?
Thanks!
In addition to the length requirement, there may be another consideration (requirement).

I believe the XTAR 26650 cell you reference, in addition to being too long, is a 'button-top' cell (which is required by the vast majority of my own lights). The documentation for the light states that when using 18650, they should be 'button-top' design. I note that some of the 26650 recommendations you're getting are 'flat-top' cells. Should the 26650 you select also be of 'button-top' design as would be the case when using 18650?

EDIT: I also don't see anything in the documentation for this light stating that it has 'low voltage warning / protection', so that should possibly influence your selection as well.
 
Last edited:

lampeDépêche

Flashlight Enthusiast
Joined
May 15, 2012
Messages
1,241
Thanks, aznsx -- those are both good points.
The button-top issue can usually be finessed with a discreet drop of solder or a low-profile disc magnet.
The lack of LVP in the light is an issue, true. I'll have to keep that in mind.
But I see that the Lumintop description actually specifies an unprotected 18650, so maybe that means that the light can cope with unprotected cells?
 

aznsx

Flashlight Enthusiast
Joined
Apr 24, 2015
Messages
1,677
Location
Phoenix, AZ USA
The button-top issue can usually be finessed with a discreet drop of solder or a low-profile disc magnet.
Some do, but I don't. I don't approve of modifying li ion cells in any way, especially the addition of anything conductive which could shift position or come 'loose' in the batt compartment and potentially cause a short circuit. However: To each their own, as always.

Lumintop description actually specifies an unprotected 18650
I can't find that note anywhere at the URL you provided, but my eyesight ain't what it used to be, either! The only 18650 note I find is regarding the button-top. EDIT: @lampeDépêche I just found the note you mentioned regarding recommendation of 'unprotected button-top' 18650. The user manual doesn't appear to mention it - only the button-top requirement, which is mentioned twice. That does not assure that the light has low-voltage warning / protection, but might just be an acknowledgment the of overall length limitations. Generally if a light incorporates that feature, it will be mentioned in the user manual - therefore I still wouldn't bet on the light having it without something explicit in the docs. Usually if a light has a feature, the manufacturer will want to tout it in their docs - but not always.

maybe that means that the light can cope with unprotected cells?

Perhaps, but probably not a safe assumption. The light won't care. The manufacturer may very well not care if you overdischarge your cells either, but you probably should - I do.

10-0
 
Last edited:

KITROBASKIN

Flashlight Enthusiast
Joined
Mar 28, 2013
Messages
5,435
Location
New Mexico, USA
aznsx are you, or have you ever worked for a certain government agency?

Lumintop is pretty substantial, and perhaps consider low voltage protection a given? Or does this multi-fuel nature make it such that there is no such protection built into this flashlight?
 
  • Like
Reactions: xxo

KITROBASKIN

Flashlight Enthusiast
Joined
Mar 28, 2013
Messages
5,435
Location
New Mexico, USA
Ok I asked Google Bard:
FCF53E3B-2CA1-4FA8-B172-2FE5D2E85B12.jpeg


But the option to "Google it" is not there…curiously.
 

xxo

Flashlight Enthusiast
Joined
Apr 30, 2015
Messages
3,010
aznsx are you, or have you ever worked for a certain government agency?

Lumintop is pretty substantial, and perhaps consider low voltage protection a given? Or does this multi-fuel nature make it such that there is no such protection built into this flashlight?
I still kinda doubt that they have LVP since running on a D cell would be impossible with a Voltage cut off, unless they figured out a way for the light to detect which type of cell it is running on and turn the LVP on and off. Either way, they should have made the battery tube a little longer to accommodate protected cells.
 

lampeDépêche

Flashlight Enthusiast
Joined
May 15, 2012
Messages
1,241
I really appreciate all of the feedback and responses.

AzNSx, you can find the stipulation about using unprotected 18650s at the URL in the fourth graphic from the top, labeled "Battery Compatibility" in big blue letters. It's right below "650 Meters" and above "Compact Design". It has a grid laying out the various battery options, their outputs and run-times, and in small print right below the grid it says, in italics, "A 18650 sleeve is required, and an unprotected button top with a max length of 67 mm is recommended".
I take your point that I have reasons to care about over-discharging cells even if the mfr does not.
Good point, XXO, about LVP complicating the dual-fuel setup. Other mfrs have figured this out, eg Zebralight, which allowed both AA and 14500s in their older lights. They had a bit of extra circuitry to keep track of whether the cell was a 1.5v or a 3.7v, and judge what counts as "low voltage" relative to that. If ZL can do it, maybe Lumintop, too?
Kit, I would not trust Bard for this kind of question. The new AI bots like ChatGPT are known to make stuff up, like just say totally false things, and they are currently terrible at math. That will probably improve over time, but currently there is a lot of GIGO happening.
Thanks again, all!
 

knucklegary

Flashlight Enthusiast
Joined
Feb 11, 2017
Messages
4,183
Location
NorCal, Central Coast
I like the Vapcell K62,15a.. It is a shame they don't offer protected circuits.. My flashlight tubes (Maglite) can handle extra battery length
 

knucklegary

Flashlight Enthusiast
Joined
Feb 11, 2017
Messages
4,183
Location
NorCal, Central Coast
I have a few Maglites, and one with LVP UI..
Afaik KP 26650 (protected) are the only flat tops that sit out far enough to make contact to each other running in series.

@chillinn, even if Vapcell D62 were to contact properly when stacked, such as adding blob of solder, or magnets, etc.. Are you positive protection circuits are not required (or recommended) when driving any li-ion cells in series?
 
Last edited:

chillinn

Flashlight Enthusiast
Joined
Jul 19, 2014
Messages
2,527
Location
Mobjack Bay
LiCo cells have an inherent danger that if they are discharged below 2.5V, dendrites can form, which can lead to a short if placed back on a charger, which could be bad. INR chemistry doesn't behave this way, dendrites won't form, no issues placing them back on a charger, though given enough overdischarge, they will lose capacity. Overdischarge does damage the cell, iow, but there is no danger. Though protection circuits also protect against thermal runaway, and INR chemistry is capable of it the same as IMR chemistry, these chemistries are tolerant of high amps and high heat, so thermal runaway is less of a risk than with ICR/LiCo.

Yeah, I am pretty sure. The only INR cells I have ever seen protected were Sony VTC4, but they were also sold without protection, and then we stopped seeing VTC4/5/6 sold with protection. Putting protection on them in the first place was probably done out of an abundance of caution, but after a few years when INR chem was fully tested, the chemistry more mature, and the behavior better understood, those protected INR cells disappeared.

For a few years after protection started disappearing from all chems other than ICR/LiCo, a lot of old timers on CPF still insisted on protection and couldn't find what they wanted in any other chem but ICR/LiCo. IMR cells never had protection, and the chemistry matured years ago, and the old timers complained they couldn't find them protected. It was just out of habit and a minor misunderstanding about the differences in cell chemistry that caused this, and eventually they all quieted down because they understood, and they couldn't get protected IMR anyway, and ICR/LiCo chemisty cell were starting to be phased out, still in progress, there are less of them available. Instead there is more NCR, INR, IMR, etc. All new chems are hybrids, and they don't need protection because they don't have the issue of blowing up your charger.

These cells are not made for end users. They are made for builders of cell packs. The protection circuits were never placed on there by the manuracturers, but instead by resellers catering to folks like us. The big manufacturers moved away from LiCo, and eventually the resellers realized they didn't need to sell other chem cells with protection, and they moved on.

But if you really want a protection circuit on an INR cell, you can probably special order it or get the materials and do it yourself. But it's really not necessary because the risk of dendrites forming and shorting the cell no longer exists... except still, again, with ICR/LiCo chemistry, which is still barely available.
 

knucklegary

Flashlight Enthusiast
Joined
Feb 11, 2017
Messages
4,183
Location
NorCal, Central Coast
INR in series, I doubt there would be a serious imbalance that would create issues.

Although, as friend Craig Shih mentioned earlier today "I prefer to err on the side of caution and use protected cells when running in series"

Keepower offers 26650 (P2660C) protected, or unprotected. They bumped up capacity from 5500 to 6000 mAh and shortened cell length .5mm (and widened dia. 0.4mm) So what's under the KP wrapper, a new hybrid cell, doubtful old tech LiCo ?
 
Last edited:

turbodog

Flashaholic
Joined
Jun 23, 2003
Messages
6,425
Location
central time
Maybe it's the new emitters, which are more efficient... but even w/ an unprotected cell in a 'dumb' light... it seems VERY obvious when the cell voltage starts to drop significantly.
 
Top