Newbie electrics struggle

shinobidef

Hi all,

I've spent quite a while reading books and articles on electrics but I just can't seem to get my head around it - either the books go into more depth than I need, or are more to do with electronics components, or they describe someone else's set up which means I can't really adapt as I don't know or understand the knowledge behind their choices!

I've attached a rough schematic I've done and whilst I understand a bit more about the fuse boxes and fuses, can anyone help with the following:

I have 6 12V downlights and I'd like these in 3 x pairs (1 x pair on each of 3 walls) and I'd like each pair to be controlled by a switch.

  • Do I run one cable from the fusebox and split it into 3 separate circuits (so 1 x 1A fuse at the fuse box as the lights are 2W each)? If so, what do I need to use to split it? I'm confused with the difference between connector blocks, bussbars, etc. so I'm not sure what I should be looking for! Also, if I were to use a large cable and split it, would I be splitting into separate purchased smaller gauge wires for each pair of lights, or can the large one be split into 3 different circuits?
  • Or do I run each pair of lights direct to their own place in the fusebox?

I've been referring to wiring gauges using a table but (and this is quite a basic question!) it says to use the "roundtrip" length when working out the sizes. Suppose the lights are 2 metres away, does that mean I need 4 metres of positive cable and 4 metres of negative, or 2 metres of positive and 2 metres of negative? Do the +ve and -ve go all the way to the appliance AND all the way back?

I'm also having problems understanding which wire to use for the solar panels and if I should be wiring in series or parallel. I have 2, each at 315W and a Vmpp each of 30.4, which I think makes them just over 10 amps each. The lmpp current is 7.58 per panel. However, nearly all the guides I read say your solar panels will be 6V, 12V or 24V - where is that figure coming from? My electric system is 12V so are they referring to the output once it's gone through the MPPT controller?

Thanks in advance!
 

shinobidef

Thanks - reading now! If anyone else can help with the lighting issue, that would be greatly appreciated :)
 

Rob H

Newbie electrics struggle.

Sounds like you're pretty well there with the research you've already done, here's a couple of ideas, because there's more than one way you could complete your project.

This company below just as an example, supplies cable and connectors and advice within the catalogue to help you choose your solutions when adding to your vehicle electrics.

Cables > Home > Vehicle Wiring Products Ltd

Each of your lights at 2 watts uses next to no electricity, 6 X 2 watts = 12 watts, thats only 1 amp draw at 12 volts, so, you could use from the above catalogue, cable of (14/0.30mm which can carry 8.75 amps .... Typical applications. Side & tail lights, alarms, reversing & rear fog lamps, electric aerial, horns general wiring.
Available per metre or 50M reels).

Always suggest disconnect positive terminal your vehicle battery and or vehicle habitation battery while doing work on the electrics.

Most metal vehicles use 'earth return', that means the metal vehicle body is the negative (usually .. so check) conductor, back to your habitation battery negative terminal, so you could ... wire the negative terminal of each light to the nearest suitable bit of vehicle metal body with a ring crimp connector and self tapping screw to earth it.

However as the cable is cheap as chips, for simplicity I would use one length of positive cable from the positive output of your fuse box say fused at 5 amps, and one equal length of negative cable from your fuse box earth or vehicle metal body.

Here's a way to do one side of your vehicle ... you can make a simple wiring loom. Measure how much cable you need to run past each of your lights to the furthest light pair on one side. Add a bit extra cable ** .. Pick your colours for negative and positive cable, suggest you match the original positive +, and negative -, wiring colours in your vehicle. (VW for example use brown for negative and black for positive).

Pick your wiring 'route', bind your two cables along their length with black fabric tape ( additional abrasion resistance) when you reach your 1st switch position, carefully remove a band of insulation from the positive cable so you can now see 10mm band of copper multi strand, ** bare 10mm end of a length of positive cable, twist it around the exposed bared 'band' , electrical fluxed solder it, slide a piece of heat shrink insulation over the joint, shrink it, run your positive 'spur to one terminal of your first single pole switch and from the output switch terminal onward to each positive of your first pair of lights. Do similar, slightly staggered (so no chance of positive and negative cable bared bits coming into contact with each other) with the negative wire, run the negative 'spur direct to each negative terminal of each light in the pair. carry on binding with tape to the location of your next light 'pair', same again ..

Your switches and lights may have spade terminals, you could buy a cheap crimp insulated terminal kit, or, as a world of vehicle wiring opens up, lol, a variety of terminals and crimp tools ...

Good luck with your project.

Rgrds,

Rob H.
 
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