Basic Electrical Questions

Okay, I've forgotten what I was taught...

Can somebody hook me up with something on what size wire to use for how many amps (like 30 amps you should use 10g) please?

Also, I'm running a 4g cable from teh battery to the back of the cargo area, this is powering a secondary fuse box that I built. In this box I have two fuse blocks (was the cleanest way to do this), so the question is, I have to split this 4g wire so half goes to one pole, half to the other. Can I just hook the 4g up to a terminal on one end, and put two 8g's on the other? (I have to turn that one wire into two because of the way this thing is set up) I don't remember quite how this works out ...

Thanks
Sequoia

Oh, also, anybody know offhand about how much amperage to expect a 500W inverter to draw? (I plan to purchase one in the future, so I might as well have hte infrastructure in place now)

Depends on the length of the run of wire as to what the gauge will be. According to my calculations:

500W inverter= 500 / 12 = 41.666 amps
15'-20' run @ 42 amps = 4 ga. recommended for this application only,this will result in a .15 volt drop at the end of the run,6 watts total loss from the equipment,and only .003 ohms of resistance for the run of wire. If this is all you will be running from the 4 gauge wire,it should be fine. Place a 40 amp fuse within 12" of the battery terminal for safety (remember--YOU'RE PROTECTING THE CAR *NOT THE EQUIPMENT*!!!!). If you plan on running other accessories on this same run as well,you may want to upgrade to a 2 ga. or even 1/0 wire. If you do not plan on running all this stuff at once,then the 4 ga. should provide you with plenty of juice for your needs!

Groovy. (I'm wiring it up with 4g because I will not be running everything at once) From what I understand, the inverter itself has two 8g leads running off it to get power (it's a Cobra inverter). Do you think that I can split that 4g wire into two 8g's for the runs to the fuse blocks? (the 8g runs will be about, oh, 12 inches max)

Sequoia

yep, you can split it.

I would look into distribution blocks that are used in car audio applications. I know they make blocks that go 4ga -> (2) 8ga. That would keep all your connectors sealed.

I was goign to do that...but I ended up having to get 2g wire (no 4g available...) So i'm buliding my own (got a small ABS box to use...)