First off, let me say that i'm not planning on doing anything to my electrics myself, i just want to get an idea of what is required and therefore what disruption to my house.
I have a fair understanding of ring mains/lighting circuits.

Anyway i digress.

I would like some basic power in my shed. Nothing high wattage like power tools. Just running a small tv/radio/fan/lights for a max of 2 hours a day (not every day either).
With it being (basically) a shed i think wiring it up to the house electrics seems a bit overkill so i wondered about a solar panel and a leisure battery to store some juice.

Something like:
Solar panel -> Charge Controller -> 12v battery -> 12v inverter.

This seems fairly straightforward to me, but the thing i'm confused about is the earthing. It seems the regular use for these inverters is in cars/motorhomes etc where the battery is negatively earthed (is that correct??) to the chassis and this earth gets passed to the inverter when they are connected
If i remove the vehicle from the equation where can i/should i get the earth connection from? What is easiest?

If i run from the earth point on my house's electric board (which is 40ft of garden and 2 rooms away) then can i run this above ground across the garden seeing as its "just earth"? (don't rip me apart for the "just earth" comment please!)

Also, i assume the panels also need to be earthed for lightning purposes?

If anyone could point me in the right direction i'd appreciate it as i'm not even sure if my idea is even viable at the moment!

Thanks.

if you remove the the and fan and tv from the equation then a reasonable solar may work
where you planning on covering the whole shed roof or just a large panel!!!

this one quotes 120w per hour in the sun
http://www.maplin.co.uk/Module.aspx?ModuleNo=97380
that probably equates to an average off 30w over daylight hours so in the winter the output would be around 250- 350w

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we are all ------------------still learning

I was planning on getting something like a 40W solar to charge a 70ah battery.

Am i right in thinking that a fully charged 70ah battery would run 100w for 7 hours?
If so, that should be plenty. TV is about 55W, light about 11W, fan 25W (???).

I only want power for a couple of hours a day so it shouldn't drain the battery down fully and should be topped up by solar panel.
Even with power conversion and loss it seems reasonable to me.

I'm pretty sure if it could do this i'd need the battery as i'd want power in the evenings.


Just a bit worried about earth.

have you noticed my edit!!

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we are all ------------------still learning

ok, this is something like what i was after:
http://www.solartechnology.co.uk/whoopi ... r%20v7.pdf

Although buying the parts separately is MUCH cheaper than their price.

It seems they just connect the output of the inverter to an RCD protected socket, looking at page 2. I can't find anything about earth unless i'm looking so hard i'm missing it!

you have to work on the useable output being around 25% off the maximum for the daylight hours in other words if your kit claims 350w peak your talking 700w a day in the cold dark winter days
700w would keep a 70w mains tv going for about 55 mins

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we are all ------------------still learning

Yes, i think so. Thanks.
Pointing me at the maplins product?

If so, i'm confused how that would work in the evenings without the use of a battery.
And if adding a battery to that, does it need to be earthed, especially when using an inverter?


The maplins product says it is suitable for what i want to do in theory, but in reality i'm trying to work out how much work it will be to get up and running if i need to run an earth cable or get another earth rod installed.

I could completely over complicating this, i'm not an electrician!

you cant earth a battery lol
a battery can use the chassis off a car as the return on the circuit marked up as earth but its not earthed in the safety way
just go for double insulated products and possibly an rcd wait for a definitive answer from fro a sparky
you must have energy store what ever method you use normaly a battery

basicly if you have a panel battery inverter that is rated at 350w peak then during the winter you can expect 25% efficiency so you would chare 700w a day or 4.9ah per week so to fully charge a 60ah battery would take 3 months without any use or battery losses

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we are all ------------------still learning

Awesome big-all. Thank-you.

I didn't know you couldn't earth a battery. Like i said i'm no electrician.
I was just confused about normal AC having earth but the AC from and inverter not having an earth. Plus the whole earth thing in cars.

However, after hours of reading i've realised that an RCD socket will protect from the current leaking to earth through you by tripping.
Is that the idea of earthing also? So that the current will more readily travel down that rather than through you??
Although why would you have both earthing and RCD on ring mains?

I need to do more reading!


Thanks for the help!

Have you tried a caravan accessory shop for ideas? They will have a range of devices for charging 12v batteries,

Skip the inverter completely.

Invest in 12V TV's etc and LED lights.

Get the power consumption DOWN to make the project feasible. Inverters are an unnecessary 'loss' in the power chain.

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Not tried a caravan shop, project is in it's very infancy as you can prob tell from my understanding! Will try and find one though.

I'll research dc powered stuff too.

Thanks for the tips.

If your supply or invertor or transformer or battery's not earthed, RCDs won't work. That's why you have an isolation transformer for a bathroom shaver or 120V site supply. The secondary side is not earthed so you can't get a shock if you touch one of the two output wires.

A 12V 60 Ampère-hour battery will be charged in one day if the PV array provides 700 watt-hours in a day. That's because the energy in the battery is 12 X 60 = 720 watt-hours.

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I should be dead; I've cheated the Grim Reaper yet again by surviving my third heart attack in June.

Thanks Stoday.

That brings me back to my original question though :-(
How do i earth the supply (solar panel), battery or inverter? Do i have to run earth all the way back to the house electric board?

Or have i misunderstood your post?

You don't need an earth.

The earth wire (safety protective conductor) is fitted on normal mains wiring to provide a low resistance path from any exposed metal case parts to compelete the circuit. The idea being if the live wire connects to the case then the earth connection causes a massive current to flow which quickly blows the fuse. This is only needed just in case you happen to touch the case and if the earth was not present you would complete the circuit. And yet this still is only needed as the neutral terminal of the substation transformer is bonded to earth. (so what the exact reason is is beyond me).

Anyhow, I digress. Think of the output of the inverter as the same as the outout of a shaver socket - they are both what you would called isolated and floating with respect to earth. If you touch one of the contacts in the saver socket you would not get a shock as the current has no where to go - the supply is isolated from earth. You only get a shock from a shaver socket by being unlucky (or daft) enough to touch both at the same time. The output from an inverter is the same. It's not referenced to earth so needs no earth connection. You will only get into trouble if you get between the two connections.

So ... you don't need one.