21700 to 18650 battery adapter sleeve -- options?

22 posts / 0 new
Last post
xevious
xevious's picture
Offline
Last seen: 1 hour 35 min ago
Joined: 02/27/2013 - 21:55
Posts: 2562
Location: Hoboken, NJ USA
21700 to 18650 battery adapter sleeve -- options?

I’d been looking around for a battery adapter sleeve to convert a 21700 battery tube to hold an 18650 battery without rattling. I have seen some people use plastic o-rings or thin piping, but I wanted to buy something well made. I saw on the Fireflies website a really nice one for just $1.50, with a removable brass button (in case of going from flat top to button top). But an order I placed with them has gone nowhere. No response from customer service for 2 weeks. It’s a real pisser, because I’ve enjoyed this brand. Anyway, I looked around but couldn’t find something equivalent for a decent price.

Anyone here have suggestions on what to get, or a nice DIY approach?

Lightbringer
Lightbringer's picture
Online
Last seen: 13 min 25 sec ago
Joined: 08/30/2016 - 14:12
Posts: 15735
Location: nyc

Paper towel.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

jeff51
jeff51's picture
Offline
Last seen: 1 day 5 hours ago
Joined: 03/26/2019 - 17:36
Posts: 1186
Location: Middle of Texas

I use some O rings I got from the hardware store. 2 per 18650.
Best part is the rubber doesn’t rattle like some of the plastic sleeves.
All the Best,
Jeff

Correllux
Correllux's picture
Online
Last seen: 10 sec ago
Joined: 04/27/2019 - 22:23
Posts: 523
Location: USA

Could message Sofirn and ask if they’d sell you some of the ribbed tubes they include with lights. I don’t really use them myself but in toying around with them they fit their lights and all but one of my others pretty well and the 18650s all fit great except a particularly fat Keeppower protected cell. I’m sure those are available on aliexpress for cheap but watch out because a great many of them that look the same are actually 26650 adapters.

I saw this awhile back when helping a friend find a lens for his Eagtac….not sure if it’d work with all tubes or what the dimensions actually are but to me it looks a bit fat. It’s a can, kind of the reverse of those shorties you saw on the Fireflies site.

https://illuminationgear.com/shop/ols/products/eagtac-18650-to-21700-spacer

https://www.aliexpress.com/item/4000480931380.html

xevious
xevious's picture
Offline
Last seen: 1 hour 35 min ago
Joined: 02/27/2013 - 21:55
Posts: 2562
Location: Hoboken, NJ USA

@Jeff51 – Trying to avoid rubber o-rings as they tend to grab a bit too much to the tube sides. Something like a flexible plastic that will slide easily but take up the diameter slack. Maybe a plumbing supply plastic washer could do the trick. Will have to take a flashlight with me to Lowes or Home Depot and fish around.

@LightBringer – Paper towel could certainly work in a pinch, but hoping for something a little more robust. But actually you give me an idea—those packing foam sheets cut to size might do the trick.

@Correllux – Those EagTac tubes look great, but at the price of a 21700 cell, not really worth it IMHO. If it was $12 for 2, would consider that. I’m hoping FireFlies wakes up after the Chinese National Holiday and let’s me know about availability of their solution.

Correllux
Correllux's picture
Online
Last seen: 10 sec ago
Joined: 04/27/2019 - 22:23
Posts: 523
Location: USA

xevious wrote:
@Jeff51 – Trying to avoid rubber o-rings as they tend to grab a bit too much to the tube sides. Something like a flexible plastic that will slide easily but take up the diameter slack. Maybe a plumbing supply plastic washer could do the trick. Will have to take a flashlight with me to Lowes or Home Depot and fish around.

@LightBringer – Paper towel could certainly work in a pinch, but hoping for something a little more robust. But actually you give me an idea—those packing foam sheets cut to size might do the trick.

@Correllux – Those EagTac tubes look great, but at the price of a 21700 cell, not really worth it IMHO. If it was $12 for 2, would consider that. I’m hoping FireFlies wakes up after the Chinese National Holiday and let’s me know about availability of their solution.

Yes…a bit too pricey. Those Fireflies ones can be found all over ali, ebay, and even amazon but the prices are all over the board. Pretty standard adapter and they come in a few colors..

If you have any cylindrical tube holders that various drill bits and tooling bits come in and are around 3/4” ID, they’re often about the right thickness and a slit along the length would make sure they’re snug on the cell. Those handi-pak tubes of solder might also work but I think they may be a bit thin.

SIGShooter
SIGShooter's picture
Offline
Last seen: 44 min 8 sec ago
Joined: 07/14/2013 - 02:10
Posts: 2264
Location: northern california

I’ve used left over toilet paper rolls and cut them to the desired length, then to the width needed by cutting them up the middle, rolling them around, and wrapping them with tape. Probably not describing it too well haha.

In the end I decided it’s easier to use o-rings. Big Smile

raccoon city
raccoon city's picture
Online
Last seen: 2 min 47 sec ago
Joined: 10/06/2010 - 02:35
Posts: 17104
Location: रॅकून सिटी Palm Desert CA USA

I think Boaz suggested cutting up a cereal box.

I thought the idea was genius.

Cereal box cardboard is a very good thickness for an 18650 to 21700 adapter, though a proper plastic one for a dollar or two would be better.  :BEER:

Tatteredmidnight
Offline
Last seen: 4 hours 15 min ago
Joined: 09/11/2021 - 19:32
Posts: 4
Location: United States

Fenix ALF-18 maybe?

Sidney Stratton
Sidney Stratton's picture
Offline
Last seen: 4 hours 11 min ago
Joined: 01/28/2018 - 22:59
Posts: 684
Location: Canada

This issue has been the bane of some of my lights – the rattling of the cell.

Unfortunately, I never found the ideal commercially available plastic tube to make adapters. So scrounging about my place I found some ‘fish paper’ that with a few wraps does the job. Less than the ideal replaceable sleeve, but they work. Other stiffer cardboard ‘wrinkles’ with tight bends; but I suppose I could wet them and then let them dry to form.

Stefano
Offline
Last seen: 6 days 8 hours ago
Joined: 08/30/2013 - 18:14
Posts: 45
Location: Italy

I have always had flashlights with 18650 battery, when I bought the PD36R and then the PD36 TAC which use 21700 battery I also wanted to buy the adapter Fenix ALF-18 Battery Holder.
I tried it once it works fine, with it I can use my 18650 even if flat (it has a spring inside under the positive pole)
It remains as an emergency use, it was bought for that.

xevious
xevious's picture
Offline
Last seen: 1 hour 35 min ago
Joined: 02/27/2013 - 21:55
Posts: 2562
Location: Hoboken, NJ USA

Correllux wrote:
Yes…a bit too pricey. Those Fireflies ones can be found all over ali, ebay, and even amazon but the prices are all over the board. Pretty standard adapter and they come in a few colors..

If you have any cylindrical tube holders that various drill bits and tooling bits come in and are around 3/4” ID, they’re often about the right thickness and a slit along the length would make sure they’re snug on the cell. Those handi-pak tubes of solder might also work but I think they may be a bit thin.


The Fireflies ones have appeared elsewhere but with a cost about 4x that of Fireflies. Another one I’ve seen at Banggood has the half-tube on the other side, the bottom. $9. Looks fairly well made and eliminates the button/no-button top issue. I know what you mean, about those drill bit holders. Will have to check that out. Heck, if buying a drill bit WITH the tube that works is cheaper than $9, worth it to go that route.

SIGShooter wrote:
I’ve used left over toilet paper rolls and cut them to the desired length, then to the width needed by cutting them up the middle, rolling them around, and wrapping them with tape. Probably not describing it too well haha.

In the end I decided it’s easier to use o-rings. Big Smile

That certainly works, though not elegant. Considering cardboard, yeah—cereal boxes can be very good. Especially if you order one of those jumbo boxes that uses slightly thicker material. I buy Nature’s Path cereal all the time and save the cardboard for packing material when shipping things in bubblewrap mailers. I was thinking… of just taking that, rolling into a tube, and secure with some tape having adhesive that won’t ooze out.

The Fenix ALF-18 looks decent. Battery Junction has them for $5.99… but I think shipping minimum with them is usually $8.

Sidney Stratton
Sidney Stratton's picture
Offline
Last seen: 4 hours 11 min ago
Joined: 01/28/2018 - 22:59
Posts: 684
Location: Canada

No such luck on my end.

Edit: The outside dims are across the ridges. The actual plastic wall thickness is much less – 0.71mm.

G0OSE
G0OSE's picture
Offline
Last seen: 6 hours 23 min ago
Joined: 09/03/2014 - 12:34
Posts: 2312
Location: UK SW

Just wrap some insulating tape around the top and bottom of the battery, works fine, done it myself.
To use it in another light if needs be remove it, though I tend to keep 1 battery to 1 light normally so never need to remove it.

Lightbringer
Lightbringer's picture
Online
Last seen: 13 min 25 sec ago
Joined: 08/30/2016 - 14:12
Posts: 15735
Location: nyc

Howbow those… nfi what they’re called… makeup-scrubber-offers.

Little round/square disposable poufs that women use to scrape off the spackle at the end of the day.

This sort of thing: https://www.amazon.com/dp/B07DCJ1SVQ .

Nice a few from wifey…

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

pennzy
pennzy's picture
Offline
Last seen: 4 hours 21 min ago
Joined: 12/10/2017 - 19:45
Posts: 3843
Location: United States , Pa.

Cut up a plastic jug and roll it up.

strayz
Offline
Last seen: 19 hours 7 min ago
Joined: 10/09/2012 - 18:01
Posts: 719
Location: In the land of the Midnight Sun..

Have you asked around for someone that has a 3D printer? Might be a buck or two but they are out there and can be shipped to you. If you know someone that has one they could make a ton for 10 bucks. Just remember that because they can make it doesn’t mean they will do it for you for free.

Ask around, you might be surprised by local makers.

xevious
xevious's picture
Offline
Last seen: 1 hour 35 min ago
Joined: 02/27/2013 - 21:55
Posts: 2562
Location: Hoboken, NJ USA

pennzy wrote:
Cut up a plastic jug and roll it up.
Yeah, this may be a sensible way to go. You don’t even need to fully wrap the whole cell. Just 75% of it. And with the heat generated, it should warp the plastic to conform… Will give it a try. Thanks!
Sidney Stratton
Sidney Stratton's picture
Offline
Last seen: 4 hours 11 min ago
Joined: 01/28/2018 - 22:59
Posts: 684
Location: Canada

Here I use a sheet of ‘fish paper’ to reduce the body tube inner diameter: MantaRay 21.86 ID, Molicell 20.53 OD (20700 format)

The material can be found here
Comes precut at 65mm and is quite economic at $1.00 for 10 feet (but they get you on the shipping). Should be some without the sticky backside in Ali.

Mine is .40mm (.016”) thick and has a natural roll. It stays within the flashlight body.
For converting the 21 to 18mm, using 2 or 3 concurrent rolls (.4mm x 3 = 1.2mm per side; close enough to 1.5 but tight fit – 2 rolls has just the right play).

Plastic jugs and the like are usually made from polypropylene. Rather stiff and too high a melting point (135 to 175 ºC) to mold with the battery therms. Also, most probably thinner. Hence more ‘rolls’.

raccoon city
raccoon city's picture
Online
Last seen: 2 min 47 sec ago
Joined: 10/06/2010 - 02:35
Posts: 17104
Location: रॅकून सिटी Palm Desert CA USA

Sidney Stratton wrote:

(but they get you on the shipping).

Wow, you're not kidding!

I haven't done the research, but maybe Amazon has something similar with free shipping for those with Prime?

Sidney Stratton
Sidney Stratton's picture
Offline
Last seen: 4 hours 11 min ago
Joined: 01/28/2018 - 22:59
Posts: 684
Location: Canada

The merchants adjust (lower) their prices as clickbait and compensate with shipping. When you try to negotiate the shipping, all I got was “sorry, not us but shipper” as a cop-out.

Well, their ploys are childish and anyone can see thru them. Much like the phishing scams in my junk mail.

And then there are the eBay Chinese sellers that don’t ship Canada because of ‘extra shipping’. Critical electronic component at about $4; extra $5. If he had posted such, I would be inclined to make the purchase. As it was hidden, I had no choice. Eventually found such merchant on AE and purchased from Ali with Free Shipping.

I think they have little geographical knowledge, less of GDP and potential sales.

BOO5TED
BOO5TED's picture
Offline
Last seen: 1 hour 26 min ago
Joined: 04/16/2019 - 20:53
Posts: 731
Location: ATL

Amazon

Eagtac Amazon

Ebay Fenix

Little more expensive but all have free shipping.

"America has three cities, New York, San Francisco and New Orleans. Everywhere else is Cleveland."- Tennessee Williams