Maxflex and 7up XP-G too much?

[marcopolo]

I'm just wondering maybe with good heat-sinking if the maxflex could stretch to 7 XP-G. It does boost up to 24v which is above 7xVf's @ 1000mA? (probably question for George if you are reading!!)

If it is a question of limits on total power then what about using the 800mA table on the maxflex instead?

Cuttter have the 7up board ready to take XP-G and optics at 40mm. So it's just a question of which driver / combo to run them with. Would be nice to do it with just 1 driver though.

Hiplex could drive 2 strings of 3 but that leaves 1 LED redundant (just had an afterthought - could maybe run the last LED off a resistor at a fixed brightness)

Marco.

 

[ifor powell]

I was wondering this as well, by the specs the answer is no but I suspect that if you are lucky with the leds you get it may be good but I also expect that if you are unlucky it will not be good. I think we need to get some reports from people when they get there XP-Gs to see what the vf actualy is and what sort of variation people are getting.

Ifor

 

[jar3ds]

if you can have 7 XP-G's w/ a vF of 3.4v or lower... then provide at least around 12v at the low end of your Vin...

to avoid over heating issues w/ the maxflex you must keep input current around 2amp... w/ 3amp being the max.

I always error on the side of caution when planning out a driver's role... but george's drivers are the best available...

 

[trout]

I have just measured 6 XPE R2 leds in series running from a maxflex4 with
15.7 volts input in one of my lights here are the results


700 ma setting VF 19.23 current draw from the power supply 940 ma

1000 ma setting VF 19.5 current draw from power supply 1390 ma

so on that reckoning 7 XPEs would be 22.43 v @ 700 ma
and 22.75 v @ 1000ma

I also have a 7 up XPG R4 board on order from Cutters and was planning to use a Maxflex to drive it

as I understood it the XPGs have a lower vf

 

[marcopolo]

So now I guess it really just comes down to whether or not the maxflex can handle the total power. I'm sure enough heat can be drawn away from the board through a heatsink that connects the Maxflex heatplane to the lightcvase chassis - that would also give you a way of attatching the board internally.

Point of note: 5S lipo might be out of the question as it's 21v hot off the charger (18.5v nominal). What happens when the battery voltage on the Maxflex rises slightly above Vf total? I would guess the regulation drop out will just put a bit more current through the LED's than should be the case so you couldn't access the lower power levels!

If low power settings give 7x2.8vf = 19.6v then it may only be out of regulation forthe first 10-20% of the battery charge. Otherwise it'll have to be a 4S li-po/ion.

Marco.

 

[herulach]

Wait a couple of weeks and hit this up:
http://www.candlepowerforums.com/vb/showthread.php?t=242634

 

[georges80]

You guys have read: http://www.taskled.com/leds/max4_thermal_guide.pdf yes???

If Vin > Vf at a particular V-I spot of the LED then maxflex will be in direct drive - just like any other boost driver. Boost drivers have a DC path from VIN+ through an inductor, through a schottky diode and through the current sense resistor(s) to the Output+.

So, if you have 5 li-ion cells and they are hot off the charger at 21V and your total Vf at 1A is 21V you would basically lose all dimming levels until the battery pack dropped below the Vf at the lower current levels.

Anyhow, if you READ the above thermal guide you will see that maxflex would have absolutely no issues driving a load around 21V at 1A from 4 li-ion cells ***IF*** you provide a good heatsink path.

cheers,
george.

 

[marcopolo]

Thats basically what I understood about boost regulators.

I had missed your thermal guide somehow though:thinking:.

I guess at the time you wrote the spec/PDF for maxflex 1-6 3W LED's (as is in your chart) was a safe limit. So what you are saying is: 7 is do-able with the correct thermal design. thats what we suspected!

And stick to a 4S lithium probably.

Excellent. Thankyou George.:twothumbs.

(You know how us modders love to blow up your drivers if you already havn't done so testing them for us anyway!!)

Marco.

 

[marcopolo]

OK I just checked my 5S Li-PO graphs against some XP-E Vf's and it really would only be out of regulation on the 2 LOWEST power settings for only a few minutes. Of course if XP-G Vf is significanly lower than the XP-E......it all gets a bit speculative now.

 

[trout]

Hey Marco
I just got one of those boards today and hooked it up to a Maxflex .
from a 4s li ion running at 1000ma

vf was 23.2 v
and the light was awesome

 

[marcopolo]

Excellent. I'm glad it runs at 1A with the Maxflex. It looks more floody than the XR-E but more throw than the MC-E . I'm looking at your other beamshots just now here and on MTBR for comparison. It seems the light is somewhat warmer than WH.

Actually I've also just looked at your 4 MC-E with 1 CMC-RS and 3 CMC- SS and that still has a stupid amount of throw AND maybe same brightness as this one! We're so spoilt for optics and emitters these days that it's dificult to do comparisons!

Regardless I think 7up XP-G will be perfect for all riding conditions be it technical trail (my favourite) or xc both without the need for helmet mount.

Marco.

 

[peteredm]

troutie that 7up pic looks stunning, also just seen your website and liking the machining of those housings, good to see a bit of Yorkshire engineering!

Anyways wanting to go down the route and make my own 7up with nflex etc, could you confirm nflex model and batteries used (18650?)

What kind of runtime would get out of just 5S?

Thanks in advance, looking to be a killer first project!

 

[javiole]

hi all, interesting stuff.

would someone post a detailed pick of the board with the 7 leds? (please better than the one you can see in cutter), just to see the the connections

cheers

 

[trout]

troutie that 7up pic looks stunning, also just seen your website and liking the machining of those housings, good to see a bit of Yorkshire engineering!

Anyways wanting to go down the route and make my own 7up with nflex etc, could you confirm nflex model and batteries used (18650?)

What kind of runtime would get out of just 5S?

Thanks in advance, looking to be a killer first project!

Thanks Peteredm
Maxflex 5 is the driver and 4 cell li ion series

no idea on runtime but it is drawing 1.5 amps from my bench power supply at 15 volts

Pic for you Javiole

and another beam shot showing the 6 degree optic

 

[javiole]

cheers Trout! That looks great.

I have a mag head with a tri-p7 (Der Witchel version) , and a hipflex with an exposure bar mount. Excellent light, I like the shape of the mag!! No complaints, I thought I would have had enough, but this is an adiction :shakehead

I was thinking to try the 7 up xp-g in a mag head with a multisink heatsink (download) and a maxflex. But, seeing your picks, i think it will be about the same results as the tri-p7. And maybe a little too big host for that set up.

So I've changed my mind and I will try a mag head with 4 3-up xp-g, with a multisink and a hipflex, they fit almost perfect. 12*350 = 4200 lumens. That should be a significant improvement w.r.t the tri-p7. what do you think?

 

[poisonspider]

I've got all the components for a 7 XP-G Mag head conversion in the post right now. This is my first attempt at a home built light so fingers crossed it'll work.

I need some info though on setting up the Maxflex 5 low voltage warning LED.

I'll be using a 14.8V 4.4Ahr Lumicycle Li-ion battery.

As I understand it, Li-ion batteries have a very liner discharge curve therefore the output voltage will stay pretty high (above say 13V) right up to the last few minutes. If I set the Maxflex's Vmed limit to half way. ie 7.4V (recommended in the Maxflex notes) it'll be practically flat by the time the warning light comes on.

Also, assuming I let it get to 7.4V, the drop in input voltage into the Maxflex will send the power (and heat) dissipation in the board sky high. (This assumes, 7 LEDS and Vf 3.3V, 1A). Also, from the Maflex notes, it says not to run it with more than 3W power dissipation in the board, if I work that backwards it's about 9.something volts from the battery, again if I used this as the limiting factor for Vmed, the battery would be almost flat by then anyway.

Does anyone have any advise on an appropriate half way house?

Many thanks.

 

[poisonspider]

I've got all the components for a 7 XP-G Mag head conversion in the post right now. This is my first attempt at a home built light so fingers crossed it'll work.

I need some info though on setting up the Maxflex 5 low voltage warning LED.

I'll be using a 14.8V 4.4Ahr Lumicycle Li-ion battery.

As I understand it, Li-ion batteries have a very liner discharge curve therefore the output voltage will stay pretty high (above say 13V) right up to the last few minutes. If I set the Maxflex's Vmed limit to half way. ie 7.4V (recommended in the Maxflex notes) it'll be practically flat by the time the warning light comes on.

Also, assuming I let it get to 7.4V, the drop in input voltage into the Maxflex will send the power (and heat) dissipation in the board sky high. (This assumes, 7 LEDS and Vf 3.3V, 1A). Also, from the Maflex notes, it says not to run it with more than 3W power dissipation in the board, if I work that backwards it's about 9.something volts from the battery, again if I used this as the limiting factor for Vmed, the battery would be almost flat by then anyway.

Does anyone have any advise on an appropriate half way house?

Many thanks.

 

[poisonspider]

Oops, apologies for the double post.

Also, I've since had info from George at TaskLED who's answered my question.

For what it's worth all I need to do is double the default settings as it comes pre-programmed for a 2 cell 7.4V battery.

 

[Mark2c]

Oops, apologies for the double post.

Also, I've since had info from George at TaskLED who's answered my question.

For what it's worth all I need to do is double the default settings as it comes pre-programmed for a 2 cell 7.4V battery.

Could you please confirm/post the info from George - ie settings for LiPo are the same as LiIon? Cheers