Got a crazy idea - RCRs' same length as 123 but FATTER....

[KDOG3]

Theres' a feeler thread in the Custom forum about possibly making 17500 bodies for Ras' My problem is that 17500s' have actually less "power" available than a primary - 1100mah vs. 13-1400mah. So I suggested that if they are going to make them they might consider allow them to be 18500 capable. But I started to think as I looked at the battery area of the body on my 170T.... Hmmm theres' quite a bit of difference there ... why don't they make RCRs that are the same length as a primary (34mm) but considerably FATTER like 19mm? Would it be possible to get the same available current as a primary in a RCR without having to go a LONGER body/light? Which means you could switch back and forth between primaries and RCRs' in the same body. You would still need to change bodies of course, to one that could accomodate the fatter cell but afterward you wouldn't need to worry about spacers. I think a Ra would look great with a body the same diameter as the head and tail. I wonder how fat a battery it could actually hold? I realize there is a side to side issue but the "teeth" on the contacts in the Ras' look like it could do a good job of holding a battery securely. I also thought of having bowed springsteel(?) strips that would compress into the sides of the body when larger batt is used and then spring out when a primary is used to keep it centered.

Just an idea....

 

[mfm]

18350 cells already exist.

 

[Kestrel]

My problem is that 17500s' have actually less "power" available than a primary - 1100mah vs. 13-1400mah.

"power" isn't 'mah', power is 'watts', which needs to take the cell voltage into account as well.

I think what you're looking for here is energy, which in this case will be in watt-hours:
17500: 1.1 amp-hrs x 3.7v = ~4.1 watt-hrs
CR123: 1.4 amp-hrs x 2.5v = ~3.5 watt-hrs

So a 17500 actually has ~20% greater total stored energy than a CR123.

 

[copperfox]

Kestrel, CR123 is 3v, so it would be more like 4.2 WH

 

[csshih]

CR123A are not 3V under load.. they can drop to even 2.2V with high draw incan bulbs.

I always though ratings of primaries compared to rechargeables was strange... primaries get labeled with unloaded voltage, rechargeables get labeled with loaded voltage.

 

[pae77]

18350 cells already exist.

+1. Just ordered some from KD. Looking forward to trying them in my L2P with a high voltage XPG drop in I got from DX. It's pretty bright on a 18650. I'm curious to see if it will be brighter on a pair of 18350s. Too bad nobody is making a protected version yet, however.

 

[Kestrel]

Kestrel, CR123 is 3v, so it would be more like 4.2 WH

CR123A are not 3V under load.. they can drop to even 2.2V with high draw incan bulbs.

From this thread by SilverFox, copperfox (LOL, just noticed that), check out what voltage the Panasonic (which is the company making our Streamlight & SureFire & BatteryStation & Energizer & Rayovac & Duracell) cells provided at the 1.0 amp discharge current:

FYI the Malkoff M60 draws 0.6 amps from 3x CR123 @ ~2.65 V ea., and 0.8 amps from 2x CR123 @ ~2.55 V ea. (Voltages taken by an approximate interpolation of the above test data.)

So in the interest of accuracy, I would be happy to recalculate my earlier comparison:

17500: 1.1 amp-hrs x 3.7v = ~4.1 watt-hrs
CR123: 1.4 amp-hrs x 2.5v = ~3.5 watt-hrs

CR123: 1.4 amp-hrs x 2.55v = ~3.6 watt-hrs.

So the AW17500 has ~15% greater watt-hrs than the US.mfg. CR123, compared to my earlier estimation of ~20%.
In the interest of accuracy, of course.

 

[KDOG3]

So a 17500 will last longer than a primary 123?

 

[csshih]

assuming that the cells will actually do 3.7V at that drive current, yes.

 

[ElectronGuru]

Depends on what you're running. A direct drive type setup will turn the extra voltage into more output, so the extra energy would not necceassarally translate into more runtime.

 

[copperfox]

But isn't it generally agreed upon that 1x18650 and 2xCR123 have about the same energy?

So lets assume 2400ma 18650 and 1400ma CR123s:

Using my calculation this gives
18650: 1x(2.4x3.7v) = 8.88wh
CR123: 2x(1.4x3v) = 8.4wh

Using your calculation gives:
18650: 1x(2.4x3.7v) = 8.88wh
CR123: 2x(1.4x2.55v)) = 7.14wh

I was under the impression that to get a value for stored energy you multiply the amp-hours by the nominal voltage. Li-ion nominal voltage is given as 3.7 (or 3.6) volts, and nominal voltage for primary lithium CR123s is 3v. My calculations suggest a closer proximity between the math and what we observe in the real world. :shrug:

 

[hoongern]

I was under the impression that to get a value for stored energy you multiply the amp-hours by the nominal voltage. Li-ion nominal voltage is given as 3.7 (or 3.6) volts, and nominal voltage for primary lithium CR123s is 3v. My calculations suggest a closer proximity between the math and what we observe in the real world. :shrug:

The nominal voltage (being understood as the average voltage over the discharge) for primaries isn't 3V. 3V is the open voltage, when there is no load. Under load, it decreases to ~ 2.5V.

In the same way, the open voltage of Li-ion is actually 4.2V at full charge, but its average voltage is generally ~3.7V.

(Of course, average voltage is dependent on how heavy the load is)

 

[copperfox]

I've measured CR123s with an open voltage upwards of 3.2v (I think).

Like you said, average voltage is dependent on how heavy the load is. So for very light loads, wouldn't the voltage sag be minimal? I certainly don't think a fully charged li-ion will sag to 3.7v under a light load such as 50ma (although I have not tested it myself).

 

[Canuke]

+1. Just ordered some from KD. Looking forward to trying them in my L2P with a high voltage XPG drop in I got from DX. It's pretty bright on a 18650. I'm curious to see if it will be brighter on a pair of 18350s. Too bad nobody is making a protected version yet, however.

Apparently these guys are www.madvapes.com/Protected-18350-Lithium-Ion-Battery_p_2041.html

They seem to be a topic of some popularity among the e-cigarette crowd.

What I'd like to see is some 18350's from someone other than Ultrafire, like AW.

 

[pae77]

Now that I've had a chance to put a few cycles on the Ultrafire 18350's I got from KD, I'm quite pleased with the way they are performing, at least so far. . . I'm also kind of spoiled by the great price they are offered at. I find it difficult to pay almost twice as much for another brand when these have been so satisfactory. Of course, it still remains to be seen how well they will hold up over more time. But so far I'm very satisfied.

 

[mvyrmnd]

I'm a big 18350 fanboy myself. I use a bunch of them.
I run 3 in a JB M1X, 2 each in my RRT-2 and Jet III-M. One in a SST-50 EDC, one in a L2m with nailbender Linger Special.

I find running 2 18350's in the Jetbeams gives the same runtime as a single 18650, but because the voltage is higher I don't have the sucky regulation issues that's common with the Jetbeams.

All of my cells are unprotected, so that's not really a worry for me.

The cell I use in the SST-50 EDC is pushing 3A at a full charge, and after quite a few charges seems none the worse for wear. This little guys can hold up to a fair bit of work

 

[KiwiMark]

I was under the impression that to get a value for stored energy you multiply the amp-hours by the nominal voltage. Li-ion nominal voltage is given as 3.7 (or 3.6) volts, and nominal voltage for primary lithium CR123s is 3v. My calculations suggest a closer proximity between the math and what we observe in the real world. :shrug:

Absolutely not! If you use the nominal voltage of 3V when the actual average voltage is 2.5V then you will over estimate the watt hours by 20%. To get an accurate value for the stored energy you need to multiply the amp-hours by the AVERAGE voltage - using the nominal voltage is a very rough and inaccurate way of doing it. Even with rechargeables you should calculate the average voltage - it is likely to be closer to 3.7V than the primaries would be to 3V but depending on the current draw it could be higher or lower. You will get more watt-hours from any type of battery when draining at lower amps than at higher amps.