Rosewill 400W Power Inverter with 1x 2.1A USB Port $15.99 with free shipping (orig. $50)

Having said all of this devices limitations... it still may be worth a flyer @ $15.

I think I paid almost that for a replacement cord from Radio Shack... (could have found cheaper online but needed it fast/local).

Quote from AkumaX : so glad i waited! awesome! what is the cigarette lighter capacity?

Depends on your car. I believe most are 5A (up front). Some are 10A-20A in newer cars and especially SUV's for rear ports where it's somewhat expected to use higher current drawing devices.

Quote from gmanvbva : Possibly true but now that I think about it... I don't know how the USB port is powered/wired electrically within the unit.

I agree. Since the USB does not require a change from DC to AC, this likely does not diminish the 400 Watts AC power. The 5VDC @ 2.1A is likely just using a resistor from the direct 12VDC input.

Ohms Law V=I*R therefore by adding a 2.3Ohm resistor would get the 5VDC @ 2.1A.

So really max input might require 33.3 Amps to power the 400 AC converter + 2.1A for the USB. Also factor in inefficiencies and it is likely approaching 50 Amps total input to power this at max capacity.
Also on a side note, most car charging systems are at 13.2-13.5VDC not 12VDC. This will skew the calculations above slightly but most people are already confused.

Cigarette lighter ports and power ports are fused at different amounts depending on car. The old lighter in my old truck was fused at 30A but my new car is likely 15A. Still a 15A power port should be enough to charge most laptops unless you have the first laptop ever made. Not sure it have enough to power a blender to make daiquiris while rolling down the road.

Just a warning to anyone that might decide to run a power cable directly to the battery. Be sure you add a inline fuse as close to the battery as possible. Also make sure that you use heavy enough wire (probably 10ga) or larger. I had a truck that had a add on power cable run to the dash. The wire shorted out and the fuse did not pop because it was located directly behind the power port. Since the fuse did not pop, the wire got red hot and nearly burnt my truck to the ground. A simple fuse at the battery end would have prevented this. I ended up spending the afternoon that day rewiring my main cluster of wires on the truck. The red hot wire melted the insulation on all wires near the shorted out wire. By the time I stopped and smoke cleared, all electronic power items were powered on. Winshield wipers, horn, lights, pretty much everything was on. Since it was a 10 ga wire that shorted out it took several minutes for it to burn in two and I was stuck hoping flames did not burst out since I had no tools to unhook the battery.

Quote from gmanvbva : Depends on your car. I believe most are 5A (up front). Some are 10A-20A in newer cars and especially SUV's for rear ports where it's somewhat expected to use higher current drawing devices.

hmmm.. i have a device that uses 300w sustained (maybe?) for about 2 minutes. (i should check w/ my kill-a-watt to see if it really draws that much).

12V * 20A = 240w... cutting it close :\

Quote from imabass : I agree. Since the USB does not require .....

I think we are both confusing the input and output side of the inverter. At least I was a bit in my explanation.

The draw from the unit for the input voltage (from a cigarette lighter) and the supplied 120v power (to plugged in AC devices).

Input
400w = 12v * 33.33A theoretical current draw from cigarette lighter

Output
400w = 120v * 3.33A theoretical current supplied to AC devices from inverter.

As you began to lead into.... the device will likely never draw a full 33 Amps when plugged into a cigarette lighter due to fuses/circuit breakers and wiring resistance that is typical of these circuits.

In for one, thanks subby.

And yes, you will want to wire this directly to the battery if you expect to use anything above 50 to 100 watts.

Something to keep in mind -- 400W continuous, 800W peak is enough to run most refrigerators, and you only need to run your refrigerator a few times a day to keep it cold enough for food to keep.

It's not something that immediately comes to mind, but if power gets knocked out in your area, you will likely lose hundreds of dollars of food after a day. And... if you can't get more food due to a natural disaster, it's not even the cost of the food that matters at that point...

Jut make sure you use an extension cable rated properly for the wattage, keep your vehicle vented, and protect yourself from theft while the car is running. (also check your local laws about running a car without supervision)

Your car makes for a lousy inverter, with a huge 1.6+L engine producing only 400W (at least with this inverter). That pales in comparison to a purpose-built, 0.8L inverter generating 2000W, but hey, that will cost you $2k. This only costs you < $20.

To anyone who has this model: Does the power switch control the USB port or is the USB port always powered? I really would buy this if the inverter could be controlled independently from the USB.

Quote from sodakar : Something to keep in mind -- 400W continuous, 800W peak is enough to run most refrigerators, and you only need to run your refrigerator a few times a day to keep it cold enough for food to keep. It's not something that immediately comes to mind, but if power gets knocked out in your area, you will likely lose hundreds of dollars of food after a day. And... if you can't get more food due to a natural disaster, it's not even the cost of the food that matters at that point... Jut make sure you use an extension cable rated properly for the wattage, keep your vehicle vented, and protect yourself from theft while the car is running. (also check your local laws about running a car without supervision) Your car makes for a lousy inverter, with a huge 1.6+L engine producing only 400W (at least with this inverter). That pales in comparison to a purpose-built, 0.8L inverter generating 2000W, but hey, that will cost you $2k. This only costs you < $20.

I dont know if 800 peak is enough for a fridge. Thats kindof pushing it, IMO. Compressor startup surge is enough to have most fridges rated at 15 or 20 amps, which is more like 1800 or more peak watts. Though if it would handle the startup surge, its probably in line with what it takes to keep a fridge running.

In for 1

Not related but, I bought a Peak inverter which is also 400W and it burnt by both cig lighter fuses and did not work with cig lighter. I have 15A fuses in both and have a 2005 model car so fairly newer model...not sure if this will be the same

Anyone know if this would power a 7 cu ft chest freezer? The side of the freezer says max power rating of 5 amps but I dont know if that means surge or not.

Wow, guys this thread is DEEP, making me flashback to my EE classes at UT@A, and my days as a Nuke Electrician in the USN . Thanks Op, got one!

Regarding the fridge post, (and any other devices that require high starting currents), there is a HUGE difference between the start-up requirements and running requirements. On a sub, we had a particular order to start/restart systems as we changed power sources (reactor to battery, start-up to go underway, etc.), because of that huge difference. BUT, in many of the devices on a sub (and in devices meant to be portable I hope, don't have any, so I do not know), large capacitors can by used inline to provide the start-up current required without causing voltage droop. SO, let pretend that you want to use a mini fridge from home from your 12VDC car system through this inverter. You could purchase multi farad caps and with some simple wiring, put your "surge power source" between the inverter and your device.

As also recently having my home without electricity for about a week, I spent roughly 48 hrs straight rewiring the majority of my home to run from a generator. Basically I wired the generator into a transfer switch, and the transfer switch to a fused mini power panel, and then ran certain breakers for "necessity loads" like fridges, freezers, lights, etc. from my main breaker panel to my emergency breaker panel. It was 5000 W I believe, about 1/4 of what I needed for whole home power... but it was the biggest one I could find locally (most were sold out obviously), and my lesson learned there is that refrigerators SUCK . Steady sate (when their internal temp is below threshold to kick on compressor), they take almost no power. As soon as someone opens the dang door, of course the threshold is hit and the compressor will kick on, drawing that huge starting current AGAIN, and AGAIN, etc. So for devices like that, if you want them running off of a system like this, either buy one built for it (which will most likely have the charging cap, etc. built into it or a much lower power requirement), or make the DIY starting power source a permanent attachment to the device. Also, get a Killowatt, multimeter, etc. and run whatever device through its starting, steady state and power off cycles and watch the peak amperage. If you are actually planning on several devices(say a couple of week camping trip with all of the conveniences of home), then you should have multiple circuits with their own protection, use a mini breaker board, DON'T rely on your cars fuses (unless you bring an assload of extras to replace them as they pop ).

Quote from patsman99 : Anyone know if this would power a 7 cu ft chest freezer? The side of the freezer says max power rating of 5 amps but I dont know if that means surge or not.

Best way to figure that out is to test it. Use either Kilowatt (the good one that records peak amperage) or a multimeter, the coolest ones are the inductive ones, where you just need to put a loop around the wire that you want to see the current draw for.