electrical energy from your car
May 23, 2010 11:11 AM   Subscribe

How can you run a large appliance (e.g. a washing machine machine) off of a running automobile? What's the best way to convert the huge amount of power generated by the car into 110V A.C. at a high wattage?

The difficulty seems to be that small inverters won't handle the big AA.C. loads and the big inverters (e.g. Xantrex DR series) aren't really designed to be hooked up to a single battery being simultaneously charged by an alternator. But there must be a way, somehow!
posted by grizzled to Technology (5 answers total) 1 user marked this as a favorite
The problem you're going to run into is that cars don't produce a "huge" amount of electricity. Sure, they have lots or power, but it's mostly mechanical power. The electrical output of the car is determined by its alternator. Typical output is 110 amps at 12v. That only gives you 1320 watts of power to work with, and that's before conversion to AC. (DC/AC conversion is lossy...anywhere from 50% to 90%, depending on load). Typical washing machine motors require about 2200 watts to get going and 1150 to continue running once started. That's more than your little alternator, battery, and inverter can put out. Now if you were to get a bank of batteries and charge them with the little alternator, you could probably store enough juice to do a load or two, but it would be cheaper and easier to buy a generator.
posted by cosmicbandito at 11:29 AM on May 23, 2010

Best answer: Some vehicles - such as those that are used for ambulance chassis - have space in the engine compartment for a second alternator to run the high-current accessories.

You could have a look at this company, who sell equipment for ambulances and similar. They'll happily sell you a packaged system putting out 3000W AC, or a 5kw direct generator system.

There's also an article here about a guy adding 120v AC to his truck which might have some information.

Another option is just to just fit your vehicle with a secondary generator which puts out AC directly - I once saw inside a fire service "mobile command centre" which did things that way.
posted by Mike1024 at 11:54 AM on May 23, 2010

There are a few exceptions to what cosmicbandito said. For a few years (ending in 2007 I think) the Chevrolet Silverado 1500 series hybrid offered built-in 120v/20amp outlets, which would be sufficient to run a washing machine. The hybrid drive train included a proper generator, which was what powered the outlets.

Along those same lines, there are people investigating using other hybrids like the Prius as a generator. Testing suggests that a Prius can produce 2.2kW at 220VDC; with conversion to AC that may or may not be enough to power a small washing machine.
posted by jedicus at 12:01 PM on May 23, 2010

You're going to need to start off with a heavy duty vehicle designed for that sort of application. Like mentioned above, there are vehicles with extra alternators (limos, ambulances, etc) or work-oriented diesels (think tow-truck) that have high output charging systems. There are also, of course, camping vehicles, RVs, and tour busses equipped for that sort of thing, too. Some hybrids come with a 110 outlet, as well.
There are power inverters available that hook up to the cigarette lighter and transform the 14v DC into 110AC, but I don't know if they make enough power run a washing machine or what (if any) kind of extra electrical load that power draw would put on the vehicle's charging system.

If you're going to rig something up, start looking high-powered car audio set ups. If it's critical that you're able to run a washing machine off of the power output of a regular car or truck, you should think about adding extra batteries and capacitors in order to support the potential draw of hooking a large appliance up to a 110 inverter that's probably only designed to run a laptop or two.
I'm not even certain that something like that would work, but it's where I'd start looking.
posted by Jon-o at 1:06 PM on May 23, 2010

If the question is, "how do I do this with my existing car without buying another car" then the answer is you don't, because the alternator is likely too small. It doesn't matter how much energy the engine puts out, the only portion of it that is being converted to electricity is the tiny amount that the alternator sucks off.

If the question is, "how do I run a washing machine in the middle of the woods at the lowest cost, assuming I don't already have an RV with high output alternator" then the answer is buy a generator. Harbor Freight has a 2.2kW model for $400 and a 6.5kW model for $600.

Sure, you could probably jerry-rig something whereby you jack up one drive wheel and attach a belt and use that to turn a larger alternator (or better -- an AC generator so you can skip the whole messy inverter thing altogether) but by the time you factor in the cost of parts and the cost of making things safe enough that this setup isn't going to accidentally kill you, it would cost more than just buying a generator.
posted by Rhomboid at 2:00 PM on May 23, 2010

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