# Inverter - quick advice



## AlanMo (May 14, 2005)

What should I buy to power and LCD 17" TV, + DVD player + Freeview box?
Only needed for use when travelling (with g'kids) and occasionaly on site when not hooked up.
Alan


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## DABurleigh (May 9, 2005)

Add up the power consumption of the devices in watts and if less than 150 watts (probably, but worth checking), buy one of these:

http://www.maplin.co.uk/Module.aspx?ModuleNo=48722&&source=14&doy=26m7

Dave


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## zulurita (May 9, 2005)

A 150w inverter will probably be ok but I went for a 300w so that I could use it if required for other things.
Its worth checking where you will be sitting the inverter, will it be too far from the leisure battery? if so there would be a drop in voltage and may affect how much you can use it in terms of amps. Also the wire they use for the 12v socket in MH's is usually thin and for up to 4 amps. I had another 12v socket added with a thicker wire 10 amps this works fine. Had problems trying to recharge the laptop battery before that as the alarm would go off soon after plugging into the inverter (300w).


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## DABurleigh (May 9, 2005)

If 150W is enough for those devices simultaneously, then this has the advantage of silent operation as no 150W inverter has a fan. 300W ones do, though some are on all the while, some thermostatically switched on and off and some go at different speeds, which I find more intrusive than a constant one the brain can have a stab at filtering out.

If the appliances are a long way from the battery and you have freedom to mount and perhaps remotely switch the inverter, stick it close to the battery as cable losses aren't an issue at mains voltages, but certainly are, as zulurita points out, at 12V.

Dave


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## geraldandannie (Jun 4, 2006)

DABurleigh said:


> ... as no 150W inverter has a fan.


Mine does :roll: Only a little one, though.

Gerald


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## DABurleigh (May 9, 2005)

Gerald,

Well that's a first for me. What make/model is it? The small fans can be the noisiest (think PCs) :-(

Dave.


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## geraldandannie (Jun 4, 2006)

Hi, Dave

It's this one (bought from a different supplier)

>> Ebay inverter <<

Seems to work fine, and the fan is a quiet whisper. I'll only be using it to charge phones / laptop, so a bit of noise won't be a problem.

Gerald


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## 97051 (Dec 27, 2005)

Sorry if I seem to hi-jack this , but , which inverter 300w £40 or 600w £70 , 0r 150w £15 , most use would be for a 14in tv / dvd player , possibly freeview box ( when not on hook-up ) , and would you put it into battery box , then run mains wire from it , is it safe :!: , and how long could you use it without battery recharged :?: ,


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## DABurleigh (May 9, 2005)

Your question is partly answered earlier in the thread, for your requirements are the same, and for that part which isn't, there is insufficient information, such as what size battery, presumed still healthy and fully charged (a thread in itself), what other demands you are taking out of it, the total consumption of your appliances (a 150W inverter is merely its MAXIMUM consumption, what it consumes depends on what, in detail, you plug into it), etc.

A ROUGH estimate might be obtained by dividing half the capacity of the battery in Ah by ~7 amps, to give duration in hours with nothing else using the battery.

It is safe provided you connect it to the battery, and route the wiring, appropriately. The inverter should be disconnected or switched off when not in use.

Or I misunderstand your question.

Dave


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## AlanMo (May 14, 2005)

Many thanks for the advice - I will get the 150W - the cable will be about 3 yards long. 
I presume it will be recharging while driving and hence, run forever from the battery?
The advert mentions it is only for use with components which accept a 'modified sign wave'. I know little of this therefore, will the LCD TV, DVD and Freeview boxes be OK?
Sometimes it comes as a shock to realise how little you know about these technical issues!!!!!
Alan


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## 96088 (Aug 22, 2005)

AlanMo said:


> The advert mentions it is only for use with components which accept a 'modified sign wave'. I know little of this therefore, will the LCD TV, DVD and Freeview boxes be OK?
> Alan


Yes they will, you may have a problem with your electric toothbrush though (or so I have been told)


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## DABurleigh (May 9, 2005)

As to the modified sine wave with those devices, you will almost certainly have no problem. In any case, the thing to do is buy one at £15 and check this. There is plenty on this on MHF already - just use the search facility. 

As to recharging, if you are connecting it to a cigarette lighter socket powered from the vehicle battery, yes, the battery will be charged, but beware these sockets can have a 10 amp limit and you may exceed this. Another reason to tally up the consumption for your specific appliances.

If powering it off the leisure battery, it depends on the state of any split charge relay wiring as to whether you will be recharging the battery as well as powering the appliances.

Dave


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## AlanMo (May 14, 2005)

Many thanks

It will be from a designated socket in the TV cabinet and separate from the cig lighter and auxiliary socket in the cab. Is this likely to be OK?

Alan


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## DABurleigh (May 9, 2005)

Then, as zulurita and I say, you MAY find the motorhome manufacturer's wiring is inadequate, causing your inverter to shut down because of the low voltage it sees, and you MAY find the leisure batteries don't charge as well when motoring, for the same reason. It is solely down to how professional versus how skimpy a job they did on your van!

Dave


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## geraldandannie (Jun 4, 2006)

I think that the issues are so complex to the uninitiated, it's worth spending the 15 quid and trying it. It may work fine, but there's not much people on here can do to help when you're looking at the voltage drop along long, thin wires.

Maybe we should organise an electrical meet sometime?

Gerald


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## 97051 (Dec 27, 2005)

Thanks , Dave , it's a mine field for the inexperienced , 12v system that is :roll: , battery is 100 ah and new , I would be using lights , water pump , off battery , battery box is at rear nearside in a locker sort of underslung plastic carrier , ( if you know what I mean ) , room for an additional battery and an inverter , length of 240v wire would be about 2:5 to 3 metres , ( would prob use freeview box on 12v , as it would be to far to route 240v wiring , it's on offside behind drivers seat in an upper cupboard ) , many thanks Allan


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## AlanMo (May 14, 2005)

Advice much appreciated. I've ordered a 150 will let you know if it works.
Alan


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## geraldandannie (Jun 4, 2006)

AlanMo said:


> I've ordered a 150 will let you know if it works.
> Alan


Please do. It will add to the communal knowledge that lies here 

Gerald


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## 96783 (Nov 23, 2005)

I've read this thread with interest and, like one or two others probably, had some difficulty with all the technical matters even though very simply and well explained. We had an inverter professionally installed. It came with all wiring and I confess to being astonished at the thickness of the cables. It is separately switched and does a fantastic job. We can power almost anything that we use from the two installed sockets, taking care with the wattage, and so far have not used two appliances at the same despite the nominal 2000w capacity. We also have twin 110Ah batteries to cope with the extra power requirements and a 125w solar panel.

Why 2000 watts? Well we used the same principle that we used with cars when towing caravans and also computers. Calculate the maximum power you think you will need and double it. You, or at least I, always use more than I think and power supplies deteriorate over time.


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## AlanMo (May 14, 2005)

Thanks for very usefull advice - have ordered a 150w and will report back.
Alan


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## DABurleigh (May 9, 2005)

PhredC,

Two points. 

1) Doubling your inverter capacity over anticipated maximum demand is not a bad rule of thumb given most inverters operate at peak efficiency when at half their maximum continuous load. You just need to bear in mind that efficiency drops off massively at low percentage loads, so if 90% of the time you only need a 150W inverter, but 10% of the time you NEED 1kW plus, and you don't have an embarrassment of riches in the battery capacity department, then best to get 2 inverters!

I have a 150W one hard wired and dedicated to cope with TV, satellite dish, satellite control box and digibox, as this combination is on for long periods and is well under an average of 150W. And a bigger inverter for the rest, which brings me to:

2) I agree on the convenience of plumbed in inverters. I use any or all of my 3 mains sockets as required, whether I am on hookup, genny or just batteries, and irrespective of any site supply limit (because the van system will not trip the site system, taking temporary excess from the batteries). A 1.2kw hair dryer can be switched on, and its user would not notice a hookup being plugged in or taken out, genny switched on or off, etc.

Obviously in order to conserve battery energy, one needs to appreciate what various devices take out, so on battery you don't use an electric kettle, electric water heater, aircon or its heating element, fridge on mains and in particular you need to be present to tell the wife when her hair is dry enough.....

A battery monitor set to alarm at 50% usable residual capacity in amp-hours is a good backup, too!

Dave


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## geraldandannie (Jun 4, 2006)

DABurleigh said:


> A battery monitor set to alarm at 50% usable residual capacity in amp-hours is a good backup, too!


Good idea, Dave. Any recommendations? I must admit, I was thinking about a digital display for my batteries - the little needle doesn't tell me what I'd like to know.

Gerald


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## DABurleigh (May 9, 2005)

Gerald,

Well an MHF search ;-) for "battery" and "monitor" picks up, inter alia:

http://www.motorhomefacts.com/ftopicp-104818.html#104818
http://www.motorhomefacts.com/ftopicp-104731.html#104731
http://www.motorhomefacts.com/ftopicp-124476.html#124476
http://www.motorhomefacts.com/ftopicp-116213.html#116213
http://www.motorhomefacts.com/ftopicp-120682.html#120682
http://www.motorhomefacts.com/ftopicp-53202.html#53202
http://www.motorhomefacts.com/ftopicp-63679.html#63679

and if you search on Victron mentioned above in posts by me you get 20 threads. There is an ultimate accolade (see Victron Multiplus) from the unique George Telford here:
http://www.motorhomefacts.com/ftopicp-114004.html#114004

Dave


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## geraldandannie (Jun 4, 2006)

DABurleigh said:


> Well an MHF search ;-)


WILL YOU STOP DOING THAT??? :evil:

Thanks a lot, Dave. I thought I did well to search Outdoorbits for something (no product there). So, Victron eh? Heading that way now .....

Gerald


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## 101430 (Oct 17, 2006)

AlanMo said:


> Thanks for very usefull advice - have ordered a 150w and will report back.
> Alan


So, was it any good?


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## JustRadio (May 21, 2005)

DABurleigh said:


> PhredC,
> 
> you need to be present to tell the wife when her hair is dry enough.....
> 
> Dave


I went for 2000 watts too, Ok I can run the telly but the main things were (A) microwave off site, and (B) you guessed, hairdryer off site. The only thing I have to remember is to unplug the battery charger or the inverter tries to re-charge the battery it's draining!


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