Using a large inverter while car is in motion?

Xorr · January 2019

I am wanting to power my xbox 360 slim and play it while the car is in motion. I like to play it in the car while we are on long road trips. I have a simple 150w inverter that plugs into a 12v socket. I was able to plug my xbox into that inverter and it powered my xbox. When I would play the xbox for about an hour, both the xbox and the inverter would experience extreme overheating to the point where my xbox wont power on until it is cooled or the inverter wont work until it is cooled down. The inverter was given to me by my mother and I simply hooked everything up to it and played, but I now know that I was dumb for not looking into it to see if it would cause problems. It powered the xbox, so I assumed it worked just fine. Now I am trying to look for a proper inverter and how I can hook one up to my car (and please dont bash me over my ignorance).

But anyways, here is what I have gathered:

My xbox will require about 370w to 470w and will draw 3.7 amps.

My screen that I use runs of off DC and draws 0.8 amps. This doesnt need an inverter since I can plug it into another 12v socket.

My car manual says that the 12v sockets can handle a maximum of 10 amps. It doesnt say anything about a watt limit.

From my understanding, I will need an inverter that is around 500w. I have looked around for an inverter about this size and was around $50. I found one at home depot that was 500w. The inverter https://mechanicguides.com/best-power-inverter/ sayed that it will only be 100w if plugged into a 12v socket, but it will be 500w when hooked up directly to the battery. I decided not to buy it.

Now here is my big question: Is there an inverter around 500w that I can plug directly into a 12v socket? OR is it possible to hook an inverter up to the battery when the car is in motion? I am thinking that there could possibly be a way i could string the cables from the battery to the cabin of the car where I would plug things into the inverter.

Any help is appreciated!

(And just to clear this up, I am well aware of the risks involved with the xbox scratching up disks. I actually dont use disks though, I have all of my games downloaded onto the hard drive. And i already have a well ventilated area in my car for my xbox).

Estragon · January 2019

The small inverter likely outputs a "modified sine wave" AC waveform. With loads other than purely resistive ones (eg filament lights), this waveform can be problematic and could cause the heating you describe. Using a small pure sine wave inverter would likely help...
https://www.solar-electric.com/samlex-pst-120-12-inverter.html

If the xbox ran off a 150w inverter, it likely doesn't take anything like 470w, and you shouldn't run that big of a load off a 12v plug socket in any case. That's ~40A at 12vdc - far more than the plug can handle. 10A at 12v is 120 watts. Anything bigger would need a different connection to the DC source. Plugging a 500w inverter in would either blow a fuse, or start a fire!

If you look at the xbox power brick, it should have a spec for input AC voltage and current, and a spec for DC output. My guess is the 3.7A may be the DC current, ~40 watts at 12v.

jonr · January 2019

My somewhat educated guess (based on published measurements) is that the Xbox draws about 120 watts and this is too close to the limit of a cheap 150 watt inverter.

Something like a Bestek Pure Sine 300W should work. Might even work from the cigarette lighter socket. It's close - 13.5V x 10A = 135 watts (no, cars aren't 12V when running) minus inverter inefficiency.

mcgivor · January 2019

Probably one of the most bizarre posts I've read so far, simple Ohm's law, the 12V socket can provide a maximum of 10A or 120W, this is not a continuous rating, but intermittent, the car's wiring simply isn't designed to cope with such demands, which are are less than requirements. So to achieve the goal there would have to be a connection directly to the battery, let's use 500W, that would require ~42A, with at least #8 gauge conductors, both negative and positive with a 50A fuse, on the positive. Now the big question is the alternator capable of supporting such a load, or is the battery going to be over taxed, leaving you and your family, stranded? You really need to find some portable forms of mental masterbation, or resort to being creative, like playing odds and evens with license plate numbers of passing cars, that's what we did in the absence of video games, or cell phones for that matter. Modern problems, why are the youth of today so demanding? however I digress, .all in good humor, no offense Implied .

Estragon · January 2019

FWIW, xbox power supply bricks apparently vary from 120w to 203w depending on model:
https://support.xbox.com/en-CA/xbox-360/console/power-supply

Kinda pushing it for a 10a 12v plug if it actually draws that much sustained. Could be some of that is for initial inrush to charge caps etc though. Ideally, the actual sustained current draw should be measured with something like a kill-a-watt.

bill von novak · January 2019

Xorr said:

Is there an inverter around 500w that I can plug directly into a 12v socket? OR is it possible to hook an inverter up to the battery when the car is in motion? I am thinking that there could possibly be a way i could string the cables from the battery to the cabin of the car where I would plug things into the inverter.

I would strongly advise NOT connecting it to a cigarette lighter. Instead, find or add a 30A circuit and wire that to an Anderson connector or something so you can plug in your inverter. A 30A circuit should be good for a 250 watt inverter.

BB. · January 2019

More or less, you need to connect directly to your battery terminals (look at connection systems that people use for "way to big" car stereo systems).

https://www.walmart.com/c/kp/battery-terminals

And you need to add the ability to "turn off" your AC inverter when not needed.

And watch the battery bus voltage when using the inverter... A lot of car alternators are rated at >100 Amps, but in reality, once things get warmed up (and alternators get hot), they seem to fall way back on their output current.

Your run you your vehicle down the road running your AC inverter (and any other big loads), the car's electrical system may actually not be able to keep up with the AC inverter+nighttime loads (headlights, markers, heater fan, electric window defogger/defrosters, etc.--Another 10-20+ amps).

Modern cars (hybrids, etc.), everything is a toss up... For example, a run of the mill Prius is supposed to supply 100 Amps of current to the Aux 12 volt battery pretty reliably.

Other vehicles can have pretty "smart" battery management systems and may not even use "standard 12 volt FLA batteries".

-Bill

bill von novak · January 2019

BB. said:

More or less, you need to connect directly to your battery terminals (look at connection systems that people use for "way to big" car stereo systems).

https://www.walmart.com/c/kp/battery-terminals

I'm glad you posted that link, because the first item on the list shows a very important aspect of "connecting directly to your battery terminals" - a fuse. ANY line going to the battery must be fused or you risk battery and alternator damage and/or fire.

Using a large inverter while car is in motion?

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