driving light?

i want to make a driving light for boats using a 12volt power source. i’d like to get about 4000 lumen. i need to place multiple XP style LEDs as close together as possible to be inline with existing optics. these will run at 1A and maybe up to 2A. i’m currently using aluminum core boards fastened to heatsink with good thermal compound. i’d like to put 6 or more LEDS as closely placed as possible. will they overheat when placed close together? would copper board work?
does anybody have a good circuit design for what i’m trying to do?
are XP LEDs the best choice to get 4000lm for the lowest price?

Any pix? It’s hard to visualise what you’re describing.

Will this help any?


what existing optic do you have, what are the measurements between centers?
there are 10mm xp stars. have not seen smaller, if really needed you can solder leds to a copper bar, right next to each other.
it should not matter much as far as heat, as long as heat removed fast enough, copper boards will help, you need to remove heat from those copper boards, but all depends on the way you build everything together, with good design it may work just fine with aluminum, in bad ones even copper wont save the day.
there are many drivers that would work, depends how many leds and how they wired (s or p)

it maybe easier, to build one from scratch, than retrofit existing parts. i gad pretty good results with 38mm 4* lenses and xpg2 leds, i suspect xhp 35 would do even better

Then an XHP35 can pack a little more oomf. Same XP footprint, more chips.

For 4000 lumens on like 4-6 XML2 or XPL high binned LEDs you need about 35W
Of course if you add optics you need more LED lumens
So if you have enough radiation for 50ish watts the heatsink is fine
Passive CPU heatsinks work fine

I highly recommend using DTP stars you can drive less LEDs harder, even at same current you gain lumens just by the enhanced cooling, the heatsink can get hotter at same LED temperature

If you stick with cheap aluminum stars stay at 2A per LED

The other attempt is using a single XHP70 LED N4 binned with a 6V buck regulator at 5A
XHP70 LED is 4 XPL emitters close together on a single 7x7mm case

Use the 6V one, as the 12V needs about 12.8V

1 mode driver for car or boat

WOW, this is the kind of knowledge i’ve been looking for. i should have given better information.
i was planning around 40W with 4 to 6 LEDs but if i can do it with 1 or 2 xhp70s, that’s ok too. whatever gives me 4000+ lumens at lowest price and wattage.
i design my own metal core boards so any LED is possible. i prefer to put the driver circuitry on same board. i was planning on 2 separate 2A buck drivers since power is limited to 12V. i like the price for that driver board but a separate driver complicates my design. i’d like to have the schematic for that design or similar.
i want to use existing aluminum light housings and optics to avoid tooling costs. i understand heatsink size requirements. that’s why i was looking at multiple LEDs. there are many more housing choices available for 4 to 6 LEDs but i’m open to any idea.
what does DTP stand for?
where can i buy optics for testing beam angles? i’m probably stuck with what comes on the light housing i choose. i’m not sure what angle i want. what is typical beam angle for auto headlights? i think that is what i want. would i be better off using an auto headlight bulb instead of LEDs and going to the trouble of building circuit boards, etc.? most of the lights i’ve tried are either too narrow or beam is too wide and weak. i plan on making a beam angle measuring arrangement to know what works best.
THANKS EVERYONE, great info. i’ll be back for more.

you can get 4000 lumens from one XHP70 on a copper DTP star slightly overdriven
a N4 flux bin has 3400 lumens @6.43V and 4.8A,
they run very good up to 8A

N2 flux bin tested

you can calculate lumens from Cree LEDs here


xhp70- can be a thrower, but it needs huge tir, digikey sells one like that, ledil sienna, it’s about 7 in. in diameter. 4,3* beam

here is a thread of a build using sienna lens. https://budgetlightforum.com/t/-/35300

reflector with spill should be more useful and easier to find

Yeah, anything can throw with a big enough reflector. An xhp70 throws much better than 4 xp-l's 10mm apart crammed into one optic. I wouldn't like having to push to top bins though.

Lexel are those your plots? Even if they are, you should credit yourself, so others can. As it is now I wouldn't dare repost that because I don't know who to credit. I know the noctigon images aren't yours.

References list isn't needed on a comment board but I wouldn't ever post anything like that without mentioning where it came from.

sorry guys, i’m a noob when it comes to some of the lingo.
what is ‘dtp’, ‘tir’, and ‘spill’?

Spill is usually less than on reflector lights

DTP was my 2. last post with pictures

if i was building a driving light for a boat, i’d use 6-8 xhp35, and 38mm ledil iris 4* tir, easiest way is to build it, is in a shape of a light bar, but there are other ways too.
also i would not be over driving leds, i’d prbly go with 70% of max current. overdriving is good for “wow” flashlights with little to no practical use,but for something that would be used often, i would not. it is not just life span, it is potential issues with heat, it maybe ok to do for a flashlight that is not running for long periods of time, but when it has to work for hours, you do not want to have any heat or other issues, you investing time, effort into the build, might as well make it last.
or you can pick up aux lights for cars, and use them on a boat, some are pretty good throwers, especially hid ones.

alp, that sounds like good advice and about what i thought about doing, but i’m still open to any ideas.
i prefer a square or round housing due to different mounting requirements on different boats. it may have to be mounted horizontal or vertical.
where can i buy the optics?
and i need to educate myself more on optics. all help appreciated.
thanks again.

I like TIRs (get 20mm and 26mm from LEDsupply.com), but you can get fairly big reflectors from fasttech, like


which take 20mm stars directly. The layer of aluminum negates the benefit of DTP, but is easier mounting. Just don’t overdrive the LEDs.

Again, no pix of what you want to reuse, so these are all generalities.

something similar to this:

one of my board shops has dtp capability. would i need it for xhp35s at high amperage?

You are wrong with this overdriven is bad for LED lifetime

Watch this video

The picture before it plays shows the aging with current, the solid line shows longer life for 350mA, while the other for 100mA shows less for the same LED temperature, a DTP star keeps the LED a lot cooler than conventional cheap aluminum stars that are used in most application to save costs

There are tests that clearly show that if the LED keeps cool enough on the LED die a higher current makes in fact the LED age less than on lower current
LED ages from a process that is mainly rapidly increased at low currents like moonlight or low the LED can age 10 times faster than on full current

I watched this video multiple times

And I am native german, so I did understand well why low currents are far worse than heat to kill LEDs

The current protects the very thin active light emitting zone from electrically defective spots to migrate into it from the surrounding material, this active zone is a lot thinner than the rest so migration is a huge issue
Of course heat also increases the migration of electrically defective spots

On our CC moonlight flashlight the LED can age over 10 times faster than on max. rated current
You see the plot at 16:00 of the video
And that plot shows the LED running on 3% of its normal current
Our moonlights and firefliey modes on CC lights get below 0.1%

The odd thing is if we get good cooling an overdriven LED ages slower than at rated current when they got the same junction temperature

that particular optic, is sold on either digikey, or mauser. that is the places i know sell those, but there may be others selling it.
this is the one i’m talking about,
with hxp35 it is 8* angle. with xpe 4* but you’ll need 3 xpe to match xhp brightness
i also like that i can use screws to hold the holder and the star at the same time, majority of other lenses use either glue or tape, which is fine for flashlights or stationary lights,. but not good for vibrations.

i tried 20-26mm carclo lenses from led supply, they are great for flooders, they even throw ok, but only with xpe, which is a bit outdated and underpowered.

use dtp stars whenever possible, it is always better to use dtp stars, unless you using leds that do not have electrically insulated heatpad, but lately most have insulated one at least cree.

i’ve build quite a few light, that are basically light bars with handles and batteries.