12v lights

[seabreeze1]

hello could somebody help me. I am trying to wire up 6 20w 12v lights off a 12v battery bank, powerd off a 400w wind turbine. My distance between lights from the battery are 8m 6m 3m 3m 2m 2m.Could somebody tell me how thick wire i need to use from the battery to the lights .I work it out at 4mm. If i am right is there any way of reduceing the thickness THANKYOU seabreeze1

 

[ban-all-sheds]

I work it out at 4mm.

I don't. What makes you think that such a high % voltage drop would be OK?

If i am right is there any way of reduceing the thickness

You're wrong, and it needs to be thicker.

http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html


Also - I don't know where you are in the UK, but if it's England or Wales, are you aware that all of this is notifiable and you're required to get Building Regulations approval before you start?

 

[JohnW2]

Edit: pressed button too soon!

 

[JohnW2]

I work it out at 4mm.

I don't. What makes you think that such a high % voltage drop would be OK?

I really don't know what criteria to apply to deciding what voltage drop to accept for ELV lighting - I'm really not at all convinced that the BS7671 limits for voltage drop are intended to apply to ELV circuits, are they?. I make the VD to the last light as about 1.925V. Although that 16% of the supply voltage, some people might accept that for 12V lights - although it obviously wouldn't be ideal (in terms of brighteness, colour or probably lamp life).

To get the VD to the end of the circuit down to below 3% (per LV lighting) would require 25mm² cable, which is obviously ridiculous. If the OP wants lower voltage drops and sensible sized cable, I suspect that (s)he is going to have to run separate cables to each light.

Kind Regards, John.

 

[EFLImpudence]

what is the 'plan' (in-line, circle, etc.) of the lights?

 

[JohnW2]

Edit: pressed button too soon!

The following user says thank you to JohnW2 for this useful post: seabreeze1 (today)

I would normally moan about such a smart**** response, but since seabreeze1 only joined the forum today, I would explain to him/her that what I did is the closest one can get to 'deleting' and accidentally-posted message on this forum.

Kind Regards, John.

 

[ban-all-sheds]

Edit: pressed button too soon!

Premature calculation?

To get the VD to the end of the circuit down to below 3% (per LV lighting) would require 25mm² cable, which is obviously ridiculous.

Ah - the inevitability of Ohm's Law.....

 

[seabreeze1]

could i wire 2 lights on 1 wire having 3 wires coming off the battery to feed 6 20w 12v bulbs as the lights have there own on/off switches

 

[ericmark]

A one increases size the volt drop will fall even 1mm will take 10A but the voltage would be:-
8.48
6.28
5.4
4.74
4.446666667
4.3
Clearly 4.3 volts on last bulb is not enough.
4mm will give:-
11.12
10.57
10.35
10.185
10.11166667
10.075
And 6mm will give:-
11.416
11.051
10.905
10.7955
10.74683333
10.7225
So 10mm seems to be within reason at:-
11.648
11.428
11.34
11.274
11.24466667
11.23
That's 6.4% volt drop on last bulb. One could start with 16mm and then drop size with each bulb but to run separate cable to each bulb is more likely a better method.

To keep all bulbs at a set brightness wiring is series with higher voltage would be method, but once looking at a higher voltage then one needs to look at using inverters for whole system.
Using a 12 to 230 volt inverter then 230 to 12 volt inverters at each lamp would of course give you bang on 12 at each lamp.

Not sure what you can boost wind generator to but something like a Rutford will go well over 12 volt once the regulator is doctored. Using 3 amp 7812 voltage regulators at each lamp or even simple resistors you can compensate for volt drop. So with 15 volt rather than 12 volt at origin you can use 1 ohm resistors for first 2 lamps and 0.5 ohm for next 2 lamps and you will be some where need volts required for each lamp.

The other idea is 24 volt and three circuits with two bulbs is series in each circuit. I say that as some wind generators will do either 12 or 24 volt.

But much depends on control methods with a MPPT charge controller the voltage at the wind generator will likely vary anyway and to alter the output voltage may not be an option.

Also if batteries are used then the charge voltage will be over 12 volt anyway up to 14.8 volt with a step regulator and a RB108 dynamo regulator was set at 16 volt open circuit. So not really enough info.

 

[EFLImpudence]

could i wire 2 lights on 1 wire having 3 wires coming off the battery to feed 6 20w 12v bulbs as the lights have there own on/off switches

Edit - wrong information

 

[EFLImpudence]

distance between lights from the battery are 8m 6m 3m 3m 2m 2m.

Please clarify.

Are the distances between lights or from the battery?

 

[JohnW2]

distance between lights from the battery are 8m 6m 3m 3m 2m 2m.

Please clarify. Are the distances between lights or from the battery?

Well asked. I initially read it to mean the latter, and got a max VD of only 0.33V (2.75%) using 4mm² cable throughout (as a single radial). I then decided (hence my 'false start' posting!) that the OP probably meant to former, which leads to a max VD of 1.925V (16%) with 4mm² cable throughout (again, single radial)!

Kind Regards, John.

 

[JohnW2]

Edit -What do others think about a 4mm² Ring to every other light?

Can you clarify what you mean by that? Thanks.

Kind Regards, John.

 

[ban-all-sheds]

Two rings.

Each with 3 lights.

I was going to suggest a ring as a possible way to minimise VD, but the usefulness of that that would depend on the positions of the lights.

 

[EFLImpudence]

From battery to light 1 3 5 6 and back to 4 2 and battery.

or back from 5 with light 6 on a spur.