8 3.7-4.5V LEDs to 12V car battery HELP

[jefey3707]

I have 8 LEDs that are 3.7typical V , 4.5V max input and 20mA and i want to run them from my car battery 12V, ~13.2V when car is running how shoul di go about making the circuit. where should i put the resistors and what ohms should the resistors be, i also want the LEDs to shine their brightest, thanks for you time and help.

 

[melone]

What configuration(s) have you considered?

 

[peebee]

There's been a LOT of recent threads on this -- have you searched the site?

 

[StukaScott]

I would make use of one 500-ohm resistor in series with each LED. .5 watt is overkill butt at least you don’t have to be concerned about a fire. 470 or 510 ohms should be fine.

Here’s how:
LED VF = 4volt
Supply V = 14volt
Supply V – LED VF = 10
LED I = .02
10 / .02 = 500 ohm
(.02 *.02) * 500 = .2 watt