cable current carrying capacity

[nickruf]

Hello folks. I'm writing from England where I'm building a wilderness cabin that will use a 12V electrical system. I've no idea what kind of cable (in terms of square mm copper core) I need to install or what capacity fuses to use. Can anyone help? I suspect I'll only be using a 12v electric fridge, lighting and maybe a radio/CD player.
The cabin is 10m long and the system will be powered by a sealed battery - perhaps a tractor battery which will be charged by a wind turbine. Any advice gratefully received. Thanks
Nick

[Brian_UK]

Hi Nick and welcome.

I think that your questions should, perhaps, have been directed towards an electrical forum somewhere or maybe caravaners.

Low voltage electrics and refrigeration do not run side by side that often.

Something like the '12 volt bible' might be a starting point.

[The MG Pony]

10M you'll need very thick wire like #3 or #0 gauge, it is better to use an inverter if you need to go any length.

Low voltage high current, hence high voltage drop across even larger wires.

Plus get your self a couple of Double D cells rated for deep cycle use and a really good intelligent charger. Place the cells as close as possibly to place of use, and use higher voltage on your wind mill to transmit the power to your charger. This offers you the least losses and lowest cost of wire.

May I suggest you read up more on this as there is allot to consider to make your 12V system operate to its best and ensures your success! Good luck and have fun! I certainly have enjoyed making these systems

[monkey spanners]

A welding supplies store would have heavy duty multistrand (flexible) wire. Was going to buy some to make some HEAVY duty jumpleads for my truck but it has since been stolen so don't need to now. Oh and fuse it near to the battery to protect the cable in case of short circuits.

[The MG Pony]

Get your self a book called "The secrets of lead acid batteries" it will help you with sizing wires and every thing.

http://www.otherpower.com/otherpowerfront.shtml < Check this site out mate.

[chiller-man]

Your problem will be the 12vdc fridge, if it is an absortion cabinet similar to that used in a caravan it would normally be fused at 20amp, this sort of heavy current draw will flatten your battery very quickly.
If your fridge is fitted with a 12vdc hermetic compressor, IE the danfoss BD2.5, It would be fused at 10 Amp, this is a much better option for the battery, these type of compressors can be found on many small boats and yachts, most coaches and cross country busses have these compressors fitted to the drinks fridges on board.
Choose a big battery, IE tractor as you said,(although most big deisel engined vehicles would have two 12vdc batteries in series), Wire from the battery with at least 10mm TRI-Rated cable to a 80amp fuse (fuse to be as close as possible to the battery), Then run your 10mm cable to a convenient point an fit a small fuse box (say 3 or 4 fuses), Feed each appliance with 4mm TRI-Rated cable and select a fuse rating to suit that appliance, IE fridge 20amp, radio 10amp, lighting 10amp etc etc, You will need to follow the instuctions that come with your wind generator, but make sure you fuse the cable between the battery and the wind genrator, Finally consider a solar panel also, Maplin do a good range.
Hope all this helps, Good luck,

[The MG Pony]

Yes you want a fairly large bank of batteries, the Double D size are used on large marine applications to power living quarters or on large machinery. They are big, heavy with massive Ampacity.

The goal is to never really discharge them, So a wind/Solar set up is definitely the way to go.

During a rather nasty affair I ended up living in the bush for 2 months and I never appreciated my solar set up more! (One of the few things that didn't get stolen or screwed up)

You really need to get the best charge controller you can for both the wind geny and the Solar cells, this will make or break your system as the health of your batteries is more important then the source of the power to charge them! I grew up in a logging camp where most of the power through the day was 12V and seeing the diff a high quality smart charging system makes it is night and day!

I can not stress enough How direly critical it is for you to invest the most money on your charge controller(s) That is the CORE of any off grid system! If you cheap out on that component you will forever regret it this I will put my life on! A good charge controller will make even garbage batteries last and will maximize even the smallest of generated power.