Explain in layman’s terms (1 Viewer)

Jun 8, 2019
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What is the difference between a inverter, a pure sine wave inverter, modified inverter.
And what is each used for. Is it worth buying one with lots of spare capacity looking to the future? Remember I am a dummy when it comes to electrics. I have read Reno on the net it makes no sense to me at all.
 
Jul 12, 2013
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I have been told by an electrician that both can almost do the same job. What I learnt that a modified Inverter cannot do, is charge my toothbrush. It broke it.
Most mechanical things work with either. The price difference can be quite large, the Pure sine wave being more expensive.
I use my Modified Inverter to charge my electric bikes and to charge phones etc.

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pappajohn

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Mains power is always pure sinewave.
It formed in an oscillating wave.... 120v above and below a zero point
A modified wave is more stepped as it oscillates
A square wave is..... Well, square.
A pure wave will cope with anything which runs on mains.
A modified will be OK on some electronics but not all.... And most other plain electrical.....kettle etc
A square wave will be fine for electric fires, kettles etc...... Basically anything which produces heat.
The larger the inverters output the more battery capacity you'll need as you plug more power hungry devices in.
 
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OP
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Vipar
Jun 8, 2019
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Have you a link? I have found plenaty of American chaps but no english
 
Oct 2, 2008
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an inverter can be pure or modified , the designation describes the profile of the power output . Some electrical items don't work with other than the pure wave variety . Due to efficiency loss the output should not be excessively more than the required load , but this may be acceptable if you have battery capacity and intend future expansion of usage .

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OP
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To be honest my inverter packed up. But I don’t know what purpose it had/does in the van the wires vanish into the walls never to be seen again ☹️
 

pappajohn

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This shows the shape of the 3 wave forms.
Red is pure... The best all round.
Blue is modified wave form.... OK for some things.
Green is square wave form.... OK for things producing heat.

Pure-Sine-wave-Inverter-With-Code3.jpg
 

DBK

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An inverter is used to turn the 12 volt DC electricity from the batteries to a 240 volt AC electrical supply. 240 volt AC is what you have coming from the sockets in your house so in theory you can run these mains voltage devices in the MH.

But there are a few limitations. The cheaper inverters produce what I'll call a very rough alternating voltage which changes polarity very abruptly. The "pure sine" inverters produce a much smoother supply which more closely resembles what you get from the sockets at home.

The problem with the rough voltage from the cheaper inverters is it isn't a smooth curve but is only a crude approximation of a sine wave. They call it a "modified sine wave" but it is much closer to a square wave than a pure sine wave. This is where the limitations begin because a square wave carries other high frequency harmonics within it which devices with electronics can take exception too.

At a practical level if you intend to only run hair driers or electric kettles a modified sine wave inverter will be fine. Beyond that it becomes a game of chance if you stick with one of these and want to plug in coffee pod machines, electric tooth brush chargers and perhaps expensive ebike chargers. For these I would go with a pure sine wave inverter.

The sizing depends purely on your expected load but I would go for caution and over-spec if you can. :)

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Campervan_man

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Jun 24, 2019
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A 12V inverter converts 12V from a leisure battery to 240V for a limited amount of time.
A 12V battery is connected to an inverter using appropriate sized cables to the inverter.
12V feed IN, 240V supply OUT.
A single average leisure battery can usually supply power 1KW or so of 240V power.
2 linked leisure batteries can supply power to 2KW or so of 240V power etc
Modified Sine wave is a crude basic 'no frills' 240V electricity for basic appliances such as low wattage 240V kettles etc.
Pure sinewave inverters produce a smoother more refined 240V power suitable for
more delicate appliances with PCB boards like laptops etc
Some appliances require a LARGE surge of initial power { PEAK Power } also intermittently when running
eg air conditioning, electric drills, microwave ovens etc
This surge power needs to be considered when buying an inverter.
Normally an inverter makes a buzzing noise to alert the user when it struggles to
provide 240V power, eg, the 12V supply battery is starting to wane / fail / deplete.
Remember it is just a 12V battery supplying the power not a power station.
 
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ctc

Oct 12, 2015
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To be honest my inverter packed up. But I don’t know what purpose it had/does in the van the wires vanish into the walls never to be seen again ☹️
I think you will find that your inverter can supply you 240v sockets when not on ehu

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Sep 10, 2012
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I understand these distinctions but assuming I fit a pure sine wave inverter does its capacity have any affect on battery consumption?
So to clarify does a 1 kilowatt one consume more battery than a 5 kilowatt one when sitting there actually doing nothing other than being switched on?
Similarly does a 1kw one running a 1kw device(100% of capacity) use more battery than the 5kw one running the same 1kw device (20%)?
Or to put it another way at what power useage band are inverters most efficient?

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Lenny HB

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I understand these distinctions but assuming I fit a pure sine wave inverter does its capacity have any affect on battery consumption?
So to clarify does a 1 kilowatt one consume more battery than a 5 kilowatt one when sitting there actually doing nothing other than being switched on?
Similarly does a 1kw one running a 1kw device(100% of capacity) use more battery than the 5kw one running the same 1kw device (20%)?
Or to put it another way at what power useage band are inverters most efficient?
Depends completely on the inverter, cheaper ones ofter draw more current in standby mode than good quality expensive ones. A cheap 1000 watt one can draw 2 amps in standby and a good quality 2000 watt one can draw well below one amp.
Shouldn't be much difference in the onload consumption apart from the efficiency of the inverter a good one will be 90% or better a poor one 85% or worse.
With inverters you get very much what you pay for a £150 will probably do the job a £400 one will do it properly.

If you are buying a new one Vic Vipar if you have and sensitive equipment to run buy a good quality Pure Sine wave one. The cheap Pure Sine Wave ones are not that pure, I know I have one it's OK for what I use it for but if I replaced it I would spend 3 times the amount on a decent one.
 
Mar 23, 2012
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sleights
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To be honest my inverter packed up. But I don’t know what purpose it had/does in the van the wires vanish into the walls never to be seen again ☹️
If you don't use your sockets when not on hookup and don't use anything wired in like a microwave etc you might well not need to replace it at all. If you do think what you use and post on here then people can advise.
When did it pack in if you can use your van fine don't bother.
 

Sundowners

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For me------ I would (do) buy a pure sine wave inverter with a very generous power margin on what I expect to run off it when the sun is shining and a reasonable battery bank-------- we watch battery voltage and decide what we can run---------- the system we have just fitted to our off grid cabin( too big for motorhomes) is set up to run air con during the summer---- obviously if the sun is not shining we only have a short time before we would have to switch off to protect the battery bank---------- the point is---- use what is available---- in a uk winter use gas kettle unless battery level is good------- in sunny summer use all your electric stuff!!!
Btw we try to keep as much gear as possible at or below 1kw, then if you use several things at the same time you inverter is not struggling!!!----- we have used 3kw inverters for several years, in the motorhome, a remote switch made it easy to switch on/off as required------ in our cabin it is on 24/7 as we now run a big 240v compressor fridge/freezer------ we are now into winter and battery voltage in the night is constantly above 12.8-- most nights 13+v
Dont be afraid to get a larger size inverter---- you are in control of what comes out of your batteries!!!
In my honest opinion you should stick to PSW. even though they are more expensive!!

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Apr 27, 2016
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I understand these distinctions but assuming I fit a pure sine wave inverter does its capacity have any affect on battery consumption?
So to clarify does a 1 kilowatt one consume more battery than a 5 kilowatt one when sitting there actually doing nothing other than being switched on?
Similarly does a 1kw one running a 1kw device(100% of capacity) use more battery than the 5kw one running the same 1kw device (20%)?
Or to put it another way at what power useage band are inverters most efficient?
There's no easy answer. Manufacturers calculate the headline efficiency of the inverter when it is working at full power. For example a 1kW inverter that is 90% efficient will waste 100 watts when running at full power.

What they don't say is how much power is wasted running at only 10% power. The cheaper inverters will still be wasting that 100 watts, where the more expensive ones will waste a lot less.

The upshot of this is that it's best to use an inverter at near its full power if it's a long-running load. So for a compressor fridge that takes about 100W when it's running, use a dedicated low-power inverter, maybe a 200 to 300 watt model. If you want to run a microwave or hairdryer as well, get a second high-power inverter to run only when required.
 
OP
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Jun 8, 2019
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Thanks for all the replies and advice. At the moment as I said I don’t know what it being used for. I suspect that it powers an inboard cab battery charger. I can’t get out to use my multi meter to find out where the 240 v supply from the inverter goes to. I suffer from osteoarthritis and this cold weather kills me. Also can’t bend down to get under the van to check wires etc. I will have to leave it until the weather gets better. Or bite the bullet and take it to a dealer
 
Apr 27, 2016
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Thanks for all the replies and advice. At the moment as I said I don’t know what it being used for. I suspect that it powers an inboard cab battery charger. I can’t get out to use my multi meter to find out where the 240 v supply from the inverter goes to. I suffer from osteoarthritis and this cold weather kills me. Also can’t bend down to get under the van to check wires etc. I will have to leave it until the weather gets better. Or bite the bullet and take it to a dealer
Most inverters are installed so that appliances like a microwave and hairdryer can be used. Sometimes a motorhome has a 240V devices that require an inverter, for example an electric drop-down bed or an electric wind-out awning. You could easily check that by switching off the inverter and seeing if it still works.

If there's a cab battery charger, you could check that if you can see the battery voltage. Does the battery voltage rise, to over 13.0V, when the inverter is on, and does it fall to about 12.8V when the inverter is off?

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Mar 23, 2012
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Thanks for all the replies and advice. At the moment as I said I don’t know what it being used for. I suspect that it powers an inboard cab battery charger. I can’t get out to use my multi meter to find out where the 240 v supply from the inverter goes to. I suffer from osteoarthritis and this cold weather kills me. Also can’t bend down to get under the van to check wires etc. I will have to leave it until the weather gets better. Or bite the bullet and take it to a dealer
If it's only for a cab battery charger ditch it and fit a battery master.
 
Mar 23, 2012
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sleights
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Most inverters are installed so that appliances like a microwave and hairdryer can be used. Sometimes a motorhome has a 240V devices that require an inverter, for example an electric drop-down bed or an electric wind-out awning. You could easily check that by switching off the inverter and seeing if it still works.

If there's a cab battery charger, you could check that if you can see the battery voltage. Does the battery voltage rise, to over 13.0V, when the inverter is on, and does it fall to about 12.8V when the inverter is off?
I think his problem was the inverter doesn't work!!!. I would just try everything worked that I wanted and if there isn't one get a battery master.
 
OP
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Vipar
Jun 8, 2019
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Ok I have a BM but can’t fit it until the weather improves.

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