Which converter?

[ErickThakrar]

Been looking through the Shoppe and I'm somewhat confused over the profusion of different converters. So my question is this:
I have a Longbow Micra. I want to make a McCapsule with a 3 Watt Luxeon emitter in it, but this McCapsule should work with 2 CR123 batteries as well and retain as much brightness as is possible. I was thinking similar brightness on both input voltages, but shorter runtime with the single battery. Is there a converter board that can do that, or should I just build two and be done with it? If two are the best solution, which converter is best for getting the most out of the smaller Micra form factor?
Sorry for the questions, I'm more than a little clueless when it comes to this kind of thing.

 

[Billson]

You should use a badboy or madmax for 1x123 and downboy for 2x123. There is no single converter board that can be used with both configurations due to the big difference in the input voltage limits required by the converters. Too high will blow it and too low will result in direct drive. Try reading the specs for each converter board to determine what your requirements will be. I posted a thread here not too long ago asking the same questions you have.

 

[ErickThakrar]

ok, thanks!

 

[kj]

The Wizard converter can handle both 1x123 and 2x123. But it's quite inefficient IMO so I would recommend having two separate modules for 1x123 and 2x123.

 

[ErickThakrar]

So with a Badboy, how much juice can I realistically expect to get out of it with 1X123? Will I be able to get the full 1 amp out or should I aim for 700 instead? And what kind of runtimes to expect?
I'm also planning on using this mod with an Eco tube for the Micra eventually and put two of the Energizer Lithiums in it. That shouldn't pose any problems should it?

 

[albert]

BB500/600 should be enough.

Using this mod with an Eco tube for the Micra and put two Energizer Lithiums in it might fry the circuit board. Try at your own risk. (Correct me if i'm wrong.)

 

[ErickThakrar]

The Badboy can't handle lithium AA's? It should be the same input voltage and since they're both lithium batteries, shouldn't the internal resistance be the same?

 

[Billson]

I think two lithium AA's will put out 3.4v which is more than the badboy can handle. If you want to use AA's, alkalines or nimh would be a better choice. A lot of the people here have said that a cr123 cell can handle no more than 650ma max current. Anything more than that and you won't get any respectable runtime from it. Runtime will depend on the vf of the led your using. A J vf should give around an hour regulated runtime at 650ma. I have no personal experience with what I'm telling you. These are info I've gathered from the months I've been around here.

 

[ErickThakrar]

So a lithium AA is actually 1.7 volts rather than 1.5? Interesting. Thanks for all the information.

 

[tylerdurden]

If the Vf of the Luxeon is high enough, running it through a badboy on two lithium AAs should be OK. If the Vf is lower than 3.4v at whatever current you have the badboy set to, you risk damage to the converter. I don't know how likely you are to actually fry anything at 3.4v, though.

The "K" Vf bin is 3.51V - 3.75V, and that's at 700ma for Lux III, IIRC. I don't know how much current two lithiums can supply relative to a single 123 cell, but I know a 123 can't run a lux III through a badboy much higher than 600ma. In this case, with a K bin, you very well might damage the board, since the Vf at 600 will be lower than the rated Vf. I wouldn't risk it unless you have a "L" or higher Vf emitter. Even then, I'd probably just build a 500ma badboy and only run it on 1x123.

 

[ErickThakrar]

Thanks Tyler. Appreciate the information. With a 500MA Badboy could I still run it with two AA's in either Alkaline or Nimh? I would really like to be able to go with the two AA option if it's at all possible. Perhaps another type of converter?
The main reason I was thinking about the Lithium AA's was for both runtime over the single CR123 and for longevity in the light itself. And with the added length of the light, it suits itself perfectly for use as a pocket stick.

 

[cy]

I've got a BB500 R2H and a MM+ R2H sammie. Both run fine on 2X AA lithiums (your milage may vary). The output is difinately brighter. I get 1.731 volts from Energizer AA.

One of the most versitile setups is BB750 w/5watt. You can run 1X 123 or 2x 123. the drawback is not all 5watts will run w/1x 123 config. 5watts will suck batteries quick.

 

[tylerdurden]

If the output is brighter on Lithum AA than it is on Alkalines, you're probably put the badboy into direct drive mode (which isn't surprising given the H Vf bin of your emitters).

Now that I think about it some more, I seem to remember Wayne saying the badboy can handle about 0.5v over Vf before self-destructing. I don't know for sure, though. It may be that anything over Vf is out of spec, but some parts have survived up to 0.5v over, or it may be that the circuit can handle that much by design. Hopefully someone else can clear this up for us.

 

[dat2zip]

My testing long time ago showed that the regulated drop out for a BB700 is around 4.2V which is well above a single 123. That's not to say that running wide open on a single 123 and a 5W won't be bright. Yes, it will be bright, but, possibly not in regulation. This is perfectly fine and will still be bright.

yes, the BB will still be OK with Vin greater than Vout (Vf) up to Vf + 0.3V. No more. After that, input battery current will rise exponentially as it goes into hard DD mode and there is a high risk of letting out the magic smoke of the converter board.

yes, L91s open circuit voltage may be 1.731 or some high number. But, what is the voltage when you are drawing 1A? Like 123s, Alkaline and NiMH, the internal battery resistance reduces the battery voltage to something less than the open circuit voltage. So, L91s fresh under load might be 1.5V/cell or 1.6V/cell. I think the datasheet ot web page documentation will lend some clues here as what voltage to expect with a fresh set of batteries.

 

[ErickThakrar]

So for a LuxIII I should be able to run it at say...500 mA with both a single 123 and two L91's with no major problems? Is there a particular bin coding I should look for in order to make sure that the Vf matches up correctly?
I feel like an idiot for asking these questions, but last time I messed with electronics on any level greater than flipping a switch, I was all of 16 years old. I'm 28 now. I've forgotten alot /ubbthreads/images/graemlins/frown.gif

 

[tylerdurden]

I think the answer is "maybe" /ubbthreads/images/graemlins/frown.gif

 

[Billson]

Go to the Sandwich Shoppe and look around. Wayne has a page with the information on bin coding including the voltage range of each specific bin. You should be able to figure out what you need.

 

[ErickThakrar]

From what I can gather from the page, it looks like the Madmax might be a better option? Atleast the page states that you can run it with two L91 batteries or a single CR123. I guess the best thing to do would be to just get a lux emitter with a higher Vf than 3.4...
Heh...I have a feeling this is gonna be a costly hobby /ubbthreads/images/graemlins/smile.gif
You guys have corrupted me!

 

[ErickThakrar]

Or perhaps I should just go with the BB700. I've seen that in numerous places running off a single 123, so that should be possible I guess. **** it, I'll just experiment and see what I can come up with. Thanks for all the help guys and your patience with a noob and his questions.

 

[Billson]

The madmax and the badboy are different converters. It depends if you are looking for voltage regulated or current regulated.