# Invertors?



## peterandirene (May 9, 2005)

Advice required please. We have a 15 inch LCD TV which is 240 volt. I want to be able to use this when not on hookup and also a portable computer, when I get round to buying one. What sort of invertor, think that’s right, should I buy?

Peter


----------



## DABurleigh (May 9, 2005)

A 150W fanless modified-sine wave inverter should do the job nicely.

Dave


----------



## captainking (Jun 16, 2005)

Hi peter we have just bought a 130w bog std maplin inverta also cheap plug in surge protector which can also be used with our genny......For my laptop I bought a computer laptop converta supply which plugs into the gigar socket and is switchable from 15v upwards DC and works fine our 17" rilyisis ldc tv will not work straight from our 12v socket but works fine useing the 12v to 240v inverta and supply adaptor which came with the tv allthough it go's from 240v back to 12v ( well it dose work but screen is a little dark) did your tv come with power supply adaptor? if it did what dose it change down to? if you are thinking of running a few items of different current at 240v but not all at once then you could buy say a 1000w one then you could use a hairdryer or toaster and several other items that are limited to max 800w but dont forget the more power you run from 12v will have to come from somewhere so make sure your battries are upto it

Regards

Captainking


----------



## peterandirene (May 9, 2005)

Thanks for the prompt replies. The tv adaptor actually converts to 12v but as I understand it I can't just make up a plug straight to the 12v supply as the battery doesn't actually give 12v? The leisure battery is 110amp so I assume I should be able to watch tv without hookup on occasional nights. Generally we use hookups but I am thinking ahead to a time when perhaps none is available at a site. I will look at the Maplin invertor later tonight.

Peter


----------



## ActiveCampers (Jun 17, 2005)

battery can give anything from 9 to 14v (ish).

You just need a DC voltage regulator which takes any old voltage (within reason) and gives you a nice even output. You can then plug this direct to the TV (assuming TV input is 12v)

May not work for laptop.

150w inverter is currently £19.99 in maplin - bargain.


----------



## Paulway (May 9, 2005)

Dave,
Just curious, why did you specifically say 'fanless' inverter. Is there a problem with fanned ones, made me panic as I just bought a 200w one with a fan!!


----------



## captainking (Jun 16, 2005)

If you have a new maplin store opening near you....they were selling as an opening offer 600w invertas for £ 19.99 YES £ 19.99

regards
Captainking


----------



## DABurleigh (May 9, 2005)

Paul,

Nothing deep involved. The heat dissipated by just a 150W invertor doesn't warrant a fan; for a 300W and above it almost certainly does. I had a 300W one but if I had my time again I would have bought a 150W simply because that was sufficient for my purposes at the time and silent, whereas the 300W one has that slight fan whine.

Now I have a Victron 1600VA sine-wave inverter charger integrated into the van, though a separate small 150W one services the TV, digibox and satellite dish controller.

Don't buy a bigger inverter than you need as you will pay for it in more energy wasted from your batteries.

Dave


----------



## Paulway (May 9, 2005)

Thanks Dave,

Thats put my mind at rest.


----------



## james (May 15, 2005)

> Don't buy a bigger inverter than you need as you will pay for it in more energy wasted from your batteries.


Dave,
Most of the inverters I have looked at quote efficiency as a percentage. Surely that percentage is of the wattage used not the maximum the inverter can handle? And since that percentage seems to be around 90 percent for both small and large, it follows that a large inverter used only lightly will only waste the same as a small inverter used heavily?
My 2500 watt inverter has fans that come on only when needed which is probably the best solution as far as noise is concerned.
James


----------



## 88724 (May 9, 2005)

Hi James

Yes you are correct, on the invertors I have tested running 150w at full tilt is less efficient than running 300w invertor at 150w

I have also found the quiescent current is generally more efficient on larger invertor's too.

Both of the above not withstanding the fan cutting in.


----------



## DABurleigh (May 9, 2005)

James,

Where inverter technical specs are given efficiency is invariably quoted "at rated output". This is for a reason. If it were no worse at lower loads, would they do this?!

Some good information is at:
http://www.victronenergy.com/Techni...ting operating temperature and efficiency.pdf
See page 4. 
The efficiency here drops off at lower loads, though much less than cheaper inverters; read the text to gain an impression of what's involved.

As to the quiescent current, this is literally "no load", not "low load", and, yes, can be very low indeed on the more expensive inverters where the cost of a few more components is not an issue. On cheaper ones, just switch them off or disconnect them when not in use.

I maintain my general advice on not buying a bigger inverter than you need, on both cost and efficiency grounds. Yes, you need to switch them off or disconnect them when not in use.

Dave


----------



## Bazbro (May 9, 2005)

So, what do I do... what do I do...? 150w - no fan- poor efficiency; 300w - noisy fan - good efficiency; 2kw - auto fan - more than I need? 

And I still don't need one...yet - but I will, to run a LCD tv, computer, hair dryer, vacuum (all 'on the list' but not organised yet!)

Now you know why I haven't bought one yet! Why does 'making decisions' always get in the way of enjoying things? 

The penalty for enjoying 'toys', I suppose!


----------



## Bazbro (May 9, 2005)

For 20 quid I'm seriously tempted to just get that Maplin offer of a 300w 'soft-start', here http://tinyurl.com/ctyuk

Any comments, please, before I 'waste' my 20 quid?


----------



## DABurleigh (May 9, 2005)

Barry,

If a slight fan noise isn't a potential issue, go for it.

A 150W or cheap/value 300W will do nicely for all your applications except hair dryer and vacuum.

Dave


----------



## Bazbro (May 9, 2005)

Thanks for prompt reply, Dave.

I'm doing it... now! The time for prevarication is OVER!!!  

Cheers.


----------



## 89008 (May 11, 2005)

BarryandSue said:


> For 20 quid I'm seriously tempted to just get that Maplin offer of a 300w 'soft-start', here http://tinyurl.com/ctyuk
> 
> Any comments, please, before I 'waste' my 20 quid?


Thanks for pointing this price out.

At £22.49 Post paid and new with warranty, It looks like just the thing to keep the Laptop/tv charged. (It saves running the genny) :roll:


----------



## Bazbro (May 9, 2005)

Not sure if it'll run a laptop properly, Colpops. The guys here will put us straight about this, though.


----------



## 88724 (May 9, 2005)

Hi Dave

Re getting a larger invertor than you need, How can you say that about efficiency and then post a link which shows that you are mistaken?

I have actually measured the efficiency, by taking a reading at the output socket and measuring input ampage on a rangw of invertors and several different makes

what I found over a range of invertors was that the highest efficiency came at around 50% of rated output, its was no use doing a grid though, becase the only invertors with an honest/accurate rating were the 2 sterlings all the others are not continously rated at 40 degree's.

Dave your Victron link proves the case admirably see section 5 the highest efficeincy of the 2500 is at 1000w which is 95% eff ., hah but thats not 50% of rating I hear you say, but look at section one it shows the temperature compensation chart, at 40 Degree's the invertor is only rated at 80% of the Advertised wattage rating 80% OF 2500 is.......

2000 watts half of 2000 watts is 1000watts and that is were the Highest efficiency is recorded.

I maintain that getting an invertor over twice the size thats needed is by far the most efficient in terms of battery usage

follow this through if you wanted to run 150W at the most eff you can then a 300 w Sterling is the way to go, for victron to get the same eff is slightly more complex you have to find the Victrons TRUE rating that means dividing the advertised rate by 80 then times that by 100 so for victron you would need to get a 375 watt.

The maplins invertor 300w for 19.99 is very good value, btw these are temp controlled fans and if the unit is run at 50% ish in normal temps the fan never comes on so maintaing the efficiency.

off to buy another Maplins invertor myself now at that price.......


----------



## 88724 (May 9, 2005)

Hi 

re running laptops

Yep I run a cheapo Maplins in my car to run laptop and the GPS Navigator 4 Software.

No probs at all, thats why I am off to but the 300w when running thye laptop it will be at under half the rating and therefore most eff also t will kee the fan use to minimum or no existant, result.....


----------



## Bazbro (May 9, 2005)

Thanks, George.

That's put our minds at rest, Colpops!

What a good buy these are. The 150w is advertised at £29.99???????


----------



## 89008 (May 11, 2005)

BarryandSue said:


> Not sure if it'll run a laptop properly, Colpops. The guys here will put us straight about this, though.


I'll soon find out - quoted delivery is a few days - and with 548 in stock.

I don't think theres a problem. The laptop needs 19 volts and its ac adapter is rated at 6.3 amps ( 120 watts )
The inverter is rated at 300 watts. So it will be running well within its capability, The ac adapter will also protect the laptop from any nasties in the 'sine' wave,
I think i'll use a surge protector as well.

At that price its tempting to buy a load of them and resell on ebay 8O


----------



## spykal (May 9, 2005)

Hi barry and all

I bought the 300w one last year for £19.99, as in the ad at the moment , I have run the laptop, the TV and various chargers from it with no problem. It is in use now as the power unit for my "onboard printer" , a Canon Pixma iP1000 bubble jet ( on offer £30 with ink at Amazon) that I use to print out OS maps from the laptop while away. Powering low consumption items like the printer the cooling fan never comes on so i guess it only runs when the load demands it.
I reccommend it
Mike


----------



## Bazbro (May 9, 2005)

Thanks for that, Mike. How do they do it for the money????


----------



## DABurleigh (May 9, 2005)

> I maintain that getting an invertor over twice the size thats needed is by far the most efficient in terms of battery usage


George,

The difference between what we are saying is due to me looking at the % efficiency versus % load curve overall, rather than the smaller microstructure in the not-perfectly-monotonic curve that you are pointing out in the Victron data and in your measurements of particular units. Another example curve is:
http://www.wattsonschools.com/inverter_specifications.htm

So, your statement I quote above can indeed be true in many cases for "twice the size", but not "over twice the size" in the sense of, say, 5 to 10 times. Thus if someone has a need for an inverter for the vast majority of typical MH applications, some very low wattage, from mobile phone charging, camera charging, other consumer electronics/ torch battery charging, up to TV, say, but considers s/he might want to run a vacuum cleaner or hairdryer in future, I would say stick with a 150W or 300 W inverter rather than 600W to 1.5kW.

That is all that I am saying, nothing more.

Similar sentiments are in:
http://www.mrsharkey.com/busbarn/electrics/chapt6.htm
"Specifying wattage can be a bit tricky. Buying the largest inverter you can afford might seem the best track, but remember that a large inverter running only a small load will consume a disproportionate amount of power from the batteries due to poor efficiency at low output. The same inverter may have better efficiency when operated between 25 and 75% of it's rated output."

Temperature ratings should also be considered, as we have discussed before, because many manufactures - not Sterling, OK  - quote outputs at relatively low temperatures. In this context, getting an inverter twice the size can be very wise in any case, given the temperatures inside a motorhome can reach 40deg when shut up in the sun. But hopefully someone wouldn't want to be watching TV like that .....

As to quiescent currents, a good explanation of the issues is here:
http://www.memory-map.co.uk/popups/learn_more_about_inverters_popup.htm
"When running low power equipment for long periods, ....., it is vital to have an inverter with low 'quiescent' current (the actual current the inverter takes to run itself when in operation). This quiescent current can vary dramatically from 0.7 amps for switch mode inverters, 2 -5 amps for transformer inverters and 25 amps for rotary converters. Inverters that have a high quiescent current are usually fitted with a 'power saver' circuit to switch the inverter off when not required, switching on only when a load is detected. Beware of inverters with this type of circuit as this circuit is designed to mask the high quiescent current of the inverter when on line. It is very important to distinguish between the off load current of a inverter (with a power save circuit) and the actual quiescent current of the inverter when in actual use. This information is not readily available from most companies. "

Auto-switching fans are OK, unless the load is such they cycle on and off due to close thermostatic limits, when they are damned annoying. If 150W is sufficient, therefore, get one guaranteed to be silent.

Dave


----------



## 88724 (May 9, 2005)

Hi Dave

I only advocate twice the size (with manufacturers not using the correct figures its as to be slightly over twice the size) and thats for semi continous loads like TV's etc.

For short use high output items like running Microwave or hairdryer a larger seperate invertor is called for, and this would be scaled to suit ie if you need 2000 w thats what you would buy, because its short usage long term efficiency is not important

On my bus I have a 1800w invertor which due to fridge would be in constant use, so that being the case its worth running tv and everything from it because the losses are constant and already factored in. I may follow up another chaps idea to have the fridge switch the invertor as a later project. which would save some energy over the week.

Re the temperature thing, many invertors are hidden away in cupboards this enclosed space can soon raise the temperature due to the invertors own heat production, your van may be at 20 degree's but measure in the little cupboard where the invertor is......

Quiescent current all the ones I have checked so far are less than .7 even the cheapo maplins.

MrSharkey agrees with me that they are more efficient when not at full tilt, smack in the middle of 25 and 75% is........

And 50% of real rating seems to be the sweet spot on virtually every switch mode invertor


----------



## 88724 (May 9, 2005)

Hi Dave

BTW I do see where you are coming from, the only reason I say over twice the size at all is because all manufacturers (except Sterling) "massage" their ratings. If all were rated accurately like Sterling you could say Buy an invertor exactly twice the size of your most constant load for the best efficiency. For all other manufcturers it needs to be about 220% bigger, but even that doesnt work because they all have different ways of massaging their Advertised or Headline rate, Victron for Example quote the VA or power factor corrected figure which is higher than the real wattage, quite how this helps them to sell the invertors, I dont know in many cases people end up with less invertor than they need.

I have got to say I wished they all quoted the same figures would make explaining far easier and would Negate the need to mention Sterling so much, I would stillreccomend them but the explainations would not belittered with references as they have to be now.


----------



## badger (May 9, 2005)

Hi Perterandirene

............I bet you wished you hadn't asked now!!!!.............


----------



## DABurleigh (May 9, 2005)

I thought my original 11 word answer was commendably accurate and brief .....

Dave


----------



## 88724 (May 9, 2005)

Hi Dave

Quote
I thought my original 11 word answer was commendably accurate and brief ..... 
Endquote

So did I and as such it needed no correction or amendment.

But later on in the thread

1. James asked a question

2. I answered that question

3. You disagreed with me and posted the following inaccurate/misleading statement's

"Where inverter technical specs are given efficiency is invariably quoted "at rated output". This is for a reason. If it were no worse at lower loads, would they do this?! "

and "The efficiency here drops off at lower loads, though much less than cheaper inverters; read the text to gain an impression of what's involved. "

I then replied correcting the inaccuracies and using your own link as evidence.

The rest is just follow up evidence and explianation.


----------



## spykal (May 9, 2005)

DABurleigh said:


> I thought my original 11 word answer was commendably accurate and brief .....
> 
> Dave


Hey hang on a minute Dave there are arguably 12 words in your answer.................... :lol:


----------



## 88724 (May 9, 2005)

Mike

You are a Devil :twisted: and Damn why didnt I notice that.


----------



## DABurleigh (May 9, 2005)

modified-sine is a single, hyphenated word, and my signature is not part of the answer. There is nothing arguable about it! 

Those statements of mine you extracted, George, are not inaccurate. They are only misleading if you assume a context that was not intended. The secret is to take the whole context of a reply, not presume the individual is a plonker, and not to take him or her to task individual statement in isolation from individual statement.

In this saga, because it is beginning to feel like one, so this will be my last contribution to this thread - there's an invitation for you - you are correct, I am correct and nowhere did I claim you to be wrong.

It was simply, as I tried to explain, that you were talking about the, let's face it, MINOR drop-off in efficiency as one approaches the maximum rated output, and I was talking about the MAJOR drop-off in efficiency at small loads. See the curve at the bottom of:
http://www.wattsonschools.com/inverter_specifications.htm 
I previously quoted. You were interested in the right-hand-side; I was interested in the left-hand-side.

QED

Dave


----------



## 88724 (May 9, 2005)

DABurleigh said:


> Where inverter technical specs are given efficiency is invariably quoted *"at rated output". *If it were no worse at lower loads, would they do this?!


At the rated output (2500 in the Victron example) the eff is 90.5% (mid point between 2000w and 3000w) yet the eff quoted on the sales blurb for that model is 95% which occurs were I said it would at 50% of true rated output.
You may not have meant it to appear that way, but I can only respond to your post as written

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



DABurleigh said:


> nowhere did I claim you to be wrong.


I said buy one twice as big as you need to gain the most efficiency, your statement below directly disagree's with what I said. If not outright saying I am wrong it does imply that I am incorrect



DABurleigh said:


> I maintain my general advice on *not buying a bigger inverter than you need*, on both cost and* efficiency grounds*.


I would not presume you are a plonker ot even try to make you look one, I have the greatest respect for you and your posts, they are in general highley accurate Informative and also backed by facts data and inteligent opinion. I am sorry if you are taking my clarification of my position as an insult or attempt to make you look foolish, that was never my intention. And I apologise unreservedly if my post's have apeared to read that way.


----------



## captainking (Jun 16, 2005)

snap up the twenty squid one! what you gota loose...............I dont think you will be dissapointed with it......sometimes things can get too techie!! use it withing the spec and it should give good service


regards

Captaingking


----------



## 88724 (May 9, 2005)

Hi 

I went and bought another from Maplins today £19.99 is good for the 150W never mind the 300w 

Pretty much the ideal (max) size for campers can cope with anything that you are likely to want to run, without getting into serious system design.

Staff there thought it was a mistake as the usual offer is 150W for £19.99


----------



## peterandirene (May 9, 2005)

ERR! None of my previous posts has got past page 1 before, page 3 is amazing!

Right, so, erm, buy the 300w from Maplin, the fan won't cut in when using tv, and it will run a laptop when I get one.


Have I got that right folks?

Peter


----------



## peterandirene (May 9, 2005)

Probably a silly question! Does it plug into my 12v socket or will I have to connect it to the battery?

Peter


----------



## spykal (May 9, 2005)

Hi pete

The fan may cut in but just turn up the volume on the TV.... :lol: :lol: and with an adaptor you can plug it in to the normal 2 pin socket or just rewire a plug onto the end of one of the cables that comes with it.

Mike

P.s. see item "D" at the website below:
http://www.leisurefayre.com/websiteb/bwebsite/b2/pricelistsh02/12vacces.htm


----------



## 88724 (May 9, 2005)

Hi Pete

yes it will run the laptop no problem (will run laptop and TV and DVD and even a swamp cooler all togethor no probs)

Fan, due to the TV being well less than 50% of a 300w invertors capacity unless the ambient temperature is high its unlikely to cause the fan to cut in.

It comes with 2 sets of leads one with fairly solid 12v plug with fuse inside (this worked very well on the last one I had when testing Navigator 4 out on the laptop. It also comes with some battery clips (like jump leads) with an inline fuse (35 Amp) if it were being fitted in my camper I would remove the battery clips and wire direct to the Leisure battery, this still leaves the option of removing from camper and using the cigar lighter plug if you wantv to use in your car say.

With he 300w invertor its ideal size for laptop, Generally to big for TV alone (would be ideal with say DVD or playstation at same time) (only eff wise) but at the present price is unbeatable value.

1000w surge capacity !! got to try this on my mains fridge !!


----------



## peterandirene (May 9, 2005)

Thanks everyone for all the good info. I am off to order one immediately, sounds just the job.

Peter


----------



## Bazbro (May 9, 2005)

And I echo Peter's thanks.
I can't wait to get my hands on it...
(Toys - you can't beat 'em, can you?)


----------



## peterandirene (May 9, 2005)

Well, it's arrived, 36 hours from order, not bad! Looks a pretty solid piece of kit for the money.

Now, next set of questions.

I don't expect to be using it anywhere other than in the van so would like to semi permanently fit it. Can I wire it directly to the leisure battery and if so, should it have another switch fitted to turn it off when not in use or is the units switch enough?

Is it important for the earth to be connected? May be a silly question but I'm sure you will tell me if it is.

How hot do these things run? Can I fit it in a confined space like a cupboard?

Can't think of any more at the moment, just packing up to make a weekend trip to Lancashire to visit relatives.

Thanks in advance.

Peter


----------



## captainking (Jun 16, 2005)

Hi Just a quick note.....Get yorself a cheap plug in surge protector...if I am right it should give a little smoothing as well......although my electronics are a bit rusty!

good luck 

regards
Captainking


----------



## 88724 (May 9, 2005)

Hi 

Personally I would remove the Battery clips and wire directly, these leads already have the correct fuseinline, front switch OK for most uses.

A small cupboard will build up the heat quicker, which may cut the fan in sooner, better to have some space for airflow really depends on cupboard size.


----------



## 88724 (May 9, 2005)

Hi CK

it cant do any harm I suppose, but unlike Gennies dont think surge os a problem with invertors.

George


----------

