5watt + AAA li/ion ??

[Robocop]

Ok hear me out on this as I know it is not really practical but I was just curious if it would even work at all.....

I have a very low voltage 5 watt emitter after a recent swap to a better BIN on my TW4. The emitter ran very well on a standard 123 cell and I am trying to find something to use it in. I know run time would be horrible and heat a problem if it would even work but I am thinking of using this emitter on my old Fenix LOP using a Li/Ion AAA cell for 4.2v input on the standard LOP circuit.

I know the circuit will handle it as I have used Li/Ion very briefly in the standard 1 watt configuration. I am wondering if this circuit will even power a low voltage 5 watt and just for kicks was thinking of trying it. Yes I know I will have to worry about heat in such a small package and the little reflector will be crappy but it would just be kind of cool to have a 5 watt AAA light....even if it only ran for 10 minutes.

So first will the little unprotected Li/Ion AAA even be able to fire the 5 watt and secondly can anyone say if the original LOP circuit will simply go into direct drive using the 4.2v cell? This was just a crazy idea I had while trying to kill some time and if it will not work I will probably use the emitter in an old QIII or something similiar due to the low forward voltage.....thanks for entertaining my crazy ideas as always.

 

[worldedit]

I dont know if the L0P circuit can handle Li ion cells at all. I thought this was for the L0D only. On the other hand 5W from a AAA cell would mean a discharge rate of about 5C. I dont think the cell can handle that.

 

[ltiu]

When you say 5 watts, did you mean the Luxeon K2 or does the emmitter actually use 5 watts?

 

[SilverFox]

Hello Robocop,

For use as a "Flash" light, it sould work fine. Just don't try to do a runtime with it.

Tom

 

[Robocop]

Hello Tom nice to hear from you again....I was hoping that since this 5 watt emitter was from a very low vf lot that it may somehow work even if only for a few moments of runtime. When you say it would flash what do you mean exactly? Would it kill the circuit or are you saying it would only have enough power to "flash" for a few seconds when activated?

I knew this sounded crazy but again it would be really cool to have a 5 watt AAA light even if it were just for show.

 

[Mr Happy]

It's hard to believe that a driver circuit designed for 1.2 V input will work OK with the 4 V input from a Li-ion cell. It's also hard to believe that a circuit designed for a low power emitter will work OK driving a 5 W LED. Put the two together and it's hard to believe the setup will run for more than a short while before something goes poof. JMO. YMMV.

 

[TigerhawkT3]

The ordinary L0D-CE uses about 4.8W with a 10440. That may not quite be a 5W light, but it's close enough for me.

What exactly is the Vf at the currents you want? I think it's pretty much a coin toss as to whether the L0P's circuit can handle such a high Vout, not to mention the Vin from the 10440. Still, it couldn't hurt to try (unless you short the cell, or burn yourself while soldering, etc.).

 

[Robocop]

Hi TigerHawk....

I am not sure as to how long the LOP circuit could handle the 10440 however I have used such a cell to power the LOP for a few minutes at a time. Of course this was with the factory 1 watt emitter and I have no idea as to the BIN of that emitter. It worked fine but did get pretty hot for those few short minutes.

I am not sure as to what you mean by what current at what vf as I really dont know much of the technical stuff about circuits nor emitters. I am basically basing my idea on the fact that the 5watt I wish to use ran great from a standard 3v 123 cell....it even ran pretty good on an old cell showing 2.75 volts. Of course this was with the TW4 circuit and not the LOP but again I thought it would not hurt to try. I assumed if nothing else it would run but be kind of under driven if anything.

If it would even work I would be happy to simply say I had such a light. If it ran under spec it would still be pretty neat just to see that wall of light from such a small package. With the cost of todays 10440 cells I would simply buy more if the drain killed them quickly anyway.....thanks for the input and I may just go ahead and try it. If nothing else I would only have to remove the emitter if it did not work and if it kills the circuit then I have a good host for something else.

Before I tried this I really wanted to make sure it would not destroy the actual emitter as I would like to use it for something else. I really did not think the little LOP circuit and 10440 could hurt the emitter even if it did not work....but again that is why I am here because I have no idea as to electronics anyway...hehe

 

[SilverFox]

Hello Robocop,

My comments were aimed at only the battery. I don't know if your circuit can handle the voltage. You will have to figure that out.

Li-Ion cells can handle high pulse loads without problems. That is where my comment about the "flash" light came from. If you only use it for brief periods of time, the battery should be OK. However, if you decided to turn it on and run it all the way down in one turn, you may run into problems with battery life. Long runs will heat the battery up and you will end up with poor cycle life from it.

Tom

 

[TigerhawkT3]

Hi TigerHawk....

I am not sure as to how long the LOP circuit could handle the 10440 however I have used such a cell to power the LOP for a few minutes at a time. Of course this was with the factory 1 watt emitter and I have no idea as to the BIN of that emitter. It worked fine but did get pretty hot for those few short minutes.

I am not sure as to what you mean by what current at what vf as I really dont know much of the technical stuff about circuits nor emitters. I am basically basing my idea on the fact that the 5watt I wish to use ran great from a standard 3v 123 cell....it even ran pretty good on an old cell showing 2.75 volts. Of course this was with the TW4 circuit and not the LOP but again I thought it would not hurt to try. I assumed if nothing else it would run but be kind of under driven if anything.

If it would even work I would be happy to simply say I had such a light. If it ran under spec it would still be pretty neat just to see that wall of light from such a small package. With the cost of todays 10440 cells I would simply buy more if the drain killed them quickly anyway.....thanks for the input and I may just go ahead and try it. If nothing else I would only have to remove the emitter if it did not work and if it kills the circuit then I have a good host for something else.

Before I tried this I really wanted to make sure it would not destroy the actual emitter as I would like to use it for something else. I really did not think the little LOP circuit and 10440 could hurt the emitter even if it did not work....but again that is why I am here because I have no idea as to electronics anyway...hehe

The Welcome Mat has a bit about Vf. Basically, it's the voltage that matches a particular current. Most manufacturers rate the Vf of their emitters at 350mA. Your L0P and TW4 may or may not be running the LED at 350mA. The higher the current, the higher the Vf. Since LuxVs are actually four dice (2S2P), the Vf will be higher than that for ordinary single-die LEDs at the same current.

Like I said, it all depends on whether a particular driver can boost the voltage up enough to activate the LED at the current level it's trying for (this is assuming a constant-current driver, which attempts to keep the current through the LED at a constant level). If you've used this emitter in a different circuit intended for LuxIs, you can have a bit more confidence that it'll work in another circuit intended for LuxIs, but it's still a gamble. The following possibilities are the most likely ones I can think of:

1. It works fine. Hooray.
2. The LuxV doesn't light up, so you remove it, reassemble your L0P, and it's back to the way it was. Oh well.
3. The LuxV doesn't light up, and the driver s. Dang.

Remember that a light's wattage is only determined by its emitter in marketing speak. In reality, a light's wattage is just its voltage multiplied by its current. A "3W" Cree could be driven at anything between 0-ish and 4 or 5W, and a LuxV could be driven at anything between 0-ish and... I don't know how many watts at most. I don't have much experience with LuxVs. I think I can guarantee, though, that the beam will be pretty different (as you surmised). I can't tell you exactly how it'll be, though, because, again, I don't have much experience with LuxVs (i.e. I've never tried a LuxI reflector with a LuxV).

If I were you, I'd go ahead and try it. If you can remember to check Vf and current going through the LuxV before you solder down the second leg, that'd be cool. :thumbsup:

 

[matrixshaman]

Robocop - if you are talking about a Luxeon V I don't think it will work as even the lowest Vf's on them are way above what the LOP likely puts out even with a 10440. I think you'll either see no light at all and possibly fry the circuit in the LOP or you'll get a rather dim light - making all the work a bit frustrating. At best the LOP circuit probably puts out between 3 and 4 volts and with that 10440 it's probably at best about 4 volts so here's what I'd do. Get your 5 watt LED and either get a 1 or 2 ohm resistor or a long wire - say 20 foot of something like 18 ga. or smaller and use it as the resistor and hook that battery up direct to the emitter with a resistor or wire in between and see what kind of brightness you get. That brightness will likely be more than what you'll see out of the LOP since the LOP isn't going to boost the voltage any higher and it will definitely not be feeding it more current than what you just did direct driving it since you can't get current out of thin air - that is voltage times current = power in watts and if you have a same voltage in each case the current won't be any more than the battery is capable of. I could be off a bit on this but I think that's more or less correct.
BTW I didn't read this whole thread so I see some repeat but I also haven't seen it mentioned that a TW4 IIRC is essentially like the KL4 running on a single Li-Ion but that KL4 has a boost circuit that is still putting something like 7 or 8 volts to the LED. I don't think there is anything you could do that would get that much voltage out of the LOP circuit so I reaffirm that you will probably just see a very dim or not lit at all 5 watt Luxeon if this is the LED we are talking about.

 

[Robocop]

Matrixshaman I had actually thought about simply trying the simple direct connection to a freshly charged Li/Ion however have not yet had time to play with this idea. I really do not know what the lowest vf is for any certain 5watt however the TW4s were basically a KL4 that were hand picked because they had a very low vf and would work pretty well on a single cell.

If I remember correct their is no difference between the TW4 circuit and the KL4 circuit as they were originally sold as the same unit designed to power from 2 standard 123 cells....but the TW4s would work on a single cell due to their unusually low vf.

I have an LOD-CE to replace my LOP and think I will try this swap as soon as I have time to sit down and do it. The worst thing could happen would be I fry the circuit and if this happens I have plans to use the body as a host for something else anyway.

If all this trouble to swap only left me with a very dim 5watt performer I would probably be better off swapping out a nice LuxIII and using the 10440 cell. My idea with this mod was not to really expect a big output light but to really see how well it would work if even at all. Still not sure if I want to risk the circuit as I am now thinking a nice TWOK I have would be a better choice. Regardless I will keep you all posted when I get time to experiment and I appreciate all the education on this.