Inverter Dilemma
I need some help deciding where to position an inverter to provide mains power in my MH when not on hook-up.
I plan to get a 1500w pure sine wave model to run small appliances, such as hairdryer, kettle, toaster, laptop charger, electric toothbrush etc. - none of them will exceed 950w and will be used on their own.
My Autocruise Gleneagle MH currently has 2 x 85ah leisure batteries wired in series, plus a 120w solar panel. The leisure batteries are mounted in a compartment in the false floor just behind the cab, but there isn't enough space for anything else.
I gather the shortest cable run possible between inverter and battery is advisable (to limit power loss) - 2 metres at most - and the inverter also needs to be located in a well ventilated area to allow heat to disperse.
I would like to keep it out of sight but handy for maximum convenience. Any suggestions ?
Comments
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Merve might be along to help you as he uses his large inverter in the same way.
on one of the threads there is a link to a Clive Mott webpage (MMM electrics guru) where he illustrates how his whole 'mains' system can be switched over to the inverter at the flick of a switch....
i have an inverter which i use (primarily) for running a mains-only Sky HD+ box...
with regard to some of the items on your list, id avoid the heating stuff unless absolutely necessary...
how about using the gas hob rather than an electric kettle, the gas grill rather than an electric toaster, also try 12v USB sockets for charging ipads/phones etc.....all easily done without the inverter....
....which leaves the tricky one.....the hairdryer.....one of our pals uses a gas powered 'dryer/styler' thingy......
my inverter only had leads about 12" long so is mounted close to the batteries and then i run an extension lead into the locker for the Sky box then i need it.
the battery locker is quite large and i can (handily) set up the inverter for the mains-only chargers for our electric bike batteries when off grid....
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Thanks BB. It's the need for a hairdryer which has prompted us into thinking about an inverter as we don't want to check in to a site just for EHU. The dryer will only be used for about 10 mins on the lowest setting.
We already use 12v USB adaptors, gas for toast and a kettle for the gas hob, but mains appliances are so much easier.
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I hope they're actually connected in parallel or else you'll get about 25V, but you are aware that you'll be pulling around 75A?
You can run a longer cable that 2m, but need to use heavier cable to reduce voltage drop. 110A cable is 16mm2 and would be the minimum I'd use, it should be good for up to 3m.
Under a seat maybe, but plenty ventillation.
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You are correct, they are in parallel ! Just goes to show how much I have to learn. Thanks for the tip regarding heavier duty cable. There is space in our underbed lockers in the vicinity of the batteries, but I was hoping to avoid using them as they are
already full of various essential items (mainly wine) !0 -
Clive Mott is the expert but be aware that an appliance rated at 950watts can draw more than that at startup and an inverter (even a quality one) does not efficiently convert 12 V DC current to 240v AC. If you look on the site Europe by Camper at the article.
Home » Electrical » Essential
Guide » Hairdryer from 12v in a Motorhome - The Solution! You will see how Adam solved the problem but note that he only uses this solution with the vehicle engine on and he is using a bigger inverter.Personally I would abandon using electricity for heating when gas is much more thermally efficient and trouble free. The inverter route won't "easier" either if you run your vehicle or leisure batteries flat which an inverter has the propensity to do.
Sorry if this sounds negative but sometimes simple is best
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Thank you BVM, a link to a very interesting article . I like the idea of running the inverter off the starter battery as it rarely has any load (apart
from starting the engine of course) and, as added insurance, my MH has the facility to switch to an emergency start from the leisure battery if necessary.Using an inverter to power a hairdryer is still my preferred option as it will save me a lot of hassle from the OH !
Thanks also to BB for the tip to use an extension lead - I hadn't thought of that; too busy thinking about voltage drops, which don't apply quite as much on the supply side of an inverter presumably.
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Jim....Inverter, starter battery......dont do it......
starter batteries arent made like leisure batteries....one is happy for a huge slug to be taken out of it every so often....the other is happier giving out juice over a longer period....
also, if you drain the vehicle battery......ooops.
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If the hairdryer is only to be used on its lowest setting, and then for only a few minutes, is it really needed at all?
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1500w Sine wave generator will need about 150 amps. It will probably run at about 85% efficiency so your leisure batteries will be down to 50% in 30 minutes and batteries ruined in 45 minutes.
A 1500w Sine wave generator will be about 50% efficient when powering smaller items like computers and tooth brushes. So at 200w it will be using about 33 amps.
You really need to match the load to the inverter. If you use a 200w inverter then it will only use about 19 amps at 85% efficiency. A 200w inverter is considerably smaller and wiring far simpler.
The kettle will take a considerable amount of power but a normal kettle on a gas ring uses far less.
So it's down to the hairdryer and toaster. You can get a flat plate to cook toast on you gas hob.
That leaves the hair dryer. Find one that does not use to much power. Try it at home then buy the inverter to power it.
When working out cabling you measure the cable from the battery to the inverter and double it. There and back. You get a voltage drop going both ways. Size of cable is going to be something else. Then you need to sort out how you are going to attach them to your battery as you already have terminals connections on the batteries already.
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My 750w inverter and battery charger are installed at the back of cupboard just above the 200 APH battery. A thin plywood panel with ventilation vents cut into it covers the compartment and forms the back of the cupboard. May be you could do something similar
in your under the bed storage area or elswhere?peedee
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Assume you have a 25w 240/12v TV. If you connect it up to the caravan battery via an inverter to use the 240v side would it use more consumption than if you connected it up direct to the 12v system in the caravan?
Yes,
The inverter is not 100% efficient.
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Assume you have a 25w 240/12v TV. If you connect it up to the caravan battery via an inverter to use the 240v side would it use more consumption than if you connected it up direct to the 12v system in the caravan?
Yes,
The inverter is not 100% efficient.
Thanks. Any ideas fo which inverters are the most efficient, modified or pure sine wave and also any idea of a recommended brand. At present we have a 300w Ring modified sine wave inverter which is about 12 years old and we don't think it is very efficient
at all.We only need it to power the Sky Digibox which is about 45w and to recharge the laptop battery. Obviously the two will not be done at the same time. Also thinking that a tablet may be more efficient as battery seems to last a few days.
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Regarding efficiency I don't honestly know which is the most efficient.
I do know that pure sine wave inverters are reccommended for sensitive electronic equipment such as Laptops, radio equipment etc. as they are kinder on the electronics.
By the way I have the same inverter and whilst it works for charging camera batteries it would not power a Tesco 22 inch portable TV. It just shut down and illuminated the red LED on the front. Bit useless really
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Regarding efficiency I don't honestly know which is the most efficient.
I do know that pure sine wave inverters are reccommended for sensitive electronic equipment such as Laptops, radio equipment etc. as they are kinder on the electronics.
By the way I have the same inverter and whilst it works for charging camera batteries it would not power a Tesco 22 inch portable TV. It just shut down and illuminated the red LED on the front. Bit useless really
Thanks for confirming that we are not the only ones with the issue. We have the Avtex and could not understand why the battery alarm in the form of Phantom was notifying us of low battery. We then bought another 110ah battery solely for the Sky box and
even that was running low after about 5 hours.I think we will look at investing in a Victron inverter and probably go with modified sine wave as we have not had any issues with Sky box or laptop.
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Do you not run your Avtex direct from the battery Surfer? FYI my Victron manual states they are 90 percent efficient.
peedee
Running the TV and the Sky box plus other items would be too much for the onboard 110ah battery ehnce the secong battery. We would normally run the TV on the onboard battery via the 12v socket in the caravan.
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Assume you have a 25w 240/12v TV. If you connect it up to the caravan battery via an inverter to use the 240v side would it use more consumption than if you connected it up direct to the 12v system in the caravan?
Yes,
The inverter is not 100% efficient.
Thanks. Any ideas fo which inverters are the most efficient, modified or pure sine wave and also any idea of a recommended brand. At present we have a 300w Ring modified sine wave inverter which is about 12 years old and we don't think it is very efficient
at all.We only need it to power the Sky Digibox which is about 45w and to recharge the laptop battery. Obviously the two will not be done at the same time. Also thinking that a tablet may be more efficient as battery seems to last a few days.
Not a case of which is the most efficient but more a case of how much you want to spend. Sine wave one will give you same waveform as you get from the mains at home. This will not destroy an electric tooth brush. Modified sine wave is just that. It is something
similar but has lots of steps in the waveform. This is one of the reasons that transformers don't like them very much. Some electronics will cope but they use more power than if run on a sine wave unit. You pays your money and takes your pick.0 -
I cannot imagine a Sky box draws a great deal of current. An Avtex TV draws about 2.5 amps, at the most. Just running that alone should give you 35/40 hrs running time from a 110APH battery in good condition. Allow a generous 2 amps for the sky box and you should get 20/24 hours from your battery. A good 4/5 days evening viewing.
peedee
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I cannot imagine a Sky box draws a great deal of current. An Avtex TV draws about 2.5 amps, at the most. Just running that alone should give you 35/40 hrs running time from a 110APH battery in good condition. Allow a generous 2 amps for the sky box and you
should get 20/24 hours from your battery. A good 4/5 days evening viewing.peedee
abreed, Peedee.....our (built in German) tv is 12v and runs via the batteries even when on hookup.
the sky box is not that hungry and 3 or 4 hrs tv (with sky via inverter) shouldnt present a problem...
however, Surfer doesnt say how he replenishes his battery, and without adding charge back in (alternator or solar panel, gennie) it will eventually run low.....water pump, lights chargers etc...
a lowish power SP (80w) should easily keep up with this sort of usage.
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According to the internet a SkyBox draws about 40w. If you use an inverter that is rated at 200w then you will be wasting a good deal of your electricity. So if the unit is only using 40w you need an inverter around 50w. That way nothing will be wasted. 50w / 12v asuming 85% efficiency will be about 5 amps. Do the same with a 200w inverter which will be working at about 50% efficiency at 50w and you finish up with just over 8 amps.
Also remember that inverters use power even when the appliances are off so you need to switch the inverter off as well.
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According to the internet a SkyBox draws about 40w. If you use an inverter that is rated at 200w then you will be wasting a good deal of your electricity. So if the unit is only using 40w you need an inverter around 50w. That way nothing will be wasted. 50w / 12v asuming 85% efficiency will be about 5 amps. Do the same with a 200w inverter which will be working at about 50% efficiency at 50w and you finish up with just over 8 amps.
I think just because the inverter is RATED at 200W it would work perfectly well if it was only asked to draw 50W? There may be, as said, some minor difference in efficiency but it would mean that a larger range of devices could be powered? i.e. no need to have a different inverter for every type of device? Or am I missing the point?
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According to the internet a SkyBox draws about 40w. If you use an inverter that is rated at 200w then you will be wasting a good deal of your electricity. So if the unit is only using 40w you need an inverter around 50w. That way nothing will be wasted.
50w / 12v asuming 85% efficiency will be about 5 amps. Do the same with a 200w inverter which will be working at about 50% efficiency at 50w and you finish up with just over 8 amps.I think just because the inverter is RATED at 200W it would work perfectly well if it was only asked to draw 50W? There may be, as said, some minor difference in efficiency but it would mean that a larger range of devices could be powered? i.e. no need
to have a different inverter for every type of device?Quite right Doug; the invertor will only draw the power demanded from it, plus whatever systems and internal inefficiency loads there may be.
Spot on but if you are trying to save power then you need to match the load to the inverter. 3 amps is not alot but over say 6 hours it is 18 amps.
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Possible problem: My own set-up is 1.2 Kw inverter, 280 amp of battery and 240watt of panels.
We run computer, TV, and freeview recorder and here in sunny Portugal we can run all day but as soon as the clouds come we have to cut pack or flatten the batterys.
The batterys are now 3 years old and getting a little tired and doubt that they will need renewing in a year or 2. I would suggest that your proposel of usage wiith your storage and power generation do not match and even with new batterys you will be in
the dark very quickly. sorry.0 -
My comments where to the original poster of the question DD
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Just an update - taking all the comments into account, I have decided to get a 1000w inverter which will be wired in permanently off the leisure batteries by my friendly auto-electrician.
I have taken on board the comments regarding the heavy drawdown of some appliances and will initially limit use of the inverter to powering a hairdryer on its lowest setting for about 10-15 mins per use. After that, I will see how the batteries hold up and use the inverter for other low power applications, such as recharging my laptop. I rarely watch TV in the MH.
I really only intend for the inverter to be used when we are off EHU, which generally only arises when we are on the move or staying on an aire, so the batteries should be topped up from driving plus using the SP.
Thanks everyone for your feedback, there has been some really useful advice. Jim
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