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Old 10-04-2015, 07:47   #1
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Inverters / Generators

I have a morgan 384 looking to cruise the bahamas
I have a 5K generator
i was told i need sine wave inverter so to not wear out the lap top and other battery electronics ?
Was told pure sine wave versa generator clipped and clamped wave is just better on the electronics.
So do i get a 2.5 sine wave inverter? or do i get all 12 volt appliances Truckers.com has all 12 volt microwaves and tv's
There no savings eather way I just want to to do the best no hassle down the road thing Lee/ fla
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Old 10-04-2015, 08:28   #2
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Re: inverters/ generators

Get the inverter. You'll have a much bigger choice of appliances in 110 volt that you will in 12 volt. My experience has been that 12 volt appliances are of lower quality than those made for home use.
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Old 10-04-2015, 12:31   #3
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Re: inverters/ generators

Unless you want music system, DVD player and TV then 12 volt is fine. I use a 12v to 19v dc adaptor for the laptop.


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Old 10-04-2015, 14:56   #4
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Re: inverters/ generators

The 12 volt TV/DVD player is fine. I have a Skyworth. It saves running the inverter to produce 120 volts AC for the TV to convert internally to low voltage DC.

12 volt heating appliances are notoriously slow and inefficient. This is when you need the inverter so you can use a standard microwave oven, coffee maker, hair drier, heat gun, and power tools.
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Old 10-04-2015, 15:05   #5
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Re: inverters/ generators

Quote:
Originally Posted by rwidman View Post
The 12 volt TV/DVD player is fine. I have a Skyworth. It saves running the inverter to produce 120 volts AC for the TV to convert internally to low voltage DC.

12 volt heating appliances are notoriously slow and inefficient. This is when you need the inverter so you can use a standard microwave oven, coffee maker, hair drier, heat gun, and power tools.
You only need AC for appliances that heat things.

Everything electronic including good TVs and DVD players can be done easily with 12VDC. Check out CampingWorld or order online for that stuff. We have an inverter but the only thing we ever use it for is the Microwave, and we rarely use that. For laptops, use a small 150 watt micro-inverter plugged into a 12VDC cigarette lighter adapter if you can't get a direct 12VDC charger for it. Those things are cheap and easily replaced, and will work for anything that is a charger for electronics.

As for heating, just use an alcohol or propane stove. Boiling water for coffee only takes a minute or two if you just put one or two cups in the pan.
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Old 10-04-2015, 15:11   #6
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Re: inverters/ generators

I find the inverter is great so I don't have to run the generator to operate something as simple as a TV, microwave oven, espresso machine or charger for my laptop.

I'm less convinced, though, on the needs for a pure-sine wave inverter. I can see how motors might care, but for DC power supplies and resistive heating, I cannot see how the shape of the wave matters since the first stage of a power supply after the transformer is, for linear supplies, generally a full-wave rectifier, followed by low-pass filtering. For switching supplies I imagine it would be even less of an issue as they hack-up the waveform quite a bit to get the desired output voltage.
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Old 12-04-2015, 11:55   #7
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Re: Inverters / Generators

Switching power supplies get pretty hot when running on non-pure sine wave inverters because the voltage level at the moment of "pass" is higher than it would be on a sine wave.

Switching power supplies are brilliant. Instead of using a bulky and inefficient transformer to convert power at a fixed ratio, they exploit the fact that AC power transitions through all voltages from +120 to -120 VAC each wave. A fast silicon switch times how the wave is passing through and "opens the gate" just as the correct voltage is going by (actually a bit higher), and holds it open for just the amount of milliamperes needed for the device under operation. A small capacitor smooths the pulse and a simple voltage regulator is used to produce the final correct voltage.

A non-pure sine-wave cannot be timed precisely enough by the sine wave clock, so it opens earlier and stays open longer, resulting in more power being wasted to heat.

This is why they run hotter and wear out sooner on non-pure sine inverters.


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Old 13-04-2015, 00:38   #8
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Re: Inverters / Generators

Would a pure-sine wave inverter be a considerably better choice for use to run a 240V domestic house fridge from 12 V batteries aboard a sailing boat, as opposed to a non pure-sine wave inverter?
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Old 13-04-2015, 01:33   #9
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Re: Inverters / Generators

Quote:
Originally Posted by ErikFinn View Post
Would a pure-sine wave inverter be a considerably better choice for use to run a 240V domestic house fridge from 12 V batteries aboard a sailing boat, as opposed to a non pure-sine wave inverter?
Short Story
A square wave inverter would work - possibly acceptably - but the operation will be noisier, the motor will run hotter and the whole setup will be much less efficient.

Long Story
AC voltage values are expressed as RMS (Root Mean Square) values. This basically means the point of average voltage for the waveform. With a sine wave, the highest, or peak, voltage is around 1.7 times the RMS value. In other words if you have a 100VAC sine wave supply, the peak voltage is actually 170V. If you have a square wave supply providing the equivalent of 100VAC (RMS) the peak voltage is 2x which is 200V.

All things being equal, the same device will draw higher and longer instantaneous currents at the waveform peak on a square wave then a sine wave (2x vs 1.7x). Even though the total energy might work out the same, the components are more stressed than even this maths allows because the rate of change of voltage from 0 to max in a square wave (theoretically instantaneous) creates it's own set of problems as well.

Then to top it all off, electric AC motors require a rotating magnetic field. If you think about it an AC generator produces a sine wave because it is rotating and a sine wave therefore represents a rotating magnetic field. This isn't the case with a square wave and is the reason square waves cannot be generated by AC generators without additional electronics.
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Old 14-04-2015, 20:40   #10
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Re: Inverters / Generators

What a great answer, thank you!

So I understand by running a pure-sine wave inverter on my 240V fridge my batteries would last longer before needing a recharge, and the inverter should give me more service years? (and with less heat and noise)

Another Q: I have a 1500W inverter, I presume its not the best choise for running a fridge? I recall the ideal inverter wattage should be something like 3 to 4 times the wattage of the appliance? This since the "starting wattage" is a multiplier of the nominal running wattage? Is this correct? I'm putting a lot of question marks here because I don't remember the facts and don't want anyone to think I do.

What would be the ideal size inverter for running a fridge something like this (specs on foto)?
(one I'm after uses less watts but I don't have a foto of that, so this is for illustration only, quite similar after all)
Cheers
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Old 15-04-2015, 14:03   #11
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Re: Inverters / Generators

Cheaper inverters which are typically square wave have problems with some electronics. For instance the variable speed Bosch Saber Saw will not run/won't even start on my inexpensive inverter. All of my older tools work fine. Electric motors seem to do just fine unless they have some incompatible electronics in the control circuit. Years ago, a gas oven controller would blow up when connected to a square wave inverter. Thank heavens for a warranty. So it really depends on what you'll be running with the inverter. In todays world, almost everything has some form of electronics in the system, even gas appliances, so if you are looking for 110/220 power, a pure sine wave inverter might be a safety investment.

Personally, would stick with 12 volt. You can charge any battery operated components off it, or run them direct with a proper converter. You've got a stove on board, hopefully not electric, for heating things, use it. If you can't live without a microwave, get one of the manual control types which would probably do fine on a square wave inverter. I won't comment on trying to run a house refrigerator on a boat no matter what the source of the power.
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Old 15-04-2015, 14:40   #12
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Re: Inverters / Generators

Quote:
Originally Posted by stnick View Post
I have a morgan 384 looking to cruise the bahamas
I have a 5K generator
i was told i need sine wave inverter so to not wear out the lap top and other battery electronics ?
Was told pure sine wave versa generator clipped and clamped wave is just better on the electronics.
So do i get a 2.5 sine wave inverter? or do i get all 12 volt appliances Truckers.com has all 12 volt microwaves and tv's
There no savings eather way I just want to to do the best no hassle down the road thing Lee/ fla
We hardly use our 2000 freedom inverter. We run nearly everything from 12V. We've been living aboard for 18 months and we're slowing increasing our move to pure solar recharge.

We also run a startup on board. All our IT kit runs from 12V including NAS, wifi extender, hardened router and hardware firewall.

All our power tools are cordless.

There is a parasitic loss from the inverter and converting from 12V to 110V and then back to 12V or 5V USB through most device transformers makes little sense. Forget square wave inverters. You cant run most appliances from them. Motors get hot, the voltage spikes confuse the cheap electronics and they lack the robustness needed in a marine environment.

We have replaced some of our 12V cigarette lighters with blue sea double USB sockets.

More than 50% of the power consumed in the average house is now from transformers converting back to a low DC voltage. These transformers are cheap rubbish and use most of their power wasted in heat. It was the heat that initially led us to removing them.

The benefit is probably best portrayed as a quasi formula.

Solar->12V house batteries->Appliance

versus

Solar->12V house batteries->Inverter->Connector->Transformer->Appliance

We have also ditched the microwave. We only use the inverter for the juicer, iron or bar mix. We often use small fan driven 300W inverters for our laptops and tv when we are off shore power. Soon we'll be able to charge the new breed of laptops via USB C.

We do currently use shore power to heat our hot water. We'll be embedding a solar collector for hot water as part of our hard dodger upgrade.

We see lots of surprise from fellow liveaboards who have transposed a condo to their boat. We live in luxury. We certainly aren't camping.

We are slowing ditching anything onboard that is 110V. Good riddance to a lot of junk.

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Old 15-04-2015, 14:53   #13
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Re: inverters/ generators

Quote:
Originally Posted by HopCar View Post
Get the inverter. You'll have a much bigger choice of appliances in 110 volt that you will in 12 volt. My experience has been that 12 volt appliances are of lower quality than those made for home use.
This.
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Old 16-04-2015, 06:38   #14
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Re: Inverters / Generators

Quote:
Originally Posted by ErikFinn View Post
What a great answer, thank you!

So I understand by running a pure-sine wave inverter on my 240V fridge my batteries would last longer before needing a recharge, and the inverter should give me more service years? (and with less heat and noise)

Another Q: I have a 1500W inverter, I presume its not the best choise for running a fridge? I recall the ideal inverter wattage should be something like 3 to 4 times the wattage of the appliance? This since the "starting wattage" is a multiplier of the nominal running wattage? Is this correct? I'm putting a lot of question marks here because I don't remember the facts and don't want anyone to think I do.

What would be the ideal size inverter for running a fridge something like this (specs on foto)?
(one I'm after uses less watts but I don't have a foto of that, so this is for illustration only, quite similar after all)
Cheers
Anyone?
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Old 16-04-2015, 07:21   #15
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Re: Inverters / Generators

Hi Erik,

My opinions on these questions.


Quote:
Originally Posted by ErikFinn View Post
So I understand by running a pure-sine wave inverter on my 240V fridge my batteries would last longer before needing a recharge, and the inverter should give me more service years? (and with less heat and noise)

In general yes, a pure sine wave inverter will be more efficient that is use less power from your batteries than a square wave but this is not always true. There are cheap sine wave inverters that are not very efficient. You really need to look at the specs and quality of each unit. If you plan to leave the inverter switched on most of the time you should look at the idle power usage, how much power the inverter uses when no loads are using power. Some inverters have a standby mode that uses less power but may have a short delay to start up when a load is attached.

Also, yes many appliances will run better, cooler on pure sine wave power.


Another Q: I have a 1500W inverter, I presume its not the best choise for running a fridge?

Would depend on the inverter and the fridge. Is this a sine wave or modified sine wave? If you are referring to the fridge for the label you posted then 1500 Watts is more than enough power. The label shows the fridge only draws 100-125 Watts.

I recall the ideal inverter wattage should be something like 3 to 4 times the wattage of the appliance? This since the "starting wattage" is a multiplier of the nominal running wattage? Is this correct?

True for certain things like motors and compressors (like in refrigerators or air conditioners). Other kinds of appliances may not draw more on startup. 3-4 times is about the maximum you would ever see. 2 times the running power is more likely for most modern appliances.

You should also check the inverter's ability to handle this. Many will manage a short, high startup load so might not need to buy one that is larger and more expensive just for this.

I'm putting a lot of question marks here because I don't remember the facts and don't want anyone to think I do.

What would be the ideal size inverter for running a fridge something like this (specs on foto)?

If you run nothing but the refrigerator on the inverter and I read this label correctly that it only draws 100-125 Watts then an inverter that will handle a short, startup load of 300-400 Watts and constant output of around 200 Watts should work.

(one I'm after uses less watts but I don't have a foto of that, so this is for illustration only, quite similar after all)
Cheers
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