# 2D ROP: 6 eneloop or 2 18650?



## smopoim86 (May 4, 2008)

I got a 2D mag today (I saw it and couldn't stop myself). Anyway, Would I be better off with 6 eneloop or 2 18650. Battery holders are not an issue, wither is fine. I'm just wondering if output or runtime would be different. Just from manu. ratings I should get more runtime out of a pair of 18650 @ 2400mah, right? Would 2 18650 be too much for the rop bulb fully charged at 8.4v (vs around 7.5 for the eneloops) ?

Daniel


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## jasonck08 (May 4, 2008)

Well, lets see here. 6xAA eneloop's would be 1.2x2ah=2.4whr's per cell. 6 cells would be 14.4 watt hours.

2x18650's would be like 3.7x2.4Ah=8.88Whr's per cell. 2 cells would be 17.76 watt hours.

Both calculations are optimistic calculations. But the 18650's should last a tad longer and will be lighter than 6XAA. Just be sure your 18650's can handle the current draw of your ROP.

I'm not sure about 8.4v being too much for the ROP, I haven't built one yet...


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## Gunner12 (May 4, 2008)

Factoring in resistance from contact points, 8.4v should be fine.

The runtime will be similar with either battery, in this case the 18650 should have longer runtime.

There are also Li-ion D cells.


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## 2xTrinity (May 4, 2008)

Gunner12 said:


> Factoring in resistance from contact points, 8.4v should be fine.'


Yes it will. Note also that 6 fully charged NiMH cells also reach 8.4V, and some have even run the ROP on 7 NiMH.



> There are also Li-ion D cells.


The kaidomain cells require a soft starter to light the ROP. And they actually don't offer much benefit over AW C Cells for ROP high as the light would get too hot to handle long before the runtime difference would matter. If the concern is taking the light on vacation and not wanting to recharge, it's possible to buy a spare set of C-Cells, or even 18650s as backups, C's as your "main" battery.

Id' suggest if you want to run LiIons you buy a 2C. It will be a lot smaller and lighter weight, and offer you more runtime than the 2D NiMH setup.


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## Misterbean (May 4, 2008)

I am definitely a newbie but I have recently built a ROP with eneloops in a modded 8AA holder from radioshack(note it will not fit in a D sized M*g). In my experience 7 eneloops with a litte resistance will power a ROP Hi and Low very well as will 6 eneloops. 7 is obviously very very white and bright with both bulbs but six will impress you. I have done some stuff with 18650s with a similiar set up. 8 eneloops will absolutely blow an ROP hi or low(i have done it on accident...i forgot to take one of the batteries out). to answer your question in short though 6 eneloops is a great option.


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## smopoim86 (May 4, 2008)

Well, the reason I was saying 18650 or AA was because I already have the batteries and i'm on a very tight budget for this light. Eventually I may get a set of D liion, or maybe a 2c with a set of aw c cells. Right now I'm just wanting a cheap ROP(I'm planning to build a superlight out of a 4d once i get the money to quad bore it and buy a battery pack).


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## Misterbean (May 4, 2008)

what kind of 18650s are you using. protected/unprotected. like i said in my previous post the eneloops work great. they are cheap too if you can get to circuit city and find some on clearence. i got 8 for under 8$.


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## smopoim86 (May 4, 2008)

The 18650 are cheap dx batts(trustfire protected 2400mah). 

I'm guessing it's much safer to use the eneloops?


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## Misterbean (May 4, 2008)

since they are protected i would think it would be safe enough. i have heard of some protected 18650s not powering the rop but it depends on the batteries i think(don't quote me on this). i love protected lithium-ions but i still prefer ni-mh for cheapness and ease of care.


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## smopoim86 (May 4, 2008)

I may testfire it on a set of 18650, but may build a batt holder as well. Who knows. I came to this forum looking for a decne t led and now i'm a friggin flosholic with plans to build an 7500 lumen mag mod. YOU PPL ARE MAKIN ME CRAZY 

Thanks for the advice


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## Misterbean (May 4, 2008)

i know i pretty much did the same thing. i was looking around for flashlight reviews and now i'm spending every spare dollar trying to make my lights just a little brighter.


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## 2xTrinity (May 4, 2008)

If you already have a charger, the 18650s will be your cheapest option ($10/pair, vs more like $15 for the eneloops + >$25 for a good adapter) The only reason I dislike the NiMH for hotwires is that adapters that are high enough quality to not suck the life out of your ROP due to excessive resistance are pretty expensive.

What are you doing for reflector/glass etc?

You can get plainglass for <$1, or AR coated for $5 from Kai or DX. You can get reflectors from Kai for $15. If you buy two of each, you can make two ROPs down the road if you get more money. One for a ROP-Hi, and one for ROP-Lo (perhaps the 2c?).


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## smopoim86 (May 5, 2008)

Got the reflectors and glass from Kai. I'll prolly use the 18650 for now since that will be the easiest adapter to make. I could make the AA adapter but don't feel like spending the time right now, although it's going to be a while till my reflector comes. I may rob the MOP from my 3c p7 (also running on 2 18650, in parallel though). I'm trying to standardize my batteries to eneloop and 18650. 

random thought: I wish i could find another 8 pack of eneloop for 6.50


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## FILIPPO (May 5, 2008)

I think with 4,5Ah of drow you may have some problems with protection circuit...:thinking:

if you don't want to build a new adapter for eneloops you can contact LuxLutor and order a 6 cells battery pack that will fit in an unbored mag...:thumbsup:


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## MikeSalt (May 5, 2008)

I built my ROP using AA Eneloops, simply for the reason of safety. When driving cells so hard, I would rather be playing with the safer chemistry. Also, I can use the FiveMega charging plug adapter to fast-charge the cells with ease.


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## Illum (May 5, 2008)

MikeSalt said:


> I built my ROP using AA Eneloops, simply for the reason of safety. When driving cells so hard, I would rather be playing with the safer chemistry. Also, I can use the FiveMega charging plug adapter to fast-charge the cells with ease.



the "on board" rechargeable option is definitely a plus, playing with hotwires is fun, until you get to the point where you must disassemble cell holders to extract and charge the cells. that is, if you plan on using AAs.

Mike, Im using the same config as yours
FM 6AA to 2D holder
6 eneloops
Tenergy universal smart charger:naughty:

I haven't given a thought on feeding my ROP 18650s...
alright, thats what I'll do for my second ROP:twothumbs


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## Mark620 (May 5, 2008)

Illum_the_nation said:


> FM 6AA to 2D holder
> 6 eneloops
> Tenergy universal smart charger:naughty:



Dang, that sounds familiar....:nana:


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## 2xTrinity (May 5, 2008)

If you're worried about safety of the 18650s, another option is Emoli cells from the Milwaukee drill packs. Two will fit in a 3C, or a 2D, and it's an inheretnyl safe chemistry. It's also particularlyl suited for high drain, so will run whiter and brighter than any of the already mentioned options (NiMH/18650) and will provide you with more runtime (~3Ah).

They won't break the bank either at ~$16/each.


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## Misterbean (May 6, 2008)

which drill pack has those batteries in it and how large are the cells exactly.


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## 2xTrinity (May 6, 2008)

Misterbean said:


> which drill pack has those batteries in it and how large are the cells exactly.


Milwaukee 28V. They are 26700, which means 26mm diameter (like a C-Cell) 70mm length (20mm longer than a C-cell) Though there is a vendor on CPF who sells them if you search for Emoli.


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## Misterbean (May 6, 2008)

2xTrinity said:


> Milwaukee 28V. They are 26700, which means 26mm diameter (like a C-Cell) 70mm length (20mm longer than a C-cell) Though there is a vendor on CPF who sells them if you search for Emoli.


 
ok thanks alot. i think i could probably do something with that size in something i have.


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## Illum (May 6, 2008)

Mark620 said:


> Dang, that sounds familiar....:nana:




I stick with what works


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## pbs357 (Jun 23, 2008)

I just built my first ROP using 2x18650's from AW. They are protected cells, and beyond that I already had them so it saved me an additional purchase. They work 100% fine on the Low bulb, and always light the High bulb on the 2nd press.

Both bulbs give impressive light output, but the High bulb is in the WOW category! Just due to the smaller size and diameter of the body I haven't played with my Mag85 since!

Ideally I'm trying to save for AW C cell li-ion's but I think an aluminum tower upgrade would be necessary to run that High bulb at extended times.


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## Stereodude (Jun 23, 2008)

Why not use the "C" cells from AW isntead of 18650's?


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## allburger (Jun 23, 2008)

I have both ROP's. One 2D with 6 Eneloops, and one 2C with 2 18650's. 

The 2c with 18650's seems to be better output, but i ended up blowing my High bulb with the 18650s hot off the charger.

I think the 18650's will run you a little cheaper. but you gotta let the batterys sit for a while or don't fully charge them to 4.2

I vote for 2 18650's


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## Chrontius (Jun 23, 2008)

Gunner12 said:


> Factoring in resistance from contact points, 8.4v should be fine.
> 
> The runtime will be similar with either battery, in this case the 18650 should have longer runtime.
> 
> There are also Li-ion D cells.



The Kai ones are particularly unsuited to ROP-hi as instead of lighting on the second (or 115th) press, the protection circuit locks until they are placed on the charger again. Could be a failure state and my cells are defective, but that is a major limiting factor, IMHO.


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## mdocod (Jun 24, 2008)

Maybe I can sum it all up here 

-----------------------------


Advantage of 2x18650:
more available power compared to AA LSD in most cases.
Can be brighter than 6xAA, but 6 high current AAs (like Elite 1700s or Titanium Powermax 1800s) would probably match it in output.
Can be much cheaper, especially if you already have a li-ion charger.
Can fit in C cells hosts.

Disadvantage of 2x18650:
Power draw of ROP high is right on the edge of safety, I'd even consider it above the edge of 2C limit on many cells out there. Cycle life at 2C is not as impressive but still reasonable. Increased risk of a vent-with-flame from abuse (risk is still very low IMO, but noteworthy) Many protected 18650s will not light up the ROP high reliably. The use of unprotected cells is generally not advisable.

Advantage of 6AA:
No significant safety issues or protection circuits to fight with. Can be pack charged as a whole, good LSD cells will probably deliver better cycle life than 18650s at this drain rate, but this is only speculation. Little to no risk of a vent-with-flame. Can be comparable in price IF you already have an investment in NIMH charging, but no Li-Ion charging options. 

Disadvantage of 6AA:
Less available power, 
expensive adapters or pack assembly for good performance, 
requires larger D cell host.
Usually more expensive overall to put together depending on what you already have.

------------------------

other thoughts:
If you factor in a Pila ICB charger, the only 18650 charger that is a simple 2 bay consumer style device on the market that actually charges loose 18650s correctly. And then factor in quality cells, The cost of the li-ion cells plus charger can pretty quickly bounce to $60 or more. The importance of quality cells and charger is far greater when dealing with li-ion than with NIMH for safety reasons. 

You can get a decent (shameless plug) 6AA adapter for $21.50, 6 nice AA cells for $10-20, and a respectable smart pack charger for around $30. ~$70 all together will cover it 

So my argument would be that the 6AA option isn't all that much more expensive if you compare it to doing the 18650 option in the safest possible manner.


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## UnderTheWeepingMoon (Jun 24, 2008)

I recommend you go with the eneloops. I made a 2C ROP-LE running AW 18650s and I only feel comfortable using the low output bulb. The high output bulb needs to be double-clicked before it lights up and places a lot of strain on the cells. 

Since you've decided to use a 2D host, you don't gain any size advantage by running 18650s. You might as well make use of the available space with NiMH cells that can safely handle the current draw.


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## FILIPPO (Jun 24, 2008)

UnderTheWeepingMoon said:


> I recommend you go with the eneloops. I made a 2C ROP-LE running AW 18650s and I only feel comfortable using the low output bulb. The high output bulb needs to be double-clicked before it lights up and places a lot of strain on the cells.
> 
> Since you've decided to use a 2D host, you don't gain any size advantage by running 18650s. You might as well make use of the available space with NiMH cells that can safely handle the current draw.


 

+1 :thumbsup:


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## Stereodude (Jun 24, 2008)

UnderTheWeepingMoon said:


> I recommend you go with the eneloops. I made a 2C ROP-LE running AW 18650s and I only feel comfortable using the low output bulb. The high output bulb needs to be double-clicked before it lights up and places a lot of strain on the cells.


Interesting... My 2C RoP High with AW "C" Li-Ion's fires on the first try every time. oo:


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## FILIPPO (Jun 24, 2008)

Stereodude said:


> Interesting... My 2C RoP High with AW "C" Li-Ion's fires on the first try every time. oo:


 

it really depends on the total resistance of the circuit...


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## AW (Jun 24, 2008)

My C cells have a different pcb that can handle a higher surge load than the 18650s.


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## FILIPPO (Jun 24, 2008)

AW said:


> My C cells have a different pcb that can handle a higher surge load than the 18650s.


 
that's another shameless plug....but it's still fair :nana:


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## pbs357 (Jun 24, 2008)

Stereodude said:


> Interesting... My 2C RoP High with AW "C" Li-Ion's fires on the first try every time. oo:


 
*oops* nvm


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