Please Explain! Loose run-time with rechargeables?

[stevet47]

I am trying to decide whether I want my next light to use 2xAA or a 2xcr123 cells.

Particularly I am trying to decide between the OLight T20 and Fenix Digital P3D Premium Q5 which use CR123's or the Fenix Digital L2D RB100 Premium 100 which uses the AA's.

CR123's are pretty expensive, so I would be using rechargeables, but have read that rechargeables will give only 1/2 the runtime as primaries (primary just means disposable, correct?). Is this true?

If this is the case, whats the deal with the rechargeable 17670 and 18650 cells that I have heard about? They can be used in place of 2xCR123's correct? Would that be a better option? What would these do to the runtime and output of the light? Can they even be used with the flashlights I mentioned?

Also, If I can't use the 17670 or 18650 cells, what light would actually give me the most lumens? A light rated at 215 lumens running on rechargeable cr123's or a light rated at 175 lumens running on rechargeable AA's?

Thanks in advance, and sorry for the TONS of questions in there!

 

[Marduke]

Just a quick note, rechargable AA's are not li-ion, they are NiMH, and either are generally not interchangable. Also, the Fenix L2D RB100 is the one you are thinking of that takes AA's, as the P3D takes CR123's. You will gain runtime with rechargable AA's and loose it with RCR123's.

 

[stevet47]

Just a quick note, rechargable AA's are not li-ion, they are NiMH, and either are generally not interchangable. Also, the Fenix L2D RB100 is the one you are thinking of that takes AA's, as the P3D takes CR123's. You will gain runtime with rechargable AA's and loose it with RCR123's.

Wow, I think I was reading soo much, I confused myself. I edited the initial post, so that I don't confuse anyone else!
Thanks for pointing out the mistakes!

Also, you said, "you will gain runtime with rechargable AA's and loose it with RCR123's", Which is good info, I didn't know that about AA's, but what about lumens? Are they going to be any different between disposables and rechargeables?

 

[mdocod]

1 good 18650 has about as much power as 3 good low-self-discharge NIMH AA cells, so a 1x18650 light is the way to go if you want a rechargeable solution that is as compact as possible with the most power and runtime in that package possible.

see the problem with the P3D is that it doesn't have room for an 18650 and doesn't run in regulation on a 17670.... so you have to either use 2xCR123 or 2xRCR123... RCR123s are generally only about 550mAH true capacity, so even though they have higher voltage, a pair of 1300mAH primary CR123s will last about twice as long... A pair of RCR123s have about 4 watt/hours of power, a pair of CR123 primaries have about 7 watt/hours, a single 18650 has about 8 watt/hours......

So what you need to do is pick out a light that runs on a single 18650. As I understand it, that leaves the T20 and P3D out of the picture, as both require higher input voltage to run in regulation and I don't believe either are bored to fit an 18650 sized cell.

Check out the Tiablo A8, It's specifically designed to stay in regulation on an 18650.
I believe the LumaPower M1 and MRV are pretty good options as well, they hold an 18650, but don't run in regulation on through the run as I understand, but they do a pretty good job, holding above 50% initial output for several hours on high. The Wolf-Eyes 6A HO Cree also supports a single 18650, again, the entire run is not in regulation, but this one does a pretty good job of keeping most of the run in regulation.
Deree Light also offers some really great 18650 powered cree lights, the DBS thrower and the CL1H. Some of them are set up to run fully in regulation on an 18650 and some are not.. depends on what configuration you choose... worth a look as these are getting pretty good reviews overall.

The advantage of a light that drops out of regulation on an 18650 is that it will have much longer overall runtime, as it gets dimmer it gets more efficient so these types of lights often have useful diminishing output for hours..

Try not to worry too much about rated lumens on all these things, pretty much all of the lithium or multiple AA powered cree lights are driving one of the new Crees between 700mA and 1000mA, they're all pretty bright, picking out the beam pattern than is more useful to you is going to be the most important thing.

 

[VidPro]

some 123 lights also run hotter with the higher voltage rechargable, so that can make the runtime test be even shorter :-(
shorter than the fact that a Lithium primary has about 2X the total power of lithium rechargables, IN the 123 size.

its all about the lithium, its not like the alkalines, so lithium primaries are very good, and that is what the 123 COMES in to begin with, we dont use alkaline 123s

so when you go with AAs using lithium again, wouldnt compare to rechargables, the lithium primary AA will blow away the alkaline AND the li-ion rechargable (noteing that the li-ion rechargable is not compatable with 1.5v stuff usually) (and noteing that a lithium primary would toast some Alakaline only devices).

so when you compare rechargables and Alkaline, the answer is simple, but when you compare lithium primarys to rechargables its not.

agrees TOTALLY with the above 18650s kick butt, they have tons of power for thier size and weight, and handle the current of the 1 and 3 watt, and even overdriven 3 watt very well. are reasonably priced. and the size is right for pocket or hand.
there are many chargers for them, and many Quality protected cells of them.
Just not as many lights that will use them, or use them correctally.