LED conversion of spotlight

I know this is an old thread but I'm attempting to do this myself.I'm starting out with a 4V 25W H3 halogen bulb rechargeable spotlight.The battery,which is 4V 2ah sla and it had reached it usable life span so I purchased 4-LG 18650 2200mah lipo batteries and 4 single 18650 holders with wires and a lipo protection board rated at 10 amps max and am currently running all batteries in parallel and the spotlight works fine.My problem arises when trying to source another bulb.Apparently a 4V 25W H3 halogen bulbs are hard to find,I found one on Amazon but it was slightly different being it was 4V 15W H3 bulb so I ordered it and when it came it turns out to be a 6V 35W H3 bulb so I sent it back and apparently the seller can get no more 4V halogen bulbs.So....I want to convert over to led.

Reference: https://www.edaboard.com/threads/260837/

SunnySkyguy said:

Choose a good Toshiba or Cree 10W LED and heatsink then drive with Thermistor to regulate Logic level <=50mOhm Nch MOSFET with drain to cathode LED and epoxy thermistor to heatsink for 50'C to adjust 1V gate voltage from 3.7V LiPo.

LED should be 3.2V at 1.6A for a good 10W LED run at 5W

Click to expand...

Thanks,that's what I needed was a blueprint on how to do this without just burning up a bunch of led's,thanks again and will get to work on sourcing the parts needed.Already have a cree bulb saved in my watch list on Ebay just didn't know if it was the one but now I do believe it is but am going to look around some to see all variant's of said cree bulb's.

Use several good Toshiba or Cree 1W or 3W LED and heatsink then drive with Thermistor to regulate Logic level <=50mOhm Nch MOSFET with drain to cathode LED and epoxy thermistor to heatsink for 50'C to adjust 1V gate voltage from 3.7V LiPo.

If you dont know how to design an LED heatsink, buy one with heatsink and reflector.

LED should be 2.85V @ 350mA for 1W . $1.65 @10
If you do know how to design a MCPCB choose from these neutral white.
http://www.digikey.com/product-sear...1&stock=1&quantity=0&ptm=0&fid=0&pageSize=500
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These require 12V http://www.grainger.com/product/PHILIPS-LED-Lamp-34TE75

http://www.amazon.ca/niceeshop-Degr...sbs_201_4?ie=UTF8&refRID=1Y7S13S8CF3N8YN4J2W7
which is a better voltage for this power level of LED's

If you use 4 LiPo with PWM to generate 12V or regulate temp. by adjusting PWM, that will work better or monitor current and add amp and regulator

You may a have a bunch to learn to DIY.