True (Pure) Sine Inverter vs Modified Sine Inverter

[Alecadi]

Which one should I installed?
What is what and what is the difference (apart from the price)?

[Intentional Drifter]

Many AC appliances are not happy with modified sine wave current. Some won't work at all, some won't work efficiently, some will run hot. The pure sine wave gives a clean wave form and throws off less interference. Microwave ovens (for example) and some motors are very unhappy with modified sine waves and, while they might "work", they will die before their time. Some computers will simply crash.

There is no doubt that pure sine inverters are considerably more expensive. They have to be, but the quality of their construction (and presumably the operating life span) is also significantly better.

ID

[Alecadi]

Originally Posted by Intentional Drifter

Many AC appliances are not happy with modified sine wave current. Some won't work at all, some won't work efficiently, some will run hot. The pure sine wave gives a clean wave form and throws off less interference. Microwave ovens (for example) and some motors are very unhappy with modified sine waves and, while they might "work", they will die before their time. Some computers will simply crash.

There is no doubt that pure sine inverters are considerably more expensive. They have to be, but the quality of their construction (and presumably the operating life span) is also significantly better.

ID

Thank you.
For a house bank of 400A, what wattage is appropriate on an inverter?
Can I go up to 3000W
Alec

[AnchorageGuy]

ID's advise is good except the part about the true sine waves being expensive. That was the case but today there is very little difference in the price. Although your battery bank plays a part, you need to determine the usage and demand for the inverter to decide what size you need. Then you will need to match your battery bank to how often you want to recharge it after using the inverter and your other 12 volt demands. Chuck

[Intentional Drifter]

I don't see why not. If you use all of those 3000 watts, you'll just drain your bank all the faster! Just make absolutely sure your cables and connections are 100% up to the required specs and your batteries are both healthy and can take the drain.

Also, keep in mind that most inverters are only around 95% efficient. So, using 100 watts through the inverter actually pulls about 105 watts out of the batteries. Simply leaving the inverter “on” even when not using anything, will consume power. If not using it, flip it off. Since chargers aren't 100% efficient, either, that means that for every 100 watts you pull through the inverter, you've got to replace with about 140. That's one of the big reasons that, whenever possible, using a 12 volt appliance is preferable to using a 120 volt AC appliance.

For example, common inverter loads look like (assuming 12 volt bank converted to 120 volt AC):

• Blow dryers (a 1200 watt blow dryer run on the inverter uses 100 amps! Use it for 15 minutes and you have burned over 25 Amp/hours from the battery bank.)
• Microwave (at 1000 watts, it uses 83 amps through the inverter, or 21 Amp/hours for 15 minutes.)
• Ice maker (uses 23 amps through the inverter, so running it for 4 hours on the inverter will consume 100 Amp/hours from the battery bank.)
• Salon TV (at 100 watts, uses 8.3 amps through the inverter, or 25 Amp/hours to watch for three hours)
• PC (at 65 watts, uses 5.4 amps through the inverter, or 17 Amp/hours for that 3 hour movie)

Oink! Oink! Lots of common appliances are real energy hogs.

ID

[Intentional Drifter]

Nice to hear the prices have dropped! That wasn't the case 4 or 5 years ago.

ID

[Captain Bill]

3000 watts really depends on how often you're going to use it and for how long. I have a 2500 watt modified sine wave inverter on a 420 AH bank. I have actually smoked some electronic control modules on electric blankets and such using the inverter. My Ice maker will not make ice on the modified sine wave inverter, but it will keep the ice already made frozen. If I want to make Ice I have to run the genset even when motoring. The microwave takes about 25% longer to cook something when on the inverter. My plan is to replace my current inverter and my charger with a true sine inverter/charger. I think you'll be much happier with the true sine inverter.

[Intentional Drifter]

Originally Posted by Captain Bill

3000 watts really depends on how often you're going to use it and for how long. I have a 2500 watt modified sine wave inverter on a 420 AH bank. I have actually smoked some electronic control modules on electric blankets and such using the inverter. My Ice maker will not make ice on the modified sine wave inverter, but it will keep the ice already made frozen. If I want to make Ice I have to run the genset even when motoring. The microwave takes about 25% longer to cook something when on the inverter. My plan is to replace my current inverter and my charger with a true sine inverter/charger. I think you'll be much happier with the true sine inverter.

Yes, Bill, I think you'll be much more satisfied with a pure sine unit. We've been very satisfied with our Victron Phoenix inverter/charger. Truly a "no muss, no fuss" unit. We've noticed no differences in operation between shore power, generator, or inverter on any of our AC appliances. (Although if it were up to me, I'd throw the blow dryer and curling iron overboard. But, then, I'd end up being thrown overboard!)

ID

[Captain Bill]

Originally Posted by Intentional Drifter

Yes, Bill, I think you'll be much more satisfied with a pure sine unit. We've been very satisfied with our Victron Phoenix inverter/charger. Truly a "no muss, no fuss" unit. We've noticed no differences in operation between shore power, generator, or inverter on any of our AC appliances. (Although if it were up to me, I'd throw the blow dryer and curling iron overboard. But, then, I'd end up being thrown overboard!)

ID

Thanks for the info, the Victron Phoenix is exactly what I'm planning to get. The only good use for the hairdryer is a quick defrost of the fridge IMHO.

[Alecadi]

Originally Posted by Intentional Drifter

Nice to hear the prices have dropped! That wasn't the case 4 or 5 years ago.

ID

And not really evident nowodays either
I see quite a diffrence in price still

[Alecadi]

Thank you Bill and Thank you ID
that was very useful

[Jim Cate]

FWIW,

Not trying to start an argument, but I think that all pseudo-sine wave inverters must not generate the same wave form. We've had the same old Heart 600 W inverter since 1987. It's not a pure sine wave unit, but has run everything I have ever plugged into it without whingeing. Variable-speed drills, etc, don't modulate the speed as smoothly when powered by the inverter as when on mains power, but they do run, and we've never had any other problems with it.

I wonder if anyone can explain this?

Cheers,

Jim

[Intentional Drifter]

You're right, Jim. I recall seeing a PS test several years ago of various inverters. The wave forms did vary, quite a bit. I imagine that different appliance brands probably also vary as to their sensitivity to the wave form, too.

ID

[Intentional Drifter]

Oh, one quick P.S. to Captain Bill about the Victron -- I really, really hope that they have changed their battery cable connections in the intervening years. In my unit, it was quite obvious that the engineers had not talked to anyone who had to install them! Very tight spots for those very big cables! That's my only complaint about the unit. Otherwise, it powered up just fine, was easy to configure, and has been rock solid ever since.

ID

[David M]

It's actually a modified square wave. Why would anyone want to modify a sine wave to something less useful?