18650 vs. CR123A rechargeable bats

I have a question regarding batteries and my LED light.

I have a Q5 CREE LED light from ultrafire.

What is the difference between using one 18650 3.7 volt battery and using two CR123A's 3.6 volts?

Isn't two 3.6 volt batteries actually 7.2 volts?

So would I get more power/length from the 2 batteries?

The LED's operating voltage is 3.6 to 9 volts.

It really depends...
In the case of the cheap electronics from the ultafire it's hard to say exactly what will happen but let's go thru a basic comparison between the two power sources.

An RCR123 runs average 3.7V and has a capacity of around 700 mAh (a generous estimate imho) therefore we have (volts x amps = watts) ~2.6 watt hours per cell. 2 of them are therefore around 5.2 watt hours.

An 18650 also using the same chemistry runs an aerage 3.7V and has a capacity of about 2200 mAh. So we have 8.1 watt hours.

The 18650 is clearly superior on paper.

LED lights don't get brighter from more voltage like incandescant lights do. LEDs have a very specific voltage required to make the LED light up. So driver ciruits are often put into lights which allow use of a range of voltages and cell configurations.
Now depending on the driver circuit the 18650 may or may not run the LED at full power. In the case of your ultrafire I'd bet it only stays in regulation for half of the battery life on an 18650. Then after that it will start to dim slowly as the simple circuit no longer controls the voltage to the LED. However this will just give you even more runtime on an 18650 for a negledgeable drop in output.

So in almost every case I'd go with the 18650.

1 18650 powering my 6PDL (W/Q5 dropin) is a little dimmer than using 2 RCR123's. But i get about 3 weeks of use with the 18650 vs 1 week with the others.

:shrug:

Thanks Phantom!!! That's great information.

I'm hoping that being a bit dimmer isn't the case with my light. I have two of these now (i liked the first one so much I wanted another one).

One has CR123's and the new one will have 18650 battery. So we'll see which one is better.


Specifically the info on the light is below if this helps:

• <LI class=STYLE27>Material:6061T Aluminium <LI class=style67>Bulb: CREE XR-E Q5 LED, 270 lumens output(Max) <LI class=STYLE27>SuperBright, blinding Effect <LI class=STYLE27>Lifetime-above 10,000hrs <LI class=STYLE27>Working Current: 450-600mAh <LI class=STYLE27>Operate Voltage: 3.6-9V <LI class=STYLE27>Batteries: Lithium 2xCR123A 3.0/3.6V, 1x18650 3.6/3.7V <LI class=STYLE27>Runtime: 1.5-4.8 hours depend on battery capacity (continous working) <LI class=STYLE27>Body Color: Black <LI class=STYLE27>Switch: Tailcap Clickie On/Off <LI class=STYLE27 style="COLOR: rgb(255,0,16)">Waterproof, It's water-resistant ! use it in rainy day, no problem ! <LI class=STYLE27>Size(mm): 133(Length)x31(Diameter)
• NetWeight(g): 110

Please post in the correct place. This obviously belongs in the Batteries section, so I'm moving it there now.

Ok...this is kinda off target but what brand of 18650 / and charger set-up would you guys recommend!?! Battery station has a huge supply but I'm not sure exactly what I'm looking for. It would be for my Fenix TK10.

AW's 18650's are top notch. You can buy batteries and chargers here.

One other thing to point out is that lithium batteries don't like to be driven at more than 1C or so. So for a CR-123 battery you're looking at an optimistic 800 ma draw before voltage sags and you start losing more power in the batteries internal resistance, and cell chemistry limits. So you effectively have a battery that can't output as much as it's rated for. But if you must absolutely have flat regulation go for CR-123's as they'll output voltage higher than the vF of the led. The disadvatage is that you'll go from full power to no light with practically no warning since all of a sudden a cell will go into protection, or worse if you're using unmatched primaries is you're light will go

I personally don't mind my 18650's dimming, gives me warning that I need to change the batteries with freshly charged ones. And though I only get half the battery time with regulation on the light, that half is actually longer than the total runtime on 2 RCR-123's.

I think too many people were indoctrinated by Surefire and Inova to think CR-123 is the ideal power source, I mean Surfire even has a light that uses 20 CR-123 batteries called The Beast II that's just inviting trouble to try and power it with that many individual primaries, think of it as a bomb in your hand with about a 2 hour fuse before a bunch of cells start reverse charging and BOOM goes the dynamite.

Policetacteam said:

Ok...this is kinda off target but what brand of 18650 / and charger set-up would you guys recommend!?! Battery station has a huge supply but I'm not sure exactly what I'm looking for. It would be for my Fenix TK10.

Click to expand...

18650 cells do not fit the TK10, your need two 16340 cells. Many people uses the AW brand cells, they have protection and are good quality.
Your can buy them here on the market place

Many people are using the WF139 charger, including me. It is not the best charger on the market, but it works.

Policetacteam said:

Ok...this is kinda off target but what brand of 18650 / and charger set-up would you guys recommend!?! Battery station has a huge supply but I'm not sure exactly what I'm looking for. It would be for my Fenix TK10.

Click to expand...

The Pila IBC charger is widely regarded as the premier charger for Li Ion cells. Good price for it here:

http://www.flashlightz.com/product.php?p=pila_bc01-ac01&product=171829

Most folks here on CPF trust AW's cells best. I have a few 18650s and they are working out great. You can buy RCR-123s for your TK10 here:

http://www.cpfmarketplace.com/mp/showthread.php?t=184670

Glad to hear you got the TK10. I'm sure it is performing well for you.

Good luck.

What do you guys think about wolf eyes li ion cells? Don't they have robust pcb's? I am using them with my m90 rattlesnake/ lf ho-9l. And pila ibc charger I got got from flashlightz.com

I generally recommend Wolf-Eyes, AW, or Pila brand protected li-ion cells for flashlight applications, they should all be pretty darn good cells.

Protected 18650 = Wolfeyes 168a

Or am I mistaken????

Nevermind, just checked Wolfeyes site, appear to be the same type....

I'm considering opening up my 6P for use with 18650's but there's a couple points I'm still not clear on.

I've seen non-rechargeable CR123a's advertised as having 1400mAh capacity. If that is the case it would appear that two non-rechargeable CR123a's would have a longer life than 1 18650. Can that be realistically expected or is it marketing hype?

Also would boring out the body to accept an 18650 adversely affect the light's ability to reliably function on CR123a batteries? I'm concerned the slightly looser battery tube might result in contact problems.

GreyShark said:

I'm considering opening up my 6P for use with 18650's but there's a couple points I'm still not clear on.

I've seen non-rechargeable CR123a's advertised as having 1400mAh capacity. If that is the case it would appear that two non-rechargeable CR123a's would have a longer life than 1 18650. Can that be realistically expected or is it marketing hype?

Also would boring out the body to accept an 18650 adversely affect the light's ability to reliably function on CR123a batteries? I'm concerned the slightly looser battery tube might result in contact problems.

Click to expand...

mAH alone does not translate to runtime, total WattHour energy storage at the load in question does.

A CR123 primary delivers an average ~2.5V during a discharge, while lithium cobalt rechargeable cells deliver about 3.7V on average into a load. Both voltage and capacity must be factored in to describe the total energy stored in a cell.

There are also variations in the way that these cells perform at different loads. Generally speaking, the li-ion rechargeable cell starts to pull ahead of 2 CR123s when the load gets a little higher, while a pair of CR123s will have more available stored energy when discharged slowly.

In the end, a 1x18650 light and a 2xCR123 light are going to be in the same ballpark of total runtime, as both configurations have similar stored energy.

After factoring in the fact that the 18650 is rechargeable, comparing it to a primary configuration is less meaningful, it should instead be compared to other rechargeable options as the recharge-ability is a major feature that sets it apart. To get the same output/runtime from competing battery configurations would require 4 RCR123s or 3AA NIMH or 3 14500 li-ion cells. All of which would be far more space consuming.

Eric

Thanks for the reply, it's given me a few things to research.

As far as comparing CR123a's to rechargeables I understand it's a little apples to oranges but my goal isn't to be rechargeable, it's to get more runtime. I've heard a lot of people talking about the 18650's so I'm trying to understand what they can do better.

mdocod said:

In the end, a 1x18650 light and a 2xCR123 light are going to be in the same ballpark of total runtime, as both configurations have similar stored energy.

Click to expand...

I'm trying to wrap my head around this battery situation. I have been doing a lot of reading on here.....a LOT. I have chosen to go with protected batteries.

I have a Surefire 6P with an LED Q5 bulb in it. Right now I am running crappy ultrafire rechargeable 123a's. Today I overdischarged one cell by doing a run test on them.

So I am thinking of going with the AW brand as mentioned by so many people on here. It does seem like the way to go.

So I am still stuck at 18650 vs 123a's. My ultimate goal is run time. Has anyone tested run time with AW's batteries?

Or does anyone know which set up will run longer??

Lastly, do primaries run longer than rechargeables? If so, how much longer.

Hello michiganstud,

If your ultimate goal is runtime, your best bet is going to be to run a single larger Li-Ion cell to drive the module, this will reduce your output some, but will give you a very efficient use of the cell through the discharge, with a steady but barely noticeable drop in output through the discharge.

The stock 6P does not have room for an 18650 (you could run a single 17670 if you want), but if runtime and recharge-ability in that platform are the goal, then you'll want to pick up an 18650 compatible body for the light. CPF member Nite is selling some FM brand bodies that are really decent over in the custom-mod/BST section of this forum.

As far as rechargeable vs primary runtime comparisons, this is a comparison that is not really fair to make, but I will try to summarize some of the important points:

A pair of CR123s packs slightly more stored energy than a single 18650 cell when the 2 configurations are compared at a LOW drain rate (like an LED module).

A single 18650 packs slightly more stored energy than a pair of CR123s when the 2 configurations are compared at a higher drain rate (like an incandescent module).

A Single 18650, with its lower voltage than a pair of CR123s, will operate most buck regulated LED modules at a lower (read "direct drive or less") output than would be the case on a pair of CR123s. This results in less output, but much more runtime because less energy gets used over time.

So... the answer to most of your questions will always depend on the specific configurations being compared.

If your main goal is to get really good runtime, then I suggest you take the following things under consideration:
1. RCR123s are the worst option for maximizing your stored energy.
2. Something with multiple modes will allow you to run for extended periods of time with less power consumption.
3. Just because a pair of CR123s technically has more stored energy than an 18650 at low drain rates, does not mean that you will always be leaving the house with a fresh set of CR123s loaded. With Li-Ion cells, you can "top off" your cells whenever you feel like it. This means that you are always starting "fresh" and never have to play the guessing game of how much of the batteries you have used up and whether you need to bring along spares.

-Eric

mdocod said:

The stock 6P does not have room for an 18650 (you could run a single 17670 if you want),

Click to expand...

That right there pretty much solves the issue then! I don't really want to invest in a new tube for the light I have. And it seems the CR123's are going to be sufficient as long as I get good cells, right?

As far as rechargeable vs primary runtime comparisons, this is a comparison that is not really fair to make, but I will try to summarize some of the important points:

A pair of CR123s packs slightly more stored energy than a single 18650 cell when the 2 configurations are compared at a LOW drain rate (like an LED module).

A single 18650 packs slightly more stored energy than a pair of CR123s when the 2 configurations are compared at a higher drain rate (like an incandescent module).

A Single 18650, with its lower voltage than a pair of CR123s, will operate most buck regulated LED modules at a lower (read "direct drive or less") output than would be the case on a pair of CR123s. This results in less output, but much more runtime because less energy gets used over time.

So... the answer to most of your questions will always depend on the specific configurations being compared.

If your main goal is to get really good runtime, then I suggest you take the following things under consideration:
1. RCR123s are the worst option for maximizing your stored energy.
2. Something with multiple modes will allow you to run for extended periods of time with less power consumption.

Click to expand...

All great information and exactly what I was looking for! :thumbsup:

3. Just because a pair of CR123s technically has more stored energy than an 18650 at low drain rates, does not mean that you will always be leaving the house with a fresh set of CR123s loaded. With Li-Ion cells, you can "top off" your cells whenever you feel like it. This means that you are always starting "fresh" and never have to play the guessing game of how much of the batteries you have used up and whether you need to bring along spares.

-Eric

Click to expand...

Now this is news to me. Does this mean that Li-Ion's don't have the memory effect and I can charge them any time I want to "top off" the batteries? Say before a patrol shift when I knew I used it several times the night before.

michiganstud said:

Now this is news to me. Does this mean that Li-Ion's don't have the memory effect and I can charge them any time I want to "top off" the batteries? Say before a patrol shift when I knew I used it several times the night before.

Click to expand...

Actually, "memory-effect" as the industry has tried to convince you of, doesn't exist in any common type of rechargeable cell in any sort of normal consumer usage, there are other issues that can crop up that are often mistaken for "memory" effect.

Li-Ion cells are perfectly fine being shallow cycled. You can use them for 10 minutes and top them off and that's perfectly fine. The only issue here is making sure you have a charger that can properly top-off cells without over-charging.

Generally speaking, yes, you can top these off as you please, which in many ways makes them preferable to CR123s even though you may or may not have as much total energy stored.

-Eric