AA vs 14500

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cmwr
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AA vs 14500

I was watching a you tube video about a cheap flashlight that could use either 1 AA battery or 1 14500 battery. The guy said the 14500 was brighter than the AA but the runtime was significantly worse. He said you got about 20 minutes on high with the 14500 vs 1 hour on high with a AA. What gives? I would think a 14500 lithium battery would be superior to an off the shelf AA but apparently not.

Edited by: cmwr on 02/13/2016 - 21:22
Wrathbringer27
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14500 has smaller capacity but high amps

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ReManG
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Relatively speaking, they may both have the same power available. The Lithium Ion is a 3.7V battery and the Alkaline is a 1.5V battery. If the LiIon has 600mah and the Alkaline has 1500mah then the power is about 2250mw on each (3.7V x 600ma= 2220mw vs 1.5v x 1500ma =2250mw) so being roughly the same the only difference is the efficiency of the driver.

I would bet the 14500 battery was brighter for those 20 minutes than the Alkaline was during the entire run. If the LED has to have 3+Volts to even light up (most do) then the driver has to boost the 1.5V to 3+ volts before it can drive the LED to make light. The 3.7V LiIon 14500 was already above that voltage so it could drive the LED directly, but still had to go through the driver and suffered some losses.

If you could measure lumen output of the light on each battery and the 14500 drove the light at 300 lumen for 20 minutes, it would be the same as if the alkaline was 100 lumen for three times longer, which is what I suspect is closer to reality. On some of those videos, you have to think beyond the statements from the reviewers, none of us can know everything. And the difference between 100 lumen and 300 lumen would only show about twice as bright visually, so that would seem deceiving as well… Vision is non linear from what I understand in regards to brightness, so three times the lumen only looks about twice as bright.

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Rufusbduck
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First of all, a AA cell is the same size as a 14500 not a 14650. Next, Compare the power of each cell, a AA has a usable voltage of 1.6-.8V and a 14500 4.2V-3V which means the nominal for each is 1.2 vs 3.7V so multiply those by the Amp hours for each and you get 2.5 × 1.2 = 3 Whrs vs .8 × 3.7 = 2.96 Whrs. So a primary cell has a slight edge in power but alkalines can’t drain quickly without a major loss of usable power. At anything over 100mA draw the 14500 will be superior. Nimh cells have much higher drain rates but boost drivers for small lights are still limited to ~1A and even that much led current will draw close to 3A from a nimh cell.

For that particular light it boils down to the driver not regulating both cell types to the same current. The AA needs a boost driver and the 14500 is probably pushes it into direct drive so you’re not comparing apples to apples.

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Firelight2
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Wrathbringer27 wrote:
14500 has smaller capacity but high amps

This is incorrect.

Most 14500 has a higher capacity than any AA when measured in watt hours. (watts = voltage * amps).   If you have a driver that allows your light to run on both AA and 14500 at the SAME output, 14500 will probably give longer run time. The reason why you get shorter runtime in most lights with 14500 compared to AA is the driver pulls more amps to run the light at higher output.

 

Compare:

  • ICR li-ion: 840 mAh * 3.7v = 3108
  • Eneloop Pro: 2450 mAh * 1.2v = 2940

The li-ion cell stores more energy than the Eneloop Pro.  Li ion also weighs less than most 1.5v cells making it a nice choice for portable flashlights.

CRX
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What 14500 battery was used?

cmwr
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CRX wrote:
What 14500 battery was used?

It never said. It was just a video for a particular light at gearbest and it was telling about the light and options. Look at minute 4:29 so you don’t have to watch the whole video. I am not in the market for a new light. I just like researching this stuff for fun. I may be in the market down the road Wink

Bc412
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Originally I thought this was one of my videos… but obviously not.

I ran into the same problem while testing out the Olight S15

The reason for the short runtime with AA alkalines is that the flashlight draws more amps than they can handle.
14500’s and Ni-Mh can handle more amps and got better runtimes.

However… the opposite is usually true in flashlights. AA alkalines usually are the dimmest but last the longest. 14500 are brightest and shortest and Ni-Mh run in the middle. In this case the flashlight was too much for a alkaline so it bonked out fast, whereas the 14500 and the Ni-Mh did just fine.

Hopefully this clears it up.

I’m mine I did runtime tests with a Duracell AA, Tenergy Centura Ni-Mh, and a Efest IMR14500

HereAgainAgain
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cmwr wrote:
I am not in the market for a new light. I just like researching this stuff for fun. I may be in the market down the road Wink

If you eventually do, avoid this. I can almost guarantee there is a LettuceFight ( latticebright ) LED in it. I incorrectly mentioned a while back on here I had a ~2yr old Trustfire tube with an LB in it. It is actually an Ultrafire. Similar to this, that was supposedly a Q5 emitter. I was duped, but it was only a few bucks, and it’s a POS regardless of emitter.

cmwr
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Yea in the world of flashlights, as I am discovering, there is a butt load of fake crap. It’s enough to scare most people back to Wal Mart to buy their flashlight. Smile

agent80
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I don’t think a 14500 offers any advantages with such a short runtime at say 300 lumens. I think a decent runtime should be about 90 minutes on about 250 lumens and over. It appears that manufactures haven’t been able to create a driver that would do this. The Nitecore EA11 and Olight S15 both do about 250 lumens+ for 45 minutes. This is with the best possible 14500 battery. With the typical 14500 battery, this runtime would be about 30 minutes. Which is nothing much really.

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I think if you look at lumens-per-watt-hour, then the two chemistries are very similar in performance.

One thing I like about the Eneloops is the low self-discharge.

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I did a test with a cheapie AA light a while back. It didn’t claim Li-ion compatibility, but it worked with a 14500 anyway. It happened to come with a cheap Alkaline cell in it. The cheap Alkaline put out a useful amount of light for over three hours. My 14500 put out a much brighter light at first, then declined. By the time it became too dim to be useful, it had only run 45 minutes.
Full Disclosure: Although most of my cells of various sizes are quality cells, the only 14500’s I have are a handful of ****fire cells I bought off eBay before I knew better. I have no way of testing them for actual current or capacity. But, they work well enough for tests like this.

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cmwr
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My thinking is if you are after a super bright light for home defense or something around the house then 30 minutes is fine for a runtime. But for me I use my lights mainly away from the house on rides and backpacking trips. In these scenarios I don’t have electricity to charge my batteries so I carry spares. That would be a lot of spares if the battery only lasted 30 minutes. I got a mini mag 2xAA light that is the LED pro and outputs 270 lumens I believe. It is extremely bright and all this without the trouble of chargers and lithium batteries.

ReManG
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cmwr wrote:
My thinking is if you are after a super bright light for home defense or something around the house then 30 minutes is fine for a runtime. But for me I use my lights mainly away from the house on rides and backpacking trips. In these scenarios I don’t have electricity to charge my batteries so I carry spares. That would be a lot of spares if the battery only lasted 30 minutes. I got a mini mag 2xAA light that is the LED pro and outputs 270 lumens I believe. It is extremely bright and all this without the trouble of chargers and lithium batteries.

Yup, that makes sense for your needs then… There is no wrong type of light or power source, just what is right for our needs…

Myself, I have embraced LiIon batteries, but the small AA/AAA lights are still my back up and emergency kit items… They are still good for those roles in my needs..

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Rufusbduck
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Comparing the two in a host only designed for efficient use of one is an inherently poor test. A nimh or alkaline cell won’t produce any light at all with a linear or buck driver. It’s only due to the higher voltage of the liion that it works at all with a boost driver but that doesn’t mean it works well. A true test needs to compare them at equal drive currents since otherwise you are testing the driver not the cells.

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bdiddle
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It’s almost like we need lower modes to use. Like medium or low.

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What I find odd is that an 18650 offers ~3200mAh compared to ~800mAh for an 14500, but the former has a bit less than twice the volume, but about 4 times the energy capacity. Presumably the reason must be due to the construction, with more of the internals percentage wise being used to store energy in the 18650.

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Mr.Scott
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HereAgainAgain wrote:
If you eventually do, avoid this. I can almost guarantee there is a LettuceFight ( latticebright ) LED in it. I incorrectly mentioned a while back on here I had a ~2yr old Trustfire tube with an LB in it. It is actually an Ultrafire. Similar to this, that was supposedly a Q5 emitter. I was duped, but it was only a few bucks, and it’s a POS regardless of emitter.

I bought several of these POSes – intentionally.

Flashlights tend to grow legs and disappear in my house (kids). I bought a load of them, one in the pantry, in the hall closet, in the laundry room, shelf by the garage, in each bathroom. When they break or go missing I don’t care, only paid $3.29 each.

Now MY nice flashlights don’t disappear.

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Leif, it has to do with the differences in diameter. As that increases, the circumference (the length of layers inside storing energy) increases exponentially. It’s the surface area of the power-storing layers in the LiIon cell that determines it’s energy potential. With the same volume, a fatter LiIon will hold more energy than a longer one because of that.

A volume-based power comparison will only be close when comparing similar diameters such as 18340 and 18650.

Phil

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pi*R^2*H
14500= 7693mm^3
18650=16532mm^3
Or only a bit over twice the volume. The difference is greater if you remove an equal case thickness from both but I think for the chemistry and construction methods the 18mm diameter is optimum since greater diameters don’t lead to commensurately greater capacity but do have greater internal resistance. For the 14500 I thinks it’s more a case of the difficulty of scaling down layers that can’t just be shrunk in size/thickness.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

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ReManG
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I also think since the 18650 is the largest volume LiIon battery, it gets all the attention, so to speak, for improvements…

In the case of an 18350 vs 18650, the 18350 should be capable volumetrically of at least half the Mah of an 18650.. Good luck finding one with 1700mah (1/2 a 3400mah 18650) or even over 1000mah of actual milliamp hours.

The high volume and ubiquitous nature of the 18650 size means it gets all the tech/chemistry upgrades first…

I am sure in a few years the capacity of 14500’s, 16340’s, 18350’s and the other sizes will catch up to where we are now in 18650 power, but by then the 18650’s will have a genuine 5000+Mah…

I would love a real 1700mah 18350 and a 1500mah 14500….

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I just wasn’t sure that “cmwr” understood how LiIons are made. They’re not like a dry-cell with a homogeneous mix in a can where volume has a more direct bearing on things.

I think you’re both right regards the 18650- it does seem to be the optimum size and it does get the improvements first, being as ubiquitous as it is. If someone developed the smaller cells as well as has been done with the 18650, they’d have a lot of the market to themselves till it settled out.

My biggest disappointment and only decent AA-sized LiIon light experience is with my SK68 clone. The 14500 boosted the output well enough but I still wasn’t seeing the run times I had hoped for- neither lasted like I had hoped for. I just don’t like the balance of power and runtime of a 14500 compared to most other sizes; it’s neither fish nor fowl to me and I see a lot of concurrence here on BLF though we have it’s proponents too, just fewer in number. Where the AA format excells is in cell availability- you can get AA cells everywhere and they’re cheap which is why they’re my BOB/GHB battery of choice. Now I just need a couple lights which can make the best of those cells.

Phil