Cobra 800Watt inverter, what gauge wire?
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Forum Name: Vehicle Wiring Information & File Requests
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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=84783
Printed Date: May 02, 2024 at 6:18 AM
Topic: Cobra 800Watt inverter, what gauge wire?
Posted By: milkshake
Subject: Cobra 800Watt inverter, what gauge wire?
Date Posted: October 28, 2006 at 8:23 PM
Hey guys this is my first post,
I just ordered a the Cobra CPI 850, 800Watt continuous power inverter.
I wanted to install it on the passanger side under the glove box of my 1990 Lexus ES 250.
I went to NAPA auto parts and they handed me 10 gauge wire with a 12 gauge wired fuse box for up to 50 amp fuses.
My question is, did they give me too small of a gauge?
What size gauge do I need to run it from the passanger side to the battery and also what size fuse should i use?
thanks!
Replies:
Posted By: master5
Date Posted: October 29, 2006 at 12:00 AM
I = p/e I= 800w/12v I = 67amps max Ohms law. What you didn't tell us is the length from the "passenger side" to the battery. I will assume 12 feet on my wire ga. calulator. I don't know what you are using this inverter for, or its current draw. If for anything of 30-50a I would go with a 4ga. For anything less an 8ga. should suffice. Never hurts to use a larger wire then needed, it can only help. Too small a wire = voltage drop = problems Remember, the power supply itself won't draw too much current on "standby". It is what you hook up to it that will decide. A 50amp fuse should be fine, but if you are blowing anything over that I would consider a larger inverter, they tend to be quite underated in actual power output. It is ok to use a smaller ga. for the fuse holder since there will be less resistance in the short length, however I would try to use at least an 8ga., but once again, this depends on the current draw of what you are connecting to it. The fuse itself is mainly there to protect the wire in case of a short. The device you hook up will only draw the current it needs to operate. hope I helped -------------
Posted By: milkshake
Date Posted: October 29, 2006 at 1:21 AM
Thanks for the reply!
Sorry I forgot to mention the length. I was thinking 10 feet, I havent figured out exactly how I'm going to wire it, where I'll go through the firewall etc...
So I should return this 10 gauge and go with some 4 gauge wire?
Do you happen to know a site that has a calculator or table for amps vs awg vs length? I found a couple but they have terminology I don't quite understand like "chassis wiring".
Yep you helped :)
Posted By: master5
Date Posted: October 29, 2006 at 1:50 AM
I would think there should be a wire ga. calulator somewhere on this forum, however I am fairly new here and haven't done enough exploring yet. So far it's been a great experience. I used one of the charts from my old MECP study guide to determine the ga. for your application. However, even though I know the length, I can give you a more accurate reccomendation if you know the power or max current draw of the device you are using the inverter for. If you don't know for sure...use this logic when dealing with wire gauge.....when in doubt, go bigger. I would return the wimpy wire you have and use the 4gauge. That can't do anything but help and well worth the extra money IMO. If you have an 800w inverter why not set it up to use for it's full potential? Take care. -------------
Posted By: master5
Date Posted: October 29, 2006 at 1:59 AM
oh..for going through the firewall tips..check out the forum. a bunch of us left some great replies on this very topic yesterday .Try "last 100 topics" above on "select forum".
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Posted By: Mad Scientists
Date Posted: October 29, 2006 at 9:03 PM
That particular inverter can surge up to 1600 watts and can operate on input voltage from 10v to 14v.. so my question is, what are you planning to run off it?.. This will help determine what size wire you need. What is the fusing on the inverter itself? Jim
Posted By: master5
Date Posted: October 29, 2006 at 10:09 PM
ah yes..the old surge..gotta compensate for that. You are not powering up anything motorized with that inverter..are you? -------------
Posted By: milkshake
Date Posted: October 29, 2006 at 10:45 PM
Nope nothing motorized. Well if I really am worried about the surge, which I'm not, I could always get a slow blow fuse.
I'm sure I wont get up to 800watts but I figured i might as well set it up for full usage, whats the point in having a 800 watt inverter if you set it up to draw a max of 400 watts? I got the 800 because its cheap, at the most I want to run a computer, tv and dvd player off of it.
Posted By: Mad Scientists
Date Posted: November 08, 2006 at 5:49 PM
TVs can surge the inverter.. especially if they have a built in degaussing coil. It's recommended with inverters to have the input cables as short as possible, and run length on the 120vac cables..less current on them. https://www.the12volt.com/info/recwirsz.asp Cable sizing here.. 10ga 60 amps, 8ga 100 amps, 4ga 150 amps. You can probably get away with the 10 gauge, 8 gauge would be better, 4 gauge might be some overkill.. it depends on what you're powering. A slow blow fuse is only good if the wiring is rated for the current!!.. keep that in mind. Keep in mind that inverters generate a fair amount of heat.. is under the dash a good place for that? Jim
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