Making 21700 flashlight body compatible with AAA's?

[Marquis07]

Hey,
What do you guys think of a 21700 light that could run on AAA's as backup?It would be identical in size to a regular 21700 light. I like how 14500 lights can use regular AA's as backup, and this would be a similar concept.

I think the idea is sound enough, but I don't think anyone has done it yet.

I can design a 3D printed version of it, but if this is a bad design, then I don't want to waste my time.

What would the pros and cons be for something like this?
I'd really appreciate any feedback.

-Mark


Edit - added content


I built a simple design in tinkercad here.
Flashlight Design
There is a 2D and 3D model of both configurations.

It fits a regular 21700 or 6 AAA's. the red and green pieces are screwed together in the center. In order to fit the AAA's, the green piece is removed and threaded in reverse. The tailcap screws on whichever end of the green that is sticking out.

 

[thermal guy]

You taking about making an adapter so you can use AAA in a 21700?

 

[Marquis07]

@thermal guy Not really, it would need to be the entire body of the light, but it would let you change from 21700 to AAA "instantly," and you wouldn't need an adaptor. I added a rough model of it above if you care to look.

 

[fivemega]

Hey,
What do you guys think of a 21700 light that could run on AAA's as backup?

It would be easier to carry full charged spare 21700 cell with much more capacity.

 

[Marquis07]

@fivemega I agree with you. The AAA's would be inferior in almost every way, except they can be found everywhere. Say, if there was an extended power outage, you wouldn't be able to charge your 21700 easily, but you could find spare AAA's. Similarly, if you were in a third world country or somewhere with little or no power, you could still get AAA's from somewhere.

Maybe that's what dedicated AA lights are for?

You can already use 18650s and CR123s in your 21700. This would just add to the flexibility of it.

-Mark

 

[RWT1405]

To be honest with you, I cannot see any use for a AAA adapter/whatever for a 21700 flashlight, IMO.

I also cannot imagine anywhere (at least that I go/have been) that if AAA batteries were available, AA were not also available.

AA batteries are far superior to AAA in every way, with the exception of keychain flashlights, IMO.

If I was headed somewhere that AAA/AA batteries were all that were readily available, I would carry a flashlight that uses those (AAA/AA), and without doubt would prefer AA to AAA for a primary flashlight.

 

[chillinn]

Say, if there was an extended power outage, you wouldn't be able to charge your 21700 easily, but you could find spare AAA's.

Since an Alkaline AAA cell is roughly 1/5th the capacity of a 21700, or less at any current to speak of, with 3xAAA for each swap you'd need 15 times as many AAA cells, nearly 4 quads, to match the capacity of a single 21700 cell.

 

[thermal guy]

You're not going to have the voltage to run a 21700. Unless you use 4-5 cells and then run time would be minutes With AAA

 

[orbital]

+

Mark,
If someone gave you a 500 pack of AAA alkalines for Christmas, get a couple 2xAAA lights to get rid of them.

for a 21700 light, use a 18650 in a pinch

 

[scalpel_ninja]

I agree with all of the above. Also, not every 14500 light can use AAs, and the reverse is true. It would depend on the driver to enable use of two different voltages.

I guess an adaptor could be made as a proof of concept, but impractical for real world use. If you're looking for a true omnivore (post-disaster) of batteries, the Malkoff MD3 with a few drop-ins of different voltage ranges plus spacers and adapters can run practically any cell with a diameter of 18mm or smaller. 3D printing dummy cells (with brass conductor posts) and sleeves would serve very well to allow for use of many different cells.

 

[Marquis07]

@RWT1405 @chillinn @thermal guy @orbital @scalpel_ninja

Woah, I rest my case! Seems like a lot of negative posts. :sad

Just kidding, this is exactly what I was looking for. Thank you guys.
Your points are all excellent. I shall abandon the design.

Let me know if there's anything else I should invent. :grin

-Mark

 

[xxo]

Let me know if there's anything else I should invent. :grin

-Mark

how bout a flux capacitor?

Just kidding...good idea but probably something most people would not be interested in.

 

[chillinn]

Let me know if there's anything else I should invent

CR123A, 18650 and 14500 dummy cell spacers are easy to find. What isn't easy to find is a smaller dummy cell spacer to run a 14500 in a 2xCR123A light, which would be pretty useful, at least I'd like a couple myself. You could invent that.

 

[Marquis07]

@chillinn I could probably do that. The spacer would be 18650 size right?

 

[hsa]

Yes.

 

[orbital]

... Let me know if there's anything else I should invent. :grin

-Mark

+

If you 3D printed a P60 host for 21700s',, that accepted Surefire or Solarforce heads-
you'd sell quite a few.

 

[xxo]

Something like this?

 

[bykfixer]

In a pinch triple a fuel is better than no fuel. And if one has a supply of triple a size eneloop pro batteries that could add a bit more run time. Or ultimate lithium in triple a size.

Eh, there's a reason it hasn't been done before. Lack of fuel capacity. But who's to say down the road when technology advance to a new level it will be a more palatable idea.

Perhaps a series of sleeves in an adapter "kit" starting with a triple a that fits in a double a that fits in an 18650.....

 

[orbital]

+

---- or just have a couple extra 21700 on hand couple in the car, couple over by your charger.

forget using one coin cell with 3 aaa & two well used cr2 and >

 

[Marquis07]

Perhaps a series of sleeves in an adapter "kit" starting with a triple a that fits in a double a that fits in an 18650.....

I just saw Megawoodswalker's video about the Malkoff MD3 yesterday. He was doing just that. It was crazy to see him running a 3 x cr123 light on a single AAA! If you can run something like that on just a single AAA, that's a much easier and better opinion imo. Maybe I'll start saving up for something like that.

forget using one coin cell with 3 aaa & two well used cr2 and >

I'll build you a spacer...