Cr123s OR 18650???

Simple question - I hope.

I've got a Romisen RC-G4.... with a Cree Q4. Would it run longer and brighter on 2x CR123s or 1x 18650?

Waddya think?

Brighter on CR123's, longer runtime on 18650's.


CR123's will be regulated, 18650 will be regulated for about the first 1/4, DD with declining output for the trailing 3/4 (approximately)

Thanks Marduke,

very interesting, a nice simple answer - finally I'm beginning to clear the confusing fog around this technical industry - so how do these batteries compare with Nimh batteries - I've got a brilliant focusable Q5 that runs off 3x Nimh AAs in a remote battery pack.

And whilst I'm at it - would cheap 2500 mah Nimh from Lidl (approx $2 for 4) show the same performance as the more expensive ones

I know these are very basic questions that probably need far more accurate info - but alas I'm only starting to learn, and get addicted to, flash lights!!!

JimmerG said:

Thanks Marduke,

very interesting, a nice simple answer - finally I'm beginning to clear the confusing fog around this technical industry - so how do these batteries compare with Nimh batteries - I've got a brilliant focusable Q5 that runs off 3x Nimh AAs in a remote battery pack.

And whilst I'm at it - would cheap 2500 mah Nimh from Lidl (approx $2 for 4) show the same performance as the more expensive ones

I know these are very basic questions that probably need far more accurate info - but alas I'm only starting to learn, and get addicted to, flash lights!!!

Click to expand...

Is the brilliant focus Q5 a headlamp? Using NiMH cells, you will have a number of hours of pseudo-regulation (the light is direct drive, but NiMH will give a pretty constant output).

2500 cells are usually duds. They are known to turn to crap with only very few cycles. The best general performance is obtained using either quality high capacity cells (like Sanyo 2700's or Duracell 2650's), or very robust low self discharge (LSD) cells like Sanyo Eneloops. For general purpose, I always recommend LSD cells like Eneloops. They can generally be found for about $2.50 each, and the initial slightly higher cost is offset by the fact that they will keep excellent performance over at least 500 cycles. Cost per cycle is less than 1 cent per cell.

I know AAAs dont usualy fit the same Flashlights as CR123 or 18650's but where would they fall in comparison to these two in brightness and battery life?

AKCamper
Brightness depends upon almost everything except the cell you're using to power it usually. Mostly the LED and the driver. But if you're talking about alkaline AAAs then there's no comparison at all - alkaline is terrible for high power flashlights.

Runtime, well 3 AAAs almost = one CR123. And 2 CR123's almost = one 18650. At least if we're talking in very general terms.

Why is alkaline so bad for high powered flashlights???

Mardukes comment was, imho, meant for that specific light, not in general.

In general a single 18650 can give more power and for a longer time than 2 CR123s, because it holds more spice than the 2 CRs.
But it needs another driver - one that is meant for the lower voltage.


PS: alkaline batts can not stand the current draw, therefore rechargeables are better - for high powered lights.

AKCamper said:

Why is alkaline so bad for high powered flashlights???

Click to expand...

1) They leak. A 20 cent cell can easily ruin a $70 light

2) Under load, their voltage sags as their internal resistance increases. This leads to the light being dimmer, and having as little as 1/4 of the runtime as using the equivalent NiMH cell.

3) They are expensive. A CHEAP alkaline cell might be 20 cents. An "expensive" NiMH costs less than 1 cent per cycle.

yellow said:

Mardukes comment was, imho, meant for that specific light, not in general.

In general a single 18650 can give more power and for a longer time than 2 CR123s, because it holds more spice than the 2 CRs.
But it needs another driver - one that is meant for the lower voltage.


PS: alkaline batts can not stand the current draw, therefore rechargeables are better - for high powered lights.

Click to expand...

Yes, thank you, I should have spelled that out.

Wow i had no idea AAAs sucked that much LOL
So how are all these lights producing comparable numbers(lumens&runtime) on 2AAs ??? I asume they are using the NiMh cells right?

AKCamper said:

Wow i had no idea AAAs sucked that much LOL
So how are all these lights producing comparable numbers(lumens&runtime) on 2AAs ??? I asume they are using the NiMh cells right?

Click to expand...

Question is a little vague, but 2xAA cells have much more stored energy than 3xAAA (nearly twice as much).

How bright a light is depends on the circuit driving it more than the power source.

Pretty much every AA light you see reviewed here on CPF is reviewed with NiMh, L91 Energizer Lithium AAs, and/or 14500 Lithium Ion cells. Alkiline just doesn't have much of a place for higher current (1 or more amps) applications. And even for lower current the above AA alturnatives perform better usually.

AKCamper said:

Why is alkaline so bad for high powered flashlights???

Click to expand...

IMHO Alkalines do perform well in low current kinds of lights. Gerber IU/Tempo, E01, Inova X1V2. These lights draw ~50-80mah and alkalines are OK for these kinds of loads. I read somewhere that the Gerber IU runs better/longer with Alkaline AA than Energizer Lithiums.

IMHO Alkalines should not be used in any light that you intend to keep, for simple fact that they WILL leak. 1-week, 1- month, 1-year... its hard to say exactly when they'll spew their toxic guts, but they will, and if you let their spilled guts sit dormant your light will be toast:candle:.

LSD NiMH or Lithium is the way to go.. IMHO.

OK,

So these LDS batteries - can they be charged using a normal intelligent nimh charger?

JimmerG said:

OK,

So these LDS batteries - can they be charged using a normal intelligent nimh charger?

Click to expand...

Yes, they work just like all other NiMH, except they do not lose the charge.

Marduke said:

Brighter on CR123's, longer runtime on 18650's.


CR123's will be regulated, 18650 will be regulated for about the first 1/4, DD with declining output for the trailing 3/4 (approximately)

Click to expand...

Whee.
Perfect answer I was going to give you but as usual one of the long standing members beat me to it!