Seoul P7 direct drive concern

[KrisP]

Hi,

I made a 3D Mag with a Seoul P7 CSW0I (Vf - 3.25v) that runs from 3 Tenergy D-size Ni-MH cells direct drive. I chose direct drive because so many people on here have said it's fine with Ni-MH cells.
Anyway, I put in 3 cells I had laying around that were partially discharged and it ran fine. I measured that it was only drawing 1.8A so I decided to charge the cells... They've settled overnight and have a total voltage of 4.27v when measured direct to the cells (I know this isn't accurate with Ni-MH cells). I put the cells in the light and measured the numbers below, then put 3 other D cells that were partially discharged and measured again.

Freshly charged settled overnight:
- 3.6v across the LED
- 3.8A measured with the meter between the base of the cells and the tube

Partially discharged cells:
- 3.2v across the LED
- 1.8A measured with the meter between the base of the cells and the tube

As you can see, there is an issue with fully charged cells... 3.8A @ 3.6v!!!! Also, I don't think the Vf is 3.25v @ 2.8A like the binning indicates, 0.5v increase isn't going to draw an extra amp.

Can anyone else with a P7 Mag, running direct drive from Ni-MH, please measure their voltage and current?


Thanks 🙂

 

[Drewfus2101]

Wow, thats a huge swing in current with just a 0.4V drop at the emitter. I was just about to build the same setup later this week when my heatsinks arrive, but now I'm having second thoughts. I might have to go with a 4D Mag and use 2 AMC7135 1400mA boards driving it at 2.8 amps. Maybe others will chime in.

 

[phantom23]

I don't think the Vf is 3.25v @ 2.8A like the binning indicates, 0.5v increase isn't going to draw an extra amp.

Binning says 3,25V at 1,4A (350mA for each die)!

 

[Tidra]

For I= 3.25 -3.5V

Yes it is just the way you measure it, so I don't know who is willing to DD P7 with 3D NiMh, because it draws too much A from the battery...

Personaly I would not recomend that.

3NiMh (NiCD) or 1 Li-Ion is the optional solution for P7 and:

1.)
http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=3215

+ one

http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=1806


2.)
http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=4338


in 4D there is too much voltage on the driver and too much heat is produced on the driver,...


Cheers,
Iztok

 

[Supernam]

This is why I do what Drewfus does with the 2 AMC boards. I run 4C nimhs so that it holds a flat output longer, but the PVC tubes can be taken out for 3D nimhs also. Either way, the AMC boards are there to bleed off any extra power. So it's a safeguard against overpowering it.

I'm pretty sure that in a mag host with proper heatsinking and thermal compound in the right places, that your overdriving the P7 won't be too harmful. However, keep in mind that each individual die is not equal to each other and that the one with the lowest Vf may be the first to go should you overheat.

 

[Drewfus2101]

For I= 3.25 -3.5V

Yes it is just the way you measure it, so I don't know who is willing to DD P7 with 3D NiMh, because it draws too much A from the battery...

Personaly I would not recomend that.

Cheers,
Iztok

That is not an educated statement. No emitter will "draw" any more current than it is designed too at a given voltage. If it is spec'd to draw 2A at 4V, and you feed it 4V, it will draw 2A. It is that simple. You can't give it 4V and it "draw" 8A. All we can do it give it a certain voltage and the current will take care of itself.

That is of course only talking about direct driving and does not include any drivers.

NiMH batteries are very capable of outputting 4 amps continuous discharge without breaking a sweat.

There are plenty of people who are DD the P7 with great results. You are better off to use a driver, but it is much more complicated at this point and there is only 1 off the shelf product designed to work with the P7.

 

[Drewfus2101]

For I= 3.25 -3.5V

Yes it is just the way you measure it, so I don't know who is willing to DD P7 with 3D NiMh, because it draws too much A from the battery...

Personaly I would not recomend that.

3NiMh (NiCD) or 1 Li-Ion is the optional solution for P7 and:

1.)
http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=3215

+ one

http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=1806


2.)
http://www.kaidomain.com/WEBUI/ProductDetail.aspx?TranID=4338


in 4D there is too much voltage on the driver and too much heat is produced on the driver,...


Cheers,
Iztok

You will be fine with 4 x NiMH batteries and the AMC7135 drivers. Even hot off the charger a NiMH won't be over 1.4V, so 4 of them equals 5.6V. The AMC7135 is designed to function up to 6.0V, although heat is an issue.

I would recommend letting the batteries settle back to 1.2V before running them just to be safe.

 

[uk_caver]

<puts on sunglasses and moves to workbench>

With my experimental P7 setup (on decent heatsink, not getting very warm), running DD from 3xNiMH 17670s at various states of charge, voltage measured across LED leads.

2.96V @ 0.71A
3.06V @ 1.10A
3.15V @ 1.62A
3.27V @ 2.05A

Then, with a freshly charged pack
3.41V @ 3.41A
3.33V @ 3.00A
3.28V @ 2.75A
3.27V @ 2.66A

wait for couple of minutes to ensure LED cold (though it wasn't very warm before the wait)

3.30V @ 2.65A (taking an instant reading)
3.21V @ 2.30A (after couple of minutes running)
3.22V @ 2.20A (after a short rest)

Basically, it does seem like heat is causing a little extra current flow - after cooling, the voltage is slightly higher, but the current is lower, even though the LED isn't warming up to much beyond skin temperature.

It's also worth noting that this is a new LED, only received very recently, and until just now, barely run at high current for more than a few minutes.

After having run for some minutes at high current, even when it then cools down completely to room temperature, at 3.22V, the LED is drawing ~2.2A in instantaneous measurement compared to 3.27V @ 2.05A earlier on, so there does seem to be a 'burn-in' effect going on and dropping the Vf compared to the new LED.

However, even leaving those factors aside, it's clear the voltage/current slope is very steep.

Direct drive doesn't seem to be great for someone wanting even vaguely stable output.

 

[Supernam]

It really depends on how you have the board mounted. I ran mine hot off the charger, 5.6v with 4 Accupower LSD C's. The boards are Arctic Silver'd with the chips touching the inside of the Mag tube, where I also stripped the anodizing. The boards are mounted 180 degrees from each other, not sandwiched together like the KD ones. It is also sitting on the top of the switch assembly, as far away from the emitter's sink as possible, as I found the heatsink to get way hotter than the boards. I can feel the boards get warm, but It was nowhere near hot as I left the light on for 15 minutes straight.

EDIT: UK_Caver.... Why do you suppose that you can have 2 nearly identical voltages, but with different current draw? Do you think it could be the type of battery that you are using? Perhaps they can only provide a certain amount of current depending on their discharge state.

 

[uk_caver]

I think the differences between early and later results at similar currents are probably down to burn-in effects combined with heat effects, both dropping Vf, one permanently, one reversibly.

I don't see how differences of current at a given voltage can be down to any differences between batteries.

However, re-running tests with the flatter cells gives very similar results to before at low currents - it only seems to be at higher currents (~2A and above) where there seems to have been a definite small drop in Vf of a few tens of mV for a given current with a cold LED.

 

[IMSabbel]

That is not an educated statement. No emitter will "draw" any more current than it is designed too at a given voltage.

One phrase: Thermal runaway.

Also, direct drive sucks.

 

[KrisP]

Binning says 3,25V at 1,4A (350mA for each die)!

Ahhh... That makes more sense 🙂

This is why I do what Drewfus does with the 2 AMC boards. I run 4C nimhs so that it holds a flat output longer, but the PVC tubes can be taken out for 3D nimhs also. Either way, the AMC boards are there to bleed off any extra power. So it's a safeguard against overpowering it.

I'm pretty sure that in a mag host with proper heatsinking and thermal compound in the right places, that your overdriving the P7 won't be too harmful. However, keep in mind that each individual die is not equal to each other and that the one with the lowest Vf may be the first to go should you overheat.

Will 4C cells fit into a 3D? Does anything need to be modified other than needing a PVC tube?
I'm still worried that 3.8A is going to rapidly decease the LED's life 🙁

uk_caver... Thank you for your tests. I really doesn't look like DD is a good option anymore. So much for Ni-MH having a flat discharge curve and not having high enough voltage to over drive the P7 (what has been said all over this forum).

 

[darkzero]

I had one running 3 C NiMhs. 3.1-3.2A fresh off the charger then dropped to 2.8A shortly after. Never built 3D DD P7 mod though, I don't care for the D size anymore. If you don't want to run 4 cells with AMC7135s a simple resistor will take care of the issue.

Curious, at 3.6A, doesn't the color shift?

 

[KrisP]

At 3.8A it was only on for 1-2 seconds to see the reading on the meter and facing at the floor but it still just seemed white. It's still under 1A per die, which P4's do without colour shift anyway.

 

[darkzero]

At 3.8A it was only on for 1-2 seconds to see the reading on the meter and facing at the floor but it still just seemed white. It's still under 1A per die, which P4's do without colour shift anyway.

That's true. Hmm, maybe I will build me a D size & drive it at 4A to see what happens. :naughty:

 

[Tidra]

That is not an educated statement.

Educated or not, try it yourself and you'll see how much current P7 could draw from one 18650 Li-Ion or 3D NiMH, you'll be surprised,...

I didn't say that AMC7135 couldn't take 4 NiMH, but that the heat will be produced from de driver.

Cheers,
Iztok

 

[TexLite]

That's true. Hmm, maybe I will build me a D size & drive it at 4A to see what happens. :naughty:

With a Tri-Flupic in Burst mode,I have close to 3.6a at the emitter.I have run it like this for extended periods without worry or damage so far.No tint shift or any visible or measureable (lightbox) loss over time(~3 hours).Thats only 900ma to each die.Everything is sinked very well,including the Flupic.Output is WoW.It does get very warm,but kinda stabilizes after a while.

Michael

 

[darkzero]

With a Tri-Flupic in Burst mode,I have close to 3.6a at the emitter.I have run it like this for extended periods without worry or damage so far.No tint shift or any visible or measureable (lightbox) loss over time(~3 hours).Thats only 900ma to each die.Everything is sinked very well,including the Flupic.Output is WoW.It does get very warm,but kinda stabilizes after a while.

Michael

Forgive me but how do you get to the burst mode? I have a Triflupic running a P7 now but in a small light. This is my first Flupic and I'm not familiar on how to fully use it yet. I only know mode 3. I highly doubt I can get 3.6a out of a R123 anyways.

 

[Timson]

That's true. Hmm, maybe I will build me a D size & drive it at 4A to see what happens. :naughty:

Ahh - A true flashaholic statement :twothumbs

We're here to push the boundaries ....Who care is it doesnt last thousands of hours.... Way before the thing's given up the ghost you'll be ripping it off and installing the latest new development anyway. :laughing:


Tim.

 

[KrisP]

We're here to push the boundaries ....Who care is it doesnt last thousands of hours.... Way before the thing's given up the ghost you'll be ripping it off and installing the latest new development anyway. :laughing:


Tim.

That's the way i'm thinking now... No point spending any more money on this as i'm sure it will last until the next generation of LEDs are released 🙂