Which size inverter. (1 Viewer)

Wildge

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Have to run a piece of equipment for approx.1 hr x 4 times a day. It's 115-230v....50/60Hz 150watt.
What size inverter would we need ..? At present have 180w solar and 2x80 batteries.
Thanks for any help :)
 

pappajohn

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300 watts will allow it to run cooler than a 150watt version.

You may struggle replacing 50amps per day even with a 180 w panel....the sun doesnt always shine.
 

JeanLuc

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As pappajohn says, anything above a 150 watt inverter will suffice but I would allow some headroom so 300 is a good option. Also, before buying one, check whether the equipment is sensitive to wave form. Some items will not run off the cheaper quasi, or modified sine wave inverters and need a pure sine wave (PSW) model. If in doubt, go for a PSW version.

Your power consumption will be 150 watts divided by 12 volts = 12.5 amps (but you will draw a bit more due to the inverter's inefficiency - say it's 90% efficient) so assume 14 amps;

x 4 hours per day = 56 amps or 35% of your maximum battery capacity.

To replace that from the solar panel(s) I would guess you will need around 6+ hours of good sunlight in the 'high' season. Possible between May and September - not practical at other times (unless you are on the Med or North Africa). Either mains hook-up or a generator required between Oct and April/May in UK.

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Wildge

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As pappajohn says, anything above a 150 watt inverter will suffice but I would allow some headroom so 300 is a good option. Also, before buying one, check whether the equipment is sensitive to wave form. Some items will not run off the cheaper quasi, or modified sine wave inverters and need a pure sine wave (PSW) model. If in doubt, go for a PSW version.

Your power consumption will be 150 watts divided by 12 volts = 12.5 amps (but you will draw a bit more due to the inverter's inefficiency - say it's 90% efficient) so assume 14 amps;

x 4 hours per day = 56 amps or 35% of your maximum battery capacity.

To replace that from the solar panel(s) I would guess you will need around 6+ hours of good sunlight in the 'high' season. Possible between May and September - not practical at other times (unless you are on the Med or North Africa). Either mains hook-up or a generator required between Oct and April/May in UK.
Thanks ... just tried today...that was the reason for the question, already have 300w pure sine wave and when I connect get a load of beeping .....:(
 

Don Quixote

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Not long enough, but a little common sense helps..........
Thanks ... just tried today...that was the reason for the question, already have 300w pure sine wave and when I connect get a load of beeping .....:(
The "beeping" is because the inverter see the voltage dropping at the batteries and will not work. This tells me that your batteries are below 50% charge and are not up to the job and will soon be dead and unrecoverable. Try a full charge without any load on the batteries for 2 / 3 days then test again.

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Wildge

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The "beeping" is because the inverter see the voltage dropping at the batteries and will not work. This tells me that your batteries are below 50% charge and are not up to the job and will soon be dead and unrecoverable. Try a full charge without any load on the batteries for 2 / 3 days then test again.
(y) Thanks , away at present will do that on return.
 
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(y) Thanks , away at present will do that on return.

I would also investigate whether the manufacturer has a 12v lead available as this might draw less amps overall. There is often one available. I recently bought one from Resmed for my machine for £67.26 including postage.

Colin
 

JeanLuc

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How is the inverter connected to the batteries? If the cable is not thick enough you will get voltage drop causing the inverter to give a beeping warning. I have a Sterling 150W PSW inverter that came with a cigar lighter connector. When I connected it into a socket fed by standard cable from the Elektroblock and plugged in a MacBook Pro to charge and a small speaker system, it beeped. Once I had wired it directly to the habitation batteries with decent cable the problem went away. Here is my installation if it helps.
http://www.motorhomefun.co.uk/forum/resources/install-a-small-inverter.17/

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Wildge

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Thanks JeanLuc....not very technical I'm afraid . It was installed with the sat. dome and solar panel. Just about to have Hab. Check so will get them to look at it.
Just pleased you have confirmed, that if everything operating as it should then the machine will work.
Thanks again.
 
Dec 23, 2014
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The "beeping" is because the inverter see the voltage dropping at the batteries and will not work. This tells me that your batteries are below 50% charge and are not up to the job and will soon be dead and unrecoverable. Try a full charge without any load on the batteries for 2 / 3 days then test again.
That's interesting. I'm new to using an inverter and I recently tried the one fitted to our MH. 1800w driven by 2 x 85 amp batteries (new). I ran a 1000w kettle until 1.7 ltr of water was boiled. In the first instance there was a lot of beeping and the unit kept cutting out (no power to the kettle). I persisted with resetting it and suddenly it settled down and completed the job. The batteries started at 12.8v dropped to 12.2 in use and then recover to 12.7v as the load switched off. With the aid of the SP on a very grey day they then recovered to 12.8v in about two hours and 13.0v in about four. Does all of that sound reasonable or should I be concerned?
 

Don Quixote

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Not long enough, but a little common sense helps..........
That's interesting. I'm new to using an inverter and I recently tried the one fitted to our MH. 1800w driven by 2 x 85 amp batteries (new). I ran a 1000w kettle until 1.7 ltr of water was boiled. In the first instance there was a lot of beeping and the unit kept cutting out (no power to the kettle). I persisted with resetting it and suddenly it settled down and completed the job. The batteries started at 12.8v dropped to 12.2 in use and then with the aid of the SP on a very grey day recovered to 12.8 in about two hours and 13.0v in about four. Does all of that sound reasonable or should I be concerned?
To be honest your asking too much from your batteries to boil a kettle and will kill them after a period of time. There is no way in two hours you replaced the amps taken out of your batteries in the UK sun. Even in Spain where we live it would take about 5/6 hours and I have 200watts of solar. So to answer your question yes be concerned as your will kill your batteries boiling a kettle. I'm in Norfolk right now and on an average day might and I say might replace about 10/12 amps over the whole day.

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funflair

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You only know what you have replaced when the sun goes down as the reading you are seeing with the sun on the solar panel is the voltage at the battery terminal so you are partly connected to the higher charging voltage from the regulator if you are fully charged it should be higher than 13 volts in the sun, I see the voltage going up to around 14.3 and then the amps being delivered cuts back relative to the amount of sun as the batteries cant take any more.

I have to agree with John that kettles are not the best thing to be using on a small battery bank but that said your batteries seem to be performing OK if they held 12.2volts while you were hammering them.

What batteries are you using @Dorset Diver

Martin
 

funflair

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Why on earth use 12v to power a 1000w kettle? Gas is the most efficient way to boil water.

Well he did say he was new to using an inverter, possibly he just wanted to see what it would do.

Martin

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Dec 23, 2014
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As you say I was only testing / trying the system out. In reality the only use the inverter will get is running the Nespresso machine (1260w for about 4 minutes) a couple of times in the morning and my wifes hair dryer (1400w) for about 15 mins twice a week. The batteries are 2 x 85 amp AGM's. I will always do my best to keep usage to a minimum.
 

funflair

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As you say I was only testing / trying the system out. In reality the only use the inverter will get is running the Nespresso machine (1260w for about 4 minutes) a couple of times in the morning and my wifes hair dryer (1400w) for about 15 mins twice a week. The batteries are 2 x 85 amp AGM's. I will always do my best to keep usage to a minimum.
The Nespresso machine takes next to nothing out so that will be fine, 15 minutes continuous with the hair dryer will be too much in my view so you had better supervise the usage.

Martin
 
Dec 23, 2014
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Our off EHU usage tends to be 2-3 nights followed by a couple of nights on a site with EHU. Where possible hair drying will be whilst on EHU but ... well as you know SWMBO cannot have her schedule interrupted.

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JeanLuc

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Apologies, I had not appreciated this was just an experiment.
Some things have to have 230v and an inverter can be invaluable in these cases; my view is that wherever gas can be used instead, that is the best option when you don't have access to a mains hook up.
 

pappajohn

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That's interesting. I'm new to using an inverter and I recently tried the one fitted to our MH. 1800w driven by 2 x 85 amp batteries (new). I ran a 1000w kettle until 1.7 ltr of water was boiled. In the first instance there was a lot of beeping and the unit kept cutting out (no power to the kettle). I persisted with resetting it and suddenly it settled down and completed the job. The batteries started at 12.8v dropped to 12.2 in use and then recover to 12.7v as the load switched off. With the aid of the SP on a very grey day they then recovered to 12.8v in about two hours and 13.0v in about four. Does all of that sound reasonable or should I be concerned?
Assuming it took 5 minutes to boil you will have used just 7amps.
In good sun it will take maybe 2 hours to replace that 7 amps.
The voltage you see after the kettle boiled will be solar output, not actual battery voltage.
 
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Assuming it took 5 minutes to boil you will have used just 7amps.
In good sun it will take maybe 2 hours to replace that 7 amps.
The voltage you see after the kettle boiled will be solar output, not actual battery voltage.
Thanks @pappajohn. In fact it took about 10 mins to boil; so about 14 amps? How much for 15 mins at 1400w?
 

JeanLuc

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My wife uses a gas powered curling thingy for her hair, it takes small butane cartridges.
 

Zigisla

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Just bought my Wife a gas powered brush. Dries and styles all in one. £24:99 bargain!! No need for the hairdryer(y)
 
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Wildge

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Just bought my Wife a gas powered brush. Dries and styles all in one. £24:99 bargain!! No need for the hairdryer(y)
There are some lucky ladies around ;)
To get back to my probs with the equipment I now find that although the machine is labelled 150 watt, on checked with the technicians to see if there was a 12v lead obtainable, found out that the warmer has a heating element that is 24 volt. !
So back to the drawing board?? what size inverter would run said piece of equipment. (It is literally just a small plate that warms fluids)
As before any help appreciated :notworthy2: as a complete numpty with anything that sizzles apart from bubbly and barbecues :wine:

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SWMBO dries her hair every day but it is not long. I have observed her and it takes around 5 minutes but most of the time the hairdryer is on its low power which I have measured as just 300w. I would have thought 15minutes to dry hair is a bit of a long time. I also dry mine daily but that takes seconds :(
We use hairdryer and toaster off the inverter, with occasional use of the microwave. We also use the low wattage (1kw) kettle on inverter under certain circumstances;

a. Motorway services where the use of gas is forbidden
b. Channel tunnel when the gas is switched off
c. Tea stops in hot weather when the gas heats up the interior.
d. When we can't be bothered to retrieve the gas kettle from its storage position :).

We have 400w of solar and reckon on a good sunny day we can recharge the batteries in the time it takes to drink the tea, not forgetting that around 20% (20A) of the electricity used is being supplied by the solar even as the kettle is still heating.

In the winter we also run an electric blanket on the inverter for half an hour or so before getting in. Uses 50w at full power so only 2-3 amp hours a time.
 

Zigisla

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I must confess after a very very lengthy debate and assurances of using the gasbrush, I had an 1800 w inverter fitted to power Jane's hair dryer and straighteners. After drying and straightening at 09:00 and during the weather last weekend the batteries were replenished from the 150w solar by 13:00 the same day. Now where did I put that Tassimo machine(y)
 
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Wildge

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To get back to my probs with the equipment I now find that although the machine is labelled 150 watt, on checking with the technicians to see if there was a 12v lead obtainable, found out that the warmer has a heating element that is 24 volt. ! (have 180w solar power and 2x80 batteries)
So back to the drawing board?? what size inverter would run said piece of equipment. (It is literally just a small plate that warms fluids) and is it just a case of replacing the existing 300w with bigger model ?
As before any help appreciated :notworthy2: as a complete numpty with anything that sizzles apart from bubbly and barbecues :wine:

BUMP

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