# What size inverter ?



## CLS (Jul 25, 2005)

Not very technical when it comes to electrics......
Looking to buy an inverter mainly to power the t.v when on the move (and ps2) or overnighting with no hookup.....what size inverter would be best for this job ? Also can they be plugged straight into a ciggarette lighter or connect to the liesure battery ? :? 

Cheers Mark


----------



## teemyob (Nov 22, 2005)

*Inverter*

Hello there,

First thing is budget! Depends how deep your pocket is.

I would suggest you decide what your requirements are in watts then buy an inverter with at least twice what you require continuous or 2-4 x for peak.

In other words if you need 300w of power buy a 600w inverter.

There are 2 types

Modified Quasi sine wave and pure sine wave, the latter is for sensitive electronics and will cost you a damn site more.

Only small ones will run from a cigar lighter and can be subject to overheating the connections. Also beware of small inverters that state 150w but wont run a 75w TV!

My advice is if your on a budget buy a 1kW modified sine wave. It works everything right up to a small toaster (it does say not suitable for heating appliances but for the short time the toaster is on I have had no problems) This size will require connection direct to your battery(ies) and the only small downsize is you may get a few lines on your Tv images.

We use it for:
Laptops, Phone chargers, TV, DVD, Toaster and we have an extra domestic fridge freezer in the garage that we power when on the move.

Ours is connected to all our mains sockets in the MH by way of a relay that switches between hook-up and inverter automatically this is available from RS, RS part number: 369-1952 or you could buy a manual one.

If you want a more detailed instructions on fitting, it was featured in a feature of MMM magazine earlier this year. Please get back to me if you want me to find the Month of issue or require any further information.

Other tips

* Try www.ebay.co.uk they can cost as little as a 1/4 what the leisure sites and stores charge. 
* If buying off ebay might be best to buy from a UK seller. 
* Ring and Waeco are good brands
* put an inline fuse in the Inverter to battery cables 
Need any other bits try www.maplin.co.uk www.rswww.com www.cpc.co.uk

regards
Trev


----------



## spykal (May 9, 2005)

Hi
Nip down to your local Maplin pronto....they were selling 300w models for £14.99 last week.

Mike


----------



## teemyob (Nov 22, 2005)

*Fantastic*



spykal said:


> Hi
> Nip down to your local Maplin pronto....they were selling 300w models for £14.99 last week.
> 
> Mike


Not only the price but Great Photos Spykal


----------



## 88724 (May 9, 2005)

Teenymob as Just about covered the lot

For TV and PS2 a 150Watt would do the Job, but for efficiency its best to Double the wattage at least.

The only advantage of sticking with a 150Watt is there is no fan (usually) 300w Plus and you will have a small computer type fan running (sometimes they are temp sensitive others permanent)

TV getting Lines due to Quasi or Modified Sine wave, I have yet to see any TV suffer from this yet.

I would avoid 1000Watt unless you have a use for that amount of power, it makes the fitting more complex and battery requirements are greater.



George


----------



## mota-oma (Nov 30, 2005)

Hi, you have probably covered this subject hundreds of times before - but whilst on the size of inverters can you tell me what is the best size to have fitted to enable a 700w microwave to run off of it ????? Learning loads from this excellent site - keep up the good work all !!!


----------



## 88724 (May 9, 2005)

Hi Moto-oma

700watt cooking = 1050Watts Input check the plate on yours.

So a good 1000 Watt invertor should cope, but will your batteries? You need at least 2 and the charging needs to be good (ie not Split charged or the usual onboard charger's that are fitted to motohomes)


----------



## sallytrafic (Jan 17, 2006)

I would just add the following for anyone thinking to run an inverter from a cigar lighter socket. Wiring to these may be protected by 10A fuse (120W) or 15A (180W) if the socket is part of your cab dashboard. The socket and plug of some cheap designs do not give a reliable connection for that sort of amperage. Consider what it is designed for, the occasional use of a lighter, not to power something at or near its full power rating for long periods of use. If you do it, I would recommend that you feel the socket from time to time to see if its running hot.

Regards Frank


----------



## KRO (Feb 27, 2006)

hi, is anyone able to tell me if a 150W inverter would be sufficient to run a 15" LCD TV via an 85amp liesure battery, if so any idea roughly of how long it would last ?


----------



## 88724 (May 9, 2005)

Hi

A Goodmans 17" LCD flatscreen uses 25 Watts when one average settings for Vol etc. so thats 2.2 Amps Thru an Invertor (sized correctly)

Now it depends how charged the battery is, if its been charged by a 3-4 stage charger, then there is 85 Amps in the battery, now it depends how far down you want to take the battery, Personally to maximise battery life (in Yrs) I reccomend 50% this is generally what the Manufacturers reccomend too.

That gives max of 42 Amps at 2.2 Amps that gives you 19 Hours (assuming no other drains on the battery)


----------



## KRO (Feb 27, 2006)

thanks for that george, now if i were to run a similar sized LCD tv but 12v would i get any longer ?


----------



## 88724 (May 9, 2005)

Hi Kro

Now it wont last any longer, actually it will last less time, here is why.

In reality 12v Battery is not actually 12v unless it is flat, fully charged it will be 12.8 Volts thats 7% too high, If the battery is charging on zig say then the voltage will be 13.8 V thats 15% too high, If being charged via a decent charger then the Voltage could be as High as 15V this is a massive 25% to high. If being split charged the DC is dirty (ac crossover) and also around 14V

The usual answer put forward is use a voltage regulator, unfortunately these are even less efficient than an invertor and of course have less uses and actually cost more than an invertor.

If you were to chance running the TV without an invertor you would gain 2 hours viewing on a full battery, if you stuck to 50% discharge, it would be better to use the invertor and over discharge the battery by 2 hours, batteries cost less than LCD Tv's.

I'll get me coat then


----------



## KRO (Feb 27, 2006)

thanks again george, so it would seem you are very much in favour of going down the inverter route (thats ok cos i have a 15" LCD TV suitable for the job) can you please just confirm that the 150W inverter will do what i need, thinking about it the only other power i will be using from the liesure battery at the same time will be the occasional bit of lighting, electric water pump / toilet flush, many thanks again for your help.

ps i take it, it would it be best to connect the inverter directly to the liesure battery ?


----------



## 88724 (May 9, 2005)

Hi Kro

Yes


----------



## KRO (Feb 27, 2006)

great stuff thankyou, can i really push my luck now and ask if there is any specific inverter you would actually recommend that i purchase and install ?


----------



## 88724 (May 9, 2005)

Hi 

Maplins Nikkai Invertor cheap and does the Job.

Sterling Invertor a bit dearer, but higher quality.


----------



## KRO (Feb 27, 2006)

many thanks george...


----------



## daveandcarol (May 21, 2005)

Size of inverter isn't just governed by how much power you want to pull, it also depends on how much power you have available.

I read somewhere that you shouldn't pull more than 10% of a batteries capacity for a sustained period?

i.e. If you have a 110 ah battery then you shouldn't pull more than 11amps for a sustained period.

11amps @ 12v = 132w , so maybe a 300w inverter max.

Pulling too much power from a battery will cause it to overheat and buckle plates, then scrap it. :roll: 

Anyone know different? I'd be interested to hear your comments.

Regards, Dave.


----------



## DABurleigh (May 9, 2005)

Dave,

From memory lead acids can sustain very high discharge rates, so I think the issue is more that the effective capacity drops off considerably at these higher rates, rather than the life is buggered per se.

Dave


----------



## daveandcarol (May 21, 2005)

I understand that they can sustain very high discharge rates, but I thought that was only for a short period, such as cranking an engine for a few seconds?

Regards, Dave.


----------



## DABurleigh (May 9, 2005)

Dave,

Pop round to my van when Alison's drying her hair. If that's not sustained high currents, I don't know what is 

I guess it depends on what you mean by sustained. If it means the battery dies because it is depleted far earlier than the user expects, this can have a detrimental effect on battery life! But if the user anticipates this and doesn't let the battery get that low, then there is no effect on life whatsoever. To see the reduction in capacity for a given discharge rate, see page 15 onwards of (large!):
http://www.victronenergy.com/upload/documents/ElectricityonBoard_rev8_july2004.pdf

Dave


----------



## 88724 (May 9, 2005)

Hi all

10 % is an ideal Max draw figure. Why ? Drawing at a greater rate increases the effect Peukerts Law will have on available capacity.

Consider it like sprinting, sprint your hardest for 10 Secs, you will not want to carry on, you still have energy left but are not in a fit state to use it. A similar thing happens with batteries. The victron chart doesnt show the full picture as after resting most of the missing capacity returns. Consider starting, keep starting a vehicle and switching off as soon as it catchs after a while the battery will show 11V leave it for half an hour and the Terminal voltage will recover. Peukerts in action

Will it decrease battery life too? ( a regular high demand ) probably, although with modern plate construction shedding is not the problem it once was, thrashing the battery with High ampage discharge is probably going to adversly effect longevity.

PS the above is a simplified version to help average Joe get the picture.


----------



## eddievanbitz (May 1, 2005)

> Ours is connected to all our mains sockets in the MH by way of a relay that switches between hook-up and inverter automatically this is available from RS, RS part number: 369-1952 or you could buy a manual one.


Good advice Teemyob, but I would be careful advising putting an automatic switch to switch between mains and inverter. Many vans now Hymer for example only have a RCD and a single MCD on the end of the mains input. This means that the charging system and AES (Automatic Energy Selection) fridge are on the same circuit as the 13 amp sockets (power points) and, if fitted electric elements for heating and hot water.

Simply interrupting the mains supply and fitting an automatic switch will cause a huge conflict in this situation, the charger for example would be trying to replace the battery discharge, drawing inverted AC from the inverter which would discharge the batteries, causing the battery charger to work harder!! (perpetual motion doesn't exist (or we haven't found it in this universe yet) The AES part of the fridge would say "great, 220 volt lets switch to that" and try and use mains, it goes on and on, and all you wanted to do was watch Eastenders.

So unless you are sure that you have a totally independent ring main or series of 13amp sockets, it would be best to have a couple of dedicated sockets which work off the inverter to save causing your self some real headaches.

Hope this helps 

Eddie


----------



## DABurleigh (May 9, 2005)

Yes, DIY integrated inverter/ mains requires a lot of thought, as I've mentioned in previous posts.

I chickened out and used a Victron single integrated black box, a fridge with manual switching between energy sources, and a battery monitor with alarm in case I'm sucking juice out of the batteries without realising it.

Dave


----------



## 88724 (May 9, 2005)

Hi Dave

Have you been Had? Victron boxes are Blue.............


----------

