Feeling stupid...

OK so I'm working on this little project and part of it is a wee 300 watt inverter. Call me stupid but I think it calls for 25 amps @ 12 volts. (seems high to me???) Any how I have very short runs in this project, 4 feet or less.

I have looked at a few wire sizing charts and seem to come up with 10 gauge wire as being the answer for such short runs. I don't want to build a fire hazard so decided to ask. 10 Ga. or 8 Ga. for a 4 foot run on 300 watts at 12 volts, of course it will be fused.

Thanks,
BW

hi bw,

that 25amp current sounds about right. 300/12=25. technically we might go with 300/10.5=28.5amps..some may even say to figure in any "surge" ratings into that as well and that might be as high as 3x, that would be 900w/10.5v=85amps! YIKES. (only a few seconds)

our handy pdi manual from sei.. (isbn#978-0-86571-520-2) gives us 4 feet with the #10 and 6 feet with the #8 for a 2% voltage drop in a 12v system.

a lot may depend on what terminal lugs are available in your area..in my area i would end up using an awg#2 wire because those terminals are readily available here with 3/8 and 5/16ths holes and the #2 can be had for less than a dollar a foot.

so i vote for #8 or better with "proper" terminal lugs (crimp AND solder) i'd stay away from those set screw type terminals, they suck for the inverter runs..and most everything else.

always interested in what other folks are working on, it's all good fun! :D

do tell us more.
cheers, dave

Now you get to hate me Dave, both the fuse block and buss bar I am using have those set screw type terminations. I suppose I could drill and tap the connection to the fuse block and replace the ground buss bar with a screw type bus bar. (insert ARRRG! :roll: factor here)

I was going to follow up with a question regarding the set screw type terminations. Logic would dictate that mashing the wire would give you more contact area between the buss bar and the wire while tinning the wire would make the finished product look much more refined. I value function before form so at this time I guess the point is moot.

Thanks for the input and I'll have to send you an email letter bomb now! ;)

Cheers!
BW

BW,

hold off on the e'bombs! :lol:

sometimes we can't help but use these set screw terminals, some equipment comes with them -other times it's all we have available.

might do with some crimp on ferrules? adds alot of mechanical strength and we can torque the set screw down without cutting the wire.



no worries bw..always a way to get up and running..i've used my share of bailing wire at times and it's all good fun!

cheers. dave

Ummm... wouldn't I get the same end result by tinning the wires?

OK no e bombs but the must be retribution! I've got it. :twisted:


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What I do bushwacker, although this might not pertain to your situation..

When using an inverter, my inverters are mounted next to my batteries - from there AC extension cords are much cheaper than heavy gauge wire, although my wife does complain about the mess of cords now and then :o

My largest inverter is 1500 watts, but generally I use small 150 watt units.

Tim

This setup will have the battery, the 300 watt inverter, a lighter plug 75 watt inverter, AA & AAA charger, a 36 (I think?) led light, and 12V outlets all on casters. Park it during the day and solar charge, use it at night for ambient lighting and if the power goes out you have a 150 AH @ 12V reserve.

It's not much but it beats the heck out of 2 D cells in a flashlight and a transistor radio. ;) I'm pretty sure you could run a lap top off of the 300 watt modified sine wave inverter using the laptop transformer as a buffer.