# inverter information required in a simple 'blonde' format!



## ezzy66 (Mar 31, 2009)

i have just perused the previous posts on here about inverters and i am left with just as many questions as when i started!

sooo...

could someone please explain simply how they work and how they can be recharged if they can?! or do they simply invert the current available in the leisure battery? any rule of thumb as to how long an inverter would run for? does it use the same amount of power as if on 12v power? 

am i right in reading that the leisure battery can simply be recharged when an inverter is fitted by running the engine for a short while - less than a normal road trip?

does it pay to have the largest wattage possible? 
how bulky are they in size? does the inverter itself use power?

any recommendations as to makes would be a boon too

thanks a bunch people

p.s. the pros n cons of inverters as there are bound to be some - would also help make up my mind ...


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## JeanLuc (Jan 13, 2007)

I suggest you read the inverter guide in the link below.
It is well-written and comprehensive. The large number of questions you have posed, suggests you need to study the subject of inverters a bit more deeply and then ask specific questions if anything remains unclear, although I doubt you will have so many questions after studying the guide.

Philip

http://www.motorhomefacts.com/ftoptitle-65101-inverters.html


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## Vennwood (Feb 4, 2007)

*Re: inverter information required in a simple 'blonde' forma*



ezzy66 said:


> i have just perused the previous posts on here about inverters and i am left with just as many questions as when i started!
> 
> sooo...
> 
> ...


As Philip says the guide is a good starting point. Certainly read through this before setting out on the "inverter trail" as you will also get several opinions on the size and worth.

To start off with your questions
Inverter can't be recharged - they require a battery, usually 12 volts leisure battery and they convert the 12 volts into 230 volts so you can use some appliances.

The sort of appliances you can run depend on the power rating of the inverter. So a 150W inverter can run appliances up to around 150W (not strictly true as people will point out) so not suitable for boiling a kettle.

Inverters themselves consume a little power to run so again bear that in mind.

Now its no use in getting a massive 3000W inverter and connecting it to a 85AH battery and boiling a kettle or running the microwave as very quickly you will flatten your battery.

You need to decide what you need the inverter to do. Add up the items you would like to run and the average time per day you will run them. The total wattage will determine the size (read output) you need but then work out how many amps it will take - this will give you an idea of the size of battery(s) you need.

At the end of the day its a compromise.

EDIT: Forgot to mention to work out amps needed you have to divide the watts by volts to arrive at amps. So a 900W low watt kettle will draw (230/12) 75 amps so if you used it for 5 or 6 brews then your 85AH battery would be about flat and that's assuming you don't use it for anything else.


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## ezzy66 (Mar 31, 2009)

*inverters again!*

daves article nothwithstanding a few queries remain

does the battery have to be charged up as normal for re-use by the inverter? ( i have seen people not on EHU running their engines 1st thing in the morning for an hour or so - is this for this reason?)

i have a 20i HONDA genny for large or long use high wattage appliances

i would like the convenience of the inverter for smaller medium wattage (900-1100 watt) appliances or for roadside use where a genny is inappropriate or impractical

these would be like toaster, microwave or hairdryer but would be for short burst use from 2-4mins - is this realistic with 2 x 110aH leisure batteries?
i had niaively thought that the larger the invertor the better but surely to power hairdryer etc it would need to be in the region of 1200-1500 watts? i am missing the point (probably from my minimal technical understanding and the inherent electrickery) of how it will drain down the batteries quicker if i do the sums and find 220ah will power my micro and hairdryer - i fully understand that the leisure batteries have a finite amount of power available but ....

any help/explanations/advice gratefully received as ever

thanks


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## gaspode (May 9, 2005)

Hi

Yes, you will be able to recharge your leisure battery by running the engine but you'll need to run it for some considerable time to put any meaningful amount of charge in, partly because the engine is unlikely to charge the leisure battery until the starter battery is fully charged. What the people who run their engines early in the morning are doing is running a large inverter from the starter battery - and stopping that battery going flat by keeping the engine running all the time the inverter is in use. This is a reasonable strategy and works OK as long as you have a nice big alternator. Can be useful at breakfast time when you want to use the toaster/microwave etc. Don't forget though that even with the engine running the battery may go flat, you could be drawing 150 amps from the battery to run a hair drier whilst your alternator may only be capable of producing 60 amps - a deficit of nearly 100 amps. 8O 

Personally I would only use an inverter for small appliances (maybe TV, radio, video, phone chargers etc.) for which a 150w is usually sufficient. Bear in mind that any inverter larger than 150w will need to be wired directly to the battery terminals to be used reliably and safely, a 150w can be plugged into a 12v socket. Large inverters draw extremely high currents from your battery (around 90 amps for a 1000w appliance) so will need permanent heavy wiring and will drain your leisure battery in a matter of minutes. If you do intend to fit a large inverter, be sure that your leisure batteries are in tip-top condition and that you have an efficient charger fitted.
One last point worth making is that some people carry an extra battery, solely for inverter use (usually for ladies who insist on using a hair drier). They also carry a fairly hefty battery charger which they use to re-charge every time they're on hook-up. This means they don't risk flattening their starter or leisure batteries.
I'd be inclined to just buy a small inverter and rely on your generator for the occasional large appliance usage. Maplin usually stock a range of reasonably priced inverters and do provide some measure of product support if you have a problem.


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## LPDrifter (Aug 17, 2005)

gaspode said:


> ....................................
> 
> Personally I would only use an inverter for small appliances (maybe TV, radio, video, phone chargers etc.) for which a 150w is usually sufficient. ..............................
> 
> .


That would be exactly my advice too. I only use a 150W inverter plugged into cigarette lighter outlet and I only use it while driving. It does all kinds of useful little jobs such as charging batteries for camera, and laptop. (my phone and Ipod have dedicated 12v chargers)

I hear some people talking about 1000w inverters and for the life of me I can never understand why such a product would be needed. If someone makes an absolute determination that they need 1000W of electricity, I think they would probably be better off buying a small generator.


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## ezzy66 (Mar 31, 2009)

*inverters again!*

thanks to gaspode and lpdrifter

i am beginning to think the same myself as i dont think it will be doing what i first thought it would & anyway its going to save me £600! my small appliances, tv, laptop and sat dish are all wired to work on 12v anyway and do happily enough for a couple of days with 2 x110aH batteries (not hours of use i hasten to add too busy walking, fishing etc to be glued to a tv/pc) it seems a lot of hastle and expense with BIG genny as well but i just thought on quick roadside stops and rainy cold days it might avoid lugging out the genny n chugging it into life lol!

i will keep stewing over it - when oh when can we ladies have a super duper 12v hairdryer lol! ( please don't reply to that in all serousness my blondeness is only bottle deep i do really know why!)


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## DABurleigh (May 9, 2005)

*Re: inverters again!*



ezzy66 said:


> i am missing the point (probably from my minimal technical understanding and the inherent electrickery) of how it will drain down the batteries quicker if i do the sums and find 220ah will power my micro and hairdryer - i fully understand that the leisure batteries have a finite amount of power available but ....
> 
> any help/explanations/advice gratefully received as ever
> 
> thanks


OK, Ezzy, you can't say you didn't ask; I was content to leave it in the guide as "electrickery will get you"! 

> Peukert's Law <
and if that leaves you cold, plough through this:
http://www.smartgauge.co.uk/peukert2.html

Dave
Edit - crikey it's a pain getting a hyperlink in properly when it has an underscore character


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## JeanLuc (Jan 13, 2007)

I fitted a 150W pure sine wave inverter, mainly to power a laptop and speakers when we used it to watch DVDs. Now we have a fitted TV system that runs from 12V I use the inverter rather less. However, it is useful for charging the laptop, mobile phones, electric shaver etc. Despite what has been said about running a 150W inverter directly from a 12V socket, I found this problematic; not because the socket could not supply the power, but because of voltage drop. This occurs when the wires supplying current from the battery to the inverter are too thin. In my case, the inverter would "scream" when the laptop demanded full load, although it has only an 85W power supply.

The reason for the heavy current draw (amps) required by an inverter is explained by Ohm's Law. This leads to an equation that can be re-arranged to give all sorts of useful electrical information (forgive me if I am teaching you to "suck eggs" here).

Amps = Watts / Volts

So, a 100 watt device powered from the mains (230V) will draw a current (amps) of 100 / 230 = 0.43 amps

The same device powered by an inverter is relying on an input voltage of 12V (before it is "inverted to 230V) so the equation becomes"

100 / 12 = 8.3 amps

In fact it is worse than this as all inverters are inefficient to a degree - say they are 85% efficient. This makes the above equation

(100 / 12) / 0.85 = 9.8 amps

If you increase the load to that of a typical toaster or hairdryer (that other apparently indispensable device), the load might be 1,800 W and the equation looks like this:

(1800 / 12) / 0.85 = 176 amps

Run this for 10 minutes and you have taken 30 amps out of your batteries. Now you can see why you need a large battery bank and big cables to connect the inverter to the batteries.

If you have a Honda EU20i you have the perfect unit for running power-hungry devices and for recharging your batteries. Don't bother with a big inverter. If you want to install a small one for light duties, I put a paper in the downloads section called "Installing a small inverter"; it might be worth your while reading this.

Finally, although people do it, it's probably not a great idea to run the motorhome engine on tick-over to recharge the leisure batteries. Firstly, you will be chucking diesel fumes and particles all over the site; secondly, it is inefficient to use such a big engine for such a small task, and thirdly, it is not a good idea to let a modern diesel road-engine tick-over for long on a light load. It can lead to cylinder bore glazing that causes compression problems. The Honda generator is small and designed for the job - use it.

Philip


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## peribro (Sep 6, 2009)

We have a 1000W inverter for the sole reason of powering the hair dryer, although obviously it is also used for laptops, phones etc. The hairdryer is a 700W/1400W model and when not on EHU it is run on the low setting for not much more than 5 minutes. This draws about 6 or 7 amps from the two 110A batteries and that combined with moderate recharging of laptops etc is is usually mostly replaced pretty quickly by the solar panel.


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## Vennwood (Feb 4, 2007)

Hi Ezzy66,

All good replies and it just goes to show that we are all different. If as you say you will only use small appliances then go for a small inverter so you have the freedom to use chargers and laptops without getting the genny out. 100W inverters from any of the accessory shops shouldn't cost you more than £20 to £40 - job done

I think you have to take a step backwards and decide on the type of use you will be getting from your motor home. Will you be using mainly camp sites like the CC and C&CC 0 if so then really not much need for an inverter as they will all have EHU. If however you plan on exploring more and either wild camping or using the European Aires/Stellplatz or Sostas then inverters maybe make more sense. 

In my view an inverter is only part of a solution and should be combined with additional batteries and or a reasonable method of recharging the batteries. Gennys are one solution but there are others such as Efoy, Solar , LPG generaters etc. but now you are getting into serious cost issues.

Remember your MH is designed to recharge only the leisure battery(s) that comes as standard, with a charger usually around 18amps. What many people don't grasp is that when you add another battery it more than doubles the time it takes to recharge both. For example if you have 2 x 110AH and you drain off say 75Amps over a say a weekend then it will take your Honda genny well over 5 hours to recharge the batteries. That's an awful long time to be running and expensive in petrol - maybe even upset the neighbours

In practice running a genny every time you want to use the hairdrier or charge up the laptop will cause problems - either its raining, you are near too a neighbour, its early morning or late night or the campsite forbid the use of gennies etc. or its just packed away behind the bikes or whatever and you can't be fussed. 

Either go into it properly or go for the simplest minimal solution.


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## ezzy66 (Mar 31, 2009)

*thank you thank you thank you

yet again another excellent set of replies - i concur vennwood.

if ever anyone wanted to know why i joined and why i wouldn't hesitate in recommending MHF to newbies it was for this simple reason - travelling alone as a woman with my young son and elderly mother i am limited in my access to information or help and this MHF forum is just perfect for either simple issues and queries to major decision making processes or simple chit chat and also when wanting to grumble to manufacturers lol (tongue in cheek!)*

the learning curve get less and less over time with help and hopefully i will get the opportunity to help others if i can! not always confident my reply would be correct though esp on electrickery !! dave i bow to your superior knowledge - i am not worthy ... :wink:

[i solved the expensivemost often problematic gas cylinder replacement issue when in france single handedly quite a proud moment for me lol! it was minus 17 and i did have to find a solution but thats me one of lifes triers!no doesn't exist just maybe ... my father instilled that in me!]

dave you win i will never be so blonde as to ask again! electrickery is fine for me i did read some of peukerts law and i did take some of it in and i have a better understanding of what is going on now ... not sure it will help tho :roll:

jean luc please don't take this the wrong way but i find men who mention about our indispensible hairdryer and other hair related equipment are often bald or certainly follicly challenged in some way!  8O  :lol: so i think to myself no wonder they cannot understand they are to be pitied and cuddled in a patronising way  and most certainly not chastised as they are really only envious i find! ( we ladies must also always try our best to look nice whatever the occasion even if it is raining cats and dogs and the dog is desperate for a 'walk' to relieve itself - you never know who you might bump into and appearances are important but also deceptive .. am i waffling or is it just me ... :wink: )

anyway to more pressing and serious matters P O W E R or the lack of it

i have read everyones input and i am back to square one i think but much better informed

as vennwood says its an all or nothing approach do it properly or not at all. [ i must say vennwood very honest and fair answer thank you very much - you have said exactly what has been going through my mind! common sense and helpful advice without being patronising or condescending  without sounding greedy it would be nice to have it all but some power solutions would not be necessary for us...]

i suppose i hadn't really thought about the time taken to recharge the batteries which is the main issue! then also 2 or 3 taking 2 or 3 times longer very valid point!

a 150w inverter is not much use to me - my needs are different as are everyones - not to say the posters input on those is of no use it may be to others it served to reinforce that it would be pointless when most small appliances are running direct 12v anyway it is the medium appliance and convenience that are suffering. a genny is excellent power source and honda do make good ones but there are occasions when it is simply not possible to use one (see vennwood)and that is where i hoped an inverter would come in handy - occasional but convenient power for 240 v appliances ie microwave, HAIRDRYER and dare i say it at all?? even the tumble dryer for the towels?    

we nearly always wild camp in uk and europe if we stay on anything they are CS or CLs and usually only for EHU to charge the batterys to get going again away from it all!so power is an issue but solar panels are out as we go out of season when the sun is v limited uk or otherwise (we run a campsite in the season )

peribro thankyou for your honesty not everyone admits to using the invertor for that but i am at an age i like to care about how i look and the MH being clean & tidy - my camping days are over!motorhoming is hardly the roughing it holiday :lol: i am keen to know if you only use the solar panel abroad or do you find our grey skies esp in winter any use for charging. what size panel do you have and how long does it take to charge your 'same as mine' batteries? [sorry to go off post will be happy to pm peribro if i get a smack on the wrist/s!] i only intended to use a low wattage hairdryer or lessen the heat setting at least so it would be nice to know i could do it for a few mins and not lose total power!

microwaves by their very nature are not run for long so i do not think they are the issue.

jean luc/philip thanks again for the explanation i see it more clearly now and thank you for taking the time to write it all out the maths written down and explained were exceptionally clear i must say and helped me see it more simply and basically and work out what is going on!i did wonder whether they were trying to recharge batteries and i must agree not a nice practice and wearing on the engine and MH generally. i will most certainly not be doing that as you so rightly say that is the gennys job so much cheaper if goes wrong! and yes for those of you it too will chuck out pollution but not at the same rate.

thanks to one and all for your help it has been indispensible and helped me reach a conclusion i am thinking somewhere in the region of 1000w or just above should do the job

i will talk to eddie at vanbitz to whom i am due a call to him re the dome and a small outstanding bill :roll: - might even see him at the show!

*£10 what excellent value - not even an hours worth of advice for that elsewhere - don't let me see anyone complain - absolute bargain is all i'm going to say!!*

happy travels peeps


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## JeanLuc (Jan 13, 2007)

It's a fair cop - I admit to having little need of a hairdryer. That's why certain past work colleagues nicknamed me JeanLuc as they perceived some likeness with the Star Trek character played by Sir Patrick Stewart. (My family fails to see the similarity.)

However, I can claim some knowledge of the problem faced by ladies who motorhome. My wife's solution is to use a gas-powered styling gadget from Braun. It runs on small disposable cylinders. I realise it will not dry a full barnet such as sported by Scarlett O'Hara, but it is a useful low power addition to a lady's kit.

Philip


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## Stanner (Aug 17, 2006)

Despite frequently having longer hair than my wife (I just can't see the need to have it cut as often) I still cannot appreciate the need for a hair dryer. Even at it's longest it just dries on it's own.

Having said that I can appreciate that some with even longer hair may not be away long enough for the natural solution.

Most m/homes have blown air heating, so my thought is why not have a hose made up to plug into one of the outlets at one end and accept hair dryer attachments at the other.

Close all heater outlets except the one the hose is plugged into, turn the heating on and dry your hair no need for hook-up/inverter/whatever - simplez.

If any m/home accessory manufacturer wants to implement my idea my royalty fees are quite moderate.


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## ezzy66 (Mar 31, 2009)

*inverters and hair!*

thanks jean luc for your honesty

and theres me thinking you were a sophisticated french man  ( zut alors) and all the time you were masquerading as a bald man from star trek tut tut!  the truth will out in the end i always tell my boys that ...

the only man i knew ever needed a hairdryer and that was a long time ago was kevin keegan! :lol: (definite hair envy there i feel!)

i too have a gas tongs thing and it does for the days in between washing (yep i know yet another wash day most men aren't involved in!) but then its back to drying with an electric source - unless we could have gas hairdryers - image the men at H&S on that one - would keep 'em going for months! 

sometimes i think a no:1 and a hat would be simpler but there are times a hat just won't do!


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