Need advise: What to use to for 750mA from 2 D?

I need some advise, and this advise just might make someone's day. First of all, I want to power a Luxeon III at 750mA and need to know what I would need to use to get this mA from two D cell batteries. Something that will boost the volts/amps and constant until the batteries drop below their volts to power it.

Also, if this is do-able, how long would the setup last as far as battery power?

Thanks!

Its close,,, but a BB750 should be able to do that.
Or maybe a MM WO.

I know for a fact, that a BB1000 will NOT be in regulation with just 2 cells.
I dont have the link with me,,, but goto the Shoppe, and on the converter pages, shoud be a runtime calculator, (similar to mine) that will tell you what the dropout voltage is.

[ QUOTE ]
Orion said:
I need some advise, and this advise just might make someone's day. First of all, I want to power a Luxeon III at 750mA and need to know what I would need to use to get this mA from two D cell batteries. Something that will boost the volts/amps and constant until the batteries drop below their volts to power it.

Also, if this is do-able, how long would the setup last as far as battery power?

Thanks!

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Assuming that you use a BB750 or other converter with similar efficiency and assuming that you are talking about alkaline D cells: I would expect that you could stay in regulation somewhere between 0 and 90 minutes. It would depend mostly on temperature and the particular cells used. This will be a very heavy load for the cells and some do better than others under heavy load. This would be a good application for NiMh cells.

If I went with 3 C size batteries, would it be a good idea to use one of these boards, or just drive the Lux III directly?

you could direct drive it then,, it just would have quite as flat of a brightness level over time. (not regulated)

You might want to use a resistor to get down to around the 750mA though.
Direct Drive would be much more than that.

I had a similar question so I guess I'll post it here. Is there enough room in a 2C mag for one of these boards if I remove the bulb post compleatly?

Or can you stuff 3 123's into a 2C or 2D m@g then use something like a downboy?

I hope you don't mind me posting this here, if so let me know and I'll remove it.

IIRC, the BB and MM boards are designed purely to boost the input. So if you use them with 3 alkaline cells, the board just passes the current right through and you are almost in direct drive mode with a little bit of loss through the circuit. Only when Vbatt drops below Vf of the LED then will the board start operating as it was meant to.

These boards were originally designed to fit in a 2 AA MiniMag, so I think they would be the diameter of an AA cell. With some creativity and the correct tools, there should be heaps of space to put them in a 2C Mag. Check out the Hotlips from CPF member Hotbeam.

Re: Need advise: What to use to for 750mA from 2

I modded a Blaster 1R (before Wayne came out with the HB-1R) with a 3W and a BB750. Works GREAT.

Doug S: I haven't done a run-time test on mine but <90 min seems awfully low considering Wayne claims 8hrs with dual PowerPucks in the HB-1R. I know mine has run (intermittently) much longer than this.

Re: Need advise: What to use to for 750mA from 2

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mhejl said:
I modded a Blaster 1R (before Wayne came out with the HB-1R) with a 3W and a BB750. Works GREAT.

Doug S: I haven't done a run-time test on mine but <90 min seems awfully low considering Wayne claims 8hrs with dual PowerPucks in the HB-1R. I know mine has run (intermittently) much longer than this.

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Mikey, I don't know what a Blaster 1R is powered by, but from context I will assume 2XD. I know <90 min seems short. I will stand by this statement. It is my [well informed, I think] belief that many folks running high current BBs off of alkalines are not running in regulation when they think that they are. The way to tell if your BB is in regulation is to monitor the voltage across the sense resistor on the board. If it reads 50 mV +/- a few mV you are in regulation. If <50mV it has fallen out of regulation. Intermittant use will get you much more time in regulation. My initial comment was based on the assumption of continuous operation. R.e., Wayne and his Powerpucks, are you sure that they are current regulated?

Re: Need advise: What to use to for 750mA from 2

So basicaly, a 2C or 2D magmod with a BB 750 will be slightly less bright and about the same runtime as a 3C or 3D DD in runtime respectively?

It will be a bit smaller and less bright but will cost about $30 more for the regulator circuit is this correct?

Re: Need advise: What to use to for 750mA from 2

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Doug S said:
R.e., Wayne and his Powerpucks, are you sure that they are current regulated?

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I haven't looked at the data recently but I originally wanted a 1R with a BB350 because it was current regulated as opposed to the MicroPuck which was voltage regulated; I didn't particularly care about run time, just a relatively constant output over whatever time I could get out of the 2Ds - the MicroPuck dims as the batteries go.

Still, the 3W with BB750 is way brighter than the original 1W with MicroPuck. I wouldn't go back.

Time to do a run test... Will report back...

Re: Need advise: What to use to for 750mA from 2

Quick informal test with 2 partially discharged D Energizers (1.46V each): 2 hrs, 4min until the BB750 w/3W dropped out of regulation. Ending voltage 1.24V each.

Wish I had a light meter but output seemed pretty constant until a sharp dropoff just after the 2 hrs. Broke that 90 min estimate anyway /ubbthreads/images/graemlins/thumbsup.gif

Re: Need advise: What to use to for 750mA from 2

I've also been thinking about doing a mod like this. I'd be real interested in the typical run times of 2Ds with the BB750.

Re: Need advise: What to use to for 750mA from 2

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Doug S said:
It is my [well informed, I think] belief that many folks running high current BBs off of alkalines are not running in regulation when they think that they are

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mhejl said:
Quick informal test with 2 partially discharged D Energizers (1.46V each): 2 hrs, 4min until the BB750 w/3W dropped out of regulation. Ending voltage 1.24V each.

Wish I had a light meter but output seemed pretty constant until a sharp dropoff just after the 2 hrs. Broke that 90 min estimate anyway /ubbthreads/images/graemlins/thumbsup.gif

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Mikey, if you judged regulation by "seemed pretty constant" I suspect that you are one of the folks that I am talking about. When it occurs slowly, a drop of 20 or 30% just doesn't get noticed. On the other hand, if you monitored the 50 mV sense voltage, then I stand corrected /ubbthreads/images/graemlins/thumbsup.gif

Re: Need advise: What to use to for 750mA from 2

Okay, so new D cells should produce light a bit longer. However, the D cells still have a fair amount of voltage after the test. I wonder what one could do with them. Put them in a Blaster III? Well, that's beside the point.

I may consider the BB750 with 2 D cells, but if anyone else has another option, please let me know.

Thanks for the great thread! Very informative!

Re: Need advise: What to use to for 750mA from 2

Sorry, Doug, I must be "one of those folks" then. I really couldn't care less about sense resistors and quantified output. All I wanted (at the time) was a 2D with a 3W driven close to spec and the only choice was a BB750; the dual MicroPucks weren't discovered until later. I may have to try the dual MicroPucks now...

Re: Need advise: What to use to for 750mA from 2

So, would the dual micropucks be better? Constant Current? More efficient for 2 D cells?

Re: Need advise: What to use to for 750mA from 2

Doug, I doubt even with NiMH they are staying in regulation for very long anyhow.

Anyone have brightness/time voltage/current plots for the high current BBs?

Re: Need advise: What to use to for 750mA from 2

dual micropucks will be less out put. I think it's 620ma. Plus using 2 converters to do the same job as one I would imagine it would be less efficient... /ubbthreads/images/graemlins/icon3.gif

Re: Need advise: What to use to for 750mA from 2

I guess I'm still looking for an answer to my original post.

If you have an idea, please let me know!

Thanks!