On Sat, 10 Nov 2012 01:28:48 -0800 (PST), harry
wrote:

On Nov 9, 12:36Â*pm, "HeyBub" wrote:
harry wrote:
On Nov 9, 2:37 am, "HeyBub" wrote:
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 without discharging the battery.

Making rough calculations, your Mazda RX-8 probably came stock with
a 100 Amp alternator (at 13.8V) = ~1400 Watts, so anything much more
than that is overkill (not to include peak rating). You can get
aftermarket high output alternators, usually in the 160-200A range;
my older Toyota only has a 60A alternator.

But some of that power is needed to run the car (20-40 Amps), so for
a 100A alternator the best case is 1100W available for the inverter.
These output ratings are at normal driving engine RPMs and at idle
you are lucky to get 75% of the rating (and as low as 50%) so we re
now down to 800W (max, probably lower), which will provide you with
~7A @120V AC, enough to run the refrigerator (130-200W) and more.

You ll need at least a 750W inverter ( peak 1500W inverters typically
have a peak rating 2x the normal rating) to handle the starting surge
current for starting the refrigerator (~1200W) with the extra energy
coming from the battery regardless of how much power your alternator
produces.

To run a 3000W inverter continuously without discharging the battery
you need a 300A alternator, what you would typically find on a fire
engine.

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Tch. What drivel.
Automotive alternators are not continuously rated.
You Â*only get the full output at fairly high engine revs anyway.

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.

Why is 20-40 amps needed to run the car?

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.

What 2000 watt amplifier is this?
A car needs less than an amp for the ignition circuit.
If you have a diesel car,not even that.
You won't need anything else whilst you're trying to use your car as a
power source.

You are very uneducated. Best to keep silent.

Actually, an electronic ignition can require in excess of 5 amps. Some
as high as 7 and even more - and is dependent on engine speed.

A motorcycle twin electronic ignition runs 3 to 5 amps

TheMSD 6A performance ignition specs 1 amp per thousand RPM on a 4
cyl.

EFI pumps run 3.5 to 10 amps depending on system pressure and engine
HP. The fuel injection system is USUALLY fused at 20 amps - so a
good guess is 12-15 amp operating current.

High Beam headlamps are generally 60 watts each - so 10 amps for the
pair, add another 10 amps for all the other lights in the car, not
counting fog or aux driving lamps. Add another 3.5 nominal for the A/C
clutch, and about 10 to 15 for the radiator cooling fan, and 7 to 10
for the heater fan.