Check with the RV crowd - they have been doing 12 volt lighting and a bunch of electrical based on what you are thinking for years. If you have a big RV store close, they will have lots of 12 volt fixtures, lights, wires etc. You will also find a lot of good information. Be nice to the service guys and they can give you a bunch of tips too!

There are also some very good reference books on 12 volt electrical in RV supply stores and also marine supply stores for the bigger boats.

Paul -

One caveot on the Rv stuff though, I find much of it to be very cheaply made. You have grandma and grandpa living on SSI in their RV so they can see the country and they don't have a lot of $$ to spend so you tend to get a lot of cheap chinese import stuff.

"...you tend to get a lot of cheap chinese import stuff..."

Most RV stuff may be cheaply constructed, but it isn't "cheap." This I know for a fact.

Campingworld has some LED lighting stuff. Most is designed to be wireless, running off of AA batteries, but you might be able to do a re-wire into a DC system I guess...

yea, sorry, cheap as in quality, usually overpriced for the quality as well.
Thats why I prefer the standard automotive stuff. I have the cap of my truck setup for camping with dome lights from vans and suv's, light weight, and decent quality for $5 on ebay.

Hi ToddW

http://www.dealextreme.com/details.dx/sku.13842

You would probably need about 4-6 per room.

These are MR16 replacements for 12V Halogen lighting systems that have a mains 120-240V 60Hz US or 240V 50Hz UK to 12V DC power supply.

Many of Halogen 12 volt systems will use a 120-240V 60Hz US or 240V 50Hz UK to 12 volts 'AC' transformer instead.

You will need a single high reliability 120-240AC 50-60Hz to 12V DC power supply convertor if you intend to power the LEDs directly from the mains electricity. Typically the power requirement would be a 200W 12V high efficiency switching regulated DC power supply to power the whole domestic 12V lighting circuits (enough to power about 60 LEDs).

If using solar PV and battery bank then a solar charger such as the Steca PR1010 Solar Charge Controller will provide DC regulation for your 12V lighting project.

http://www.alternativeenergystore.co.uk/..._Controller.htm

You should then be able to use standard MR16 light fittings with these high effieciency LED Halogen replacements. You should also be able to use the existing wiring that is already in place despite it being a DC system using these lower power rated LED type replacement. You do need to be careful though as domestic lighting wiring may use only 1.0 mm diameter copper wire cable. This will give a resistance of 0.02 ohms per metre length. This may no sound like a lot but if the cable run is say 40 metres or 135 feet in length and the DC current drawn is 5 amps (i.e 20 of these MR16 LEDs turned on) then the voltage drop will be 3.9 Volts with nearly 20 Watts being dissapated by the wiring. With a 4V drop your MR16 LEDs may not come on. You need to make some estimates of cable run lengths and the power requirements of the overall design of your domestic 12V DC lighting system.

Once you have designed and accounted for the all the 12V DC wiring losses (as in the above example 20 Watts is lost for 60W power delivered) it might be worthwhile comparing the design against using 85-260V GU10s LEDs such as these.

http://www.dealextreme.com/details.dx/sku.13452

and by using a 12v - 120 or 240V inverter at the Solar PV Battery power supply instead and comparing the overall efficiency of the AC-DC and the DC-AC systems. Of course if the mains electricity is used then this is the simplest of high efficiency energy lighting installations.

It could be that the inverter system wins out in terms of cost and effort of implementation especially if the 12V DC system requires replacement thicker copper wiring to be installed to be competative.

Am_Fear_Liath_Mor - Holy smokes! THANKS!

Provided a charge controller is used to prevent overcharging, I would not worry about placing the battery indoors.
The amount of hydrogen emitted is very small and most unlikely to be a hazard, provided smoking, sparks and open flames are kept away from the battery.
Remember that until very recently, electric wheelchairs used vented lead acid batteries, these were normally charged and used indoors, also many garages are used as workshops without the vehicle battery being considred a risk.

Standard car batteries are not suited to regular deep discharge, golf cart batteries would indeed be far more suitable.

I would use 12 volts, not 24 since a greater range of lamps are available.
Remember that you may need to oversize the wires compared to a 120 volt circuit since voltage drop would otherwise be a problem.
I suggest a minimum of #12 wire on a 10 amp fuse, it would be prudent to install at least two circuits.
12 volt compact flourescent lamps and LED lamps have about the same efficiency, but the LEDS are generally available in smaller wattages.

If your going to do 12v lighting stuff order automotive wiring (waytekwire.com for example), the resistance is less there and therefore less loss. Unless your running from one end of the house to another then you won't really need to worry about the loss on automotive wire. Using 120v wire for 12v stuff is where you have the most loss, it typically has a higher dc resistance because its designed for a lower impedance (impedance is basically resiatance for AC).
There are also plenty of charts on the internet where you can look up the proper size for length and current.

I'm not an electrical engineer, I just play one at work. I'm not sure where you got your info on the impedance of household AC wiring, but I have to disagree. So long as they are all made out of the same copper in the same AWG, Romex, automotive, whatever wire will all have the same DC resistance.

But as you say, tables can be found online.

solid vs stranded. automotive wiring is always staranded and the copper in wall is solid. I've found the losses to be different when tesing the two.