Inverter - Modified Sine Wave vs Pure Sine Wave?

[wgoodbye]

When we bought a new boat, it came with a Wagan Tech Pro line 3000. Which is a modified sine wave inverter. I had a lot of concerns in the beginning after reading all the forums about modified sine wave inverters causing problems. I had actually planned to replace the unit with a sign wave inverter. The Wagan unit costs about $350 and a true sine wave unit would have been 2-4X the cost to replace it. I have to say, my apprehensions were totally unfounded. after 2 years of use, we have had absolutely no problems using this modified sine wave inverter with everything. We use it with computers, microwave, power tools, shop vac, air compressor, whatever and have never noticed anything overheating or behaving other than normal.

I'm convinced that not all manufacturers of modified sine wave inverters are equal so your mileage may vary with other makes/models. We have been very happy with the Wagan unit and see no reason to replace it with a true sine wave inverter at this juncture. The Wagan 3000 can peak to 6000 watts for short periods to handle inductive loads from motors etc.

[ex-12m-guy]

If the output of a modified sine wave inverter is run
through an isolation transformer, the output of the transformer
will be close to a pure sine wave.

The "hysteresis" of a transformer (magnetic equivalent of
mechanical inertia) will knock off the sharp edges of the square
wave steps.

If a boat is already equipped with an isolation transformer, consideration
can be given to placing the modified sine wave inverter output on the "shore power" side of the transformer (with appropriate isolation / transfer switching and circuit protective devices as required.)

[davefrediam]

Hi I originally installed a sterling modified sinewave charger/inverter and reading the product information you would think it would work with most things but in practice very little did. The dehumidifier smoked, the microwave made an awful racket, etc. So sold it on ebay and got true sinewave one from Studer, everything works seamlessly with it but it is complicated and simple things like switching the inverter on & off takes at least 20 button pushes, going through menus.

[roverhi]

Our square wave Xantrex inverter works fine for everything but a Bosch variable speed saber saw. The saber saw won't turn on/is dead when powered from the inverter. Years ago had a Sears gas oven that blew its control board on square wave. Sears fixed it twice then took it back and refunded my money. It really depends on whether you want an inverter that will run everything or a much cheaper one that will run almost everything. If you go the square wave route be sure and test everything that you will want to run with it as soon as you buy it. You want to be able to return anything that doesn't work so be sure any toys can be returned. Some electronics stores/parts have a no return policy.

[GrahamHO]

I had trouble with my MacBook battery after charging it with a square wave (modified wave) inverter. The pure sine wave inverter I replaced it with is fine. A pure sine wave looks like a graph of the rise and fall of the tide with the voltage smoothly alternating. A modified sine wave leaves out the smooth curve having just the top and bottom voltage suddenly alternating.


If you are wanting to charge sensitive electronic equipment you could consider having a second smaller pure sine wave inverter dedicated to that use. It's best if you do that to use the hard wired variety of sine wave inverters rather than the lighter plug input variety. A pure wave inverter I initially tried had a lighter plug and although the rated output seemed more than sufficient it couldn't draw sufficient input current to charge the laptop. A replacement hard wired sine wave inverter worked fine. We charge all the usual laptops iPads and cell phones on it with no problems. A domestic multi output box is plugged into it with no other AC wiring.



With any inverter use quite heavy + and - cables on the battery side. They should be of a size in keeping with the screw terminals on the inverter. Take them on their own circuit to the boat distribution panel with their own circuit breaker ( or fuse )


You can of course do your own cost analysis to decide whether a large square wave inverter plus a small pure sine wave inverter for sensitive use is worth while.

[PamlicoTraveler]

Sometime the easiest thing is just to pay up and avoid any future issues. I have done fine wih the Freedom 20, but it is a bit old, and it will fail in some other way eventually even if I remove I and fix the fan. The Xantrex pure Sine is expensive, but maybe it's better for electronics like computers and power tools long term.

We live on the boat, so quality and durability is an issue. We can't go to our local West Marine when we are in a foreign country if something fails. That's why i used a fan plugged into a cigarette lighter and duct taped it to the inverter when I was using it to keep it from overheating. We are in North Carolina now, so I am going to address the issue while we are here.

[senormechanico]

Why is everyone so fixated on Xantrex?
There are lots of stories of people who have been burned (me included) by the fall of their quality.
Magnum, several others mentioned on this board, Xantrex SW series and similar, yes. Cheapo Xantrex NO !

[SeaSon]

Too much science. The old Freedom 20 is at best a modified done wave. Has it done the job for you for 10 years? If so...

[motion30]

TE=senormechanico;1876426]Why is everyone so fixated on Xantrex?
There are lots of stories of people who have been burned (me included) by the fall of their quality.
Magnum, several others mentioned on this board, Xantrex SW series and similar, yes. Cheapo Xantrex NO ![/QUOTE]

I agree totally, every xantrex product I owned was terrible. And xanTrex. Customer service is insulting.

[transmitterdan]

Originally Posted by PamlicoTraveler

We live on the boat, so quality and durability is an issue. We can't go to our local West Marine when we are in a foreign country if something fails. That's why i used a fan plugged into a cigarette lighter and duct taped it to the inverter when I was using it to keep it from overheating. We are in North Carolina now, so I am going to address the issue while we are here.

Mastervolt inverter/chargers are a good choice for your criteria. I would avoid today's Xantrex models. I think what you have is the old Heart Interface version. It was a really good design and you can sell it pretty easily as they are still in demand.