A few last minute "Pre-Build" Questions before the weekend build..

A couple of last minute "pre-build" questions before I start to
put this project together this weekend.. First off, the list:

1. Maglight 2D
2. 5700K SST-90
3. Britelumens SST-90 Heatsink
4. H6Flex
5. 6AA to 2D Adapter (Bought on CPF, using Eneloops)
6. Britelumens Reflector
7. Malibu Coconut Rum and Kahlua (50/50) on ice.

I have done a ton of searching & researching about this, but really can't find much about the following last questions I have...

Questions:
1. Do I need a resister in between the H6Flex and the SST? I guess after burning up my first SST-90 I am really paranoid about burning up another SST. I would rather avoid that obviously. My first build was identical only using a D2Flex, and with the 6AA-2D it burned it up as I had nothing in between the D2Flex and the SST. Oops. :sick2:
2. The Britelumens heat sink, on the back side as many of you know, is recessed, thus when you put the H6Flex onto the backside of the heat sink, only the outer edge of the H6Flex contacts the heat sink. Can I fill this void with anything to make better contact between the H6Flex and heat sink? I know I can have a spacer machined, but was hoping for other options.
3. Is there anything I need to do electrically other than just hooking up all the connections?
4. Is there ANYTHING else I need to worry about doing to this little project? I think I have it all covered though, but that might just be my ignorance.. :laughing:
I have all the standard stuff covered, thermal epoxy, thermal transfer goop, modifying the maglight switch, the booze, etc..

Any help/advice/thoughts will be much appreciated..

1: i don't think you should and i cant see how it would have tosted a previous sst-90 unless you hooked it up to the led backwards.
2: i suppsoe you oculd fill it with epoxy or thermal grease (grease might run and make a mess though and epoxy would mean you cant get it out)
3: shouldn't be but be careful not to power the driver without the led hooked up, i hear that kills drivers.

what configuration is the 6AA to 2D? 3s2p? so with each cell having 1.2 volts you would get 3.6 volts and 4000mAh?

yazovyet said:

1: i don't think you should and i cant see how it would have tosted a previous sst-90 unless you hooked it up to the led backwards.
2: i suppsoe you oculd fill it with epoxy or thermal grease (grease might run and make a mess though and epoxy would mean you cant get it out)
3: shouldn't be but be careful not to power the driver without the led hooked up, i hear that kills drivers.

what configuration is the 6AA to 2D? 3s2p? so with each cell having 1.2 volts you would get 3.6 volts and 4000mAh?

Click to expand...

1. I used a D2Flex on the first build, which let wayyyy to much V get to the SST... It has a very nice very blue tint to it now..
2. I was thinking about Epoxy, just didn't know if it would be good at the thermal conductivity part of it..
3. Point noted..

The 6AA-2D is all serial, so on fresh off the charger Enelooops I have measured 8.4V max. I am sure they sagged a little after a few minutes...

What current are you planning to run? That will determine your driver heat sinking. I'm assuming the answer is "a lot" you might be better off putting a slug of copper on the back of the driver with thermal epoxy. Don't use normal epoxy and I wouldn't recommend bridging a large gap with thermal epoxy alone. How deep is the recess?

Someone more familiar with the driver should weigh in on the proper setup procedure, but I'm not convinced the problem is what you are thinking it is don't want to fry two SST90's Did you fire it up on full power with no heat sink? I think that would "cook" it rather quickly.

The d2Flex is a direct drive PWM controller. Whatever Vbatt you apply is directly applied to the LED, subject to any PWM to give you various output modes. When you presumably drove your LED with 6xAA at full power, you sent Vbatt~7.2V to the LED, when it was probably rated for less than 4V. Hence, you cooked the LED.

The H6Flex is a buck driver. Go to the taskled web site where you presumably bought the driver and read the technical information on how the driver works. Read the technical information on using the thermal pad material to heat sink the driver. Basically, RTFM.

If you plan to drive the SST90 at any sort of decent drive current, then IMO you should try to sink the driver to the Mag tube body, not to the Britelumens LED heat sink. Otherwise, you will be adding a significant second source of waste heat, on top of the waste heat generated by the LED. LEDs do not like to get hot.

Ok, so the light is built, and I don't understand this, but cycling through the power modes of the H6Flex, when on the max brightness setting is getting me I would guess ~300 lumens. I hooked up everything exactly as it should have been. Argh..

Some more info:

1. I used 20ga RC Car wire, basically silicone cased stranded wire.
2. The tailcap spring has a piece of desoldering wire soldered across it for reduced resistance.
3. Switch was made momentary, works because the light I know works.
4. I'm good at soldering, so I'm pretty sure nothings wrong there.
5. Battery pack was reading 7.74v roughly when I put it into the light.
6. The driver was taped to the back of the heatsink with the supplied thermal tape sent with H6Flex.
7. The longest wire in the system estimated to be 4".
8. Actual LED ordered from Avnet is a SST-90-W57S-F11-GN201.

That's all I can think of for relevant information as of now. Can anyone give me some pointers as to what to look at, or maybe something I did wrong?

Default, it only drives at 1400mAh.

RTFM here and see section 8.2 on setting the drive current by selecting from the pre-programmed current table.

I definitely did read through the manual quite a few times. I was able to get into the Menu for the current drive selection, and I changed it to the brightest setting it had, 6600mA, but the light still really isn't as bright as it seems it should be after looking at quite a few beam pictures from other people's builds. I am just not sure if I maybe missed something..

Do you have a meter that can read current?

Yes I do, and that was going to be the next step Monday after work. I let the eneloops charge up over night and today, so when I get home I can make sure they are ready to go.

Wasn't there a thread on here one time about how to measure the current through the tailcap? I do have my amp clamp, but I don't think it's going to fit in the small area I have in between the mag body and heatsink when it's pulled out. I'm going to try that first though.

I also have access to an ohm meter here at work that we use to test grounding bonds (accurate to .001 ohms if I remember correctly) that I was going to use to test the resistance of the tail spring. (Mostly for my own curiosity to see exactly what a piece of desoldering wire across the spring does to the resistance). However I don't think this is the problem.

I am almost ready to see if I could ship this light to someone to look over and see if they can find what I did wrong as I really want this thing to work. I would rather find it myself though for my own knowledge..

Bigchelis showed me an easy way to check the current if you have a standard meter with test leads.

1) remove head and place lens down
2) set your battery pack onto the back of the head, same as it wold be if installed in the light.
3) drop one lead onto the body negative
4) put the other lead on the tail of your battery to complete the loop.

This takes the switch out of the equation but you are just checking the proper operation of the driver...of course I don't know if the H6 requires an external switch or if you can switch modes by interrupting the power. I'm probably talking over my own head again

So I was able to measure the tailcap current last night, and the light is running around ~4.5 amps.

1. The H6Flex drive mode is set to the brightest setting, 6600mA's.
2. I noticed all the Voltage warnings are going to have to be changed, as my 6AA Eneloop's dont come close to the Voltage warning settings.
A. Here is what I was thinking for the Voltage Warning Settings, please do offer advice on these!:
i. VCut (Turn driver off) - 5.4V roughly? (Figures 0.9V per cell)
ii. V Warning Low (Starts to warn) - 5.9V roughly? (Figures 0.98V per cell)
iii. V Warning Medium (Warns of half discharged pack) - Set to Zero - I don't feel as though I need this.
3. Now, after all these are set, The light is still only pulling ~4.5 amps at its brightest setting. I am *assuming* that after this kind of amp level, resistance mods might be helpful?

I noticed that when checking the light amps with my Fluke V88, the light was brighter than when the tailcap was on. I am thinking that the grounding connection via. the cap/body
tube is not optimal because of this. I am going to hit the end of the tube with some 2000 grit sand paper I have as well as the ring around the tailcap to eliminate this as a potential
"weak spot" in the circuit.

Since the H6Flex is set to run 6.6A, but I'm only getting 4.5A running through it, this would come down to "resistance" mods (Need to improve electrical paths), would it not?

The only other area I imagine can be improved is where the set-screw through the switch contacts the inside of the body creating the ground path in the body..

The wires I used are big enough, correct?

when pulling pulling 4.5 amps from an eneloop we will assume they put out 1.15 volts. haveing 6 of them you will get 6.9 volts in.
thats 31 watts. at 6.6 amps the sst-90 should use about 3.6 volts and thus 23.7 watts. so this would imply you are burning off 7.3 watts in the driver and resistance of things here and there.

so you said you were 'only' getting 4.5 through the tail, i think the idea is that you would want to get a lower tail cap current (than you are right now) to indicate there is less battery sag and less power being burned off due to inefficiency?

do you think it is not putting out ~2000 lumens?

I do have to say that I have not personally seen a 2000+ lumen light in front of me, so the only thing I have to judge it against is the pictures I see online.
The pictures I see online makes it look like a monster of a light, to me this light just doesn't seem like the "monster" I thought it would be.

Judging by that, I would have to say absolutely not. I do have a Solarforce L2R with 2x14500 AMR's and a Lighthound Cree R5 Drop in and I would say the Mag is marginally brighter, but nowhere near 2000.

If I had to guess, I would say 500 OTF maybe.. I will do a comparison side by side tonight against my Lego Solarforce and see how it compares. I am just a little disapointed now because if I was to
grab a light and run out the door, I'm still grabbing the Solarforce lego vs. the Mag that cost 2x as much $ and 10x as long to build.

Maybe I'll do a beamshot of both lights tonight too so I can post them as reference. Sometimes thats kinda hard though as it doesn't get really dark here till 9:30-10ish and I get up at 4:30am. My playing around at night is limited..

(On another note, a Cheap plug for George, I am still very impressed by his driver boards, excellent products!)

The H6Flex is a buck driver. It is not direct drive, nor a linear regulator. Tail current values are not the same as drive current values (unless the buck driver has fallen out of regulation).

If we assume the same driver efficiency as the H6CC, then for one LED driven at 6.6A, efficiency is about 83%. Referencing the Luminous SST-90 datasheet, Vf is about 3.4V at 6A. Let's assume that Vf is also 3.4V at 6.6A. At 4.5A draw, Eneloops probably hold about 1.15V quasi steady state.

Thus,

0.83 * (6*1.15V) * Ibatt = 3.4V * 6.6A

Solving for Ibatt gives a calculated tail current draw of 3.9A. That's a little low compared to your measured value of 4.5A. But that could easily be due to lower than assumed driver efficiency, lower than assumed cell voltage, and/or a higher than assumed SST-90 Vf. As a quick sensitivity analysis, let's make some small changes and assume driver efficiency of 80%, cell voltage of 1.12V, and Vf of 3.45V. Now, Ibatt ~4.2A. Getting there.

So it appears that your driver is running properly and you are delivering full or near-full 6.6A drive to the LED.

However, there is the possibility that Vbatt is too low and the driver is not running in regulation. Thus, the 4.5A that you measure is also basically the drive current to the SST-90.

The potential issue I see is that your 6xAA Eneloop battery configuration may be a little low on available Vbatt. The calculations above suggest that under load, your Eneloops might be running at a total Vbatt of about 6.7V. You should contact George at TaskLED for advice. The paper specs for the H6Flex state a Vin range of 7V to 21V. You can get away with Vbatt less than 7V if your LED has a low Vf or you use a lower drive current. But neither exception seems to apply to your case. That may explain why the LED gets brighter when you complete the circuit using your Fluke vs the tailcap. You aren't running in full regulation.

I would power your light with either 3xLi-ion (IMR18650s or bigger) or with 7 or more AA Eneloops and re-evaluate the light. What is the perceived output? What is the tail current draw?

Tkklemann said:

I do have to say that I have not personally seen a 2000+ lumen light in front of me, so the only thing I have to judge it against is the pictures I see online.
The pictures I see online makes it look like a monster of a light, to me this light just doesn't seem like the "monster" I thought it would be.

Judging by that, I would have to say absolutely not. I do have a Solarforce L2R with 2x14500 AMR's and a Lighthound Cree R5 Drop in and I would say the Mag is marginally brighter, but nowhere near 2000.

If I had to guess, I would say 500 OTF maybe.

Click to expand...

If your 4.5A tail measurement is also the drive current, then for your flux bin SST-90, I'd estimate about 1100 emitter lumens. Taking 50% or 60% of that gives about 550-660 OTF lumens.

I'd give the driver more voltage, say from a 9AA->3D adapter in a 3D Mag or using 3xIMR26500 in your 2D Mag (you'll need a PVC spacer or some rolled-up newspaper and a tail spring mod). It looks like you are not running in full regulation with only 6xAA Eneloops.

This forum still continues to amaze me at how willingly helpful and civilized everyone is. Some of the car forums I am on are nowhere near as nice and helpful as this..

Justin Case, what would you think about putting 5 AW 14500's in my adapter with a spacer for one? (I already have two 14500's for my Solar Force Lego.)

Reason for 5 is the sixth will put it over the max input V per George's recommendations. They would all fit into my battery holder I already have too.

It's a 2D Mag too, FYI..

justin: according to page 10, second graph; shouldn't the the voltage to the LED be near 3.6 volts at 6.6 amps or am i reading it wrong?

but i agree that it looks like that driver says it needs 7 volts, so you should try sticking another AA in series (with the tail cap off as a quick test) and see if that brightens it up and if it does that would be your issue.

I was looking at Rev 3 of the SST-90 datasheet. Yes, in the current Rev 5 datasheet, the Vf looks to be about 3.6V at 6.6A drive.