2AA vs. 2 consecutive uses of AA

[Walden]

+1 !

The main disadvantage of 2x AA (and any other 2x light) is that you will virtually never find two equal cells. Consequently, one of the two will deplete earlier and the output will suffer it not cease.

Rather soon than later the less capable cell will die, leaving you with x-1 cells, which usually will be an odd number of cells. So, what will you do with the other, good cell ? Place on the shelf until another cell dies and you have an even number of cells again ? Great....:duh2:

I have a whole bunch of AA and AAA cells, each with a different age and capacity, which I can easily use in my 1x lights with no hassle.

+1000 for any 1x light ! :thumbsup:

but if one uses rechargeable cells, then this problem of varying power will not exist, correct?

 

[Walden]

I suggest you get one of each. 1 AA for EDC and 2AA for outdoors. That's what I do, and I like it.

for EDC surely, I will go for a form factor smaller than a 1AA, maybe a AAA or something smaller. For EDC purposes I really don't foresee using my light more than 15 minutes at max.

 

[sims2k]

+1 !

The main disadvantage of 2x AA (and any other 2x light) is that you will virtually never find two equal cells. Consequently, one of the two will deplete earlier and the output will suffer it not cease.

Rather soon than later the less capable cell will die, leaving you with x-1 cells, which usually will be an odd number of cells. So, what will you do with the other, good cell ? Place on the shelf until another cell dies and you have an even number of cells again ? Great....:duh2:

I have a whole bunch of AA and AAA cells, each with a different age and capacity, which I can easily use in my 1x lights with no hassle.

+1000 for any 1x light ! :thumbsup:

That is why I use a cheap battery tester from Radio Shack all the time so I know how good each AA, AAA or C and D batteries are.

 

[AlexLED]

but if one uses rechargeable cells, then this problem of varying power will not exist, correct?

It especially exists with rechargable cells (which age over time).

 

[Tohuwabohu]

I did some runtime tests with my Fenix L2D Q5.

The 2xAA L2D Q5 has a rated output of 107 lumens for 4 hours, the 1xAA L1D Q5 107 lumens for 2 hours.
According to what I have read in this forum the head of the L2D is the same as that of the L1D.
With a single AA and a spacer my L2D should perform like a L1D.

I charged a pair of Eneloops and recorded the runtime in high mode with 2 AA's.
After this test I recharged both Eneloops and used them one after the other together with an AA-sized spacer in my L2D and combined the runtime graphs.

The total light output of 2 consecutive uses of single AA Eneloops is approximately 80% of a single run with 2 AA Eneloops.

I think that with alkaline primaries instead of NiMH rechargables the difference would be bigger.

 

[jasonsmaglites]

baterija :thumbsdow you've pretty much killed it for all of us who wanted to say something useful in this thread. i was about to reply that marduke pretty much stole the comment i was about to make then you go and give us specs and schematics to top it off. its guys like you that make this hobby unbearable. i'll just be in my mothers basement thinking of other ways to contribute. :tinfoil:

my .02 i love the single aa form factor. find yourself a light like the d10 that takes 14500 and then you

1. lose the voltage conversion factor marduke first mentioned, about a aa having to work harder when boosting its 1.2 volts to make 3.6 to drive the vf of an led.

2. 14500, although the same size as a aa, holds slightly more usable watts and doesn't self discharge.

 

[jasonsmaglites]

Tohuwabohu, you're going to push the information level of this thread up to sticky, especially if you can back my point up and run a 14500 through there and compare it to aa, 2aa, and 14500 all on the same graph. any chance of that?

 

[Tohuwabohu]

jasonsmaglites, I don't want to put a 14500 in my L2D.
I don't have a flashlight that I could safely run on 1aa, 2aa and 14500.
Sorry.

The result with one 14500 would't be directly comparable to the other graphs anyway.

 

[KiwiMark]

Contemplating whether to buy a 2AA or a single AA light. In Urban landscapes I guess form factor is important and a AA light would be the best. But for hiking/camping a 2AA light would be good.

While that was my original reasoning, I then feel that if a 1AA light can help me pass a considerable amount of night time (assumption=>I won't need the light for the whole night), then the next day anyways I will be able to replace the cell and be ready for the next night.

And that makes me wonder, what are the differences (in running time, for instance) between a 2AA light and 2 consecutive uses of a 1AA light?
If these are negligible, then the 1AA would be the best choice, right?

:thinking:
thanks,

1xAA if you want to fit it in a pocket easier - definitely.

Seems like it is going to be an unfair comparison, at least in terms light output. The higher voltage on the 2AA light will beat the lower voltage on the 1AA light.
eg.: noticed that Fenix LD20/L2D boasts a max of 180 lumens while LD10 has a max of 120 Lumens.

So,
2AA:
Pros:
* Higher light output
* Longer running time without the need to swap the battery
Cons:
* Form factor

and the reverse holds good for the 1AA lights.

100% true, unless you run a 14500 in a 1xAA light, then it is just the run time difference and form factor.

I did some runtime tests with my Fenix L2D Q5.

The 2xAA L2D Q5 has a rated output of 107 lumens for 4 hours, the 1xAA L1D Q5 107 lumens for 2 hours.

The total light output of 2 consecutive uses of single AA Eneloops is approximately 80% of a single run with 2 AA Eneloops.

So there you have it! The answer it Walden's question is yes - form factor is what it comes down to. On high you will get a bit more light from more voltage, but on lower settings the 1 x AA light + spare battery will run for a similar time to a 2 x AA light. Thanks Tohuwabohu for doing the tests to confirm it!

For daily carry try the Jetbeam Jet-I Pro with a 14500 for more light than a 2 x AA version, but in a small easily pocketed torch. For camping you can take a couple of 14500 and a couple of eneloops and have all the light from the 14500 and all the run time from the eneloops - you could camp for a couple of weeks easily with a Jet-I + 4 cells.

Or you could go the flashaholic way:
Jet-I Pro with 14500 for EDC
Ti Infinitum with 16340 for EDC2
L0D with eneloop for EDC backup
+
For camping
L2D
Jet-I Pro EX
2xAA Minimag with Nite Ize x 2
Jet-IIIM
M20 Premium
Maglite 4D with Malkoff drop-in
and take the EDC lights as well.

I don't think I will ever run out of light while camping!!!! Sure I could choose 2 lights and one set of spare batteries for each and be good for weeks, but if I don't take all my lights with me then when do I get the opportunity to play with them?

 

[flashlife]

+1 !

The main disadvantage of 2x AA (and any other 2x light) is that you will virtually never find two equal cells. Consequently, one of the two will deplete earlier and the output will suffer it not cease.

Rather soon than later the less capable cell will die, leaving you with x-1 cells, which usually will be an odd number of cells. So, what will you do with the other, good cell ? Place on the shelf until another cell dies and you have an even number of cells again ? Great....:duh2:

I have a whole bunch of AA and AAA cells, each with a different age and capacity, which I can easily use in my 1x lights with no hassle.

+1000 for any 1x light ! :thumbsup:

Strangely, I never found that to happen with my 2AA lights that I know of. (Just lucky ?)
Using standard Energizer, Duracell, ROV alkalines, etc, whenever I had a light start to dim, both batts measured the same open circuit voltage (to the nearest 0.01V, anyway).

There is, however, the possibility that the cell voltages may 'droop' differently under load, so that one cell is trying to drive the light and 'recharge' the sagging cell.

If you use 2 new batts from the same package, with the precision of today's mfg methods, there's very little chance that one batt will be much different than its brother.

Don't know, tho', about rechargeables, etc.

 

[loneranger]

If you are contemplating buying a Fenix L2D/LD20 you can also purchase a L1D body that will accept the L2D/LD20 head, therefore effectively meaning you can have both an AA and a 2xAA light by swapping the head and tailcap. The LD20 and LD10 heads are identical.

The folks at Lighthound said that the L1D body is not compatible with the LD20 head due to slight differences in the threading.

 

[jasonsmaglites]

jasonsmaglites, I don't want to put a 14500 in my L2D.
I don't have a flashlight that I could safely run on 1aa, 2aa and 14500.
Sorry.

The result with one 14500 would't be directly comparable to the other graphs anyway.

wouldn't the l2d take a 14500 if you used a spacer like you did with the aa's. i used a 14500 in a l1d body, it just didn't have lower modes. if you dont want to thats one thing, but that fenix head is capable of taking 3.6 volts.

why wouldn't it be directly comparable to those other graphs?
we could see its brightness go higher than the aa, and we can see if it even last longer too. basicly we can see how much surface area of the graph it takes up compared to 2aa's also, much like your mentioning that runtime of 2aa's run seperately is 80-90% as much as the 2aa's at a time.

look, i'm not trying to pressure you into doing it if you dont want to. i'm just saying it would be cool, and worthy of adding to my bookmarks of flashlight links i want to save for reference later.

 

[baterija]

The total light output of 2 consecutive uses of single AA Eneloops is approximately 80% of a single run with 2 AA Eneloops.

I think that with alkaline primaries instead of NiMH rechargables the difference would be bigger.

Outstanding. :twothumbs

Just because now I HAD to run the numbers(neither looks at efficiency side changes with different voltages than the NiMh.)
- Using the Rite Aid data from the alkaline shootout at 1 amp it has 54% of the power capacity that it has under a .5 amp draw. Using the same efficiency factor (89%) it give you 44% of the output.
- L91 data give 93% of the power capacity going from .5A to 1A draw. 83% of output singly versus together.

I actually like single cell lights for a lot of uses. It's rare that you can make a direct comparison. Even Tohuwabohu shows about the same runtime. It's lumen-hours where the single cell takes the hit in his test because it's not as bright. Every choice has compromises. At least we seem to have a better idea of the power compromise between AA (with spare) and 2AA now than we did.

 

[Burgess]

to Tohuwabohu --


Great Job on your run-time graphs !


:twothumbs:goodjob::thanks:
_

 

[Glock27]

The folks at Lighthound said that the L1D body is not compatible with the LD20 head due to slight differences in the threading.

I just screwed my LD20 head onto the LD1 body that 47's shipped me with no problem. The threads felt fine.
I like the anti-roll, crenelated bezel and more aggressive knurling of the LD20 compared to the L2D. I'm keeping them both.
G27

 

[2xTrinity]

I'll throw in another point I haven't seen covered so far:

With exgtremely high quality, low-internal-resistance cells like Eneloop, the difference betwen 2AA vs 1xAA with two separate cells is pretty minor, thus IMO 1xAA is the clear winner due to nicer form factor, and the fact that spare cells are easy to carry.

However, if you want to use Alkaline cells at all, 2xAA is the only way to go. Remember power lost due to resistance is proportional to the square of the current. Alkalines have a lot of resistance, and 1xAA lights draw more than double the current of 2xAA lights for the same output. That means even on the minimum setting on these Fenix lights, Single Alkaline AA's won't be able to cope with the high current-demand broguht on by hte boost driver, while 2xAA on low settings will likely give comprable results to 2xEneloops. In high settings, 2xAA Alkaline will work poorly, and 1xAA alkaline basically won't work at all.

 

[Blinding]

One advantage of 2 consecutive AA would be knowing you always have 50% (OK, maybe 40%) of your charge left. With a 2xAA light you may have used it for a while and not know how much run time you have left. With the single AA plus spare AA light you know you have one fresh AA even if the first battery quits on you.

Not as relevant if you are using rechargeables. You can always top them off. But who can afford tossing partially used primaries?

I run my P1D CE 10 minutes one day, none the next, 30 seconds here and there. I can't remember the date I put the battery in. In my typical usage it will probably last many months. No way I can keep track of when that battery is going to run out.

Of course I also believe that you should carry your spare battery in a proper container. The best battery container is a 2nd flashlight.

 

[Skyclad01]

Contemplating whether to buy a 2AA or a single AA light. In Urban landscapes I guess form factor is important and a AA light would be the best. But for hiking/camping a 2AA light would be good.

While that was my original reasoning, I then feel that if a 1AA light can help me pass a considerable amount of night time (assumption=>I won't need the light for the whole night), then the next day anyways I will be able to replace the cell and be ready for the next night.

And that makes me wonder, what are the differences (in running time, for instance) between a 2AA light and 2 consecutive uses of a 1AA light?
If these are negligible, then the 1AA would be the best choice, right?

Bottom Line

If the 1AA give you 2:00 total runtime with 2 cells an identically driven 2AA gives you about 2:28 in runtime.

Going back to Walden's original question, and breaking all this down to simply put it by what im reading (and given these lights are equal everywhere else for the most part)...

If you have 2AA batterys and a 2AA light, then you can only use the light once with a runtime of 2:28. Thus using up your only two batterys in the single use

But if you have 2AA battery's and a 1AA light, then you will have a 2:00 runtime per battery. Thus giving you a total runtime of 4:00 all together. Which in the end is a better option.

 

[baterija]

But if you have 2AA battery's and a 1AA light, then you will have a 2:00 runtime per battery. Thus giving you a total runtime of 4:00 all together. Which in the end is a better option.

That comparison was computed as 2 hours total not 2 hours per cell. It actually had absolutely nothing to do with the rest of the situation (you'd get more runtime with a single eneloop at the drive currents I used) but was just an illustration of the performance hit.


Trinity - I made the assumption that internal resistance was included as part of the loss in watt hours in data from the battery shootout. Basically that loss would be for all the reasons the cell was less effective at higher draws rolled together. It was Eneloop data in the battery shootout that I used to get the 9% capacity loss for each doubling of input current (from .5A to 4 A). That and the increased driver inefficiency led to my close to 20% loss estimate.

What that means for user choices is left as an exercise for the individual. There's plenty of other factors that affect the decision...many of which I consider more important. I think it's even more useful in planning battery stockpiles for longer periods when resupplying/recharging may be limited

To put this all as rules of thumb that might help planning (using the weightings computed earlier and assuming equally driven lights with similar efficiencies):
- You need 5 Eneloop singly for every 4 Eneloop used in pairs.
- You need 12 L91 singly for every 10 L91 used in pairs.
- You need 23 alkaline singly for every 10 cells used in pairs.

 

[marinemaster]

From my experience Streamlight ProPloy 4AA Lux 1 is the only AA light I consider......the rest of them running on 1AA are just gadgets.....not real lights. Flashlights companies that have been in business for a long time do not really bother with 1AA for good reasons. That also explains why 123 based lights are king in the real/professional world. The point of a flashlight is to make light. AA batteries by their nature are for other things, not necessary flashlights. So to have light available at all times 1x123 is best. 1xAA to have light some time. The new LED technology by itself cannot overcome the shortcomings of AA alkaline.

Now I am hoping that in the future AA Lithium will become more available and affordable for the form factor point of view.