WHAT VOLTAGE IS YOUR CAR AT???

What is the voltage or your car when the engine is on? I am trying to figure out the average voltage of volvos.. so I am better design my LED system.

Kevin

im pretty sure they're all designed to run at 13.5v - 15v

-Dana

I wasn't asking for what is was suposed to run at, but actual reading with a multimeter... I need to know if it is closer to 13v or 14v....

Voltage of a running car can vary widely depending on what you have on in the car ,on my 83 242 with the motor running and nothing turned on my battery is around 14.2. With headlites, blower fan, a/c, stereo, i can go as low as 12.5 volts at the battery. Most electrical stuff in cars is designed to work around 13.8 volts or so, i guess that is what you should shoot for. Dan242tic

About 14.5, but with the heated seats and headlights/foglights on it looks pretty grim. How does 12.8 sound to you?

damn... this is gonna be interesting... Kinda like making a car go 60 MPH and 100MPH at the same time

just set it up for the highest voltage they will see. They'll still be bright enough at 12.x volts. Not a big deal. Or, set them up for 12v, and use a voltage regulator.

was thinking about getting a 500 mA 12v regulator... but A: forgot to order them in the first shipment... and B: too cheap to get them right now

I see close to 15v with no accesories, but that's with a dash mounted VDO/Volvo gauge. Probably not very accurate, and certainly not precise, but I've had at least 3 different ones in my car that have all been the same.

own6volvos said:

was thinking about getting a 500 mA 12v regulator... but A: forgot to order them in the first shipment... and B: too cheap to get them right now

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This is going to hurt just a little. First of all, voltage regulators have some minimum voltage drop below which they will not regulate. This is called dropout voltage and can be anywhere between 0.1v and 3v and it varies with the load current. This parameter establishes the minimum input voltage that you can have and still maintain regulation.

For instance if the specified dropout voltage is 0.5V at 1A and you want to have 12V output, than your input voltage must be higher than 13 V to maintain regulation.

Your battery voltage will vary with temperature. Lead acid batteries have a negative temperature coefficient of 0.0039V / C? per cell. This means that 13.8v at 25 degrees Celsius battery voltage will rise by 1.4v to 15.2 v when the temperature drops to -40 degrees. A that point I would be more concerned about my oil turning to jello.

Since you are designing this you have a choice of picking a regulator with lower output voltage to suit your LED chain. You will still need a resistor to compensate for regulator tolerance, LED voltage drop variation, Murphy's law, etc. Do not forget that the voltage regulator will also dissipate the power proportional to the product of the current through it and the voltage drop across it.

LM2940 series TO-220 package (Digikey) could be a start but do not take this suggestion as gospel. There is a lot more to voltage regulators that it appears on firsts encounter. This one comes with 17 page data sheet. You only need 1% of the info. Do not feel intimidated.

Voltages

My 81 244- 14 volts no load, My son's 82 244 14.2 volts no load, Wife's 945T 14.1 volts no load. This is at idle no devices on.

14.7 reg. So...fully loaded (amp, head, lights, blower (not any more, too warm for heat, windows down!), about 13.5 volts

towerymt said:

I see close to 15v with no accesories, but that's with a dash mounted VDO/Volvo gauge. Probably not very accurate, and certainly not precise, but I've had at least 3 different ones in my car that have all been the same.

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Same case here although only 1 gauge.

Got a external volt/temp gauge on two of my cars ...

Off the radio acc line, my '86 245GL with a 100-amp alternator varies from 13.3v to 14.1v, depending on what's on and what engine speed. Usually, it's at 13.7v.

My '91 745Ti varies from 13.2v to 14.2v, usually at 13.6v.

And don't rule out that different alternators yield different results, so what we get still may not be what your car gets.

-- Kane

What are you trying to do with your LED's? (my 760 runs about 14 to the headlights)