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- Thread starter cherokeewind54
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There are 2 types of automotive bulbs I am familiar with that work with 12v systems, one will work from 9v-14.5v and the other will work all the way up to 30v.

Depending on which LEDs you get you could be charging your cart and have the 14.5 v models and if you turn on the lights....21v and poof, instant NFG.

I'm not sure you proved your point, more like you've been lucky.

LED's are more of a current device rather than voltage device. OK that said there are a number of things that you need to know.

1 are the multiple LED's hooked in series

2 is there a resistor already installed

3 what is its value

Calculating an LED resistor value

LED resistor circuit An LED must have a resistor connected in series to limit the current through the LED, otherwise it will burn out almost instantly.

The resistor value, R is given by:

R = (VS - VL) / I

VS = supply voltage

VL = LED voltage (usually 2V, but 4V for blue and white LEDs)

I = LED current (e.g. 10mA = 0.01A, or 20mA = 0.02A)

Make sure the LED current you choose is less than the maximum permitted and convert the current to amps (A) so the calculation will give the resistor value in ohms (ohm).

To convert mA to A divide the current in mA by 1000 because 1mA = 0.001A.

If the calculated value is not available choose the nearest standard resistor value which is greater, so that the current will be a little less than you chose. In fact you may wish to choose a greater resistor value to reduce the current (to increase battery life for example) but this will make the LED less bright.

For example

If the supply voltage VS = 9V, and you have a red LED (VL = 2V), requiring a current I = 20mA = 0.020A,

R = (9V - 2V) / 0.02A = 350ohm, so choose 390ohm (the nearest standard value which is greater).

Working out the LED resistor formula using Ohm's law

Ohm's law says that the resistance of the resistor, R = V/I, where:

V = voltage across the resistor (= VS - VL in this case)

I = the current through the resistor

So R = (VS - VL) / I

You are correct but I'm guessing the OP has no idea what your talking about.

Most automotive replacement bulbs from auto supply stores are already clustered with the resistors built in which what I suspect he's using, not the individual ones from the electronic parts guys like Jameco, Mouser, Digikey etc.

Yes, they are in series, and each one has it's own resistor.