(Floating Mind) wrote in news:4475-44DB3A3B-1511
@storefull-3116.bay.webtv.net:

It's my understanding that a person should never use a modified
sinewave
inverter with a laptop, that we should always use pure sinewave
inverters with laptops, as the modified sinewave units are harmful to
the life of the laptop's battery.

Question #1: Is this true?

No. This is how we sell much more expensive inverters to the mis-
informed.

Today's power supplies, like the one running your desktop PC as you read
this, don't really care what the input looks like. The first thing these
"switching power supplies" do is to rectify whatever input AC you put to
them into DC, which is filtered smooth by a large electrolytic capacitor.
Unless the input is so high it blows the cap or diode, it's fine. You
don't even need a "protector" because the damned "protector" is INSIDE
the power supply! Sales BS also sells "protectors". Whatever DC comes
out of the input rectifiers is fed to switching transistors that convert
the DC into an awful-looking SQUARE WAVE, that waveform your sinewave
salesman warned you about! It even has all kinds of crazy pulses
sticking out of it and is very high in frequency. The square waves vary
in pulse width, caused by the regulator IC that creates the square waves.
It's called "pulse width modulation". Those hybrid cars put these pulses
of DC to their drive motors the same way.

That doesn't matter what that waveform looks like, either, because after
a small toroid transformer drops the 170V square wave down to a 5 and 12V
square wave we're just going to rectify it, again with another group of
diodes and smooth out the pulses, yet again, into smooth DC with another
filter cap before sending it into the computer.

The little custom IC that sends the square waves to the switching
transistors has a circuit that monitors the DC output, the important
output. It then adjusts the drive pulse width on the switching
transistors to create, quite exactly, the DC output voltage,
automatically compensating for a wide variery of AC input voltages and DC
load currents. The output is a rock-steady DC voltage with no pulse
component at all no matter what the input AC is over its design input AC
voltage. It doesn't even matter if you short the output as a little
series sensing resistor, measuring the output current, feeds information
back, again, to that little IC that, "HEY! This idiot wants TOO MUCH
CURRENT!" The IC, then, simply switches off its pulses and the DC output
voltage until you clear the load or short condition and recycle the AC
input voltage...fully protected. If something tries to make the output
go too high, it also switches off the pulses. Switching power supplies
are nearly indestructable within reason.

Your inverter, by the way, is, itself, a switching power supply that
simply doesn't have a rectified output. It's waveform is created from
very high frequency pulses that vary in width over the course of the 60
Hz pseudo-sinewave from near zero to near full width. The pulses are
filtered into the actual output sinewave by a filter that passes 60 hz
and blocks 200 Khz, the pulse frequency.

This same technology is even used in AM broadcast transmitters! The
Harris DX-50 50,000 watt AM blowtorch all the US major transmitters use
is a very neat switcher, too! There are over 200 switching "modules"
that switch at the transmitter's radio frequency, from 550 to 1600 Khz.
Audio input to the transmitter is fed to a digitizer that controls each
little module's on-off switch. With no audio, half the modules are on,
putting out a 50KW carrier to the big antenna. As the audio goes
positive, more modules are turned on. As the audio goes negative, less
modules are turned on, leaving only 1 module putting out 100 watts at
full negative modulation. Voila, AM radio! The advantage is the Harris
uses 55KW from the power company....instead of 200KW the old tube-type AM
transmitter used to drink...MUCH more efficient, like your laptop's power
supply which hardly gets warm at full load.


Question #2: How do I tell the difference? I have 2 inverters I use on
my boat, each from a different manufacturer, and neither one says
anything about the sinewave characteristics.


Lionheart's Dell Latitude has a few thousand hours running off the
cheapest Radio Shack 1KW inverter, remotely mounted in the battery
compartment of the engine room by yours truly remoting its little power
switch (which turns that IC on and off with almost no current, not
turning 100A on and off.) Works just fine, even when someone gets hungry
and winds up the timer on the microwave oven.

I'm using a little 175 watt inverter Radio Shack put on sale for $30 to
run the AC power brick (switcher) of my Gateway notebook in my car. A
500 watt Tripplite inverter runs it in my service truck, the same one
that powers my workbench.

As you can see, you've been lied to, many times. The MOST important
thing you can add to ANY computer that doesn't run off a battery, like
your laptop, is a UPS (Uninterruptable Power Supply). THESE keep WinDOS
from scrambling what's being written to the hard drive when the lights
blink or go out! That's very important. Now, don't go looking at the
output waveform of ANY of these UPS AC supplies the COMPUTER STORE sold
you, the same jokers that said you needed a pure waveform from a $800
inverter. UPS output waveforms look JUST AWFUL!....but, as you can see
above, that matters not, either....(c;

Oh, and if any of you want to remote the power switch of any inverter to
the cabin where it's handy, just take the inverter apart and solder some
really small wires across the existing little power switch and route the
wires to your "control point" in the cabin. I'm using a tiny mini toggle
switch at the nav station by the computer in a little panel that also has
an AC-powered neon indicator next to the switch running off the
inverter's output AC. The neon lamp lets me see, "yes the switch is on
and running the battery down" (so my forgetful captain MAY, if we're
lucky and he notices it, turn it off before he leaves the boat) and "yes,
the inverter is working and putting out some high voltage AC" and "from
the lamps brightness, it looks like it's about the right voltage, close
enough for government work".

There, now you don't have to listen to the inverters obnoxious buzzing
noise that sounds like a housefly or its cooling fan that sounds like a
Boeing 737 taxiing for takeoff...while you're trying to take a NAP
because it's in the ENGINE ROOM, where it belongs!

Do you think it's OK for a square wave inverter to feed a UPS that feeds a
PC? I would really like to do that but was told by some one at APC it's a no
no. My feeling was he had no idea and was just covering himself.
Thanks


"Larry" wrote in message
...
(Floating Mind) wrote in news:4475-44DB3A3B-1511
@storefull-3116.bay.webtv.net:

It's my understanding that a person should never use a modified
sinewave
inverter with a laptop, that we should always use pure sinewave
inverters with laptops, as the modified sinewave units are harmful to
the life of the laptop's battery.

Question #1: Is this true?

No. This is how we sell much more expensive inverters to the mis-
informed.

Today's power supplies, like the one running your desktop PC as you read
this, don't really care what the input looks like. The first thing these
"switching power supplies" do is to rectify whatever input AC you put to
them into DC, which is filtered smooth by a large electrolytic capacitor.
Unless the input is so high it blows the cap or diode, it's fine. You
don't even need a "protector" because the damned "protector" is INSIDE
the power supply! Sales BS also sells "protectors". Whatever DC comes
out of the input rectifiers is fed to switching transistors that convert
the DC into an awful-looking SQUARE WAVE, that waveform your sinewave
salesman warned you about! It even has all kinds of crazy pulses
sticking out of it and is very high in frequency. The square waves vary
in pulse width, caused by the regulator IC that creates the square waves.
It's called "pulse width modulation". Those hybrid cars put these pulses
of DC to their drive motors the same way.

That doesn't matter what that waveform looks like, either, because after
a small toroid transformer drops the 170V square wave down to a 5 and 12V
square wave we're just going to rectify it, again with another group of
diodes and smooth out the pulses, yet again, into smooth DC with another
filter cap before sending it into the computer.

The little custom IC that sends the square waves to the switching
transistors has a circuit that monitors the DC output, the important
output. It then adjusts the drive pulse width on the switching
transistors to create, quite exactly, the DC output voltage,
automatically compensating for a wide variery of AC input voltages and DC
load currents. The output is a rock-steady DC voltage with no pulse
component at all no matter what the input AC is over its design input AC
voltage. It doesn't even matter if you short the output as a little
series sensing resistor, measuring the output current, feeds information
back, again, to that little IC that, "HEY! This idiot wants TOO MUCH
CURRENT!" The IC, then, simply switches off its pulses and the DC output
voltage until you clear the load or short condition and recycle the AC
input voltage...fully protected. If something tries to make the output
go too high, it also switches off the pulses. Switching power supplies
are nearly indestructable within reason.

Your inverter, by the way, is, itself, a switching power supply that
simply doesn't have a rectified output. It's waveform is created from
very high frequency pulses that vary in width over the course of the 60
Hz pseudo-sinewave from near zero to near full width. The pulses are
filtered into the actual output sinewave by a filter that passes 60 hz
and blocks 200 Khz, the pulse frequency.

This same technology is even used in AM broadcast transmitters! The
Harris DX-50 50,000 watt AM blowtorch all the US major transmitters use
is a very neat switcher, too! There are over 200 switching "modules"
that switch at the transmitter's radio frequency, from 550 to 1600 Khz.
Audio input to the transmitter is fed to a digitizer that controls each
little module's on-off switch. With no audio, half the modules are on,
putting out a 50KW carrier to the big antenna. As the audio goes
positive, more modules are turned on. As the audio goes negative, less
modules are turned on, leaving only 1 module putting out 100 watts at
full negative modulation. Voila, AM radio! The advantage is the Harris
uses 55KW from the power company....instead of 200KW the old tube-type AM
transmitter used to drink...MUCH more efficient, like your laptop's power
supply which hardly gets warm at full load.


Question #2: How do I tell the difference? I have 2 inverters I use on
my boat, each from a different manufacturer, and neither one says
anything about the sinewave characteristics.


Lionheart's Dell Latitude has a few thousand hours running off the
cheapest Radio Shack 1KW inverter, remotely mounted in the battery
compartment of the engine room by yours truly remoting its little power
switch (which turns that IC on and off with almost no current, not
turning 100A on and off.) Works just fine, even when someone gets hungry
and winds up the timer on the microwave oven.

I'm using a little 175 watt inverter Radio Shack put on sale for $30 to
run the AC power brick (switcher) of my Gateway notebook in my car. A
500 watt Tripplite inverter runs it in my service truck, the same one
that powers my workbench.

As you can see, you've been lied to, many times. The MOST important
thing you can add to ANY computer that doesn't run off a battery, like
your laptop, is a UPS (Uninterruptable Power Supply). THESE keep WinDOS
from scrambling what's being written to the hard drive when the lights
blink or go out! That's very important. Now, don't go looking at the
output waveform of ANY of these UPS AC supplies the COMPUTER STORE sold
you, the same jokers that said you needed a pure waveform from a $800
inverter. UPS output waveforms look JUST AWFUL!....but, as you can see
above, that matters not, either....(c;

Oh, and if any of you want to remote the power switch of any inverter to
the cabin where it's handy, just take the inverter apart and solder some
really small wires across the existing little power switch and route the
wires to your "control point" in the cabin. I'm using a tiny mini toggle
switch at the nav station by the computer in a little panel that also has
an AC-powered neon indicator next to the switch running off the
inverter's output AC. The neon lamp lets me see, "yes the switch is on
and running the battery down" (so my forgetful captain MAY, if we're
lucky and he notices it, turn it off before he leaves the boat) and "yes,
the inverter is working and putting out some high voltage AC" and "from
the lamps brightness, it looks like it's about the right voltage, close
enough for government work".

There, now you don't have to listen to the inverters obnoxious buzzing
noise that sounds like a housefly or its cooling fan that sounds like a
Boeing 737 taxiing for takeoff...while you're trying to take a NAP
because it's in the ENGINE ROOM, where it belongs!

"sw" wrote in message
. ..
Do you think it's OK for a square wave inverter to feed a UPS that feeds a
PC? I would really like to do that but was told by some one at APC it's a
no
no. My feeling was he had no idea and was just covering himself.
Thanks

Di second whats already been said here - you'd be fine. I have a small
inverter that runs my notelbook, as well as a DC-DC converter for the same
purpose. I cant remember which one is more efficient, but the DC-DC one i
mainly use for flights and such because it can plug in on the plane. In the
car, the inverter wins because it doesnt cause any interference with my
stereo ;-)

Shaun

Shaun Van Poecke wrote:
"sw" wrote in message
. ..
Do you think it's OK for a square wave inverter to feed a UPS that feeds a
PC? I would really like to do that but was told by some one at APC it's a
no
no. My feeling was he had no idea and was just covering himself.
Thanks

Di second whats already been said here - you'd be fine. I have a small
inverter that runs my notelbook, as well as a DC-DC converter for the same
purpose. I cant remember which one is more efficient, but the DC-DC one i
mainly use for flights and such because it can plug in on the plane. In the
car, the inverter wins because it doesnt cause any interference with my
stereo ;-)

Shaun



I think some UPS's use a step-down transformer to get down to the
battery voltage. A square wave inverter can wreak havoc with a
transformer expecting 60 Hz AC.

With a UPS, the PC is powered by 120 VAC that is generated from the
battery voltage by an inverter.

There is no problem powering a PC from an inverter, as Larry has made
abundantly clear. There is very likely a problem powering a UPS from a
square wave inverter.

A sine wave inverter, OTOH, should cause no problems at all.

Make sense?

Good luck.

Chuck

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There's no excuse for using a square wave inverter these days. Modified sine wave inverters
are cheap.



"sw" wrote in message . ..
Do you think it's OK for a square wave inverter to feed a UPS that feeds a
PC? I would really like to do that but was told by some one at APC it's a no
no. My feeling was he had no idea and was just covering himself.
Thanks


"Larry" wrote in message
...
(Floating Mind) wrote in news:4475-44DB3A3B-1511
@storefull-3116.bay.webtv.net:

It's my understanding that a person should never use a modified
sinewave
inverter with a laptop, that we should always use pure sinewave
inverters with laptops, as the modified sinewave units are harmful to
the life of the laptop's battery.

Question #1: Is this true?

No. This is how we sell much more expensive inverters to the mis-
informed.

Today's power supplies, like the one running your desktop PC as you read
this, don't really care what the input looks like. The first thing these
"switching power supplies" do is to rectify whatever input AC you put to
them into DC, which is filtered smooth by a large electrolytic capacitor.
Unless the input is so high it blows the cap or diode, it's fine. You
don't even need a "protector" because the damned "protector" is INSIDE
the power supply! Sales BS also sells "protectors". Whatever DC comes
out of the input rectifiers is fed to switching transistors that convert
the DC into an awful-looking SQUARE WAVE, that waveform your sinewave
salesman warned you about! It even has all kinds of crazy pulses
sticking out of it and is very high in frequency. The square waves vary
in pulse width, caused by the regulator IC that creates the square waves.
It's called "pulse width modulation". Those hybrid cars put these pulses
of DC to their drive motors the same way.

That doesn't matter what that waveform looks like, either, because after
a small toroid transformer drops the 170V square wave down to a 5 and 12V
square wave we're just going to rectify it, again with another group of
diodes and smooth out the pulses, yet again, into smooth DC with another
filter cap before sending it into the computer.

The little custom IC that sends the square waves to the switching
transistors has a circuit that monitors the DC output, the important
output. It then adjusts the drive pulse width on the switching
transistors to create, quite exactly, the DC output voltage,
automatically compensating for a wide variery of AC input voltages and DC
load currents. The output is a rock-steady DC voltage with no pulse
component at all no matter what the input AC is over its design input AC
voltage. It doesn't even matter if you short the output as a little
series sensing resistor, measuring the output current, feeds information
back, again, to that little IC that, "HEY! This idiot wants TOO MUCH
CURRENT!" The IC, then, simply switches off its pulses and the DC output
voltage until you clear the load or short condition and recycle the AC
input voltage...fully protected. If something tries to make the output
go too high, it also switches off the pulses. Switching power supplies
are nearly indestructable within reason.

Your inverter, by the way, is, itself, a switching power supply that
simply doesn't have a rectified output. It's waveform is created from
very high frequency pulses that vary in width over the course of the 60
Hz pseudo-sinewave from near zero to near full width. The pulses are
filtered into the actual output sinewave by a filter that passes 60 hz
and blocks 200 Khz, the pulse frequency.

This same technology is even used in AM broadcast transmitters! The
Harris DX-50 50,000 watt AM blowtorch all the US major transmitters use
is a very neat switcher, too! There are over 200 switching "modules"
that switch at the transmitter's radio frequency, from 550 to 1600 Khz.
Audio input to the transmitter is fed to a digitizer that controls each
little module's on-off switch. With no audio, half the modules are on,
putting out a 50KW carrier to the big antenna. As the audio goes
positive, more modules are turned on. As the audio goes negative, less
modules are turned on, leaving only 1 module putting out 100 watts at
full negative modulation. Voila, AM radio! The advantage is the Harris
uses 55KW from the power company....instead of 200KW the old tube-type AM
transmitter used to drink...MUCH more efficient, like your laptop's power
supply which hardly gets warm at full load.


Question #2: How do I tell the difference? I have 2 inverters I use on
my boat, each from a different manufacturer, and neither one says
anything about the sinewave characteristics.


Lionheart's Dell Latitude has a few thousand hours running off the
cheapest Radio Shack 1KW inverter, remotely mounted in the battery
compartment of the engine room by yours truly remoting its little power
switch (which turns that IC on and off with almost no current, not
turning 100A on and off.) Works just fine, even when someone gets hungry
and winds up the timer on the microwave oven.

I'm using a little 175 watt inverter Radio Shack put on sale for $30 to
run the AC power brick (switcher) of my Gateway notebook in my car. A
500 watt Tripplite inverter runs it in my service truck, the same one
that powers my workbench.

As you can see, you've been lied to, many times. The MOST important
thing you can add to ANY computer that doesn't run off a battery, like
your laptop, is a UPS (Uninterruptable Power Supply). THESE keep WinDOS
from scrambling what's being written to the hard drive when the lights
blink or go out! That's very important. Now, don't go looking at the
output waveform of ANY of these UPS AC supplies the COMPUTER STORE sold
you, the same jokers that said you needed a pure waveform from a $800
inverter. UPS output waveforms look JUST AWFUL!....but, as you can see
above, that matters not, either....(c;

Oh, and if any of you want to remote the power switch of any inverter to
the cabin where it's handy, just take the inverter apart and solder some
really small wires across the existing little power switch and route the
wires to your "control point" in the cabin. I'm using a tiny mini toggle
switch at the nav station by the computer in a little panel that also has
an AC-powered neon indicator next to the switch running off the
inverter's output AC. The neon lamp lets me see, "yes the switch is on
and running the battery down" (so my forgetful captain MAY, if we're
lucky and he notices it, turn it off before he leaves the boat) and "yes,
the inverter is working and putting out some high voltage AC" and "from
the lamps brightness, it looks like it's about the right voltage, close
enough for government work".

There, now you don't have to listen to the inverters obnoxious buzzing
noise that sounds like a housefly or its cooling fan that sounds like a
Boeing 737 taxiing for takeoff...while you're trying to take a NAP
because it's in the ENGINE ROOM, where it belongs!

"Chuck Tribolet" wrote in message
...
There's no excuse for using a square wave inverter these days. Modified
sine wave inverters
are cheap.

sigh~ not everywhere in the world is as lucky as the USA ;-) here in
australia we're still a bit backwards. small square wave inverters at
150watts start at $AU50, while something as exoting as a 1000watt square
wave costs about AU$400. a sine wave 1000watt inverter costs about AU$800.

Shaun

"Shaun Van Poecke" wrote in news:TNtGh.6816
:

a sine wave 1000watt inverter costs about AU$800

http://www.walmart.com/catalog/produ...uct_id=5301540
$118 for 1200 watts....sine wave output.
Walmart ships worldwide. 1200 watts - 2400 watts surge if you have heavy
enough wires to a big battery. Does Walmart charge that much in Australia?

Hmm....$US118 = $AU151. They're still probably going to hit you up for
some hefty import fees and VAT to pay for the socialized meds, etc.

Should still be much cheaper than $AU800!

Larry
--
If the damned government isn't going to enforce
immigration laws, can they at LEAST park an ICE
paddy wagon in front of WalMart so I can find
a parking place and make the checkout line SHORTER?!

I didn't say true sine wave, I said modified sine wave.
I can't remember the last time I saw a square wave inverter for
sale. With digital control, modified sine wave is ASMOP (A Simple
Matter Of Programming).

A square wave inverter goes to +120V (or whatever) for 1/120 second, then
to -120V (or ...) for 1/120 second.

A modified sine wave inverter goes to +120V for a bit less than 1/120 second,
then to zero for a bit, then to -120V for a bit less than 1/120 second,
then to zero for a bit. The net is that the area under the curve is the
same as a sine wave. (Note: the above assume 60Hz. at 50Hz it would
be 1/100 second).

West Marine (they ship international) has a 700W continuous, 1800W surge
modified sine wave inverter for US$69.99

As I said, no excuse for a square wave inverter these days.

"Shaun Van Poecke" wrote in message ...

"Chuck Tribolet" wrote in message ...
There's no excuse for using a square wave inverter these days. Modified sine wave inverters
are cheap.

sigh~ not everywhere in the world is as lucky as the USA ;-) here in australia we're still a bit backwards. small square wave
inverters at 150watts start at $AU50, while something as exoting as a 1000watt square wave costs about AU$400. a sine wave
1000watt inverter costs about AU$800.

Shaun

"sw" wrote in
:

Do you think it's OK for a square wave inverter to feed a UPS that
feeds a PC? I would really like to do that but was told by some one at
APC it's a no no. My feeling was he had no idea and was just covering
himself. Thanks



If you sold UPS products to make your living, would you want them to use
just any ol' cheap inverter....or your geewhiz technological wonder?

There aren't any "square wave inverters" left on the market that I know
of. Manufacturing inverters with sine wave synthesis is just too cheap
and easy now. I just bought a 750 watt sinewave Black & Decker from
WalMart for $70! It will even crank an 8000 Btu Samsung air conditioner
with its 1500 watt surge rating. It has three 30A fuses in parallel.
(No, you can't aircondition your boat on a boat battery....maybe a
submarine battery.) It doesn't even turn its fan on until the load gets
over 150 watts, it's so efficient. Driving my 1.6A fridge and a few
loads on my workbench, it hardly gets warm. The fan in the inverter
turns on and off as the fridge cycles...letting me know when the beer is
cold.

ALL of these little cheap inverters over the power input demand of the
laptop will run the laptop just fine and charge its battery. Mine
charges in the car from a 175W inverter that cost me $20 on sale. Your
PC is no exception, either. It also uses a switching power supply that
works perfectly with a very wide range of input voltages from DC to high
frequency AC. It matters not as the input is a rectifier feeding a big
storage capacitor the switchers use power from to create the output.
Everything is converted to SMOOTH DC at about 170VDC off the AC line,
whatever that line is. Many switching power supplies are rated from
90VAC to 270VAC input at any line frequency of whatever nation you happen
to plug it into, so the manufacturer can send any computer to any
customer, no matter where he/she lives.

AS a note, I'm using a large APC UPS to power the computers in my office.
It provides smooth power and automatically shuts down Windoze before the
battery goes dead if the power outage is elongated. That's the reason I
bought it, not for its perfectly-smooth, xtal-regulated 60 Hz at 120VAC.
There was an "electrical noise" that lasted 8 seconds the last time it
switched on to protect the equipment, probably caused by the beer fridge
or electric heater running off the same outlet its plugged into coming on
simultaneously...???

Larry
--
If the damned government isn't going to enforce
immigration laws, can they at LEAST park an ICE
paddy wagon in front of WalMart so I can find
a parking place and make the checkout line SHORTER?!

Larry wrote:
"sw" wrote in
:

Do you think it's OK for a square wave inverter to feed a UPS that
feeds a PC? I would really like to do that but was told by some one at
APC it's a no no. My feeling was he had no idea and was just covering
himself. Thanks



If you sold UPS products to make your living, would you want them to use
just any ol' cheap inverter....or your geewhiz technological wonder?

There aren't any "square wave inverters" left on the market that I know
of. Manufacturing inverters with sine wave synthesis is just too cheap
and easy now. I just bought a 750 watt sinewave Black & Decker from
WalMart for $70! It will even crank an 8000 Btu Samsung air conditioner
with its 1500 watt surge rating. It has three 30A fuses in parallel.
(No, you can't aircondition your boat on a boat battery....maybe a
submarine battery.) It doesn't even turn its fan on until the load gets
over 150 watts, it's so efficient. Driving my 1.6A fridge and a few
loads on my workbench, it hardly gets warm. The fan in the inverter
turns on and off as the fridge cycles...letting me know when the beer is
cold.

ALL of these little cheap inverters over the power input demand of the
laptop will run the laptop just fine and charge its battery. Mine
charges in the car from a 175W inverter that cost me $20 on sale. Your
PC is no exception, either. It also uses a switching power supply that
works perfectly with a very wide range of input voltages from DC to high
frequency AC. It matters not as the input is a rectifier feeding a big
storage capacitor the switchers use power from to create the output.
Everything is converted to SMOOTH DC at about 170VDC off the AC line,
whatever that line is. Many switching power supplies are rated from
90VAC to 270VAC input at any line frequency of whatever nation you happen
to plug it into, so the manufacturer can send any computer to any
customer, no matter where he/she lives.

AS a note, I'm using a large APC UPS to power the computers in my office.
It provides smooth power and automatically shuts down Windoze before the
battery goes dead if the power outage is elongated. That's the reason I
bought it, not for its perfectly-smooth, xtal-regulated 60 Hz at 120VAC.
There was an "electrical noise" that lasted 8 seconds the last time it
switched on to protect the equipment, probably caused by the beer fridge
or electric heater running off the same outlet its plugged into coming on
simultaneously...???

Larry
I found that a Zantrex "modified sine wave", really a modified square
wave inverter, would not run a Sears 115v input NiCad battery charger
for a 19.2v drill until I built a low pass filter for the inverter.
Dick, Nonsuch 26