I figured I would post this question to all the knowledgeable people here. I am trying to help my brother run and inverter in his truck (for an og xbox). As I understand it the Cigarette lighter socket wont give you the power it needs (smaller wire??) If you hard wire it with thicker gauge wire it will work fine. My question is regarding the wire. If you didn't use a high enough gauge wire wouldn't it just pull til it heated up and melted the wires and started a fire (of course I will have a fuse) and if my understanding is correct why does this NOT happen with the Cigarette lighter socket?

I gotta check this forum more often...

The cigarette lighter in most cars is fused for 15A, and that's about what current the wire that goes to it can handle. The lighter itself draws 5-7A when in use, which is short period only. Most other things that plug into the lighter sockets, phone chargers, radar detectors, etc only draw a couple of amps at most. The factory wire can handle the current that can be drawn from the cigarette lighter without a problem. It'll blow the fuse before the wire melts.

An Xbox 360 needs up to 200W of power. From 12V (Even if you had a 100% perfect inverter -- which does not exist) that means about 17A. Probably closer to 20A in real-world. For that, I'd want a minimum of 14AWG wire, and I might even go to 8AWG if there's anything else that will be on the circuit. Most likely I'd fuse the inverter at 30A for peak loading. I would run that direct from the battery myself.

There's one other thing that keeps power in check for the lighter socket. If you're reckless and put in a 30A fuse into the lighter's fuse socket, or even just short it with wire (Which I've seen people do <shudder> ) then the wire can and will get hot. Copper wire increases in resistance when it gets hot. It increases by 0.393% for every 1 deg C that it heats up. (IIRC -- that may be slightly off) So as the wire gets hotter, it increases in resistance, which reduces current. With any REASONABLE load, it will increase resistance to the point where an equilibrium is reached, probably before starting a fire.

The problem comes in with UNreasonable loads, such as a dead short somewhere. This is why fuses are GOOD THINGS.

Thanks for responding I guess my question is why is the inverter overloading and not blowing the fuse when its hooked up to the cigarette lighter.

But when I run it straight off the battery with 10 AWG and fused with a 30A fuse (like i did ) it never overloads

Some inverters have an input voltage detection circuit, usually around 10.7
With the small gauge wire, the voltage drops faster than the current supply,
possibly the inverter detects an overload before the fuse can blow

THANK YOU! I thought this same thing but had a hmmmmmm ? just a what if. What if you did not have a fuse (I would never do this) and you wire it 10awg but it was a the breaking point where you could wire or should wire 8awg. No I would think that the same thing would happen it will detect and "overload" meaning that the wires would not heat up and melt and burn the car to the ground
What do you know or think. This was just a hmmm question.

Probably, if your just marginal on the wire gauge, I think the type of load would determine if it overloads or not.
For example an resistive load ( light bulb or heater ) will draw a consistent draw, whereas an inductive load ( motor ) will draw more power to start than drop to run. PWM power supplies such as on computers are more inductive, I think>

Well, PWM supplies are what they are. They increase or decrease the duty cycle time to get more or less power.

If you're designing one that you expect to have at least 11V input, and you want to have 120V output, you would set it up so that it will provide the maximum amount of rated power at near a maximum duty cycle. If your supply voltage drops, then your duty cycle must increase to compensate.