Since there is an appreciable voltage drop over 25m of 6mm^2 cable, I suspect 1610m of 2.5mm^2 flex might just leave enough to power a torch bulb.
If it was a very small one.
And you didn't need much light.
Not quite that bad.
But the answer is somple, Get water and electricity laid in to a temporarary structure as no 1 priority.
Just use central heating fuel. Why faff about?
potential to ground.
Not far off though - you'd have about 22 ohms series resistance...
And I'd be very surprised if B&Q sold 2.5mm extension leads.
Unless you are doing absolutely *all* the work yourself (and possibly even then), as soon as you bring a subbie on site for anything your site becomes a workplace and you have to have adequate arrangements for water (not just for drinking, but for washing cement off tools and out of eyes
- health and safety), toilets, changing and storing PPE, and refreshment breaks. Your construction site insurance is likely to insist on all this even if your subbies don't.
Caravans are notoriously insecure. You can get 20' or 40' shipping containers fitted out as site office / mess hut one end, tool store with porta-loo compartment the other end, and porta-loos on hire where the 'honey truck' comes round once a week and does and empty-and-disinfect for you.
The other aspect sf if you can plan your construction to accommodate services and storage from the outset. Quite a common arrangement is to build the garage first and bring the power and water into that, it avoids the expense of temporary supplies whilst providing some storage early on in the build.
Owain
I'm sure that 110V is not widely used in France, not in this area anyway. No idea about the rest of Europe.
-- Holly, in France Holiday Home in Dordogne
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