Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default OT - 12 V. DC to AC "Automotive" Inverter

People on this group seem to have a lot of experience with stuff like
this, so I though I'd ask...

I'm going to buy a DC-to-AC inverter to run a small blower off a 12
volt battery, along with one or two other small motors occasionally.
It's all light-duty stuff -- no more than a single ~1/8 horsepower
motor at a time (but they will go for up to 8 hours or so).

I really don't know much about these inverters. Is there a particular
brand any one would recommend? Are some are particularly inefficient,
or have other problems I should watch out for?

Thanks,

~Jeff Polaski

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RoyJ
 
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Default OT - 12 V. DC to AC "Automotive" Inverter

Some of the cheap inverters have a wave form that is a really bad
version of a sine wave. This makes no difference to the average 120 volt
motor (synchronous or brushed) or lights but can play hob with computer
power supples.

Most of the small inverters can take some overload so if you size the
inverter for 50% to 75% of your continuous load, you should have no
problems. This assumes you are talking about a 3.3" form factor
(diameter) motor. If you were trying to start a bigger motor eg 1/3 hp,
you will need much more reserve capacity.

A single 1/8 hp motor will take a theoretical 93 watts, figure 120 watts
minimum for a real world motor. 10 amps out from your motor means 11 to
12 amps input to the inverter from your battery. This will kill a
standard car battery in the 4 to 6 hour range.

wrote:
People on this group seem to have a lot of experience with stuff like
this, so I though I'd ask...

I'm going to buy a DC-to-AC inverter to run a small blower off a 12
volt battery, along with one or two other small motors occasionally.
It's all light-duty stuff -- no more than a single ~1/8 horsepower
motor at a time (but they will go for up to 8 hours or so).

I really don't know much about these inverters. Is there a particular
brand any one would recommend? Are some are particularly inefficient,
or have other problems I should watch out for?

Thanks,

~Jeff Polaski

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DoN. Nichols
 
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Default OT - 12 V. DC to AC "Automotive" Inverter

According to :
People on this group seem to have a lot of experience with stuff like
this, so I though I'd ask...

I'm going to buy a DC-to-AC inverter to run a small blower off a 12
volt battery, along with one or two other small motors occasionally.
It's all light-duty stuff -- no more than a single ~1/8 horsepower
motor at a time (but they will go for up to 8 hours or so).

I really don't know much about these inverters. Is there a particular
brand any one would recommend? Are some are particularly inefficient,
or have other problems I should watch out for?


Is there any reason why you must use 120 VAC motors for the
purpose? Why not look into DC motors, which will work without the need
for conversion. Since the conversion is not 100% efficient, this means
that you will get more life from the battery with a properly sized DC
motor.

Now -- if it needs to run from AC as well -- what about a 12V
power supply to run the motors when you are not running from the
battery.

And as others have already pointed out - you will probably need
more than a single battery to run it for the required time.

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---


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Bruce L. Bergman
 
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Default OT - 12 V. DC to AC "Automotive" Inverter

On 29 Mar 2006 08:57:42 -0800, wrote:

People on this group seem to have a lot of experience with stuff like
this, so I though I'd ask...

I'm going to buy a DC-to-AC inverter to run a small blower off a 12
volt battery, along with one or two other small motors occasionally.
It's all light-duty stuff -- no more than a single ~1/8 horsepower
motor at a time (but they will go for up to 8 hours or so).

I really don't know much about these inverters. Is there a particular
brand any one would recommend? Are some are particularly inefficient,
or have other problems I should watch out for?


Please supply more details about exactly what you plan on running -
there may be more efficient ways of doing the job.

For openers, there are considerable losses in boosting the voltage
to 120VAC to run something that could be done just as well at the
native 12VDC of your power supply - and be more reliable, to boot.
The telephone and power companies run 1/10 to 1/6-HP range manhole
blowers all day on one or two 12V 105AH batteries, no problems.

And what type battery do you plan to use? You need to use a
Deep-Cycle rated battery for running all-day loads like that. If this
is to be vehicle mounted, you need to add that deep cycle unit as a
second battery (besides the starting battery), and install a diode
isolator system for charging both batteries from the alternator. And
possibly a larger alternator to get both batteries charged back up in
the allotted run time driving to work and back.

If you try putting an all-day load on an automotive starting battery
it will not take that insult for long, they do not tolerate deep
discharge cycles well - want to replace the battery once every week or
two? Plus you get to jump-start the car to go home, when it's too
dead to run the starter.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.
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