# What size inverter please and how to fit?



## aivlys (May 1, 2005)

I confess to knowing nothing about electrics so maybe you will advise me to do nothing but I have a 120W solar panel connected to my leisure battery and now I have a reasonable amount of battery life to play with when there is no EHU. 

I would like to do two things: A) use my travel hairdryer and b) use my microwave for up to 10 mins (Not at the same time!) Is it easy to fit an inverter to the leisure battery and if so, what size would you recommend? 

I had thought of running it direct from the 12V cigar lighter but a quick trawl through some of the other forum comments suggests this would not be appropriate. 

Any pics of previous installs would also be good ........


Many thanks.

sylv


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## selstrom (May 23, 2005)

Whilst you do not give the wattage of the microwave you will probably need a 1.5 KW or 2 KW inverter to cope with the starting current.

Ten minutes use will eat up 12 to 15 amp/hours.


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## aivlys (May 1, 2005)

Thanks for reply, most helpful.

The microwave is 800W, to lose 15 amps would be OK, I have a 110 amp battery and would top up within 24 hours with the solar panel. 

My other battery usage is very small, maybe 3 hours of tv and low voltage lights but mostly light a candle(s) for ambience.

Thanks again.

Sylv


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## wakk44 (Jun 15, 2006)

As has been said you will need a substantial inverter to run a microwave or hair dryer.It will have to be located close to the leisure battery(s)and substantial cable used to prevent any volts drop.

Personally I would like a bigger battery bank than a single 110 A/H leisure battery for use with a 1500/2000 watt inverter.If you know nothing about electrics it is a job for a professional installer,we have several mobile installation blokes on here who I can personally recommend.


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## Pudsey_Bear (Sep 25, 2008)

Inverter size is the easiest to calculate as they are rated by watts, so if you have a 1200 watt hair dryer you need a 1200w minimum inverter, it's a little more difficult for a microwave or any serious electric motors, as they surge when turning on and sometimes off so you need to double the watts needed IE 800w Microwave will need a 1600w inverter.

Although you have a 120w solar panel, you will struggle to run a hairdryer or microwave for very long, I wouldn't be happy nowadays with less than 2 x 125ah leisure batteries.

Antares have a useful calculator.


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## 1302 (Apr 4, 2006)

The hair dryer is the ONLY thing that has ever caused any grief in our motorhome. Its a travel one as well - its blown one inverter up, melted one lighter style connected and run one battery completely flat...


....it now stays at home. You are talking about a serious amount of load with a hairdryer and/or a microwave.


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## aivlys (May 1, 2005)

The location of the inverter would be next to the battery, with a lead running to a socket approx 2ft away. 

I would only run the hairdryer for approx 10 mins. Happy to engage a professional rather than risk damage. Was just hoping it would be a simple job.

thanks again.


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## listerdiesel (Aug 3, 2012)

aivlys said:


> Was just hoping it would be a simple job.
> 
> thanks again.


It can be, the biggest issue is the heavy 12V feed cables and the means to terminate them, other than that it's a pretty quick and easy job.

If you can cope with doing those properly, you can certainly do the rest of the job.

Peter


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## DABurleigh (May 9, 2005)

Beware electrickery - it's not simply a question of multiplying amps by hours. You have Peukert's Law and terminal voltage to worry about. 

Read the MHF's members' guide for inverters, but I wouldn't contemplate 10mins of a 800W hair dryer or microwave without three batteries in parallel.

Dave


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## selstrom (May 23, 2005)

DABurleigh said:


> Beware electrickery - it's not simply a question of multiplying amps by hours. You have Peukert's Law and terminal voltage to worry about.
> 
> Read the MHF's members' guide for inverters, but I wouldn't contemplate 10mins of a 800W hair dryer or microwave without three batteries in parallel.
> 
> Dave


It depends upon the size of the battery.


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## DABurleigh (May 9, 2005)

Err, yes. I had better make my assumptions more explicit in future when posting on MHF. I forgot the culture here.

I assumed 12V and each readily carried.

Dave
http://www.motorhomefacts.com/ftopicp-450452.html#450452


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## aivlys (May 1, 2005)

I am guessing I need to secure the positive and negative leads to the battery posts and that the terminator would be the inverter itself? My simple mind ......

The option of using an inverter is looking less and less likely. boo hoo.


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## listerdiesel (Aug 3, 2012)

aivlys said:


> I am guessing I need to secure the positive and negative leads to the battery posts and that the terminator would be the inverter itself? My simple mind ......
> 
> The option of using an inverter is looking less and less likely. boo hoo.


Don't be daft 

Sort out an inverter, suggest 1kVA or 1.5kVA (AC ratings are in VA, DC ratings are in Watts)

Having chosen your inverter, check the ratings and what you get with it.

Let us know the ratings so the collective knowledge here can check your cable sizes to use, sort out how you are going to connect to the battery, and also if the inverter has a fuse in the 12V side of things.

You wouldn't need a pure Sine Wave inverter for a purely resistive load like a hair dryer, but the motor might need something better if it is not a universal brushes type AC/DC motor, so have a look at your hair drier as well.

We've got a small inverter that we bought from a forum member, 550W only but ideal for occasional use on laptop and phone chargers.

Rita always lets her hair dry naturally, it is very fine and doesn't like heat.

Peter


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## Techno100 (May 8, 2010)

DABurleigh said:


> Beware electrickery - it's not simply a question of multiplying amps by hours. You have Peukert's Law and terminal voltage to worry about.
> 
> Read the MHF's members' guide for inverters, but I wouldn't contemplate 10mins of a 800W hair dryer or microwave without three batteries in parallel.
> 
> Dave


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## Techno100 (May 8, 2010)

The weight of the above including 3x100 watt solars would cripple most axles.


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## 1302 (Apr 4, 2006)

How do you find time to do welding whilst you are away  :lol: 

That's some serious kit!!


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## Techno100 (May 8, 2010)

Thank you
Yes I'm very satisfied with it overall. 
Completely flexible with multiple charging methods and battery changeover to select individual or combine the lot. 605AH all told.


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## peribro (Sep 6, 2009)

We have a 1000W inverter that is used to power a 1400W hairdryer on half heat settings and an 800W microwave, obviously at different times! Neither are used for more than 10 minutes and we've never had a problem doing this.


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## aivlys (May 1, 2005)

Ok, I have spotted this, look OK to me but you might tell me different ....

https://www.towsure.com/stocklevels/1000_Watt_Inverter

thanks.

Sylv


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## listerdiesel (Aug 3, 2012)

They should really tell you if it is modified Sine-Wave or Pure Sine Wave, but at that price it is almost certainly going to be modified Sine Wave.

What is the rating of your hair dryer?

For a bit more you can go to a 1000W continuous rating Sine Wave inverter:

http://www.ebay.co.uk/itm/190808269610

Peter


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## peribro (Sep 6, 2009)

aivlys said:


> Ok, I have spotted this, look OK to me but you might tell me different ....
> 
> https://www.towsure.com/stocklevels/1000_Watt_Inverter
> 
> ...


I don't know the particular model of inverter but Towsure is a reputable retailer so far as I am aware. It doesn't look as if the cables are included so its essential that you use cables of the right size and with as short a run to the batteries as well. You will also need an in line fuse. These topics have both been discussed in some detail in other threads in the last couple of months so if you search for them you should find them.


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## aivlys (May 1, 2005)

My current hairdryer is 1400 with a two speed setting. I had thought about replacing it with an 800 watt just to be on the safe side coupled with the towsure inverter.

Looked at the pure sine but it is quite a bit more than the towsure one and if pure sine is not an absolute necessity then not sure I need to spend the additional bit. Good point though about the cables - I will need to check they are supplied.

Many thanks again for all the responses.

Sylv


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## VanFlair (Nov 21, 2009)

Hi Sylv

We use a 2000W pure sine wave inverter as we wanted to run a coffee machine with electronic circuits inside as well as the microwave and hair dryer, I feel that the microwave runs better on this pure sine than it did before on the old modified sine wave inverter. 

We have 2x85ah GEL batteries and they cope fine, (they are 7 years old so when I replace them I will put at least three in) when the microwave is running the volts drops from float level to around 12.5 and then when the load is off come straight back to around 12.9 we then have 320watt of solar so they can be fully charged again in a couple of hours (more if it raining).

I had to install the inverter as close as possible to the batteries otherwise the low voltage alarm on the inverter was going off due to the drop down the excessive length of cable.

I installed a Merlin pure sine wave 2000W with remote control panel from RoadPro, the wiring from the batteries is 50 gauge which I believe is 10mm diameter and a BIG fuse.

The last thing I will add is that not all batteries are the same and some dont handle the heavy load of an inverter as well as others so be prepared.

Martin


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## aivlys (May 1, 2005)

peribro said:


> We have a 1000W inverter that is used to power a 1400W hairdryer on half heat settings and an 800W microwave, obviously at different times! Neither are used for more than 10 minutes and we've never had a problem doing this.


Just wondering how you have connected your inverter to the battery please?

Thanks.

Sylv


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## peribro (Sep 6, 2009)

aivlys said:


> peribro said:
> 
> 
> > We have a 1000W inverter that is used to power a 1400W hairdryer on half heat settings and an 800W microwave, obviously at different times! Neither are used for more than 10 minutes and we've never had a problem doing this.
> ...


I have a Sterling 1000w Pro Power Q quasi sine wave inverter that comes with the cables already fitted. It is connected directly to one of the leisure batteries but with a 200A fuse here connected using the fuse holder shown at the bottom of the link. There was a thread previously about the cable size not being up to the job when peak load was put through the inverter so you need to be sure how much you will be demanding of it. For my use it is fine.


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## aivlys (May 1, 2005)

wakk44 said:


> As has been said you will need a substantial inverter to run a microwave or hair dryer.It will have to be located close to the leisure battery(s)and substantial cable used to prevent any volts drop.
> 
> Personally I would like a bigger battery bank than a single 110 A/H leisure battery for use with a 1500/2000 watt inverter.If you know nothing about electrics it is a job for a professional installer,we have several mobile installation blokes on here who I can personally recommend.


With the assistance of the forum members it looks like I have a way forward to buy the materials but probably not enough savvy to fit them. that being the case I would like to ask if any of your known mobile installers live locally near Fareham, Southampton?

Things are looking up!

Thanks again you wonderful members.


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## DABurleigh (May 9, 2005)

"The last thing I will add is that not all batteries are the same and some dont handle the heavy load of an inverter as well as others so be prepared. "

Martin,

Absolutely. In my experience Elecsols are poor in this regard. I think the plate construction is more robust than many but the quid-pro-quo I think is that the effective plate surface area (that which you need to hold up the terminal voltage at high discharge currents) is smaller.

Dave


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## aivlys (May 1, 2005)

thanks again for the warning. not sure I understand what "elecsols" or what "plate construction" entails but think I better off not knowing!!

Meantime I have collected the towsure inverter, the cabling is 16mm - will this be sufficient?

Unfortunately I was not successful in acquiring the "CPF-520GH ANL Fuse Holder - 141050 - all sold out and will need to be ordered. If anyone knows of an alternative that would be most helpful. 

Many thanks.

Sylv


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## VanFlair (Nov 21, 2009)

DABurleigh said:


> "The last thing I will add is that not all batteries are the same and some dont handle the heavy load of an inverter as well as others so be prepared. "
> 
> Martin,
> 
> ...


Hi Dave

Wasn't going to name names but you said it for me, I decide two one year old Elecsol 110ah would be better than two 7 year old 85ah Exide GEL.

WRONG

Martin


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## Techno100 (May 8, 2010)

aivlys said:


> thanks again for the warning. not sure I understand what "elecsols" or what "plate construction" entails but think I better off not knowing!!
> 
> Meantime I have collected the towsure inverter, the cabling is 16mm - will this be sufficient?
> 
> ...


http://www.amazon.co.uk/gp/product/B000K2K7TW/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1


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## VanFlair (Nov 21, 2009)

Hi Sylv

For cable size I used something like this calculator
http://www.solar-wind.co.uk/cable-sizing-DC-cables.html

your 800watt inverter might pull about 80amps from the batteries so the calculator would suggest that the cables are just up to the job but the big issue might be the voltage drop along the cable length could be too high and if the inverter has a low voltage alarm or cut out this will operate before you batteries are actually at low voltage and the whole lot could shut down very quickly.

Martin


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## aivlys (May 1, 2005)

Techno100 said:


> aivlys said:
> 
> 
> > thanks again for the warning. not sure I understand what "elecsols" or what "plate construction" entails but think I better off not knowing!!
> ...


Thank you for the alternative option.

Just a quick question, my inverter has 3 fuses in the back, each 35 amp. Can anyone please advise why I need to put another fuse of 200+ amps between the battery and the inverter.

Thanks.#

Sylv


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## VanFlair (Nov 21, 2009)

Hi Sylv

You need a fuse straight off the batteries, if you did not have this and the +ve developed a fault on the way to the inverter it could all overheat and cause a fire or at the very least a lot of damage to batteries and cable.

Martin


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## aivlys (May 1, 2005)

VanFlair said:


> Hi Sylv
> 
> You need a fuse straight off the batteries, if you did not have this and the +ve developed a fault on the way to the inverter it could all overheat and cause a fire or at the very least a lot of damage to batteries and cable.
> 
> Martin


Thanks Martin,

I think this finally puts it all to bed until the external fuse kit arrives. Till then a big big thanks to all those that contibuted to my request for help. Your just great.

Sylv


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