powering leds from car power supply

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Thread Starter


Joined Mar 12, 2011
Hi all and thanks in advance for any input and response. My project is to drive between 35-40 SMD RGB leds in a series, but I want to power the leds using the power source from my car. I would like to have 5 rgb leds in each series and about 7-8 strings.. I understand that leds work more efficiently with constant voltage and current and therefore using the power from the automobile will be inefficient as the voltage and current fluctuate. To overcome this problem I have decided to look into some step up dc/dc converters that will output 30 -35 volts from 12-15 volts input (car battery) and output a constant current of 10 amps. My questions for this project are the following:

1. Is this the best way to increase the needed voltage and current to drive the leds from an automobile power supply?

2. If this is the best way to increase the needed power, should I connect the dc/dc converter directly to the battery or fuse box.?

3. Do I need an inline fuse ?

4. Do I need to worry about CCA blowing the dc/dc converter and the leds as the current can exceed 600 amps during start-up of the car ?

What is CCA ?: http://www.autobatteries.com/basics/selecting.asp
CCA is critical for good cranking ability. It's the number of amps a battery can support for 30 seconds at a temperature of 0 degrees F until the battery voltage drops to unusablelevels. A 12V battery with a rating of 600 CCA means the battery will provide 600 amps for 30 seconds at 0 degrees before the voltage falls to 7.20 V (six cells).

5.Should the dc/dc converter have Short-circuit Protection and what should be the Maximum Input Current:

Below I have pasted the links to several Step Up DC/DC Converters which I believe might be suitable but I am unsure. PLEASE, PLEASE HAVE A LOOK AND SEE IF THEY ARE SUITABLE FOR THE TASK.
The following are from the company site: http://www.xscyz.com/


I have also listed the specs on the leds: in case voltage and current draw becomes a factor.
FOrward voltage min typical max for. current
RED LED 2.0 2.3 2.8 120 ma
GREEN LED 3.0 3.5 4.0 150 ma
BLUE LED 3.0 3.5 4.0 150ma

Thread Starter


Joined Mar 12, 2011
Thanks for replying. Forgive me because I am naive in terms of electronics. Should they be in parallel then or how should I desigh the circuit?


Joined Jul 17, 2007
I don't think we can support discussion on your topic, as it is the use of LEDs in an automotive application.

It would likely be illegal to use RGB LEDs on the exterior, and for the interior, it would seem to fall under the "distracting" category in the "Automotive Guidelines" thread.

Link: http://forum.allaboutcircuits.com/showthread.php?t=40361
2. Any homemade wiring modifications to signal or head lighting, or penetrations through the fiewall are not for discussion. The lighting function is to too critical for non-approved wiring and connectors. Many safety issues are involved. Preventing chafing in wires passing through driver-made holes is impossible to guarantee.

3. Add-on items that exist in the passenger spaces is generally okay. Exceptions are lights flashing to music and similar driver distractions. Assurances that the color organ will only get operated while sitting still is not credible.
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