Pure Sine-wave Inverter at an affordable price : Does it exist?

[Michael GilliganParticipant @michaelgilligan61133]

One of my occasional dips into ebay is the search for a decent inverter to produce ‘Mains’ from the car battery.

Frustrations like this one are the common result:

https://www.ebay.co.uk/itm/365015987015

 

Pure Sine-wave in the headline … Modified Sine-wave in the description

 

Any suggestions ?

MichaelG.

[not done it yetParticipant @notdoneityet]

Victron

[Michael GilliganParticipant @michaelgilligan61133]

Thanks … I will have a look:

https://www.victronenergy.com/inverters

Although I am only presently wanting something to run off “the car battery”

MichaelG.

.

Edit: __ I may be mistaken, but this appears to be the smallest they do

https://www.victronenergy.com/upload/documents/Manual-Inverter-VE.Direct-250VA-1200VA-EN-NL-FR-DE-ES-IT-.pdf

[John HinkleyParticipant @johnhinkley26699]

Michael,

How about an inverter such as those used by narrowboat owners? They seem to be able to run most appliances from them – OK, maybe not an oven, but I suppose it depends what you want to run off it.

John

– I’m back after a swift Google for marine inverters.  Pure sine wave ones are very expensive.  The first one that I found (admittedly on marine chandler’s site), was a shade over £720! That gives an output up to 2000W continuously and 4000W peak that was advertised as suitable yo power a laptop or LCD tv, etc.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the sanity-check, John

… It seems you are hitting the same problem as me, in that [despite some of the headline descriptions] anything low-ish power and modestly priced will produce a ‘Modified Sine-wave’ but nobody seems keen to display waveforms !

MichaelG.

 

[John HaineParticipant @johnhaine32865]

A pure sine wave inverter will intrinsically be hard to make with high efficiency.  Think of it like an audio amplifier with high voltage output but low distortion.  If you made it class B its maximum efficiency would only be 78.5%, and either it would need a high supply voltage or a beefy output step-up transformer.  A practical inverter will have to be switched-mode and probably have quite a complex output filter.  Look at prices for high power low distortion high efficiency amplifiers.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, John

… been there, done that [over the years]
Trouble is, having used multi-step synthesised sine-waves decades ago, I keep hoping that mass-market electronics would have developed more than it seems to have … and, of course, I keep hoping that advertisers will not simply tell lies.

A ‘modified sine-wave’ with 256 steps would probably be acceptable, one with 4 would not.

But to claim ‘pure’ and then admit ‘modified’ with no further explanation gets on my wick !

MichaelG.

[peak4Participant @peak4]

The one Michael linked to is 500W12v input, so I has a look around very briefly from non-eBay sources
This one from a solar supplier claims pure sine wave; the spec sheet says 3%THD, (total Harmonic Distortion) though it doesn’t show a scope trace.
I would hope they know and can supply their market.
https://www.sunshinesolar.co.uk/Item/C60012
The other alternative might be a more mainstream supplier, such as RS, who offer both modified and “pure” sine wave converters, though disappointingly this one doesn’t give a trace example or a THD on the separate spec sheet pdf.
https://uk.rs-online.com/web/p/power-inverters/1793327?gb=s

Interesting debate here on whether the jagged sine wave is the inverter or the cheap scope.

https://www.motorhomefun.co.uk/forum/threads/checking-my-inverter-with-an-oscilloscope.232808/

Bill

 

 

[peak4Participant @peak4]

I pressed submit by accident before adding this one.
It again uses a cheap sine inverter, and a budget digital scope, which needed a step down transformer to lower the input voltage; I’m not sure how much smoothing that might add.
I only have conventional analogue scopes myself, so wouldn’t be able to compare.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

These do look promising, Bill

https://www.sunshinesolar.co.uk/Category/PureSineWave12V

although the Sale prices were only quoted to 04-Sep 🙁

It reminds me though … I should ask my brother what’s fitted in his newly-built CamperVan.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

These do look promising, Bill

https://www.sunshinesolar.co.uk/Category/PureSineWave12V

although the Sale prices were only quoted to 04-Sep 🙁

It reminds me though … I should ask my brother what’s fitted in his newly-built CamperVan.

MichaelG.

I’ve just added one to my shopping cart, which features a quick Paypal checkout, and it still lists at the supposed sale price.
Not tried completing though (yet 😉).
https://www.sunshinesolar.co.uk/Item/C60012   £99
They also do this one, which is slightly dearer; I can’t quite get my head around the differences, though the cheaper “C” series one claims CE marking, but is slightly less efficient and a tad heavier.
https://www.sunshinesolar.co.uk/Item/VPS600  £110.49

I did see this query, which doesn’t say a lot, but it looks like the cheaper one has some sort of clip for the power input, and the dearer one has terminal posts.

https://diysolarforum.com/threads/sunshine-inverter-c-series-what-is-the-difference.39767/

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Not sure, Bill, but comparing the spec-sheets, I think the  C might stand for fan-Cooled.

Also interesting to see that the smaller 300w model comes with a cigar-lighter lead

[must check some fuse ratings]

MichaelG.

.

Edit:__ I also note that they sell Victron products, as recommended by ndiy

https://www.sunshinesolar.co.uk/media/ecom/prodpdf/Datasheet-Phoenix-Inverter-VE.Direct-250VA-1200VA-EN.pdf

[peak4]

On peak4 Said:

I pressed submit by accident before adding this one.
It again uses a cheap sine inverter, and a budget digital scope, which needed a step down transformer to lower the input voltage; I’m not sure how much smoothing that might add.
I only have conventional analogue scopes myself, so wouldn’t be able to compare.

Bill

Sorry, Bill … can’t see the embedded video … could you post the link, please

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

On peak4 Said:

I pressed submit by accident before adding this one.
It again uses a cheap sine inverter, and a budget digital scope, which needed a step down transformer to lower the input voltage; I’m not sure how much smoothing that might add.
I only have conventional analogue scopes myself, so wouldn’t be able to compare.

Bill

Sorry, Bill … can’t see the embedded video … could you post the link, please

MichaelG.

That’s interesting, neither can I, it seems the post has been deleted.
I didn’t check the source of the inverter the guy was testing, so maybe it came from AliExpress or somewhere, but the reason I posted it at all, had nothing to do with a suggestion to buy the inverter itself, but was to show the form of the display on a cheap digital scope.
As an aside, I’ve just been up to the bedroom workshop to check the waveform output of a little inverter I carry in the car; I couldn’t see that either as my Phillips analogue CRT scope’s died. 😪

Bill

[Michael GilliganParticipant @michaelgilligan61133]

A bit of hopefully-useful reading, courtesy of my brother:

https://www.campingandcaravanningclub.co.uk/advice/equipment/guide-inverters/?gad_source=1&gclid=Cj0KCQjw8–2BhCHARIsAF_w1gzxplgZlgpDHVu1yce-A-u5q03ayIPJ1aRGOvFm3uNID8OW1ujWZiIaAvfJEALw_wcB

MichaelG.

[peak4]

On peak4 Said:

…
It again uses a cheap sine inverter, and a budget digital scope, which needed a step down transformer to lower the input voltage; I’m not sure how much smoothing that might add.
…

Bill

The transformer is likely to make the waveform look much smoother because sharp switching transients are choked by the core, whilst energy stored in it’s windings tend to smooth out the bumps.   Loading the transformer reduces the energy available for smoothing, so the waveform at full power as viewed by the scope might be jagged again.   Also have to be careful about digital scopes introducing display artifacts:  more expensive scopes reduce the problem by sampling faster.

Fitting a tuned filter is the obvious way of making sure the output is a pure sine-wave, or at least close enough for all practical purposes.  Problem is filters at 50 or 60Hz need a hefty inductor – lots of copper and steel – and likely to be as expensive as the total cost of all the other components.  Good filters are more expensive than simple ones.

An alternative is to convert to AC electronically and amplify the signal, which can be near perfect.  Efficiency is low though: bad news on a battery powered system, and the converter comes with a hefty heat-sink.

Worst of all is a dynamotor – these are expensive, poorly regulated, heavy, inefficient, hot, and noisy!

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Suzuki … reasonably explicit

120w from any one socket, or all three combined

MichaelG.

.

[Michael GilliganParticipant @michaelgilligan61133]

For background educational purposes:

https://youtu.be/Dn2PFebi2ww?feature=shared

 

MichaelG.

[Andy_GParticipant @andy_g]

I second Victron.

The 12/240 is the smallest one they do (240 VA for £83):

https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-250w-vedirect-enabled.html

We have the 12/375 in the camper van for laptop charging, etc. (375 VA for £107)

https://www.12voltplanet.co.uk/victron-phoenix-pure-sine-wave-inverter-12v-375w.html

It is incredibly well made and surprisingly heavy (I think it has a real transformer inside). There is absolutely no trace of radio interference or electrical noise.

The very first time that you connect it to a battery there is a large current surge, but it can be left connected to 12V and switched on and off using a low current ‘remote’ switch.

I could probably get a scope trace if you were interested.

[not done it yetParticipant @notdoneityet]

Andy,

You have a PM.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for that, Andy … a ‘scope trace from an actual product of interest [rather than some random YouTube offering] would be very helpful indeed.

MichaelG.

[Mark EasingwoodParticipant @markeasingwood33578]

It shows up for me.

(Firefox/Win 10/logged in)

[Michael GilliganParticipant @michaelgilligan61133]

It’s a forum Bug that I reported months ago, Mark

… but I’ve promised Jason that I won’t go-on about it.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

Thanks for that, Andy … a ‘scope trace from an actual product of interest [rather than some random YouTube offering] would be very helpful indeed.

MichaelG.

Didn’t get a chance today, sorry (and it was pee-ing down), but hopefully tomorrow.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Andy … much appreciated

MichaelG.

[Author]

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