A couple of electrical Q's

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TrekboxX

TrekboxX

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Sorry if this doesn't really belong here, but I'm wiring up my fridge and extra cargo lights and need some advice. I don't know which wire in the fridge cord is the positive one. They are both black, only one has some stamped writing on it. I'm trying to splice in an anderson powerpole.

The other question is the same, but for some led lights. Black wire, and black wire with a white stripe. I'm assuming the striped wire is the positive?

Thanks for helping me not burn my cruiser down!
 
are you gonna do something like this .. ?

attachment.php
 
1407driver said:
Yeah, except I'm not using that gigantic wire!
Click to expand...

Running large gauge wiring is a GOOD idea for the fridge power. You want to minimise voltage drops (due to wire gauge resistance) between the battery & the fridge. The fridge will run more efficiently if fed for 12.5V versus say 12V.

What gauge are you planning to run?

I personally would use at least 12g to run power to the fridge. Let's assume the fridge draws 5A. With the fridge in the rear of a wagon you likely have about 20' of cable from the battery. In terms of voltage drop you double that (2 wires) so 40' of cable to calculate voltage drop. 12g has nominally 0.00159 ohms/foot resistance, so 40' would be 0.0636 ohms. At 5A draw you're losing 5A x 0.0636 ohms = 0.31V. If you ran say 18g you're looking at 0.00639 ohm/foot and so 40 x 0.00639 x 5A = 1.3V voltage drop...

Max sure to fuse the battery end.

Ohm's Law V = I x R (V = Voltage, I = current, R = resistance)

You can use an online wire resistance chart to get an idea of your resistance losses, e.g.

http://www.cirris.com/testing/resistance/wire.html

or

http://www.powerstream.com/Wire_Size.htm

etc...

cheers,
george.
 
george_tlc said:
Running large gauge wiring is a GOOD idea for the fridge power. You want to minimise voltage drops (due to wire gauge resistance) between the battery & the fridge. The fridge will run more efficiently if fed for 12.5V versus say 12V.

What gauge are you planning to run?

I personally would use at least 12g to run power to the fridge. Let's assume the fridge draws 5A. With the fridge in the rear of a wagon you likely have about 20' of cable from the battery. In terms of voltage drop you double that (2 wires) so 40' of cable to calculate voltage drop. 12g has nominally 0.00159 ohms/foot resistance, so 40' would be 0.0636 ohms. At 5A draw you're losing 5A x 0.0636 ohms = 0.31V. If you ran say 18g you're looking at 0.00639 ohm/foot and so 40 x 0.00639 x 5A = 1.3V voltage drop...

Max sure to fuse the battery end.

Ohm's Law V = I x R (V = Voltage, I = current, R = resistance)

You can use an online wire resistance chart to get an idea of your resistance losses, e.g.

http://www.cirris.com/testing/resistance/wire.html

or

http://www.powerstream.com/Wire_Size.htm

etc...

cheers,
george.
Click to expand...

I agree, but I'm running 4 gauge from the battery to a fuse box, then smaller wire for the short run from there. I'll keep an eye on it to make sure it's performing!
 
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