Help with my first mod (3x5w / bb700)

hi I am trying to do a 3x5w mod (similar to Flash's), and I need some help with the electrical part (as I don't know anything about it). So some help would be greatly appreciated.

Here is what I want to do:

Leds: 3 x 5w
Regulation: Badboy(s) 700
Battery Voltage: between 15V and 24V (10'000 to 15'000mAh)

My questions are:
1) How many badboy sandwiches will I need - 3-or can I do it with less?

2) What is the maximum battery voltage that I can use (the badboy specification say to not use more then the output V, which in my case would be 3 x 6.2V=18.6 - is this correct?

3) Why is the badboy output 6.2V when the typical Vf according to Luxeons 5w Spec-sheet says 6.8Vf?

4) Why is the bb700 output voltage a range between 4.0 and 6.2V - what determines the real voltage? the Led? If so, isn't the voltage supposed to be the same all the time?

5) Why does the BB700 specification say Maximum Input Voltage 9V when the input voltage must not exceed the output voltage - which is with a 5w max 6.2V?

6) How do I need to assemble everything (wiring)? Are the 3 x bb700 (I assume here that I need 3) to be mounted parallel (each one followed by the led) on to the battery, or is there a way to do it all in series?

7) Is there anything else I need to do my mod (other then a massive heat sink?)

Thanks for helping

OK, someone please correct me if I'm wrong, I have limited experience with the badbays.

1. Sounds like you'll be doing a M@g mod or something with 3 LEDs so you won't be using sandwiches. You'll be using 3 BB boards. The sandwiches have the LED incorporated onto them. And they are 1W, unless I missed something.

2. Vin cannot exceed the Vf of the luxeon you are using. The BB is a boost only circuit. If you use more voltage in than Vf, it'll run in Direct Drive and you could fry your LEDs if you use too much voltage. You might even fry the BB. Check the tech info on the BB about this.

3. Not sure what you mean by this. Sorry, maybe someone could take up my slack.

4. I think you're referring to the input voltage. This is the range of voltage across which the BB is able to put out a regulated current for the 5W LEDs. Once voltage falls below 4v for a 5W LED it will drop out of regulation.

5. That's the maximum that the board can take. Max in is still determined by Vf. Possibly for running in series, but I've never run LEDs in series so I never checked it out.

6. If you want to deliver 700mA to each LED, you'll need to run 3 in parallel.

7. What host will you be using?

OK, someone else can give you the long answer, but that's the short of it. I think... /ubbthreads/images/graemlins/grin.gif

Thanks for the answers.
1) I dont use the bb sandwich, just the bb converter board. Here are the specifications of the converter:
https://secure3.dnsaction.com/~anlighte/shop/product_info.php?cPath=23&products_id=46

2)ok, but what is the max. Vf, is it 3 x 4.0 or 6.2 as in the bb specification, or 6.8 as in the Luxeon specifications?

3) ..

4) ok - that one is answered

5)..

6) ok so each of the 3 badboy700 connects to the battery, followed by the LED

7) I ll be using a copper tube... so not really a host.

2. OK, I must be assuming something that I shouldn't. The Vf range from the one extreme to the other for 5W luxeons is 5.43v for a R Vf 5W to 8.31v for a W Vf luxeon. Since you will be running things in parallel, you must consider each individually without adding anything together. Each BadBoy will simply be sharing the power pool with each other. In other words, you won't be getting much runtime if you use 123's. Let's just say that you're going to use 123 cells. The max you can use is two, since 3 would give you 9 volts and this would exceed the Vf of any of the 5W luxeon. If you want to split hairs, take the Vf of your luxeon. Say you're going to use T Vf luxeons. To be safe use the lower range for the T's which is 6.39v. I'd just call it 6v to be safe. In this case, you'd want to limit input voltage to 6v and let the converter do its job of boosting. If this doesn't do it for you, I apologize. Maybe someone else could be more clear.

You may want to consider a direct drive setup and maybe use resistance to limit current.

7. Aren't copper tubes kind of thin? Are you sure that you'll be able to dissipate all of the heat that's gonna be generated. I mean the KL4 is underdriven as it is and if you let it go, it's almost too hot to handle after 15 minutes.

Without going through a 5 page tutorial on converters, there's a few things that you need to know about the BB and DB's.

BB: Maximum input voltage = 9V
DB: Maximum input voltage = 16V

The BB's are step-up constant current converters. The word "current" is the operative word. LED's biased at a constant current have voltages that vary from part to part. This is what's called Vf or forward voltage. For the BB's, you need to ensure that the battery voltage does not exceed the Vf of the LED. Nothing vague about that except the Vf of the LED which we already know varies from part to part. The most conservative measure is to take the lowest possible Vf of the 5W, whatever that is, and to make sure the battery voltage does not exceed that. So let's say the minimum is 6.1V. You want to make sure that your battery voltage does not exceed 6.1V. We can get into Schottky diode drops yada yada yada and come up with a slightly higher value but this is an easier rule of thumb.

As far as running LED's in parallel, note that the BB's have a schottky diode that, I'm guessing since I haven't been corrected yet, has a MAXIMUM continuous rating of 1A. That precludes running the LED's in parallel. You can run 3 BB's with each one dedicated to one LED but that's suboptimum economically. Running the LED's in series cannot be done with the drop in sandwiches because you would exceed the input voltage rating of the DB if you were doing series connection, and you would demand too much of a step up from the BB (9V to 3xVf). So the easy solution is the suboptimum one. Buy 3 converters with each one dedicated to one LED.

Finally, have you played with a single 5W part driven to 700mA? I highly recommend you try one out just to see how much heat that sucker generates. You may decide this mod is nothing more than a "monster truck" exercise. Cool to look at and show off but absolutely no utility, IMHO, whatsoever. If you want that much light, you might be better of looking an HID's like the UK Light Cannon. It's a nice size package that packs a lot of lumens.

CM

Thank you CM, you are far more articulate than I. Especially since you actually know what you're talking about. /ubbthreads/images/graemlins/smile.gif

mobile1,
If you want to get into a 5W mod that almost anyone can do, go to Elektro Lumens' site and get what's needed to mod a M@g light. I've done several and they are easy to do. You will also be rewarded with lots of bright light. I don't have converters in any of my M@g mods. Some are resistored, some are not. I know others on CPF have mods running 5W LEDs on 3X123s and using multiple AA adaptors to fit into a D size tube. Vf of the luxeon that you use will be a consideration when choosing your source of power, but the circuit, or lack thereof, will be one less thing to worry about. That may be the way to go to start out. If you've never done any sort of modding, you may want to start out with a 1W mod running direct drive on 3 C cells in a 2D M@g. You could use a little resistance if you're uncomfortable with the direct drive. Maybe half or one ohm. This is a good way to start out because you don't have to worry about frying that $20 circuit and 1W LEDs are cheap right now. How about a 3W if you can get your hands on one. 3 C cells should deliver around 1A to the LED.

Thanks a lot for the help. I didn't know that hooking up multiple converter/leds in parallel leave the voltage the same for every converter LED.

So let me repeat this (for the example for a 6V 5w)

1)In order to run 3 x 5w LEDs in PARALLEL, I would need ONE converter that delivers 6V (1x6V) and 2100mA (3x700)

2) And in order to run 3 x 5w LEDs in SERIES, I would need ONE converter that delivers 18V (3x6V) and 2100mA (3x700)

3) Or I could use 3 Downboys 700 ( https://secure3.dnsaction.com/~anlighte/shop/product_info.php?products_id=210 ) that are hooked up parallel to a battery with max 16V.

Is this correct?


To the heatsink comments - Well the actual copper pipe walls are kind of thin but the surface area is pretty big and copper tranfers heat about a third better then alluminum. Besides of that a pretty good size heatsink connects to the copper pipe walls, so there should be plenty of heatsink. And if this still gets too hot, then I try whether 3x3w will work better, and if its still too hot, then it is going to be 1x5w.

I just want to make sure I dont fry the leds and the converters thats why I am asking all these questions...

"1)In order to run 3 x 5w LEDs in PARALLEL, I would need ONE converter that delivers 6V (1x6V) and 2100mA (3x700)"

Yes; but if there are big differences in the LED Vf then each LED will consume a different amount of current.

"2) And in order to run 3 x 5w LEDs in SERIES, I would need ONE converter that delivers 18V (3x6V) and 2100mA (3x700)"

No. In series you only need to multiply the voltage, so that would be 18-21 volt depending of LED Vf and 700mA.

"3) Or I could use 3 Downboys 700 that are hooked up parallel to a battery with max 16V"

Yes, 3 downboys with ~8-16V, or 3 badboys with ~4-6V.

What battery voltage gives me the best runtime of regulated light?

Do the Downboys convert the excess voltage in heat, or do they actually transform it so that it extens my runtime? If so, how much longer do 10'000mAH at 12V last, compared to 10'000mAH at 6V?