Questions about inverters

[Fred Mc]

What are the pros and cons of a modified sine wave inverter and a true sine wave inverter? About the only different I have come across is that you can't power a laser printer with a modified sine wave. There must be other disadvantages.

Also what are the benefits (if there are any) of buying an inverter/charger combination vs have a separate inverter and charger?

Thanks

Fred Mc.

[Sean]

What are the pros and cons of a modified sine wave inverter and a true sine wave inverter?

Lots of detail on this issue in the archives.

To make a long story short, if you plan to run induction motors, you want true sine wave.  Examples are household refrigerators, air conditioners, many air compressors and pressure washers, many 120VAC pumps, and some power tools.

If you do not intend to run motors, MSW is probably fine.  Most consumer electronics including A/V and computer equipment use switching-mode power supplies which work fine on MSW, and resistive loads will not notice at all.

...
Also what are the benefits (if there are any) of buying an inverter/charger combination vs have a separate inverter and charger?

• Single box rather that two boxes.
• Less overall wiring -- one set of AC and DC cables vs. two.
• All charging inverters have integral transfer switches to transfer the load to incoming power when available, many non-charging inverters do not.
• Many charging inverters can automatically reduce the charger draw when other loads are running to avoid overloading the incoming power.  No stand-alone charger can do this.

There are probably a couple of other minor issues that I have missed.

On the flip side, by having separate chargers and inverters, you can make a poor-man's load-support feature.  A charger designed to run on a 15- or 20-amp AC circuit can power, though the batteries, an inverter which can provide 30+ amps of output, allowing you to run an air conditioner on a circuit that, by itself, would be insufficient.

Like everything else, there are trade-offs either way.

-Sean
http://OurOdyssey.BlogSpot.com

[TomC]

I have a modified sine wave Trace 2512 with 130 amp built 3 stage smart battery charger.  The inverter makes the microwave hum and the cooking times are longer; the stove hood motor runs slower on the inverter; yet the bathroom wall heater and my wifes hair dryer run fine on the inverter.  Personally-I'm going to use a pure since wave inverter with 3 stage smart battery charger next time.  Magnum makes a 2800 watt that runs on 12vdc. I highly recommend using the all in one inverter/chargers-just makes life a bit simpler.  Good Luck, TomC

[Sean]

... a modified sine wave ... inverter makes the microwave hum and the cooking times are longer; ...

Good point, Tom, I inadvertently left microwaves off my list of things that should not be run on an MSW inverter.

-Sean
http://OurOdyssey.BlogSpot.com

[Fred Mc]

Good explanations.

Thank you.

Fred Mc.

[bevans6]

If you have a choice, use 24VDC in preference to 12 VDC, since the wiring can be smaller to support the same power requirements.  In my bus I chose PSW since the primary application is running the roof airs on the road, while in my truck camper I use MSW since the primary application is running the TV and making coffee...

Brian

[cody]

One thing to keep in mind about inverters is that they all use a step wave pattern, even the pure sine wave is still a step wave pattern, a modified sine wave inverter has a wider step pattern that some electronics and motors don't seem to like, but the higher grades of MSW have a tighter step pattern that seems to be acceptable for many of them, I had a heart MSW and all my electronics worked very well with it but I did try a cheaper brand and noticed a huge difference, I've since bought a magnum 2800 with the pure sine wave and am curious to see how well it works but the main thing here is that even pure sine wave inverters use a step pattern, the quality of the inverter seems to determine how tight the pattern is, the tighter the pattern, the closer to pure sine wave, also keep in mind that pure sine wave is a marketing phrase since they too use a step pattern, tight, but still a step pattern.  One with a built in 3 stage charger simplifies matters conciderably, especially if it has an automatic pass thru feature.