# inverter dimwit



## 100397 (Aug 7, 2006)

could anybody explain to a complete dumbo what is an inverter, how does it work etc have read most of the tech stuff after searching on the forum, but still do not understand the basic s so could some nice person please explain it in very simple laymens terms


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## spykal (May 9, 2005)

Hi Peapod

An inverter is a device that turns Direct Current (DC) voltage into Alternating Current (AC) voltage (Household Electricity). Converting DC to AC will allow you to run lots of household appliances Televisions, Radios Computers etc. 

Direct Current electricity is the sort found in batteries, smaller inverters can be run from a vehicle cigarette lighter socket or the 12v outlet in the habitation area, large (more powerful) inverters must be connected directly to the battery by short and heavy cabling. 

The right size of inverter depends on the power requirements of the equipment you expect to use on it. 

There are two main types of invertor, sine-wave and modified sine-wave. The AC electricity produced by a sine wave invertor is closer to a normal household mains supply than a modified sine-wave inverter. But a modified sine-wave inverter will operate most computers and TVs and small battery chargers ( camera, PDA etc). But dont charge your electric toothbrush with one.... and don't ask why :roll: 


Anyway there you go ...thats a start ... any questions? :lol: :lol: 

mike


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## Minerva (May 22, 2006)

An inverter does exactly what it says on the cover

you connect to a battery and it will give mains voltage out or vice-versa depending on the type of inverter.

i.e. you would reconize a phone charger plugged into the mains, that is a form of inverter.

For more detailed info you will have to keep reading what you can on the subject, try 'How things work' on the net, usually OK for talking in laymans terms.

good luck

Bil


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## 100397 (Aug 7, 2006)

*re dimwit*

Cheers Mike,
At last i understand, put brilliantly, i knew you could run tvs etc. but couldnt get my head round exactly how it worked.So now i have undestood how do you gauge what size inverter you would need? I understand the hair dryer and electric toothbrush are a nono are there any other appliances that should also not be used


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## trevorf (May 16, 2005)

Hi Peapod

Just look at the power rating in Watts of the item you want to run then add a bit for safety Ie for a 250W TV buy a 300W invertor. For a 1600W item go for a 2000W invertor but be aware this will run down your battery quickly !

Trevor


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## spykal (May 9, 2005)

*Re: re dimwit*



peapod said:


> how do you gauge what size inverter you would need?


Ah.... I knew I should not have said any questions :lol:

In most instances you can find the power requirements printed on the information label on the appliance...all should have one. But this information may not be in a form you need... most invertors are rated in watts output but many appliances are rated in amps. To find out how many amps = how many watts use this simple equation:

Watts = Amps x Volts

As long as you know two of the figures you can find the missing one. bear in mind that your calculation must use the correct voltage. ( the voltage of the appliance 230/240 not the battery voltage)

so a calculation for my laptop ... taking the figures off the back of the adaptor would look like this :-

Watts ? = 1.2amps( max) x 240 volts

288 watts

So a 300 watt invertor would be fine ( and is)

mike


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## DABurleigh (May 9, 2005)

At full whack a modern inverter would be 90% efficient, so I reckon you're lucky, Mike, probably as a result of tolerances.



Dave


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## spykal (May 9, 2005)

Hi dave

I knew we would not be able to keep it simple :lol: do not forget I was using my laptop adaptor only as an example.. there are lots of varyances ... the mains voltage is prob nearer 230 than 240 and the marked up consumton of the adaptor is way over the top of the actual usage... in fact when my invertor is powering my laptop I am guessing that it is only using about half of the figure I calculated. The cooling fan just starts to run so maybe 150 watts is being used ... in fact who cares it works that is all that matters. :lol: 

I hope peapod that you are now in a position to go out and buy an invertor... an essential for the modern motohomer :lol: 

mike


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## 100397 (Aug 7, 2006)

thanks all of you , am definetly learning, the electrics bit always find tricky anyway if i get stuck i know where to come


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## Tucano (Jun 9, 2006)

Spykal,
Reading your answers to peapod and then looking at my laptop has just got me baffled so could you please help me out.
We are picking up our new van next Friday and I would like whatever accessories we need built in from the start.

So, what size inverter will I need when the info on the adapter for my laptop reads Output 19v 6300mA The info on the back of the TV says 12v 2.7a 33w and the TV adapter reads Output 12v 4.5mA , input 240 v 65W.
With the 12v outlets in the habitation area I had assumed that I could simply plug the TV, a Sharp Aquos LCD in without using the adapter it came with, however I have read on this forum that it is unwise to do that.

I think that we need a small inverter of the type that fits into cigarette lighter sockets but that is a long way from the rear of the van where the TV will be sited. 
Do we need a professionally installed inverter, neater but expensive, or do we trail wires from the lighter socket and save money.
I hope this makes some sort of sense to you, it hurts my brain just reading it  

Norman


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## DABurleigh (May 9, 2005)

Norman,

Excellent choice of TV; you won't be disappointed (though you probably would if you powered it direct from 12V ....)

You need a £20 150W fanless modified sine-wave inverter.

If you mount it near the appliances, you need to take care your 12V wiring is thick enough. If you mount it near the leisure batteries, you needn't bother about cable thickness. Your call 

Dave


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## Arizona (May 9, 2005)

Alleluhia, well done spykal! I have always been confused on this issue. Thank you for that wonderfully simple explanation. 

regards

Arizona


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## JohnDough (Mar 3, 2006)

Please also be aware guyz that a inverter left connected to you leisure battery will run it down even if it is switched off !!!,so make sure you have a isolater switch in the line.


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## 101465 (Oct 19, 2006)

spykal said:


> Hi dave
> 
> I knew we would not be able to keep it simple :lol: do not forget I was using my laptop adaptor only as an example.. there are lots of varyances ... the mains voltage is prob nearer 230 than 240 and the marked up consumton of the adaptor is way over the top of the actual usage... in fact when my invertor is powering my laptop I am guessing that it is only using about half of the figure I calculated. The cooling fan just starts to run so maybe 150 watts is being used ... in fact who cares it works that is all that matters. :lol:
> 
> ...


Hi Mike
Hope you don't mind me resurecting this thread but you obviously know your stuff re inverters.
My question is, I have just bought a 600w inverter and the instructions say to fix the negative cable to the vehicle chassis, as it came with croc clips I imagined I would simply fix to neg & poss posts on the battery, would this be ok? or does it really need to be fixed to the chassis?

Cheers Tony


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## shortcircuit (Mar 19, 2006)

It does not need to be fixed to chassis.

Connect direct to battery and keep these leads as short as possible.

Remeber you now have 230 volts out which could kill


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## spykal (May 9, 2005)

Hi Tony

The question you have asked is one that causes many discussions ( or even arguments :roll: ) so what I say may well be disputed.

If you are going to use the invertor as a free standing power unit, not feeding the 240v system in the van.... ie.. connected to a battery and then plugging whatever portable appliance into the socket on the invertor then this is how I use my invertor and I consider myself to be safe when using it like this without any further earth bonding.

If you do a search of the forums using "invertor" and "earth" as the search words you will find several other threads discussing the implications.

Mike


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## shortcircuit (Mar 19, 2006)

Just had my mind jogged by previous posting.

Positive and negative to battery. Earth to chassis? Will stay out of discussion other than to say I do not connect.


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## spykal (May 9, 2005)

shortcircuit said:


> Just had my mind jogged by previous posting.
> 
> Positive and negative to battery. Earth to chassis? Will stay out of discussion other than to say I do not connect.


Don't over worry .... this is very confusing isn't it... and AFAIK if you do a check on an invertor you will find that

_**The wing nut chassis ground on rear of invertor is in direct connection with the following

1. on the 13 Amp plug side the neutral pin 
2. on the 13 Amp plug side the Earth pin 
3. On the 12 Volt DC side the negative pin (black connector) 
4. The case of the Invertor_

Mike

** source an old thread :lol:


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## clodhopper2006 (Aug 13, 2006)

So why not an electric toothbrush?


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## blackbirdbiker (Mar 12, 2007)

Oh please don't forget 230 volts is only the average voltage RMS, route mean square, so peak voltage is 320 times .707.........

?????????? :lol:


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## sallytrafic (Jan 17, 2006)

Its to do with the waveform. A pure sinewave from the mains is just that 50Hz (cycles per second).

The waveform of a quasi looks like this attachment and comprises lots of harmonics. Harmonics are for example twice and and three times the frequency ie 100Hz and 150Hz. Electric toothbrushes have no physical (or galvanic connection) to the supply but use a transformer coupling unfortunately if you operate a transformer at a higher frequency than it was designed for it becomes inefficient and overheats.

Regards Frank


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## 101465 (Oct 19, 2006)

Thanks to all who answered my question, its getting clearer now, What I intend to do now seeing as the batteries are difficult to access, ie under both seats, is to fit a 13 amp socket box behind the seat wired to the battery with a 13amp plug on the inverter input wires. would this be ok?
Thanks, Tony


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## 96088 (Aug 22, 2005)

Personaly I would fix the inverter behind the seat and wire it directly to the battery with a large fuse (rated significantly higher than 13 amps) in between. 

I suspect further teckie input from those that really understand is required here :?


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## DABurleigh (May 9, 2005)

"Thanks to all who answered my question, its getting clearer now, What I intend to do now seeing as the batteries are difficult to access, ie under both seats, is to fit a 13 amp socket box behind the seat wired to the battery with a 13amp plug on the inverter input wires. would this be ok? 
Thanks, Tony"

Sorry, Tony, I don't understand this at all. A 13amp socket and plug are 240V mains connectors, but you are placing these BETWEEN the batteries and inverter?

Dave


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## 96088 (Aug 22, 2005)

Tony

This seems like a recipe for fried wiring and socket :firestarter: 

I'm no electrical expert but I know how to bump a thread in the hope that somebody will talk you out of your plan


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## sallytrafic (Jan 17, 2006)

Tony (and others)

As I have said many times on this forum your battery is the most dangerous thing on a motorhome (after the driver) if you are not electrically competent leave well alone.


REgards Frank


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## 101465 (Oct 19, 2006)

sallytrafic said:


> Tony (and others)
> 
> As I have said many times on this forum your battery is the most dangerous thing on a motorhome (after the driver) if you are not electrically competent leave well alone.
> 
> REgards Frank


"oops" think I got something wrong, probably didn't express myself very well, but anyhow decided to wait and catch someone who is competent before I go ahead with this little project. Meanwhile, how is one supposed to connect to the battery? surely those silly little crocodile clips are not a very good method.

Thanks to Frank, Dave, oldscool and others who helped.

Tony


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## 101411 (Oct 15, 2006)

Hi Tony.

Its really very simple. You don't need to know how or why it works all you need to know is how to fit the thing in your m/h. All this talk about modified sine wave is very confusing. This is how you do it.

1 Locate batteries in m/h

2 Decide on position of invertor. If you want a "proper" socket (ie a socket fixed to the wall and not plugged directly into the invertor) buy a surface mounted box and a socket front. Screw the box to the position you want and attach a piece of flex with 2.5mm cable to the socket then attach a normal 3 pin plug onto the end of it. This plug then plugs into the invertor so make sure the cable is long enough and clipped safely out of the way.

3 Attach invertor to battery terminals. Do NOT extend the wires and cut off the silly croc clips and attach to battery using crimp on connectors. If you want to be really safe fit an in line fuse between the invertor and the battery. An isolation switch (on/off switch) in line with the battery and inverter is also a good idea to prevent drain on the battery when invertor is not in use.

4 Plug in appliance or plug leading to alternative socket and make sure everything works ok.

5 If your leisure batteries are fitted inside your m/h (you mentioned under seats) make sure they are properly vented to the outside or your m/h. This has nothing to do with the invertor but could prevent your m/h (and you) from been blown up by the build up of hydrogen gas under the seat. THIS IS VERY IMPORTANT!!!!!!!!

its as simple as that just don't get bogged down with all the techno stuff. The only thing that matters is that its safe!!

Dazzer


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## 101465 (Oct 19, 2006)

Dazzer said:


> Hi Tony.
> 
> 3 Attach invertor to battery terminals. Do NOT extend the wires and cut off the silly croc clips and attach to battery using crimp on connectors. If you want to be really safe fit an in line fuse between the invertor and the battery. An isolation switch (on/off switch) in line with the battery and inverter is also a good idea to prevent drain on the battery when invertor is not in use.
> 
> Dazzer


Thanks Dazzler,
This is more or less what I meant to do, except I was going to use a domestic type, fused, switched double pole socket, so I could plug the inverter in to that, keeping the wiring short, and easy to isolate by either pulling the plug or switching it off, I made the mistake of calling the socket a 13amp socket which sort of made me look an idiot, anyway before I do anything I will get a good electrician to have a look and advise or do it for me. Don't want Frank to have a heart attack, LOL.

Thanks again to all who advised me.

Tony


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