# 18650 3.7V vs cr123 batteries



## JerryM (Feb 8, 2012)

I did not see a forum that was obvious to post this in.
What is the difference between the 18650 3.7V vs cr123 batteries? Is one rechargeable and the other not? Can they be used interchangeably?
Thanks, Jerry


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## AnAppleSnail (Feb 8, 2012)

JerryM said:


> I did not see a forum that was obvious to post this in.
> What is the difference between the 18650 3.7V vs cr123 batteries? Is one rechargeable and the other not? Can they be used interchangeably?
> Thanks, Jerry



Check out the battery university. 18650 is a bit thicker and about as long as 2 CR123s, with higher voltage. 18650 is rechargeable, CR123 is primary. They make similarly sized rechargeable cells usually called RCR123. Rechargeables have about half as much power as a primary, but are rechargeable. They tend to maintain higher voltage under heavy drain, useful for high-power flashlights. They are SOMETIMES interchangeable in terms of voltage, but you have to think about the size.


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## LGT (Feb 8, 2012)

18650 batteries are rechargeable, cr123's aren't. Many lights can use one 18650 or two 123 batteries, some can use two 18650 or four 123. But you can't use one 18650 and two 123 batteries in a light that requires two 18650's or four 123's. If that's what you're asking.


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## JerryM (Feb 8, 2012)

Many thanks. That is helpful. I have lights that use the CR 123, but had not heard of the 18650 until the last few days when I was looking at lights to replace a Surefire 
E1e at less cost.
I have also noticed lights that are 7 W and 700 LM that use one AA battery. I am surprised that they can get that level of brightness using one AA.
Regards, and thanks again.
Jerry


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## D50boy (Feb 8, 2012)

I'm new to this too.... so, the single 18650 would last half as long on a full charge as two new cr123s? Is that right?


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## Scottiver (Feb 8, 2012)

In a regulated LED light one 18650 will last much longer than two cr123's because one 18650 has more capacity. Unfortunately an 18650 is usually too fat to fit in most lights that are designed for 123's. In that case, the 17670 size will usually fit. The number represent the size of the battery in millimeters. 18650= 18mm wide x 65mm long.
It's generally safer to use one rechargeable battery than two smaller RCR 123's because it the two 123's are charged at a different voltage and put in the same flashlight, they can heat up and sometimes vent with flame (explode).
The best rechargeable Lithium ion batteries are made by CPF member AW in Hong Kong and are available here:
http://www.cpfmarketplace.com/mp/showthread.php?230876-AW-s-LiIon-Batteries-Sales-Thread-*Part-12*
AW is the most on top of it seller you will ever find, it's like he never sleeps. After you place your order it's often only a few minutes before he confirms your order and creates a shipping label. It still has to be shipped from Hong Kong but i've never had to wait more than a week on the west coast to recieve my batteries.


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## tacticaltony (Feb 8, 2012)

I'm new to the flashlight game also but I wan be a seasoned vet, so where is this Battery university. I have a surefire e2dl defender and surefire told me not to use rechargeable battery's. I'm guess a 17650 would be needed, what is the downfall I I were to use it?


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## Th232 (Feb 8, 2012)

tacticaltony said:


> I'm new to the flashlight game also but I wan be a seasoned vet, so where is this Battery university.



Google "battery university". First link.


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## D50boy (Feb 9, 2012)

Thanks. I've been looking for single celled lights because of the potential hazards. So I see that the 18650s also come in several mAh capacities- what is the quick and dirty on that? Longer run time but longer recharge time? Any advantage over the other?


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## HKJ (Feb 9, 2012)

D50boy said:


> Thanks. I've been looking for single celled lights because of the potential hazards. So I see that the 18650s also come in several mAh capacities- what is the quick and dirty on that? Longer run time but longer recharge time? Any advantage over the other?



Usual the lower capacities is cheaper not only for the battery, but also per mAh. LiIon batteries are usual rated at 3.6 or 3.7 volt, but there are a significant difference in voltage on some types, this is important if you want the most brightness from a single cell light.
I have compared some 18650 batteries and are working on some more.


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## och (Jul 31, 2012)

Wouldn't there be a voltage difference when using one 18650 vs two CR123? The 18650 is 3.7v nominal, and each CR123 is 3v nominal - so two CR123s would be at 6 volts?

I see a lot of flashlights that work either on one 18650 or two CR123's - I assume they have a built in voltage regulator?


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## sidecross (Jul 31, 2012)

Th232 said:


> Google "battery university". First link.



Yes, this is a very good place to start; I went there about two years ago to start learning.


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## edpmis02 (Aug 1, 2012)

och said:


> Wouldn't there be a voltage difference when using one 18650 vs two CR123? The 18650 is 3.7v nominal, and each CR123 is 3v nominal - so two CR123s would be at 6 volts?
> 
> I see a lot of flashlights that work either on one 18650 or two CR123's - I assume they have a built in voltage regulator?




Would a voltage regulator have to work harder (less efficiently) at the higher voltage as compared to the 3.7v which is closer to the LED's voltage? I understand the batteries will not have to work as hard (less amps).


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## wrf (Aug 2, 2012)

edpmis02 said:


> Would a voltage regulator have to work harder (less efficiently) at the higher voltage as compared to the 3.7v which is closer to the LED's voltage? I understand the batteries will not have to work as hard (less amps).



In the simple case, the answer to your question is generally "yes".

However, rather than think of modern driver circuitry as a "voltage regulator", try instead thinking of it as a "power converter". Also, its intended purpose is not so much to regulate voltage to the LED as it is to regulate current (amperage). It may:
a) have "boost" capability to take low voltage and high current to deliver to the LED the intended amperage (at whatever voltage results from that)
b) have "buck" capability to take high voltage and low current to deliver to the LED the intended amperage (again at whatever voltage results from that)
c) have both capabilities

In general, the less power conversion the driver circuitry needs to perform the more efficient it will be, so providing it with a voltage that is a bit more than the forward voltage of the LED plus the overhead voltage of the driver circuitry can be very efficient. However, this is just a broad generalization, and each different circuit design with have its own range that it is most tuned for and most efficient in.

Having said that, note that not all driver circuits are of the power converting type. In particular, linear current regulators are in use for which amperage to the LED is the same as the amperage draw from the battery (cells), and the wattage from any excess voltage is shed as heat.


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## hahoo (Dec 11, 2012)

*rcr123s vs 18650*

will an aw 3400 mah 18650, last twice as long as a pair of aw 750 mah rcr 123's in a tn 11 ?


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## TEEJ (Dec 11, 2012)

*Re: rcr123s vs 18650*



hahoo said:


> will an aw 3400 mah 18650, last twice as long as a pair of aw 750 mah rcr 123's in a tn 11 ?



Probably more.

The RCR's have to drop out sooner in high draw applications, so its not just the 3,400 vs 1,500 mah difference, its also the amp draw, etc they can support.


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## hahoo (Dec 11, 2012)

*Re: rcr123s vs 18650*



TEEJ said:


> Probably more.
> 
> The RCR's have to drop out sooner in high draw applications, so its not just the 3,400 vs 1,500 mah difference, its also the amp draw, etc they can support.



thanks teej.........

and thanks to whoever moved and merged my post in less than a minute.......

guess i broke a rule here or something......


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## Shadowww (Dec 11, 2012)

*Re: rcr123s vs 18650*



hahoo said:


> will an aw 3400 mah 18650, last twice as long as a pair of aw 750 mah rcr 123's in a tn 11 ?


Real capacity of 3400mAh 18650 is somewhere near 3300mAh, and "750mAh" 16340 is 550mAh according to HKJ.
So it's 3300mAh vs 1100mAh, 3-fold difference.


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## hahoo (Dec 11, 2012)

*Re: rcr123s vs 18650*



Shadowww said:


> Real capacity of 3400mAh 18650 is somewhere near 3300mAh, and "750mAh" 16340 is 550mAh according to HKJ.
> So it's 3300mAh vs 1100mAh, 3-fold difference.




wow, thats substantial....tx for that info sir.........


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## TEEJ (Dec 11, 2012)

*Re: rcr123s vs 18650*

LOL

I try not to bury newbs with too much at a time. Nominal vs real stuff will make their heads explode.

Heck, I think it did make mine explode in the beginning too.


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## AnAppleSnail (Dec 12, 2012)

*Re: rcr123s vs 18650*

It's important to note another difference between 1x18650 &2x16340. Voltage!

We compare watt-hours (amp-hours times volts) to compare different batteries.


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