P7 LED driven by Buck driver and 4 x Li-ion 18650 cells in series

[HaloclineDiving]

OK understood. I looked up the P7 graphs and tech specs on the Seoul Semi Conductor site and it has some good info. I didn't see a "lumens to current" graph but there was lumens <> heat and voltage graphs.
I'll post some test results asap and can work out the trade off point based on that..

 

[Th232]

Hmm... were you looking at the datasheet from here? Page 6, graph 2, current vs flux. Curious as to where you saw a lumens vs voltage graph, since output is a function of current and not voltage.

 

[HaloclineDiving]

Apol - I meant graphs 1 and 2
Forward Voltage vs. Forward Current and Forward Current vs. Normalized Relative Luminous Flux
That is where I was looking..

 

[alpg88]

well, first thing i see wrong is the leds, not that P7 are bad leds, they are not, however i would get rid of stars, they are the unnessesery heat resistance point, p7 is better off without them, mount leds' heatpad directly to a ANODIZED heatsink, why anodized, cuz p7 heatpad is negative teminal as well. negative leg and heatpad has continuity.
use good quality thermal adheasive to mount leds, arctic aluminia 2 part epoxy is made exactly for that.
now the driver, use 1 driver to drive 4 leds in series, member der witchel sells exelent driver, a lot better quality than dx or kd stuff.
you would need 5 cells li ion. if you plan on taking cells out everytime to charge than protected readylast might do the trick, if you want them to stay in the light than uyou would need unprotected li ion with protected circuit as a separate part for all of the cells.
don't pay any mind to how dies in p7 are wired you only have 1 way of connecting to the led, so it is unimportant.
there is no difference in brightness from 4xp7 wired in parallel,and fed with around 11amps 3v, or in series when fed with 2,8A and 12V. but better way is to wire them in series, this way you don't have to deal with high current.
now about p7's, i would dump them, i mean they are great leds, but xm-l has single die and can be focused better, there is very little choise for optics\reflectors for p7, and all will focus into floody beam, due to large die area.
xm-l otoh are easier to focus tight, and there is wider choise of optics available for it.
i'm no diver but i did dive few times, what i understood, unless you dive in cristal clear water, there are partcles suspended in it, and wide beam reflects from them all around and you basicly blind yourself, and not much illuminting, so underwater you need cool tint, and as tight as possible beam with as little spill as possible.
you didn't get to disscussing the body of the light, but try to incorporate heatsink into it, so the water does the cooling, also if you deside to go with xm-l get ones from led tech.de, the ones mounted on 16mm copper star, they are the only ones in the world to have xm-l's heatpad soldered directly to copper star, not to copper foil that sits over unsulating film. heat transfer a lot bettter on those stars. something that is critical when you drive them at max, for long time.

 

[FBsLights]

This is a very big project for a first timer.

You said that it is working with one P7 but not as bright as you thought it should be? Do you have a way to measure the current in to the LED?

Now that you have a power source (car battery) and the driver is switching modes, you can hook two P7 LEDs in series. Each will get the same current but you driver needs to be capably of driving a ~7V load (2 LEDs in sereis at ~3.5V each) I'm not familiar with this driver so not sure if it will do this. Ideally you would be able to measure the current into the LEDs.

BTW, I hope these LEDs are mounted to something for heatsinking. On just a star, the P7 will overheat quickly.

I agree with alpg88 that XMLs may be a better option but it sounds like you already have a bunch of $$ tied up in what you have (10 P7s, batteries, etc).
P7s will work since you already have them (XMLs would be better, especially the flood/spot problem that was pointed out. Not a diver myself.)

For battery options, I'm sure Redilasts are top notch but I hear you about the price. Search around for other good options. Google budget flashlights to find another flashlight forum. Over there they really like XTAR and HiMAX as good performers for a decent price.

Other concers:
Your driver is only going to be able to handle driving two P7s (if it can even do that). Where you planning to run more of these in parallel? You will have problems keeping them in the same mode as each other. The h6flex may be a good solution. With the h6flex I would drive 4 P7s in series with a 4s battery pack. To safely run 3A for 2 hours, you would need to parallel 3 strings of 4s batteries. This is not very practical or safe with Li-ion. It is hard to have that many batteries matched well enough not to have charge/discharge problems. (even if charged individually). I recommend you build it with only 4 series batteries and just replace the batteries after each dive. One set could be ready/charging while you use the other.

FB

 

[moderator007]

4 series wired P7's at 2.8A should have a forward voltage of 14v. Depending on bin and drive current. The H6Flex needs 1v over forward voltage of the leds to stay in regulation. 15v is needed for correct operation. You will need a little more voltage to account for voltage sag and the voltage decrease as the batterys drain. 4s fully charged would be 16.8v. But with the batteries almost depleted the voltage would be less than 14v. Even less when you factor in voltage sag. You may need to go to 5s to give you a little voltage overhead. Jtr1962 tested the P7 awhile back yet his test is very useful info. I agree with the post above about the xm-l being a better choice as far as forward voltage vs lumens output. 4 xm-l's would probably not have a problem staying in regulation with a 4s battery pack. But the beam is much tighter than a P7. I assumed you choose the P7 so you could light up a large area evenly.

A rc 5s lipo battery pack may be a good choice if you have the space. You can get a ready made 5s 8000mah pack at hobbyking for around $75. This can be plugged and charged directly in to a hobby charger. Hobbyking also sells these reasonable. They can be charged at high current allowing it to charge rapidly, maybe even between dives. They have balancing wires for balancing the batteries as you charge them. They operate at around 12v. Can be charged from a car battery or boat battery if 12v. You can purchase a laptop style power supply (around $10) off of ebay that outputs 12v, to power from a 110v outlet. Or simply use a old computer power supply. Just making suggestions giving you some more ideas.

 

[HaloclineDiving]

Hi guys

This is the third time I am tryingto post a reply. The previous 2 failed to update / froze the screen so I lost 3 hours of typing!

For starters, THANK YOU again for taking the time to reply. Invaluable and I'm getting my head around this all. Just burnt quite a lot of money on this project now and feel like I'm still on first base. I am! Spend to date : $350
I've taken what you said to heart and since done as many tests as I can to prove out what works and what doesn't. Obv one can only test items higher up the stack without a guaranteed power source and driver, the LED's won't get a proper chance to shine..

To answer the questions:

LED choice. I hear what you've said alpg88. I have over $100 of P7's though and as you said they will be up to the job.
007 mentioned that they havea wide beam and luckily for me, that's precisely what I need! TO explain briefly as this might be of interest.

Underwater lighting falls in to 2 categories:
1) Lighting a path for navigation. This is usually in dark or murky areas hence the reason for a light in the first place. Ideally the tighter the beam the better as this cuts through any silt.
Beam angle is anything from 4 - 15 degrees

2) Underwater videography and photography where the light source is used to light up an object that's beling filmed. Typically lighting is only effective in the first 1 - 2 meters / 3 - 6 feet. Obv high powered lights do more but this is general. Also, animals are usually viewed up close as you can't see them further away, which means your camera can't either

The other thing is that this lighting makes use of 2 light heads not 1. These are positioned on arms which extend out to the sides and effectively shine the light on the object from the sides to avoid the backscatter. So in theory, the longer the arms the better.

I have a fancy set of lights like this that are 250watt HID bulbs and produce the best light colour. 4300 - 4800kelvin
LED's are "blue" in comparison but given their huge efficienes, output, burn time, the ability to stop and start the light, dimming options) they are taking the market by storm..
Beam angle is 110 degrees on these lights..
Diffusers are used to ensure there are no hotspots. Either frosted glass or acrylic
Apologies if this was all common knowledge but it does explain why I'm doing what I'm doing hopefully..
So that's the LED's done. I have 8 LEDs, 4 per light head

Wrt the heat sink. I have not been able to power the LEDs up enough to get them even warm yet. I have some silver paint which I was going to stick the boards on to a larger heatsink that I have. It's 8mm thick x the size the housing ends up being. I assume approx 80mm x 100mm

I have treated the LED's with kit gloves so far but I am comfortable unsoldering them off the board now and mounting them directly on the heatsink.. I'll get to this once I have a working battery and driver..

Driver :
I have emailed Witchel about getting 2 of his 4 mode drivers. I don't know what's wrong with the driver I have but either way it doesn't seem to work as expected. Given the importance of the driver, I think the cost is easily justified.

Reflector. I have some really nice reflectors machined from aluminium which I do think will work nicely. Exact fitting to be confirmed once I have a working model. Not critical path as I might not even need them given thatI want a wide beam..

Battery. Right here where I'd really appreciate a bit of confirmation help. I looked at the graphs from the testing and they're very interesting. I think given that I will have 4 per head, that should really provide a good amount of light even if running at the standard rating. I'll scale up and down using the driver settings..

007 mentioned that HobbyKing do some good batteries. I have found this:
The option I is a single 8000mAh battery which I think is the right thing to get. I'd like to know if it's the correct rated battery AND if my charger will work with it. It's a "Li-Ion charger rated for 14.8V batteries. Outputs 3A up to 16.8V. They were $60 each bought in the USA and shipped so I think they are good quality, just need to check they'll work with this battery. I have 2 chargers.)

The battery is : http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=16226
14.8V, 30C (I researched this and I assume my use would be 3A constant draw so it give a long burn time. Would something smaller be more appropriate to do say 100mins of burn time?)

The 5Cell option had a voltage of 22.2V 007, doesn't that rule it out based on the chargers or will they still work, just slower? And taking the Witchel driver in to account it's more than the 20V the driver is rated to?

Would really appreciate a line on this before I go buy 2 of them Thanks!

* The batteries at this size are larger than initially anticipated, so the standard way of doing it is to separate the battery and have a canister that connects to the light head. I am still going with the all in 1 option light head with battery and will use a foam or tube filled with air to create neutral bouyancy for the light heads.

FBsLights you asked about measuring the current. I have a medium quality multi meter (not a cheapo but not a $500 fluke). It should do the job. I was going to measure the current coming from the driver but given that it's not working properly and all my tests yielded the same amount of light regardless of number of LEDs in s or p, I want to be sure I have the right thing hence the new drivers..
I assume a multi meter measuring current will work?

You also mentioned the batteries - all good stuff but I've given up on he single cells option in favour of the above. Given the importance of the battery pack to this project I think it's worth it. Removing batteries between dives is still an option, I need to find out which battery is the ideal once before deciding as the pros and cons are : pro, unit will be almost half the weight and smaller in size, con is having to open and close the unit which isn't a show stopper but it's a significant change.

The alternative pro is a guaranteed closed waterproof solution, con is the extra size and weight. It's a trade off and I appreciate that's a long burn time! I will be switching modes though so not running at 100% constant use for 110mins. Worst case would be : enter water, switch to 70% whilst on the dive to look at things, makes a big difference otherwise everything is just blue. Switch to 100% when flming specific objects. total time 30 - 40mins. Then switch down off for the ascent.

Maybe I could get away with less burn time ie 80mins total, but for the extra size of the battery I'd rather have the burn time. Many events I film only happen once! There are no re-takes with fish

Guys, thank you once more for the help and ideas. Looking forward to my next order of drivers and batteries..
Matt

 

[moderator007]

The 5Cell option had a voltage of 22.2V 007, doesn't that rule it out based on the chargers or will they still work, just slower? And taking the Witchel driver in to account it's more than the 20V the driver is rated to?

Hobby chargers such as this should charge the pack at around 2 amps. The Accucel 8 should charge that pack at 5 amps. I dont know which charger you have or are getting.

The H6flex specs "Input operates from 7V to 24V (do NOT use more than 5 li-ion cells). Being a buck converter, input voltage must be greater than output voltage - see the H6Flex technical section (manual) for specific information. "

Now as for the 4s pack working with the 4 P7's. Like I said before I dont think this is going to work well. There's not eough voltage to keep the driver working as the batteries drain. Can someone else confirm this? 3 p7's should work well with 4s pack without problems. You are still planning on 4 p7's correct?

I know you have put a lot of effort into this and money. Sometimes more than half of building a custom light is trying to figure out which parts to use and which ones will work or where to buy them. Sometimes the easy part is putting them all together. :thumbsup:

 

[HaloclineDiving]

Right. Rock n Roll. Greenfield start. No re-use (apart from the wire!)

Wise words 007. I know you're right from other projects so here goes :


I've spent so much time discussing the parts I didn't get the to calculations.. So new plan based on learning over the passed few hours is as follows. Btw, the battery chargers I have ar ereally good, but are only compatible with battery packs with protection built in to them so in short, the batteries with this are well over $150 each so the options you suggested are exxxxcellent 007!


Plan:
Cree XM-L 1000lumens 100lumens/watt LED's, single die (4 per light, total 8) from eBay. Is this ok? 20mm or 16mm
H6Flex driver to drive the 4 Cree's (1 per light, total 2) or Wichtel - anyone got a preference? Given that the H6Flex works up to 24V I think I'll with that. Will look for a link to actually buy it..
6Amp wire
Battery : 8000mAh, 5S1P / 5 Cell / 18.5V, 25C Constant / 50C Burst Thuringy http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21439
Accucel charger listed above x 2, http://www.hobbyking.com/hobbyking/..._6_50W_6A_Balancer_Charger_w_accessories.html
Heatsink : 8mm thick by housing dimensions. Might do double thickness pending testing. This will be secured directly to the housing

So 4 Cree LED's driven from a H6Flex using the battery pack above, sound like a good start?

The only only thing I'm not 100% sure about is the battery size. The next level down is 5000mAh, I do understand the calculations, but I never know the variances so any ideas how long a 8000mAh battery listed above would last at 100% vs a 5000mAh?

Expect a flurry of photos once I get started..

 

[moderator007]

You might need these to plug directly into the battery pack. You might also need a 12v power supply for the hobby charger. Unless your going to charge from a 12v source such as a car or boat battery. You can use a old computer power supply or look on ebay for a laptop style power supply. Search for (12v power supply B6) you should find several. Make sure it has a barrel plug thats 5.5mm x 2.5mm.

Link to Taskled drivers. Seems like your changing the design now. I feel your making a improvement with the xml's and the driver. There would only be a small amount of difference between a 20mm board and a 16mm board but the 20mm would be best if it will fit. The key is to fasten it to the heatsink with screws for constant pressure with thermal compound between them. I usually buy my leds from lck-led. They do offer a cpf discount. If the link doesn't work you will have to sign up there to. It takes a week or so to get them but have been good for me so far. They also have the U2 bin xml's. They would be slightly more efficient than a T6 bin. But buying 8 I might stick with the T6 for cost savings. They are other places here in the us if you dont want to wait. From what I have seen and read, most don't have good experiences with buying from ebay with batteries and leds. While they maybe a few good sellers with good products its a chance I usually dont take unless I know its a reputable seller.

As for run time with the 8000mah pack you should get close to 3 hours. With a 5000mah pack a little less than 2 hours.

While your at hobbyking you might want to consider buying some silicone high strand count wire. Very flexible and doesn't melt while soldering to it. Easy to work with. This is all just my opinion from experience. You build it to your liking. Hope the info I give you will help. :thumbsup:

 

[HaloclineDiving]

Just read this, I'm on track now. Drivers from George are on their way. Very helpful knowledgeable guy!
Going with the 5000 battery and the acuttel 8 larger charger
I'll have a look at the forum led link. Ta for that, a week is fine
Very good call on the silicone wire, I don't like the stuff I have now, really hard to work with. That means its a total rebuild lol
Soon as the parts arrive I'll show some pics and then get to putting it all together

Thanks again, over and out till the parts arrive

 

[HaloclineDiving]

All ordered. Thanks again guys can't wait to put it all together!

 

[moderator007]

I think you posted above that you went with accucel 8 correct? The accucel 8 does not use a barrel type plug from a 12v power source like the accucel 6 does. The 8 only has big alligator clips. But a old computer power supply should work fine. How to guide here. You are only interested in the 12v black and yellow wires. And the orange wires will go to the brown sense wire.

The accucel 8 should charge the pack in about 1 hour or less depending on if your power supply will supply enough power to charge at 7amps and 21v. Some RC packs can be charged at some ridiculous high C rates. I think the one you got was 2C, should be good for 10amps.

 

[HaloclineDiving]

Great I'll check the link out. I got the 8 as in the long run, paying $20 more for something that's 3 x the power and will mean the difference between charging the batteries in time for the next dive - or not - is money we spent
I also got the thurigy 5000 5s1p lipo battery as it had the best reviews. Another reason is that it can charge at 5c
All happening now! I've got a laptop charger spare and I measured the voltage at 19v last night. It's output is 3.5A. So, that doesn't look right
The 12v chargers on hobby king were very expensive and the cheap ones at $10 were all on back order lol!
I've got my 110Ah car battery to work from initially so I'll check the mod link first..
Chat soon..

 

[HaloclineDiving]

Hi guys

EURICA he cried! Let there be light.

I got the H6Flex drivers from George and what can I say. Exceptional piece of craftmanship. Worked stright out the box, perfect soldering even for me, current supplied could be measured with NASA grade instruments to 5 places and it's simply a rock solid piece of hardware.

I powered up a single P7 to test and it blinded me. I then put 4 in series and it's plain crazy bright.
Buying a luminometer today to measure the brightness as it's currently running at the default setting of 1400mA. I will set it to 2800mA to test the difference in brightness but to be honst, right now I can't imagine needing it to be any brighter.. The 4 P7's lit up the entire lounge area no problem even without reflectors. I did add the reflectors I have and the light is obviouslymore focused so once it's in a stable condition firmly fixed to the proper heatsink I will start working on the beam.

I did attach the P7's to a 4mm thick 100mm x 70mm aluminium heatsink, taped down hard and the heatsink never got over "warm" to the touch even after a good 5 minutes of running at max output. The proper heatsink will be 10mm thick but smaller in size and attached to the 4mm thick housing but I'll test and make one accordingly. When the light is in 50F / 12C degree water for diving this should help even more so heat actually is less of an issue for me underwater than on land.

The battery packs and chargers have been stuck in customs over a week but they "should be delivered soon". Holding thumbs and can then do burn time testing..

VERY happy, thank you all for your help and advice. Here's one not-so-great photo but that's bright light! I'll reply once I have hte batteries connected and the full system running at peak capacity

 

[moderator007]

/\ Glad to hear. Keep us updated as you progress.:thumbsup:

 

[HaloclineDiving]

Hi all

I ended up running the H6Flex driver at 1.4amp, the standard setting as its INSANELY BRIGHT at that setting. I can't make it any brighter as it already makes one nauseous even glancing at it. That's just one light head and there'll be 2..

There's so much debate about the lumen rating but it measures 13800 lux at 10cm from the light with no reflector. Pretty bright..

Been working on the housing with a friend this passed time (he's been slack!) will send pics once it's a working unit..

Thanks again for all the help

 

[HaloclineDiving]

Hi all

Years later but here is an update :

I followed Moderator 007's advice and using the H6 Flex driver, high powered Li-Ion batteries and chargers from HobbyKing and the P7 (and also Cree) LED's, I have a HIGH POWERED lighting setup!
My father in law machined out some beautiful light heads and a battery cannister from aluminium that I had black annodised so it looks very professional

I've had them underwater a bunch of times and they work so nicely.. Hard to believe what a great project this turned out to be Just took time

I'll post some pictures if anyone replies to this old thread..

THANKS for all the help guys, especially Mod007

 

[AlexGroove]

A bit late, but I would love to see pictures of the finished lights, also because I can't view the original pics...