I am giving advice based on the info he gave us. I had previously mentioned that they were likely more like 3.3 to 3.6V, but he insists the are 3V.

 

The results will be interesting! And the education will be valuable.

 

Ya sorry an oversight by me, typical of this everlight Amber white LED is 3V but max is 3.6V for worst case so maybe more of a string like this

 

In that table, Balance 5.png, Vf is presented as 3.5 volts. THAT is a number I would expect. 3 volts Vf will be with the LED delivering less light than the specified level. 3.5 volts is a number closer to what I would expect.

 

The 1/2W resistor will still glow red-hot and maybe will catch on fire because the arithmetic is wrong:
1) 9 LEDs of 3.5V=31.5V.
2) Voltage across each resistor= 48V - 31.5V= 16.5V.
3) 135mA in each string.
4) Resistance of each resistor=16.5V/135mA= 122.2 ohms.
5) Dissipation in each resistor= 16.5V x 135mA= 2.2W.

 

Ya I think strings of 6x3.8=22.8
Set buck boost to 24V
24-22.8=1.2
1.2/.135=8 ohms
1.2x8=.162 Watts
72 LEDs/6-12 strings in series placed parallel to each other on the voltage rail

 

1.2V is OK for a current-limiting resistor of a string of 6 LEDs only if you buy hundreds of LEDs, test them all and pick the few that are at 3.8V.

Did you post the datasheet of your LEDs in this long thread?

 

1.2V is OK for a current-limiting resistor of a string of 6 LEDs only if you buy hundreds of LEDs, test them all and pick the few that are at 3.8V.

Did you post the datasheet of your LEDs in this long thread?

Microsoft Word - 000_00157_02500.src.docx (everlight.com)

 

Your unknown Taiwan LEDs have 3 forward voltage bins: 1A, 1B and 1C. Which one do you have?
The datasheet does not say the maximum allowed power (voltage x current) at various ambient temperatures for you to calculate a suitable heatsink. Their specs are when the solder pads are at 25 degrees C due to having a "perfect" heatsink.

 

1C

 

The 1C range of forward voltages is show for a 250mA current. You must use their graph to determine the voltages at your lower current.