ROP 2C Mag 3853 vs. 3854 100yrd shootout *NEW**Pictures***

[Mjolnir]

I think that you meant that the 3854H was getting blown by IMR cells, not the 3854L. The 3854L works fine with 2 IMR cells, even fully charged (and I use 26650s, which might sag less than 26500s - of course, the stated max continuous load of the IMR C cells is 20 amps, and the 26650s are advertised as 10, so they might not sag less).
My 3854H has worked at about 4.1 volts per cell, and I have not blown a bulb yet.

3.9 amps is lower than what I have been getting with IMRs. According to my ammeter, the 3853H bulb draws about 3.3-3.4 amps and the 3854H draws about 4.4. The 4.4 amps is also at nearly 8 volts at the beginning, so it could theoretically be a fair amount brighter than an ROP with AA cells.

 

[Jay T]

So what you are saying in essence is that what I think is a good and bright ROP HI on 6AA Hybrids is leaving almost 50% on the table?

WOW!! if true.

Just used my Craftsman DVM to amp check my ROP HI and saw about 3.90 when it stabilized. Is that reasonable?

I just ran a quick test between 2 IMR26500 in a 2C mag and 6 eneloops in a 2D mag. I used the same bulb, reflector and glass for both.

The 2C started life as an 18650 ROP and has been treated with progold, the 2D started life life with a LED drop in and was stock.

The IMRs were rested at 4.17 and gave a ceiling bounce of 82 lux with a tailcap current of 4.38A. (note: for this light 4.17 seems to be the max safe point. I have blown a bulb or two at 4.18+. Your Mag may differ)

The Eneloops were fresh charged in a FM holder and gave 57 lux with a draw of 4.0A.

 

[Mjolnir]

I just ran a quick test between 2 IMR26500 in a 2C mag and 6 eneloops in a 2D mag. I used the same bulb, reflector and glass for both.

The 2C started life as an 18650 ROP and has been treated with progold, the 2D started life life with a LED drop in and was stock.

The IMRs were rested at 4.17 and gave a ceiling bounce of 82 lux with a tailcap current of 4.38A. (note: for this light 4.17 seems to be the max safe point. I have blown a bulb or two at 4.18+. Your Mag may differ)

The Eneloops were fresh charged in a FM holder and gave 57 lux with a draw of 4.0A.

Wow, that is quite a bit of difference. Now all we need is someone to get these in an integrating sphere...

 

[lctorana]

I just ran a quick test between 2 IMR26500 in a 2C mag and 6 eneloops in a 2D mag. I used the same bulb, reflector and glass for both.

The 2C started life as an 18650 ROP and has been treated with progold, the 2D started life life with a LED drop in and was stock.

The IMRs were rested at 4.17 and gave a ceiling bounce of 82 lux with a tailcap current of 4.38A. (note: for this light 4.17 seems to be the max safe point. I have blown a bulb or two at 4.18+. Your Mag may differ)

The Eneloops were fresh charged in a FM holder and gave 57 lux with a draw of 4.0A.

Just some thoughts to ponder:

Let's assume any differences between switch/spring internal resistance between the hosts is negligible.

The 3854H must have been a whisker from it's flashpoint at the IMR voltage. I would humbly suggest that the 3854H, if direct driven and putting out that much lux, would have impractically short bulb life and be delicate in the extreme.

The Eneloops, given being freshly charged, would have delivered 7.5V-ish under that load.

The other factor to consider is that there are eleven battery connections versus three for the IMR setup, when you think about it. That means an extra eight spots that can each introduce a milliohm or two of resistance.

My 3854H-equipped RoP is a 4C with 6x 4/5 NiMH Sub-C cells, so seven battery connections. Somewhere in between your two for output.

 

[Jay T]

Just some thoughts to ponder:

Let's assume any differences between switch/spring internal resistance between the hosts is negligible.

The 3854H must have been a whisker from it's flashpoint at the IMR voltage. I would humbly suggest that the 3854H, if direct driven and putting out that much lux, would have impractically short bulb life and be delicate in the extreme.

Delicate in the extreme, Well it's been topped off several times, turned on and off a many more and it's still goin. From what I have read over the years about re rating hotwires is that instaflash territory is reached when the rated life is under a few hours. After the initial fire up (the most dangerous part) the constant drive was 4.4 amps. Looking at Lux's charts 4.4 A of drive current isn't that close to it's max voltage.

 

[lctorana]

Looking at Lux's charts 4.4 A of drive current isn't that close to it's max voltage.

True, of course. I didn't look at that. We're only talking about 7.3V at the bulb, even with the IMR's then, aren't we?

That means, if I can assume the IMRs are delivering about 8V under that load, then it follows you must have about 0.16 ohms in circuit to drop that 0.7V, including the burden voltage of the ammeter. That would be only about half-way to the flashpoint, but remember that without the meter in circuit, the bulb will be driven even harder.

 

[Mjolnir]

That is a pretty big voltage drop. According to those charts, my 3853H is only running at 7 volts, meaning that it is technically under-driven... However, If I do resistance mods then I won't be able to use the 3854H bulb without a serious risk of blowing it.

 

[Jay T]

True, of course. I didn't look at that. We're only talking about 7.3V at the bulb, even with the IMR's then, aren't we?

That means, if I can assume the IMRs are delivering about 8V under that load, then it follows you must have about 0.16 ohms in circuit to drop that 0.7V, including the burden voltage of the ammeter. That would be only about half-way to the flashpoint, but remember that without the meter in circuit, the bulb will be driven even harder.

Already ran a test on that. Doing a wall bounce test ( So the light is locked in position) with the tailcap gave a reading of 25 lux. While using the meter to measure the current the lightmeter read 26 lux. It looks like the tailcap has more resistance that the meter. My tailcap is just the stock spring, no wire bypass.

If you go by current drawn and look at Lux's charts most hotwires don't seem to be as impressive as most people claim. Most of the time people use the resting voltage and look at the chart and say "I have a 1500 lumen light". That little bit of resistance can really kill these things.

 

[lctorana]

<cracked record>

Please don't underestimate ammeter burden voltage, particularly and especially with modern DMMs. Values of 0.25V and 0.4V and even higher are quite common. This is why I advocate ye olde Avometer Model 7, as this ancient meter only has a burden voltage of 0.1V at FSD on DC current scales.
​

</cracked record>

 

[PlayboyJoeShmoe]

I have a second ROP HI running in a 5D light with 6 C Nicad from a drill pack that fell and broke.

I just found among the 14 cells 6 with 9+ Flash amp.

I got 4.14 at the tail of that light.

So I am giving up some brightness in the 2D with 6AA.

Someday I'll be able to get some nice C LiIons....