common vehicle power specs?

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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=95294
Printed Date: May 15, 2025 at 2:55 AM

Topic: common vehicle power specs?

Posted By: americasfuture
Subject: common vehicle power specs?
Date Posted: July 02, 2007 at 10:34 PM

i know its commonly know as 12v. but it is read around 13.8v sometimes. im wanting to know what the common wattage and amps are. and also how to reduce a 12v or 13.8 v system to 6v or 6.9v. like what resistance i need to accomplish this

Replies:

Posted By: DYohn
Date Posted: July 03, 2007 at 8:34 AM

12V is the nominal voltage of a car battery. Almost all vehicles operate between 13.8 and 14.4 volts when running as this is normal alternator voltage. Are you talking about determining the common current usage of a vehicle's parasitic loads? This completely depends on the vehicle and on what's running at any given time like A/C, lights, etc. It can vary anywhere from 5 or 6 amps to 30 or 40. There are several ways to design a power supply that will deliver 6V. It depends on what you are trying to power. DC-DC converters are the most voltage-stable, a simple voltage divider is the most reliable. Google the term "voltage divider."

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Posted By: americasfuture
Date Posted: July 03, 2007 at 11:36 PM

im wanting to know what the common voltage, amps and watts on any voltage output source while it is running. im trying to build some led tail lights. its just hard to do when m vehical isnt in the same state as me. i want to know how to find out what resistance i need to reduce the power to 6v. i just realized that on my tail lights, the high and low bulb filaments on the tail lights both use 12v. in order to achieve the low side por the tail lights i need to drop part of it to 6v or half of thatever the voltage coming out is. this has nothing to do with the high and low beam on the headlights. different end of the vehical.

Posted By: citrus3000psi
Date Posted: July 17, 2007 at 3:52 PM

To cut voltage in half just use two equal resistors. Heres a picture to help (from https://www.rmcybernetics.com)

If you check the voltage from C to B it will be half of the voltage.

The equation that makes this work is NewVoltage = R1/(R1+R2) * BatteryVoltage

So... 6 Volt = 10k(10k+10K) * 12

When using voltage dividers be smart with the resistors. If you have a large current draw or high volts please use an apportiate resistor.

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Posted By: americasfuture
Date Posted: July 17, 2007 at 4:51 PM

citrus3000psi wrote:

To cut voltage in half just use two equal resistors. Heres a picture to help (from https://www.rmcybernetics.com)
If you check the voltage from C to B it will be half of the voltage.
The equation that makes this work is NewVoltage = R1/(R1+R2) * BatteryVoltage
So... 6 Volt = 10k(10k+10K) * 12
When using voltage dividers be smart with the resistors. If you have a large current draw or high volts please use an apportiate resistor.

where would i go on that link to find this info? id like to bookmark it for future references.

Posted By: citrus3000psi
Date Posted: July 18, 2007 at 8:27 AM

https://www.rmcybernetics.com/science/cybernetics/electronics_example_circuits.htm

This is the page that the circuit is on. The site navigation is pretty bad but there are a lot of good info if you can find the pages. This is another good page. It tells you have to make a varible DC output. So you could run dc motors etc at whatever rpm. It allows you adjust frequency etc.

https://www.rmcybernetics.com/projects/DIY_Devices/homemade_signal_generator2.htm

Posted By: americasfuture
Date Posted: July 18, 2007 at 1:34 PM

oh sweet, thanx a bunch. great info to have