[Oz]

Calculating Amperage

Formula: Power = Current x Voltage

Example:

85 watts (Power) = Current (Amperage) x 12 volts (Voltage)

85w/12v = Current (Amperage) x 12v/12v

7.08 = Amps

Here's a Handy Calculator to help with that.

Now that you know how many amps are on your circuit here's a 12 volt Wire Gauge vs. Amps Chart.

Feel free to let me know if there's any other useful tidbits to add.

Remember to be very careful with electrical installations! None of us want this:

 

[GPzGuy]

This is a VERY handy list of formulas for converting from volts, amps, watts, and ohms. All you need to know is two values and you can find the third easily.

Now there are a few caveats: First, though we always think around 12 volts as a constant value, in fact it may be more conservative to assume 13.5 volts, which more likely what your charging system will be running at.

Second, you may measure a certain resistance (in ohms) with your multimeter, like for instance on a light bulb, but after current is flowing and the heat increases, then that resistance will greatly increase, especially on light bulb filiments.

 

[Surf and Snow]

Nice job OZ. Glad that little chart helped.

 

[Oz]

Nice job OZ. Glad that little chart helped.

Thank you, GPZguy, Xterra1102, and Rev for all of your sage advice!

 

[Rev]

ccasion5:

Adding it to my how to.

 

[Duck_Hunt00]

whats the story with that X?
so sad...

 

[1945]

Lots of useful info here: http://www.the12volt.com/Default.asp?

and here: http://www.allaboutcircuits.com/

 

[brett]

whats the story with that X?
so sad...

I'm thinking he forgot the fuse part :iconbiggrin:

 

[Xterra1102]

Thank you, GPZguy, Xterra1102, and Rev for all of your sage advice!

No problem man! :salute:

 

[GhostX]

Printed that chart and used extensively during my off road light and Ham radio install. Very handy, almost thought about laminating a small card and tossing in tool box...hmmmmmm.

Thanks Oz...and all contributors!

Satisified NewX customer #1

 

[tighthams]

It may also be useful to keep in mind that you may have less than 12 volts under heavy load or just a weak battery.

If your voltage drops to 9 under load, that 85W example at the top becomes 85/9 = 9.4 amps. You could start blowing fuses if you run accessories with less than 12 volts.

All of your electric mods are fused, right?

 

[Xterra1102]

It may also be useful to keep in mind that you may have less than 12 volts under heavy load or just a weak battery.

If your voltage drops to 9 under load, that 85W example at the top becomes 85/9 = 9.4 amps. You could start blowing fuses if you run accessories with less than 12 volts.

All of your electric mods are fused, right?

Not exactly true....if you're running 9 VDC with the motor running, you've got problems that need to be addressed immediately.

General rule of thumb, vehicles run at 12.2 VDC with engine NOT running (battery power only). And 14.4 VDC with engine running.

 

[tighthams]

Not exactly true....if you're running 9 VDC with the motor running, you've got problems that need to be addressed immediately.

General rule of thumb, vehicles run at 12.2 VDC with engine NOT running (battery power only). And 14.4 VDC with engine running.

To clarify, my example refers to running accessories with the engine not running. As the battery drains, the voltage will drop. If I run a high drain accessory (like a winch) with the engine off, the voltage will drop quickly.

 

[Xterra1102]

To clarify, my example refers to running accessories with the engine not running. As the battery drains, the voltage will drop. If I run a high drain accessory (like a winch) with the engine off, the voltage will drop quickly.

Oh ok..I got ya. Then yeah that makes sense.

 

[Oz]

All of your electric mods are fused, right?

Yes indeed!

 

[SilverBulletX]

Must have been a ****ty experience im sorry!

 

[John Dirt]

Calculating Amperage

Formula: Power = Current x Voltage

Example:

85 watts (Power) = Current (Amperage) x 12 volts (Voltage)

85w/12v = Current (Amperage) x 12v/12v

7.08 = Amps

Here's a Handy Calculator to help with that.

Now that you know how many amps are on your circuit here's a 12 volt Wire Gauge vs. Amps Chart.

Feel free to let me know if there's any other useful tidbits to add.

Remember to be very careful with electrical installations! None of us want this:

lol his rear wheel got stealthed naturally

 

[XButler]

Great write up! This is a kick in the butt motivation for me! Thank you.

 

[Old Navy]

This a site, (www.circuitlab.com), is actually fairly decent for drawing out a diagram, if you feel so inclined.