Topic: LED wiring for 12v DC system

Re: LED wiring for 12v DC system 

OK not going to get into any mud slinging here but point out a few FACTS.

AS/ZNS3000 was revised last year so 2007 no longer applies. ALL ELVDC installations were brought into it. So, you don't have to be licenced to do 12VDC work but it DOES have to comply. No compliance, no insurance when it burns your house down.

Running current through speaker wire and conduit wire without conduit is not compliant.

Running 230VAC cable and DC / data cable in the same space will shortly be non-compliant. There must be a barrier between them. Up until now it was ok as long as the minimum cable insulation was suited to the maximum voltage present but before long no go.

If you already have in inverter in the system then using 230VAC to get power to your lights is WAY more efficient than trying to run loads of copper to get voltage drop on a 12VDC system low enough to keep the lights on. It has got to the point where you are better off to spend the money on upsizing system capacity to cope with the inverter losses than upsizing wire capacity to minimise the line losses.

If you want to live a basic lifestyle without an inverter it can be done on 12VDC but as has been mentioned it severely limits your choices. Also if in 5, 10 or 15 years you want to sell your potential market is way smaller.

Presenting options for living a DC lifestyle is ok but some posts here read like it is THE way to go without highlighting the drawbacks. Some people want a large screen TV. They may not really NEED it but that is not the point. If they want to pay for a suitable system to run it because that is an important part of their enjoyment of life, so be it. It is not up to anyone else to tell them it is wrong because this is still a free country.

Re: LED wiring for 12v DC system 

Interisting discusion.
My off rid situation is run on a12 volt inverter,Lights compact flouros.I too have been wondering about running a 12 volt system for LED lights.
But really for better inverter operation I am much better to run a 24 or 48 volt inverter.
When my present inverter gives up the ghost I will change to a 24 or 48 volt inverter.
Once at 24 or more volts I would need to get a dc down converter, so more loses.

Therefore I'm in the wire everything 230 volts camp.
And as previously stated makes for easier sale should a future owner want to run a cable to the road.
I will use led lamps soon as they seem to be coming down in price and getting better.
One thing I find that many lamps don't list the lux output or the colour temp, which is the only true way to compare apples with apples

Re: LED wiring for 12v DC system 

Hi Tearai, don't fret about losses from a 230 - 12VDC driver for LEDs. If you use a good quality one it will run several lights and be up in the very high 90% efficiency range so lost power will be way less than that lost in 12VDC cabling.

Another issue around running LED's directly from a battery. You still need a driver because the battery voltage will fluctuate from around 11.5 - 12V when low to about 14.4V when bulk charging and 15 - 15.2V when equalising. With no current control these voltage swings will cause low light output at the bottom end and overdrive the junction at the higher end, shortening lamp life. With the line loss offset the total losses when using an inverter based system will really not be much greater and you don't have to spend a fortune on oversized cable.

So make life a little easier, go to the 24 or 48V battery and use 230VAC to power your lamps.

Re: LED wiring for 12v DC system 

Yep
The inveter is running anyway, so 230 volts for everything, keep it simple.

Re: LED wiring for 12v DC system 

Did some tests today, laptop draws 1.6amps running with 12v adapter, running 240v with a 600w inverter draws 6amps.

similar story for my 12v T.V.

Unless you have a hefty solar array i would be defiantly run things 12v where possible.

Heres a reply i got when asking this question on a solar power forum:
For instance, if only running 3 or 4 one watt LED's off a 1000 watt inverter, the inverter alone could be consuming 20 watts just sitting there idling, providing power just in case you might turn on a light. And when running the lights, will add it's running load to that of the lights. If you want to run the lights off AC, I definitely would use a far smaller, less energy hungry inverter - - - that is unless you're lighting up the Wal*Mart parking lot
Better still, eliminate the drain of running an inverter altogether if you have only a few small wattage lights, get 12 volt LED lights, then the only drain would be when a light is actually on, and then only the wattage of the light. Using a step-down transformer from 220 VAC to whatever voltage you want for the lights would work too, and if the transformer is small, would add little extra load to the batteries compared to the 1000 watt inverter powering it. Unless you have power to spare, have extremely long runs from battery to lights that require high voltage to cut transmission losses, or have huge lights, go with 12 volt lights, only use them at night when the voltage isn't so high (charging batteries) and keep that 1000 watt inverter shut down unless it's really needed for big loads. Unless of course you have power to spare, which most of us don't.
I have a Morningstar TS-300 running 24/7 anyway for certain items that need it, so run my LED lights off that (it's on anyway) and don't have to worry about voltage surges from battery EQ etc driving the LEDs too hard and shortening their life.

I personally do not use my lighting during the day, daylight seems to do a good job for me :P

Re: LED wiring for 12v DC system 

Stonemason: has this article convinced you to run 230V ac or stick to 12V DC for your lights?

Re: LED wiring for 12v DC system 

Horses for courses?
In my case My inverter is running all the time as the fridge needs power available to start.
I used to have a gas fridge but didn't like the idea of a pilot light running 24/7.
Also on 24 volt or 48 volt system I would need a dc down converter to get down to the 12 volts for the LEDs .

Re: LED wiring for 12v DC system 

Stonemason you say "Did some tests today, laptop draws 1.6amps running with 12v adapter, running 240v with a 600w inverter draws 6amps. similar story for my 12v T.V."

Something does not add up. Putting aside that the battery voltage will rise and fall and using a median point of 12V, 1.6A x 12V = 19.2W. 6Ax12V=72W. Take off the 20W idle for your inverter and the 19.2W for the laptop and there is a differential of 32.8W that your DC/inverter comparison does not account for. Where has that gone? Not into either the inverter or the laptop so you must have had some other AC load running at the time.

Also you say "Using a step-down transformer from 220 VAC to whatever voltage you want for the lights would work too, and if the transformer is small, would add little extra load to the batteries"

If you use a transformer the losses are going to be pretty high and it is pointless to take the 230VAC post inverter, put it through a lossy transformer / rectifier and run it through either lossy cables or larger ,expensive copper just to run the led's from DC. Might as well just run direct from the battery and avoid all the conversions.

Much better to run the 230VAC to the led's using lower cost cable and use a high efficiency switchmode driver at the lamp.

Tearai, apart from the pilot flame issue with gas fridges, the running costs are pretty high. These days around $1.50 plus per day. It does not take that long for the extra investment in PV array to offset the gas costs and then you are onto a winner by running electric. There are specialist energy efficient fridges imported from Europe to meet the off-grid market. They use significantly less energy than the best of the F&P range but they do cost more.

Re: LED wiring for 12v DC system 

Got a Samsung sr237nme fridge freezer for $560 (new). Energy star 2.5 on the new rating scale.From memory 339 kw per year. Almost matches the expensive European fridges for energy efficiency,But not the same build quality.However great bang for buck.Have checked its energy consumption over 24 hours and uses approx .9kwh.So pretty true to label.
To keep with the thread it has a led lamp inside!

Re: LED wiring for 12v DC system 

@ seeker, i will deff be sticking with running 12v lighting and everything else, only sparking up my inverter when i need to run pesky items like my printer which are not available in 12v.
Way to many unnecessary converting losses running an inverter.

@REguy, the losses im guessing are going through heat and the fan in the inverter and heat in the laptop power adapter.

Re the fridges, i have a separate system for my fridge so it does not chew up my everyday batteries.
Had it running gas for a while, while in Dunedin 9kg refills were $9 now in nelson refills are $35!!!!!

Gas gets bloody expensive!

I set up 3x 2nd hand 105AH batteries and 120w solar pv with a voltage switch, when the sun comes out the fridge turns on and a few hours after the sun goes down the fridge turns off, works out perfect.
The voltage switch is user adjustable so i set it at 12.5v to turn on and off.

Just a bummer that the fridge runs longer in winter than summer... wish it were the other way around.

Re: LED wiring for 12v DC system 

"the losses im guessing are going through heat and the fan in the inverter and heat in the laptop power adapter"

Must be either an incredibly inefficient inverter or the laptop adaptor is too hot to touch!

Re: LED wiring for 12v DC system 

Can't work this out: why does your fridge run longer in winter???

Absorption chiller run on high temp evac tube solar hot water collectors could be the answer!!!

Re: LED wiring for 12v DC system 

Not serious BTW......

Re: LED wiring for 12v DC system 

@lothiriel

Have you decided what you would like to do with your 12V lights? Stay with 12V or wire for 230V?

Stonemason shows that a separate system for lighting is workable in practice.

nzspark posted 27 Jun 11 7:53 PM the formula for working out the wire size you need to come within a maximum voltage drop of 5% (except you need to double the distance measurement to the furthest light on the limb - I have double checked this).

Do you need any more info?

Re: LED wiring for 12v DC system 

Thanks to everyone for all the posts! I didn't expect so much input!

@Seeker - I managed to find out the LED lights are a 6w Phillips brand (they haven't arrived yet so don't have any other details on hand).. I'm not sure if anyone has picked up on that I'm the wife of the builder who's building our house... so although I've been asking for run lengths etc so I can post and get confirmation - I have been assured by my other half that we're on the right track judging from all the posts!
Apparently the calculations that have been suggested have been done or taken into consideration - and we are opting for a seperate 12v dc system for lighting at this stage.

Really appreciate everybody's time to post suggestions and experiences!

Re: LED wiring for 12v DC system 

Voltage drop discussions and calculator.
May need to convert awg to metric though.
http://www.wind-sun.com/ForumVB/showthread.php?t=29

Re: LED wiring for 12v DC system 

@Tearai - thanks for the calculator: will check how we've calculated voltage drop.

Re: LED wiring for 12v DC system 

Hi lothiriel
If you are setting up off grid from scratch I would seriously consider going 24 volt or 48 volts on the dc, there are a number of advantages in doing this.
I suppose if you want to run dc lamps direct from the battery you could run them in series.
All the best with your off grid adventure,I think it will be interesting an satisfying.
That wind sun site is a mine of info, also some very experienced off grid people on this forum.
Regards Peter

Re: LED wiring for 12v DC system 

Regarding living off grid, I thought this article may be of interest to you:

http://www.ecobob.co.nz/EcoArticle/2290/0/Living-off-the-grid-and-off-the-water-mains.aspx

Re: LED wiring for 12v DC system 

IMO these guys make the best LED on the market... It's a New Zealand made product too, comes with a 7yr warranty!!
Can run either DC or AC

Something that no-one has pointed out is whether the LED are actually a constant voltage input. All LED are constant current unless they have a built in driver or resistors in the circuit.
You stated they are philips, all philips products have driver built into them. Some are 230V some are 12V.

Don't choose a product based on it's capital cost alone... So many other factors need considering. What housing are you putting these lights into? Is it sealed, ie can air transfer though it. You probably can't insulate over it therefore you will still have heat loss issues....
The cheapest product is not necessarily the best or even a good solution.

Re: LED wiring for 12v DC system 

Question for you 12v LED people:

Brief: bach (shed really) needs some lights, hot showers (gravity fed OK), juice to charge laptops/mobiles. Use is intermittent (holiday home).

What would be the CHEAPEST way to provide this in your experience?

(As I am inclined to over-design everything - 230V; diesel backed up full battery bank; solar array, water pump, SHW etc, thought I'd ask what you would do instead).

Re: LED wiring for 12v DC system 

Cheapest may not be the best.
But If you want cheep, a 12 volt sureflow pump may pump to a header tank or use as it would be on a camper van or boat. 12 volt led lamps will do a good job. A small inverter for the cell phone chargers and maybe a lap top.
My system started as 125 watt panel, 30 amp steka charge controller and 2 245 ah 6 volt battery's wired in series for 12 volts.
And a sine wave inverter.System was not properly balanced as pv was not the recommended size for batts , but as it was used for 2 days out of 7 it got me started. And got almost 5 years out of the batts.
Cheep? How much $ is your client hoping to spend?

Re: LED wiring for 12v DC system 

Thanks. Up to $3000. ????

Re: LED wiring for 12v DC system 

Probably doable, but if your client wants to expand( and most people do), There will be more wasted equipment as the cheaper bits may not be usable in any expansion.

Re: LED wiring for 12v DC system 

Dear nzspark

I have this project of village solar street lighting in which I propose to use 12w CFL or 12W LED light heads on a 3 meter pole. Because of the theft problem of battery and panel the village decided to put the solar system in the a house and then run wires to power the poles.

From the point of solar system which can be 12V/24 V and has a Controller of 20A 12/24V auto selection the last light pole is 500 meters.

Each wire line has 10 poles with 12V / 12 W light head. Please see the drawing and and also details along side.

My problem is voltage drop. I need to know what shall be % voltage drop at different pole stage and also at final pole and how do i sole this problem.

Please please help me.