Lighting Underwater XPH70 LED Build

[efine]

Idea is to build an underwater light for a boat.
Basically I want to create my own version of this:
https://www.amazon.com/Waterproof-Brightness-Underwater-Viewing-Swimming...(link is external)

I need help with the driver selection.

Constraints:
Battery
Voltage Source = 12v battery (assuming volt has a range of 12v with engine off to 14v while engine running)
Battery Source: https://www.interstatebatteries.com/products/24m-xhd

LED Option 1: XPH70.2 12v
Cree XH P70.2 P2 5700K on DTP MCPCB (mtnelectronics.com)
-High lm/w option with lower heat than 6v version due to lower current draw
-BUT, I cant figure out a driver to use. If the driver reduces the source volts, then the LED wont work while the engine is off, right?
-17mm MTN-MAXlp HP 1A-5.5A Low-Profile Buck Driver – 5V-18V (mtnelectronics.com)
-Is there a cheaper driver anyone could suggest?
-The datasheet says 1050mA preferred current, and 2400mA max current. But I’ve seen other threads where people run these much higher. Is it ok to aim for 2400mA or should I aim lower? (assuming good heat management)
LED Option 2: XPH70 6v
Cree XHP70 N4 1A on 16mm / 20mm DTP MCPCB (mtnelectronics.com)
-I could use a buck driver but then I have a lot more heat generation
-$5.21 26mm 4500mA 1-Mode LED Driver Circuit Board for Flashlight DIY – for Cree XHP70 / 6-15V at FastTech – Free Shipping
-Data sheet says 2100mA preferred current, and 4800mA max current. Which one should I aim for?
-This forum has a graph showing amps/lm & volts Cree XHP70 up to 4022 Lumens and XHP50 up to 2546 lumens – Multi-die leds. | BudgetLightForum.com
Construction:
Option 1: Water cooled
-LED covered with clear epoxy
-LED on top of aluminum heatsink, attached to the outside of the boat, in the water
- or LED on top of copper disc inside an aluminum hex bushing, attached to aluminum nipple, screwed into the drain plug
-Hole cut in boat for wires
Option 2: Air cooled
-LED against inside boat wall
-Heatsink behind LED, air cooled
Option 3:
-Boats have a 1” diameter drain plug in the back underwater
-Could leverage that as an attachment location that doesn’t require drilling holes
Thermal Heatsink Calculations:
- Lifetime Case Temp est: 100C
- Ambient temp ~ 30C
- Vf1 =12.6v | Vf2 = 6v
- If1 = 1 – 2.5A | If2 = 2 – 5A
- Efficiency ~ 70%
*HeatSink Thermal Resistance for 12v&6v is ~ 3-7.5 C / W
or 9 – 23 watts needing to be dissipated*
Formulas
dT = Case Temp – Ambient Temp
Pe(W) = Vf * If
Pd = W * Efficiency
Rth = dT / Pd
https://www.led-heatsink.com/thermal-calculation(link is external)

This guy tried to do something similar but doesn't look like he used the latest LED tech, nor did he account for heat...
Homemade Drain Plug LED - TeamTalk (mastercraft.com)

Summary:
- Can I use the 12v Led with 12v source? If so, what driver should I be using?
- What driver should I use if I cant use 12v and have to use 6v LED?
- Any ideas for water proofing an LED?
- Any suggestions for very flat heatsinks, so it be as flat against the boat wall as possible?
Thank you!

 

[wwwillie]

Battery should be at 14.4 unless discharged so that's a good voltage. Driver, I would stick to the recommended current of 1050, maybe go to 1500, keeping it there will extend the life, run cooler, etc. I would try a Meanwell LDD-1200LW It's a buck so the Vin (Voltage in) has to be greater but should fire the LED with a car battery. They are constant current so you can use any Vout between 6 and 36 volts and it will be fine. They're under 6 bucks here: https://www.ledsupply.com/led-drivers/mean-well-ldd-l-series-cc-step-down-mode


Of course YMMV, but I think it should work. Sorry I am no help with heat sink, I just go overboard.

 

[efine]

Instead of buying an expensive retail solution or having to engineer my own light, I found out about Chip-On-Board (COB LEDs). No Drivers needed. The board is aluminum and therefore waterproof and rust proof. The lights are covered in epoxy so also waterproof.

I found one that claims 3500-7000lm for $10 and is waterproof and rust proof by design. Used just two bolts to mount it on the back of my engine mount underwater, no holes in the hull, and ran two wires to my light existing light switches.

Brighter than anything else on the market for boats and a fraction of the price. It’s been on the boat the entire 2021 season with no issues so far.

https://www.amazon.com/gp/product/B08RJWDYJD/ref=ppx_yo_dt_b_search_asin...(link is external)

The manufacturer claims 12v minimum, +13watt requiring a heatsink with a 14v max.
My boat runs ~12.6v with the engine off, and >16v while running. But since the light is underwater it seems to have enough cooling. Probably killing the longevity of the light but for $10 it’s still holding up well.

I havent tested the exact lumens but it’s bright enough to light up the entire back of the boat and wrap half way around the 16’ bowrider. A second one isnt necessary at all.