# Replacing 1.5v NiMh AA with 3.7v Lithium AA?



## och (Mar 11, 2012)

I have an Energizer brand 1W LED flashlight (I'm almost positive that the LED is Luxeon) that uses a single 1.5v AA battery.

So far I've been using rechargeable NiMh 1.5 batteries, but their capacity leaves much the be desired. I could use 1.5v non rechargeable Lithium AA batteries - but they tend to get expensive. I was looking at rechargeable AA Lithium battries, but they are all 3.7v (and I know that they require a different charger).

So I'm wondering, if I was to switch to these batteries, am I going to damage the LED, or the driver will regulate voltage as required?


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## Lynx_Arc (Mar 11, 2012)

och said:


> I have an Energizer brand 1W LED flashlight (I'm almost positive that the LED is Luxeon) that uses a single 1.5v AA battery.
> 
> So far I've been using rechargeable NiMh 1.5 batteries, but their capacity leaves much the be desired. I could use 1.5v non rechargeable Lithium AA batteries - but they tend to get expensive. I was looking at rechargeable AA Lithium battries, but they are all 3.7v (and I know that they require a different charger).
> 
> So I'm wondering, if I was to switch to these batteries, am I going to damage the LED, or the driver will regulate voltage as required?


It is possible you could damage the LED, unless the light is designed for lithium ion batteries (which it is not) you are not going to increase runtime instead it will most likely be brighter for a shorter length of time (if it doesn't fry the light).


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## 45/70 (Mar 11, 2012)

Hi och. As Lynx mentioned, the use of a Li-Ion cell in your light may, or may not work well for all the reasons he stated.

I don't know what you're looking for as far as runtime, but any decent brand AA NiMh cell, in good condition, should run a 1W LED light for close to 2 hours. A Lithium primary cell, such as an L91 may extend runtime a bit at the ~1A current draw of such lights, to close to 3 hours.

You didn't mention what NiMh cells and charger you are using. If you're not getting runtimes close to this, I would suspect that either your NiMh cells are not in good condition, or are at EOL. If you have a charger such as a Maha C-9000, or LaCrosse BC-xxx(x) series, try running a few refresh cycles on the cells and see if this improves runtime. If there is no improvement, your cells may just be too far gone.

Dave


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## och (Mar 12, 2012)

Thanks guys. My NiMh rechargeable batteries I believe are Energizers, and I get roughly an hour of run time out of them. I thought Lithium batteries were much more efficient than NiMh?

I also have a 3 mode XM-L flashlight powered by a single 18560 battery, and on low power mode I can leave it on overnight and it doesn't drain the battery.


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## Lynx_Arc (Mar 12, 2012)

The battery is not any more efficient, it is the design of the light around the voltage source. If you had a light using 3 nimh cells it would be just as efficient as a lithium ion battery based light but a single 1.5v light has to be boosted to output decent light from LEDs and typical boost circuits that output higher currents have losses (heat) in boosting. A 1 hour runtime means the boost circuit is probably handling about 2 amps and at about 1.2v that would be 2.4watts while a lithium ion battery with a circuit based upon that battery type will only take about 700 ma to drive the LED at the same level. Higher currents typically have a penalty with them in all but the very best lights with the best circuits in them.


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## Gregozedobe (Mar 12, 2012)

Try some Sanyo NiMh AA eneloops (the 1500 cycle 2000mAh version), they are much more popular with CPFers than Energizers (which often have reduced capacity after not that many cycles, particularly if the charger is less than optimum).


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## bob4apple (Mar 13, 2012)

och,
I have 2 of those Energizer 1W flashlights- one has a Luxeon led,
the other has a Cree. For years I have been using 3.7V 14500 lion batteries
in both of them. The brightness increases tremendously and they get a bit warm.

I think you might like it!


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## och (Mar 13, 2012)

bob4apple said:


> och,
> I have 2 of those Energizer 1W flashlights- one has a Luxeon led,
> the other has a Cree. For years I have been using 3.7V 14500 lion batteries
> in both of them. The brightness increases tremendously and they get a bit warm.
> ...



Whoah, and no problems with the LED burning out?


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## bob4apple (Mar 13, 2012)

No, no problem, and I know there are plenty of other folks using these batteries
in the Energizer flashlight without problems. You can search the LED flashlight forum to verify.

Enjoy.


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## Lynx_Arc (Mar 13, 2012)

bob4apple said:


> No, no problem, and I know there are plenty of other folks using these batteries
> in the Energizer flashlight without problems. You can search the LED flashlight forum to verify.
> 
> Enjoy.


I think his issue was with capacity (runtime) and running 14500s will not increase runtime any at all, but instead decrease it dramatically.


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## och (Mar 14, 2012)

^^

Thats also a good point.


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## bob4apple (Mar 14, 2012)

According to another very knowledgeable member of this forum, I quote:

_"14500 has *750mAh*3.7V = 2.8Wh* of energy.
Eneloop has *2000mAh*1.2V = 2.4Wh* of energy.

So, the difference between the high capacity NiMh and 14500 is quite small.
However, note that most flashlights work much more efficiently at higher voltages -
and since the 14500 li-ion has a higher voltage than the Ni-Mh, they normally end up
having equal/longer runtime, as well as the ability to go brighter."
_
Besides, I actually own 2 of the flashlights in question, and have actually used both
types of batteries in them. The lion batteries make them appear about twice as bright,
and I don't notice any decrease in runtime. *Real World Experience beats theories any
day of the year.

*(Whew! End of rant).


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## Hi-Tech Guru (May 24, 2012)

I concur w/ Bob. I've purchased 10 of these lights; 3 different types of LED. I've given most away. But I currently use protected 14500's in both models w/ Cree LEDs (XR-C, XP-C). The lights do get warm, but I can still switch back to AA w/o problem.

The increase in output w/ a 14500 battery is substantial, rivaling the output of my Fenix L2D-Q5 on Hi (not turbo).


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## nofearek9 (May 24, 2012)

is this the flashlight you are talking? : http://www.energizer.com/SiteCollectionImages/products/lighting/work/work/large/MLT1WAAE-LG.jpgabout

In theory a 2500mah x 1.2v would be almost same with a 14500 battery i guess.


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## Hi-Tech Guru (May 24, 2012)

@nofearek9
I can't load the url you've listed. But the Energizer model used is discussed in these threads:
http://www.candlepowerforums.com/vb...rgizer-1W-1AA-Target&highlight=energizer+cree
http://www.candlepowerforums.com/vb...HLIGHT(lots-of-pics)&highlight=energizer+cree

A note of caution: Although the specifications of the LED's used in the Energizer can handle the 3.7v of a rechargeable lithium, a freshly charged 14500 can initially put out ~4.2v. This exceeds max voltage ratings, so I will use my hand as a heatsink. And if I think the light is getting a little too warm, I'll just turn it off for a minute and let it cool.


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## nofearek9 (May 24, 2012)

yep thats it.its good that you can give it 3.7v and not fail.


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## merc240d (Dec 1, 2012)

Simple answer is stay with the 1.5v battery and look into another flashlight that will meet your battery life and output requirements.

Don't depend on a LED light that is being pushed towards the upper end or beyond its rating; unless the flashlight driver has been designed to accept the voltage range. Long term reliability in most consumer products takes a back seat to preceived performance gains. As with all solid state devices localized heating is instantaneous and determines the life of the device. Bigger heatsinks and better die attachment to said heatsink brings about more performace and life from the any LED. Still, the LED operates at a higher temp and the life is shortened. It may be acceptable to go from 100,000 hrs or 50,000 hrs to 10,000hrs or even less. Example, if using the flashlight (10000hr LED) for say 2hrs/day that gives 13.7 yrs of life. A long time to be sure and you will most likely be using a new favorite by then. But since consumer products don't come with reliability data as to when the LED will fail its a crap shoot for the user. This would be unacceptable in the tactical, LE, and Emerg use. It would be much better to get a light that was designed for the 3.7v battery or had the characteristics to give the battery life and output desired. A reputable manufacturer will be balancing all of these items.

Don't smoke too many LED's ($$), but the expermenting is fun.


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