D-cell powered ROP Voltage and Amperage Results

[jwl]

Let me know how this compares to the ROPs that you guys have.

Running (6) CTA D-cells 12,000 mAh. No load voltage is 7.77 Volts.

Tested 4.12 amps (3854-H) at the bulb at 7.38V. Looks like I'm pushing the 24W bulb to 30W. Sound correct?

What would that calculate to in lumens? Bulb lumens or torch lumens.....

Thanks.

 

[SilverFox]

Hello Jwl,

I am not sure about lumens, however your no load voltage seems a bit low. A 6 cell pack should start off at around 8.4 volts.

I do know that higher voltage equals more lumens...

Tom

 

[Delvance]

Yep 30W sounds about correct. As Silverfox mentioned, your no load voltage seems a bit low although your voltage under load is fine. Actually, it's probably better than most users are getting with their smaller cell powered ROPS i'd daresay. Are you running a fixed switch or is it stock ?
Should be getting over 1150 bulb lumens. The generally used percentage factor for determining lumens from bulb to output is 65%. So should be over 750 output lumens easily.

 

[jwl]

Hello Jwl,

I am not sure about lumens, however your no load voltage seems a bit low. A 6 cell pack should start off at around 8.4 volts.

I do know that higher voltage equals more lumens...

Tom

I should have mentioned that my cells were not fresh off the charger, but have probably 1/2 hr to 45 minutes of usage in the flashlight. I will recharge the batteries and get another reading.

Got a question for you guys. I measured the voltage with the batteries out of the flashlight (is that cheating :thinking: ?, maybe :shrug: ). The reason I did it that way is that when the light was turned off I could get a good voltage reading by probing the rear of the battery pack and the bulb retaining cap. BUT, when I turn the light on the voltage shown on the multimeter was dropping to ~.5-.6V.:huh2: .

How do you guys measure the voltage with the light assembled and get an accurate measurement?

Delvance - Running a stock switch, for now. I've been reading up on the ways to reduce the resistance.

 

[Delvance]

I recommend doing the full switch fix, gain couple hundred of lumens and alot of whiteness! Measuring the voltage out of the torch is kind of cheating, as the batteries are now no longer under load plus you're not taking into account the resistance of the torch body itself and also the switch. To measure volts, you have to connect your DMM in parallel at where the bulb is...kind of tricky as it's not a bipin lamp.

I actually just measured...i used a thin piece of wire attached to the +'ve probe, at other end of the wire, i stripped a bit of housing off, and gave it an "L" shaped end. Then place "L" shaped end onto where the bulb would normally go, and then the bulb goes on top of the piece of wire (use really thin wire). -'ve probe then goes to where the bulb retaining ring would usually screw onto. I really don't advise doing this though...if the bulb explodes...very dangerous, unless you manage to do it all behind a shield.

Anyways, my results
My ROP is running 4 18650 LIons, 2S2P config.
Open circuit ~8.38V
Under load ~7.43V at the lamp.

 

[jwl]

Thanks for the explaination on how you measured yours. I've got some small wire so I will give that a shot and post those results in the first post, probably along with the first results to get a comparison.

I'm running the batteries down in the light right now, so far it has been on for 1hr-15min (not counting the messing around ~30 min+ from the last couple nights).
I will run the batteries through a condition cycle in my Maha-C808M tonight and retest tomorrow.

Thanks for you help and comments.

 

[cmacclel]

I'd leave you switch alone it's probably saving you from Instaflashes. Those "D" Cells hold much higher voltage than the AA's everyone else ir running. Hot of the charger you risk Instaflashing.


Mac

 

[SilverFox]

Hello Jwl,

A comment on the conditioning cycle on the C808M...

The conditioning cycle of the charger first charges at 2.0 amps to full charge, then discharges at somewhere around 0.35 amps, then charges back up at 2.0 amps.

If you put drained cells in and start a conditioning cycle, you can expect around 7.5 to 8 hours to charge, 34 hours to discharge, then another 7.5 to 8 hours to charge back up again.

That may take a bit longer than one night...

Tom

 

[jwl]

Hello Jwl,

A comment on the conditioning cycle on the C808M...

The conditioning cycle of the charger first charges at 2.0 amps to full charge, then discharges at somewhere around 0.35 amps, then charges back up at 2.0 amps.

If you put drained cells in and start a conditioning cycle, you can expect around 7.5 to 8 hours to charge, 34 hours to discharge, then another 7.5 to 8 hours to charge back up again.

That may take a bit longer than one night...

Tom

SilverFox..thanks for the reminder on the times. Maybe I'll just charge 'em backup and retest. I will only be the second time they have been charged.

 

[jwl]

Okay, cells fresh off charger are 8.5 Volts. Now lets pop those babies into the flashlight and see what happens........

7.56 Volts under load
?.?? Amps -- Don't know I blew the fuse Next time I guess I should wait to probe the light until AFTER it is lit, not leave it connected and get the initial burst of power. My meter can only has a 10A fuse. I know I saw double digits for a second then the display returned to 0.00.

I'm goin to bed now...:sleepy:

 

[Delvance]

Thats a very good figure Jwl Don't worry about the amps drawn, it'll be between 4 and 4.13 roughly. Easily over 30 watts fresh off the charger!

 

[mdocod]

wow- That setup (while kinda large) would provide ~3 hours runtime... seems like a winner for a seriously powerfull light, that has enough runtime to count on in the long haul- very cool...

 

[jwl]

Thanks guys. I did notice one thing that somebody needs to figure out how to prevent. When I ran it for 1-1/2 hr straight (with a fan blowing across it) the rear bulb contact got hot enough to melt and form to the shape of the cup that it touches inside the bulb mounting post. I saw this happen on somebody else's thread also, he had to add a blob of sodder onto the rear bulb contact to get the bulb to rear the positive post cup. Mine still reaches so I didn't need to do that.

 

[91101]

7.56 volts calculates out to 1314 bulb lumens and 34.8 watts.

7.56/6 = 1.26 (amount of overdrive 26%)
1.26^3.4 = 2.19 x 600 (stock lumen=600)
1.26^1.6 = 1.45 x 24 (stock watts=24)

 

[missionaryman]

My 2C ROP on two U/P 18650's measures 4.37AMPS, 8.4v unladen at the bulb contacts but how do I get the Vbulb under load? On the bi pin lamps you just put a probe on each pin but how do you do it on the PR ROP bulb?

 

[jwl]

Missionaryman - See post #4 of this thread. This is how I got my measurements also.

 

[cmacclel]

Just sneak a thin wire up to the positve spring is the easyiest way.


Mac

 

[missionaryman]

Thanks JWL & MAC - I'll give it a try, in the meantime I can't find the switch fix for the C switch, does anyone have the link or the instructions for this?

 

[wtraymond]

7.56 volts calculates out to 1314 bulb lumens and 34.8 watts.

7.56/6 = 1.26 (amount of overdrive 26%)
1.26^3.4 = 2.19 x 600 (stock lumen=600)
1.26^1.6 = 1.45 x 24 (stock watts=24)

This is a case where the formulas just don't work above 10-15% overdrive. Actual readings are much more representative of true power than re-ratings.

For the Pelican bulb to output 35 watts at 7.56v, it would have to draw about 4.6 amps. In actual use it does not draw that much current. My ROP LE running two LG 18650 li-ions draws 4.25 amps fresh of the charger. Voltage at the bulb is a measured 7.42v on my calibrated Fluke meter.

Although you may see small variations from bulb to bulb, these numbers should be fairly close. I don't think you'll get 35 watts out of the Pelican bulb before blowing it. MAYBE maybe with a soft-start or regulator.

 

[NotRegulated]

I have a 25 yr old 6D Mag that I would like to make a ROP out of. What is the best battery solution for the "D" sized light? If it is 6 D NIMH's what kind do you recommend and where can I get them? Also, what do I need to charge them?