Basic Electrical question (1 Viewer)

[Nigel L]

Hi, we are new to the MH scene, and are awaiting the delivery of our MH at any time now.
The one thing that does confuse me are electrics.
We intend to do a fair bit of wild camping, so have ask the dealer to install a second leisure battery, and may consider solar panels, depending on how we get on.
After reading up on several threads, we keep comming accross the term Inverter.
Please could someone please explain in very simple terms what an inverter is, and what they do.
Many thanks.
Nigel.

 

[dabhand]

So @pappajohn and @funflair it's great when people who know what they are talking about have these discussions as they are often enlightening, but from a practical point of view, for people like me who think they know what you mean, but often get a bit lost with the debate, does it matter if you use your inverter? Does it matter, 20 amps at 12v vs 1 amp at 240v etc? From my own point of view, I use my inverter when necessary but not for prolonged periods, I am more concerned with the state of charge of my batteries and am practically obsessive about checking they don't fall too low, particularly when using the inverter, I have to say though, I've never noticed the inverter making much of a difference to the voltmeters or state of charge even when in use, whatdayasay boys?

 

[funflair]

So @pappajohn and @funflair it's great when people who know what they are talking about have these discussions as they are often enlightening, but from a practical point of view, for people like me who think they know what you mean, but often get a bit lost with the debate, does it matter if you use your inverter? Does it matter, 20 amps at 12v vs 1 amp at 240v etc? From my own point of view, I use my inverter when necessary but not for prolonged periods, I am more concerned with the state of charge of my batteries and am practically obsessive about checking they don't fall too low, particularly when using the inverter, I have to say though, I've never noticed the inverter making much of a difference to the voltmeters or state of charge even when in use, whatdayasay boys?

@dabhand the simple answer is when off hook up, if it will run on gas "use it" if it will run on 12volts "use it" if the previous two don't apply but it will run on 240 volts OK use your inverter but be aware that it takes a little bit of battery just to run the inverter itself (very little) but then be aware of what is going out of your batteries and keep an eye on the battery level.

The more you use all the toys the more you understand them.


Martin

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[Stealaway]

I am no expert, but you may be guilty of using numbers to support your own logic, bit like the calor gas / refillables suddenly calor is 50% more expensive

My MH has a display showing Amps being drawn, probably not totally accurate, but our 12V LED TV's are around 2A each

but you are definitely right on price

I'm confused about the reference to Calor gas bottles I don't remember ever commenting on those.

Any way I thought I'd better check up on my figures.
A 12V 24" Avtec TV (£449.00) is rated at 2.9 amps. A Samsung 240V 24" TV (£109.00) is rated at - 1.91A optimum output (4.5A maximum output ?).
Not surprisingly, very similar and £340 will buy you a stack of battery's, an inverter ------ and some solar panels.

The TV's that come with a 12V transformer will of course use exactly the same amount of battery amps whether its at 240V or 12V.

As I said before I would definitely not recommend using an hair drier on an inverter. I met a guy on a boat who said his wife's hair dryer was the most expensive one in the world. As he had to buy a 2Kw Honda generator just to power that one item!
We had a 1Kw toaster on the boat and even though we did have a much bigger battery bank it still murdered the battery's, drawing a 100A while it was on.

 

[dabhand]

Have to say I don't think I would run a 1kw toaster off an inverter, probably just have a cheese butty!

 

[Robin McHood]

@dabhand It's actually very simple. There will always be more of your battery's capacity used if you run any piece of equipment via an inverter rather than direct. An inverter is a machine and all machines have losses in making them work. The very best inverters will still use about 8 % more battery power than powering a device directly. The example of a domestic TV is a good one. If you are lucky enough to have one that has a 'brick' power supply from AC to 12vDC then plug it directly to your 12v battery supply if you can as even a brick loses a bit.

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[milsh]

Has anyone ever tried taking the 230v supply from an invertor to a double socket, use one outlet to power your appliance and the other to connect back to the mains hook up via a 13A plug & blue socket extention lead, so that the motorhome battery charger kicks in... a bit like perpetual motion, obviously some conversion power losses would occour, but would be reduced by charging of the battery. Never tried it myself, just pondering!

 

[peterc10]

Has anyone ever tried taking the 230v supply from an invertor to a double socket, use one outlet to power your appliance and the other to connect back to the mains hook up via a 13A plug & blue socket extention lead, so that the motorhome battery charger kicks in... a bit like perpetual motion, obviously some conversion power losses would occour, but would be reduced by charging of the battery. Never tried it myself, just pondering!

Not sure if it is possible but why would you want to do that? What would it achieve? There is no such thing as perpetual motion and all you will do is run your batteries down with the power losses

 

[Robin McHood]

@peterc10 . Exactly, close to double the loss from just running the inverter.

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[eddie]

I have a large bank of batteries, and a large solar set up.

I have a 2000 watt pure Sine wave inverter installed with and automatic transfer switch and remote panel

When I activate the inverter the 13 amp sockets in the motorhome become available for use.

From my wife's perspective, this allows her to use her hairdryer, my main use is to run my Sky+ box which runs the two mains TV,s in the motorhome.

As there is no 12volt Sky+ box available, and the two fitted TV's are too big for 12volt I have three options

1: use mains when available
2: run the built in 6K generator
3: use the inverter

I use a mix of all three, for example if Van Bitz are exhibiting at a show, and my motorhome is parked in a trade area, I would tend to run everything from the inverter though the evening. In the morning, I'll start the generator, which runs everything and the inverter, which is a combination unit so acts as a high performance charger as well, will recharge my batteries. It is multi stage and rated at 100 amp

Once I leave the motorhome my three large solar panels, will make the most of any solar charge that is available, significant in the Spring and Summer months ( when most of the shows are)

All this is monitored by the on board power management system, telling us exactly how much power we are using, what were producing and how long we can maintain the current (excuse the pun lol) usage in hours/days

The inverter is the least effectian of the three, but it means I don't have to compromise, even if I am sat in the middle of a field

lifes too short to compromise

 

[funflair]

Has anyone ever tried taking the 230v supply from an invertor to a double socket, use one outlet to power your appliance and the other to connect back to the mains hook up via a 13A plug & blue socket extention lead, so that the motorhome battery charger kicks in... a bit like perpetual motion, obviously some conversion power losses would occour, but would be reduced by charging of the battery. Never tried it myself, just pondering!

A properly installed decent sized (around 2kw) inverter will be wired to power the whole van but omitting the circuit to the battery charger.

Martin

 

[DanielFord]

Thanks for all the replies, they have been very useful, and even I understood them
Basically, the items we would want to use, are as mostly mentioned above, ie, hairdryer for the goodlady Electric shaver, phone charge and I-pad charging.
We will be getting solar panels fitted, so with two leisure batteries, and minimal use of an inverter for the items listed above, we should be ok?

The installation you suggest is exactly what we have, ie a 150w panel, 2 leisure batteries and a 2kw pure sine inverter. We also have a battery monitor, which gives us the battery condition and state of charge etc.
Rather than giving you lots of numbers, I can give you real world examples
We often make use of BritStops, where there is no EHU, so we are totally self sufficient. Plugging the ipad charger in when the inverter is on draws very little power, similarly with laptop chargers. In fact when the sun is shining, the batteries are still receiving a charge.
Things that use a lot of power should be used sparingly. We have a coffee pod machine, which we make our morning cappuccinos with. When this runs it peaks at 130amps from the batteries, similarly, the microwave draws about 110 amps when running. My electric shaver is one that you charge up, so that doesn't use any power
On our last trip, we weren't particularly frugal with the power, we had the blown air on all night, my daughter insists on keeping her light on at night, and we watched a fair bit of telly. Coffee machine was used a fair bit also. In the morning the batteries were at 85%, but since it was sunny, they were starting to receive a charge from the panels.

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[tonyidle]

Found this invertor:

Any good?

 

[Nigel L]

Thanks Daniel, that is very reassuring.

Eddie, thank you also for replying. We have already decided from the favourable reviews that you get on here, that we will be bringing our new MH to you to get the work done. Just waiting for a delivery date now!

 

[two]

Nigel, I’m in a similar situation to you, except that I’ve had prior experience of motorhomes and boats. My advice is as follows:

Your first consideration is payload. This finite and can be used up quite quickly if you get carried away with the extras. Next comes finance, and you may need to be considerate in the way you spend your remaining cash.

Your Ah needs will depend on your usage pattern and you may not know what that is, yet, so that makes it more difficult to advise.

If your payload will happily allow for the weight of a second battery, I’d get one (as planned). Do make sure that it is identical to the one it will partner, however, or the weaker one will draw the stronger one down to its own level. They need to ‘wear’ together to keep in balance, so it’s not such a good idea to add a second battery later on.

Your battery bank is like a tank for electricity. You should avoid emptying it, though, because that shortens the life considerably. The size of ‘tank’ you need will depend on how much electricity you may need between refills, which should be as often as possible. Solar panels are good in summer (when you use less electricity) but not so good in winter. You may be better off investing in a battery-to-battery (B2B) charger. These optimise the charging from your vehicle’s alternator to replenish the habitation battery bank every time you move and, if you move often, you may not need solar panels if you have a B2B installed. They are even effective with the engine just idling. Solar would be good where there’s plenty of sun and you want to remain stationary for several days (which is not the way that I explore).

I suggest that you wait and see what your usage pattern looks like, then add your requirements in the light of experience.

If your payload does not limit you, and you have a healthy bank account, I’d get as much battery capacity as I could, add as much solar as I could fit on my roof (how about tracking solar?), and get a big (2kW minimum) pure sinewave inverter for off-grid mains. But, even if your circumstances meet the first two conditions, I’d still recommend going slowly. It’s all part of the fun. In my case, I shall fit B2B and delay the decision for solar. A good battery monitor will help you understand what your daily Ah demand looks like and how well the battery bank copes with it.

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[Nigel L]

Thanks rogher for your explanations, it is much appreciated.
Firstly, it is a new MH, so I will be starting with 2 new batteries, so that's the first box ticked
The B2B seems to make sense initially, and then solar if needed. Yes, intend to take things slowly, but you know what's it's like, we are awaiting delivery of our first MH and the excitement sometimes overtakes us!! meantime the plans start to get put together and one gets ahead of oneself!!
I have to say that we have found this site a wealth of help and information, of which we are very grateful.
It's easy to get taken for a ride being new to the game, and so all information bathed is well received.
Many thanks.

 

[hilldweller]

so have ask the dealer to install a second leisure battery
Nigel.

OK so now you run out of electricity after twice as long, the big question is how do you replace that electricity ? You've just made it twice as difficult to replace the electricity.

Say you run out in 4 days. You then have to go for a long drive or plug in somewhere. With one battery your would have gone 2 days but the drive would be shorter or the hook-up shorter. That is how it works.

What seems a good rule of thumb is one 100W panel per battery. Spot on in summer but solar in UK is not up to much in winter.

 

[Zigisla]

Thanks rogher for your explanations, it is much appreciated.
Firstly, it is a new MH, so I will be starting with 2 new batteries, so that's the first box ticked
The B2B seems to make sense initially, and then solar if needed. Yes, intend to take things slowly, but you know what's it's like, we are awaiting delivery of our first MH and the excitement sometimes overtakes us!! meantime the plans start to get put together and one gets ahead of oneself!!
I have to say that we have found this site a wealth of help and information, of which we are very grateful.
It's easy to get taken for a ride being new to the game, and so all information bathed is well received.
Many thanks.

Been there too. We tried to wait out a year to see what and how much power we used. But, having used the MH for all bar 4 weekends since mid Dec 15, we now have a good idea. We will continue using over winter time which will be the greatest power draw and weakest solar input. Although the 2 x 95 Ahr batteries lasted for 4 days, we didnt use much power and felt we were saving using some appliances. So last week we had 150W of Solar and 1800 PSW inverter fitted and this has given so much more piece of mind. Someone from my previous thread about hairdryers quite rightly stated that this motorhoming lark should be a pleasure not an endurance test, so use as much as you like, but make sure you can replenish it. Solar or EHU or Drive or dare I say the dredded Generator

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[DBK]

If its a new MH I suggest get the solar fitted from the start. A 100W panel should only weigh about 10Kg maximum so unless you have a real issue with payload it shouldn't be a factor. We found 100W was enough initially but have now added a second one and 200W is what I would recommend. There was a time when folk thought 80W or thereabouts was enough but within reason you can't have too much and they will keep the batteries all topped up when the vehicle isn't being used, especially if you fit a battery master, which will cost about £60 to buy and will keep the vehicle battery fully charged off the solar as well as the leisure batteries. A B2B charger I wouldn't recommend unless you plan on a lot of inverter use in which case they are good but be careful of the new vehicle warranty as it might invalidate it as they effectively "trick" the vehicle electrics to do something it doesn't plan to.

 

[peterc10]

Another thing to think about is that you need to make sure that the solar controller you buy can take the combined wattage of the solar panels. When I got my new motorhome I wanted to use the Schaudt LRM1218 MPPT controller so that it could work with the Schaudt Electrobloc in the new van. That has a maximum wattage of 275W. So I agreed with the dealer to fit 1 x 100W panel and 1 x 150W panel partly because that fitted the available roof space better. Those, along with the Schaudt controller and some other extras I wanted then became part of the deal we struck.

 

[Cavs]

Firstly, it is a new MH, so I will be starting with 2 new batteries, so that's the first box ticked
The B2B seems to make sense initially, and then solar if needed. Yes, intend to take things slowly, but you know what's it's like, we are awaiting delivery of our first MH and the excitement sometimes overtakes us!! meantime the plans start to get put together and one gets ahead of oneself!!

You don't say what motorhome you're buying or what electrics system it will have. If it's to be a Schaudt system do not fit a B2B or battery master - it will only confuse the charger. A new Schaudt Electroblok will charge vehicle and habitation batteries itself.

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[Robin McHood]

A new Schaudt Electroblok will charge vehicle and habitation batteries itself.

It certainly does and is very efficient too, we have 2 x 120AHC batteries and 2 x110W polykrystalline panels all Schaudt controlled. I've found the current input to the batteries good though there is a bias towards prioritising the separate vehicle battery which I don't yet understand as this occurs even after a long drive. I'd love to get my hands on the proper technical manuals for the Schaudt system!

 

[Zigisla]

It certainly does and is very efficient too, we have 2 x 120AHC batteries and 2 x110W polykrystalline panels all Schaudt controlled. I've found the current input to the batteries good though there is a bias towards prioritising the separate vehicle battery which I don't yet understand as this occurs even after a long drive. I'd love to get my hands on the proper technical manuals for the Schaudt system!

E mail udo Lang - address earlier in thread. Or do a search on this site for him. He is the guru of Schaults and speaks good English. He emailed me my manuals.