More on inverters

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From a blog post:
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Folks considering inverters should first check their automobile’s alternator
capacity to figure out how much they can power long-term from an inverter
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Tch. What drivel. Automotive alternators are not continuously rated. You only get the full output at fairly high engine revs anyway. Why is 20-40 amps needed to run the car?
Trying to use cars for a significant power sources is a waste of time. A few lights and a radio and that's it. Oh, wait you don't need an inverter to run those.
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harry wrote:

Can you work a pencil?
Depends on what you mean by "full output." Car alternators are connected to voltage regulators which hold the output voltage (almost) constant, irrespective of RPM.

A 2000-watt amplifier will use (at least) 170 amps. Add headlights, a/c fan, cigarette lighter, and, of course, the engine, and you'll be above 200 amps.
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On 11/9/2012 7:38 AM, HeyBub wrote:

bigger alternator. Auragen makes such an animal. It works well, but isn't cheap. And, for the higher outputs, it does take over the engine throttle so you have to be stationary. But for use as a backup, that's not a problem. The one I am familiar with is a 5KW unit. It, along with its box of electronics, puts out a clean 120 volt true sine wave. The company installs it in your vehicle. I had one in a video production truck in my former life.
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On 11/09/2012 05:22 AM, Art Todesco wrote:

Or you could just install an additional alternator or two on the same engine, assuming they could be connected in parallel at some point to get the desired output current.
Jon
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On Fri, 09 Nov 2012 10:27:23 -0800, Jon Danniken

You will quickly run into the limits of the belt unless you add some pulleys to the crank shaft.
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On 11/09/2012 10:39 AM, snipped-for-privacy@aol.com wrote:

Indeed; my original thought was to use an increasingly longer belt to drive additional alternators, but your idea of utilizing a "distribution" pulley (like a pillow block) would only necessitate the additional belt length for driving one extra pulley (and would, as a result, be a lot more feasible). Eventually the point would be reached where the belt was physically unable to handle the additional load, whereupon it would slip, with the generational capacity of the system resting upon that limitation.
Jon
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On Fri, 09 Nov 2012 10:27:23 -0800, Jon Danniken

Too much messing around. You can get a 200 amp alt for many cars, including my '97 Lumina. Even with the stock 100 amp alt and a good inverter setup it can start and run a fridge, power some house lighting, etc. All without breaking a sweat. Nothing wrong with that as a low watt emergency power source. You just expect only what it can give. There's a lot of confusion and false trails about this, but it gets down to simple math and amp draw. Here's one list of car component amp draw. http://www.onallcylinders.com/2012/10/17/how-to-choose-an-alternator / Your car idles in the driveway. You don't have the headlights on, or the A/C on, or the stereo cranked up, or the courtesy and dome lights on. Because that makes no sense for running your fridge. Figure ignition and fuel pump use about 5-7 amps. Figure your cooling fan(s) will kick in for whatever length of time and duration they do for your car and pulling what amps they pull. Whatever is left from the alt output goes to the inverter. I don't want to recalc it, but I think I came up with about 500 available continuous 120v watts at idle for the house. That was with inverter loss of 15% I think. My 100 amp alt car. If that's not enough, too bad. Go get more juice somewhere else. I already decided to stick my head in the sand until the outage hits, then decide what I'm gonna do. Leaving town is my favorite option.
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On Fri, 09 Nov 2012 13:38:25 -0600, Vic Smith

out your 100 amp alternator by running it at over 50% for more than half an hour.
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On Fri, 09 Nov 2012 14:59:07 -0500, snipped-for-privacy@snyder.on.ca wrote:

Need more numbers. Figure winter time driving A/C defrost on, heater fan on high, headlights on, parking and sidelights on, rear window defroster on, radio cranked up, fuel pump and ignition running. Pretty sure that's more than 50 amps, or close. I do it every winter for hours at a time. For years on the same alt. Of course I would have to measure actual amp draw on my car. Anyway, I low-balled the 120v output at 500 watts, and figuring inverter loss into it that's still less than 50 amps from the alt. I've read that a typical alt puts out 60% of rated amps at idle. If I ever set up an inverter I'd measure draws. You can burn up your alt if you want to. But you don't have to, and I don't fall for scare tactics without numbers backing them up.
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On Fri, 09 Nov 2012 15:39:28 -0600, Vic Smith

windows up and down, adjusting power seats, etc constantly while driving - and the rear defogger cycles after about 3 minutes or so. The difference between 50 and 70 amps is significant - and between 70 and 100 a whole lot more significant - and add to that the fact that while drivivng down the road there is a LOT more airflow through the engine compartment than sitting running the inverter - helping remove excessive heat.
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On Nov 9, 10:23 pm, snipped-for-privacy@snyder.on.ca wrote:

If you ever set up an engine on a "rolling road" an external fan has to be set up to keep the engine cool as there is no "slipstream".
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On Nov 9, 7:59 pm, snipped-for-privacy@snyder.on.ca wrote:

Exactly so.
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On 11/09/2012 11:38 AM, Vic Smith wrote:

Well there 'ya go!
Jon
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wrote:

current well less than 100 amps - and 2000 watts is INSANE.
Big thing is a few amps to run the alternator field, another 10-ish for ignition at full bore, and another 17-25 for EFI including fuel pump - then add cooling fan, heater fan, and air conditioning clutch.
60 amps will barely keep up.
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On Nov 9, 5:59 pm, snipped-for-privacy@snyder.on.ca wrote:

All that is nonsense. Except for lighting, 10 amps will cover everything. The alternator is larger to recharge the battery which takes a few minutes only. Which is why they have no need to be continuously rated.
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On Sat, 10 Nov 2012 01:33:39 -0800 (PST), harry

the alternator.
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On Nov 10, 7:10 pm, snipped-for-privacy@snyder.on.ca wrote:

In days of yore five amps would cover the ignition easily. Modern solid state ignition systems use less.than this. Bigger alternators are fitted to cover all the stupid unnecessary accessories in modern cars.
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On Sun, 11 Nov 2012 01:07:34 -0800 (PST), harry

No they don't. They produce a hotter spark - which requires MORE current -

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snipped-for-privacy@snyder.on.ca wrote:

Yep. But I have an insane person drive down my street every 30 minutes or so. (Not the SAME insane person.)

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