18650 / 21700 / 26650 ... what size of Li-Ion Batt to "keep"?

fuyume

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I don't really see much point in the 18650, when the 21700 is available and really only slightly larger. Although, for me, my first flashlight with "big girl" batteries was my Fenix PD36 TAC, which I purchased only a little over 2 years ago. Before that, I'd always relied on CR123A or AA flashlights.

I do also now have a Nitecore EC11, which is designed for an 18350, but I actually use a 16340 in it, because at the time I bought it, I couldn't find an 18350 with a built-in charger, and having the included plastic sleeve in the light to use the 16340 means that it is always there when I am out and about, on the off-chance I would need top purchase a CR123A in a pinch.

But, I don't see myself ever purchasing any lights that take 18650s. I was honestly surprised at how small the PD36 TAC was when I got it. Of course, as a woman, I do not generally carry flashlights in my pockets, because I mostly wear dresses that do not have pockets, and always have my handbag to carry things, so I don't worry about it when I need to carry my PD36 TAC, which is actually usually only when I park my bicycle, since I use it primarily as my bicycle headlight.
 

Monocrom

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Most 18650 lights can easily run off of 2xCR123 primaries.

Dual-fuel can be handy in certain circumstances.
 

Mike G

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I know most of you guys are talking about single-cell lights, but thinking about big full-size lights - stuff like the Convoy C6, C7, Sofirn SP70, etc - I'm kinda surprised lights like that use 26650s, and not 3x21700 or 18650 in parallel banks. I know they do that with soda can lights, but never the longer ones, where you'd think the extra mAh would be welcomed (I, for one, sure would appreciate it). Heck, even one bank of 3x21700 would already be more than two 26800s together...
 

Jean-Luc Descarte

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I know most of you guys are talking about single-cell lights, but thinking about big full-size lights - stuff like the Convoy C6, C7, Sofirn SP70, etc - I'm kinda surprised lights like that use 26650s, and not 3x21700 or 18650 in parallel banks. I know they do that with soda can lights, but never the longer ones, where you'd think the extra mAh would be welcomed (I, for one, sure would appreciate it). Heck, even one bank of 3x21700 would already be more than two 26800s together...
I'll be waiting for what comes from the 4680 battery format for those applications (most likely 46950). They have Ah to spare.
 
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Monocrom

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I do agree on the sizing. I'd rather go with 21700 as I prefer the wider tube in hand. And 18650 is too fat for edc anyway
Wurrkos TD03.... Same size as an old SureFire E-series light.
(weirdest simplistic U.I. you will ever encounter.)
 

Mike G

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I'll be waiting for what comes from the 4680 battery format for those applications (most likely 46950). They have Ah to spare.
30,000 mAh in the palm of my hand... sounds slightly dangerous, but mostly fun :grin2: Here's hoping Convoy or someone comes out with a light that runs two or three. Gonna need a charger with gator clips and some magnets for that big mama though... or charge in the light/proprietary charging, I guess. But I don't like that, so I hope that's not the direction things go.
 

blah9

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Wurrkos TD03.... Same size as an old SureFire E-series light.
(weirdest simplistic U.I. you will ever encounter.)
That is really cool! My current overall favorite light, the Fenix TK22 TAC, has the same interface basically from what I can tell from the Wurrkos. I love that interface. Do they make any others with a similar interface? I might have to check them out.
 

blah9

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I guess there are some differences and I prefer the Fenix version of the interface, but that's still really cool!
 

Monocrom

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I guess there are some differences and I prefer the Fenix version of the interface, but that's still really cool!
It's just.... You can only turn off the light from one position. First one, in which strobe is the only option. From the other two turns of the tailcap, it's literally impossible to switch the light off. So yeah, very simple U.I. but incredibly weird one too. Wurkkos markets it as a useful outdoor light. But they completely missed the mark on creating a truly affordable, genuine tactical light. All they had to do was switch positions. Put Turbo where they put Strobe. Put Strobe where they put Turbo. I would have happily bought two more, and just enjoyed the absolute best daily-use light for me.
 

blah9

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It's just.... You can only turn off the light from one position. First one, in which strobe is the only option. From the other two turns of the tailcap, it's literally impossible to switch the light off. So yeah, very simple U.I. but incredibly weird one too. Wurkkos markets it as a useful outdoor light. But they completely missed the mark on creating a truly affordable, genuine tactical light. All they had to do was switch positions. Put Turbo where they put Strobe. Put Strobe where they put Turbo. I would have happily bought two more, and just enjoyed the absolute best daily-use light for me.
Oh wow, I didn't even realize that part of it. Yes that would be annoying, and what you said makes sense.
 

fuyume

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Sodium-ion, eh? First I've heard of 'em. More familiar with sodium-iodine. I will definitely be listening for more... I do like me some salt.

How's their cycle endurance and self-discharge?
Sodium-ion batteries with Prussian Blue (ferric ferrocyanide) can have lifecycles of potentially 10,000 or more recharges, but have somewhat lower energy density than Li-ion. They are, however, expected to be cheaper and easier to manufacture.
 

jtr1962

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I'll be waiting for what comes from the 4680 battery format for those applications (most likely 46950). They have Ah to spare.
I'm waiting for either LFP or sodium-ion in that format. Yes, lower energy density than lithium-ion, but honestly something like 100 watt-hours in a potentially volatile battery chemistry isn't something I'd want to be holding. For comparison purposes a stick of dynamite is about 1 megajoule. A 4680 li-ion battery is around 0.35 megajoules. Three of them equals a stick of dynamite.
 

Mike G

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Thinking about it, won't Na-ion cells give current automatic chargers trouble? Since the voltage drops so far below nominal at the end, a lot of chargers - actually all of them, if I'm not mistaken - will mistake a spent Na-ion cell for either an over-discharged Li-ion (which might not register at all) or an NiMH, no?
 

Monocrom

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Thinking about it, won't Na-ion cells give current automatic chargers trouble? Since the voltage drops so far below nominal at the end, a lot of chargers - actually all of them, if I'm not mistaken - will mistake a spent Na-ion cell for either an over-discharged Li-ion (which might not register at all) or an NiMH, no?
If they do, guaranteed someone will make chargers for them to sell to the Public.
 

parang

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21700 makes the most sense and seems the most future proof. I'm in the cargo pants camp (no jeans) and there is no reason not to carry a 21700. Except there is no reason to carry one either, as an EDC it's overkill for my needs. I EDC 18350 lights, or if I am wearing fancy pants, then a Pineapple Mini or something like that goes in the pocket.
But my 21700 based lights are used more than my EDC, mainly in and around the house/yard/garden.
My thinking, as a prepper, is to have lights for all types of batteries, JIC.
"What are your top three (or five) battery form factors?" would be an interesting poll.
 

vicv

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This all being said and not mentioned, the newer 26800 would be awesome if they were more readily available. They're over 7000mah and good for 25A continuous discharge. And the perfect C size (perfect diameter light)
 

Monocrom

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This all being said and not mentioned, the newer 26800 would be awesome if they were more readily available. They're over 7000mah and good for 25A continuous discharge. And the perfect C size (perfect diameter light)
Would be difficult to clip-carry as an EDC though.
 
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