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Forum Index : Electronics : Mill to battery cable
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Highlander Senior Member  Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day guys, well I've neary finished everything and I need to buy 50 metres of cable. For 24v what size cable will I need? I was thinking of using 15a mains cable with all three wires wound together at each end. I'll use two cables one for pos and one for neg. Will this be enough? Central Victorian highlands |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah that sounds like it would work fine. Any cable has loss, the thicker the better, but cost has to come into it also. Domestic power cable is cheap per meter and I use it where ever I can. Is this a F&P windmill, and what sort of watts are you hoping for. Once we know watts we can work out amps into 24 volts. Then we can work out how much is lost in the cable. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day Glenn, yeah it's a F&P I've got 1 line of neo's in, which makes around 12amps into 24v batteries (300 watts) I used 21 1uf green caps at the star. I'll get this one flying and muck around with more neo's on my second mill  Central Victorian highlands |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah that cable will be fine, you wont loose much at all. My system is 12 volts, and the problem of cable loss needs more attention than 24v. Let us know how it goes. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| windman Newbie  Joined: 02/12/2006 Location: Posts: 19 |
hi occording to wire loss calcs used by electrical trades 5% voltage loss over 50 metres 24 volts 12 amps requires wire cross section area of 25 square mm |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Thanks windman. But how does that relate to 15 amp wire. How do you work out square mm when the cable is round. The cable I've been looking at is 2.5mm or 4mm 3 ply wire, so what would be the square mm for these? Central Victorian highlands |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Pi * R squared gives area. The radius of the 2.5mm wire is 1.25mm, so we use 3.14 ( Pi ) * 1.25 * 1.25, ending up with 4.9mm square. And the 4mm wire ends up as 12.56mm square. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day Glenn, silly me I should have remembered that 
I got some prices on the cable, they varied a lot for identical items. The service varied a lot too, it's amazing how some companies stay in business. The best price I got was from Middendorp 100m 2.5mm 3 core $120 +Johnny service tax 100m 4mm 3core $220 +Johnny service tax Windman, you appear to have a good knowledge in this area, how well would either of these perform? Central Victorian highlands |
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| RossW Guru  Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Glenn, if he's talking "commercial wire" I suspect he's saying the "2.5mm mains cable" - which is already 2.5 sq mm, not 2.5mm dia. In house wiring, there are two "common" sizes - a light one for lighting circuits, and a heavier one for power circuits (2.5mm^2) On this: if you have three cables of 2.5mm^2 and parallel them you just add the areas together - thus 7.5 sq mm - although I think you will find that the earth is not the same size as the active and neutrals! For 50 metres, forget it. Thats not man enough for the job. From memory (30+ years out of date), the spec was for 5% of the 240V as max allowable drop. That would be 12V drop being "allowable" over the distance specified, which is completely different to your application! I think you need to consider upping the voltage given the distances involved. If thats impractical, then SUBSTANTIALLY up-size the cables. As a guide, my house is 55m long. I'm pulling a maximum of 20 amps at 240V, and I went with 16mm^2 cables. If I was trying to pull 20A at 12V, I doubt I'd run anything less than 35mm^2 and probably bigger. (I run 35mm^2 for the 1 metre tails from the battery to the inverter....) RossW |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Guys--, All good stuff,but,,,,,, bloody expensive --Guess what I did ?? took the Rodeo along to the local electric line depot with a carton of VB's on the back seat-- "Hey mate,youse guys like a donation to your Chrissie party" ? Yep, well I've some little brown bottles on the back seat in exchange for some scrap wire for my windmill,I'm building !!- "Mate,drive Er around to that big blue bin ,Father Xmas is in there with Orange overalls on !!. Hereith ended the story of how I got nearly 300 Mtrs of decent perfect heavy sheathed electrical cable and lots of connectors,earth rods,guy wire ,terminations, and long lasting friends. ! How about that? Happy New Year Bruce Bushboy |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Well I've got a heap of 5mm guy cable, is this any good to use? I'll need to rig up some power poles, similar to the ones in the streets as the cable isn't insulated. Central Victorian highlands |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Holy Crap,,, u for real ,Ol sport. ?? (Some Mothers do have Em,!) Hahahaha, Hope you'r jokin, udderwise we'll see ya on the Channel nine news tonite. Hahaha,,and I haven't even had a drink yet. Bruce Bushboy |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Thanks for your kind reply bruce. If it's on a wooden pole with the wires well apart, or on seperate poles I don't see the problem, Correct me if I'm wrong. Anyway I went out and got some cable, I bribed him with a slab and got about 150m of 5mm thick and 30m of 10mm thick for the batteries to inverter.  Central Victorian highlands |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
bruce, I've had a good think about it and I really can't see the problem. It's low voltage. The wires are kept well apart. Where's the problem? Perhaps someone had been partaking in a few drinks? If your that much of a grumpy old man, perhaps you have marital,financial or erection problems, I really don't care. If you have some constructive criticism then please relay it to me, however if your pissed or whatever then keep your abusive tone to yourself. Glenn I'd like to apologize in advance, I really didn't want to write this but if some jerk makes personal remarks about me I think I have the right of reply. Central Victorian highlands |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Whoa take it easy guys. I cant see any problems with using guy wires strung apart, but I know bruce has a lot of expierence in this sort of stuff and may know something we dont. Either way, keep it nice, sometimes its just a simple miss understanding. So everyone say sorry please and keep this thread going, its an interresting subject. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Sorry Highlander, was having a bit of fun,didn't mean to offend you. I'm none of the above ,hahaha, but I'll check out the "old fella" ,anyhow.hahaha The guy wires---- most unsuitable for carrying power ,imho, first,they are galvanized steel and very hard to terminate,have a very high resistance and how are you going to solder/bond,Etc. at either end. Mate, stringing open wires up on poles is sort of lots of work ,just use what you have in the pictures ,but make sure you solder them very well where they have to be joined--you'll have to use a gas flame to get the required heat as the (those) copper cables will disapate any soldering iron heat like mad ,and you won't get a good solder flow ,if any. Low voltage, now this just adds to the loss problem, you see, if you were,say, running 240 volts through those guy wires ,then maybe you would lose a few volts , but running 12volts or even 24 v you will have a very big voltage drop -not worth the effort,. I run 100 Mtrs and use 16mm insulated copper ,laid where necessary ,just on top of the ground. I have paid special attention to the connection joints ,thermo heat shrinking all joints after very careful soft soldering and , multistrand soft welding type tails into the control panels _where you have to get around corners ,Etc. I have plenty of extra cable and will "double-up" one day ,making 32mm cross-sectional area. Once again, sorry for trying to be funny- I'll keep a check on the funny meter next time Bruce Bushboy |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Bruce, ya grumpy old bastard you! :) Seriously, my instant impressions were the same as yours - galvanised steel rope, or stainless steel rope - neither of which would be suitable for the main power lines, especially so at low voltages and over significant lengths, and for exactly the same reasons as you quoted. What he has photos of is NOT what I would call "guy wire", although it MAY be hard-drawn copper. Would need to feel it to be sure. Running cables off wooden poles is bad karma unless you use suitable insulators. Sure, it will "probably work" for quite some time at low voltage, but it will cause grief sooner or later. Overhead power lines, just for the record, used to be steel-cored aluminium, although I believe nowdays they have dropped the steel core. Aluminium is MUCH better at conducting power than steel. One final point on terminations: Crimping is arguably better than low temperature soldering, but it has to be done right. A proper crimp forms a connection that is basically spot-welded. It is also mechanically strong. Soldering (especially multistrand cables) makes a boundary layer where the cable flexes, work-hardens and ultimately breaks. Upside, it's easier to do a decent solder joint than a proper crimp (without the right tools, anyway). Lots of folk crimp and solder. Different schools of thought from "belt and braces, both should be better" to "one or the other please, but not both..." - raising a crimped connector hot enough to solder breaks the spot-weld AND introduces a fracture point at the boundary. YMMV. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Dead right Ross, Ol son. Now ,let me fill ya's in on the telecom crimps-- The copper wire is hard drawn,single strand tied into insulators. The Crimps--- these are pure copper WITH, cadmium particles(little balls) sprayed onto the inside surface of the tubular sleeve. The crimping tool is specifically adjusted for individual crimp sizes. The crimp material and wire material is crimped so as the material marries and becomes completly electrically continuous. No resistance . Soldering ,on the other hand is two different materials-one copper ,the other tin/lead composition. So ,therefore you have a potential difference between the two materials and resistance. Get moisture in there and you now have a battery, or electrolysis. Hope this clears things up . Bruce Bushboy |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Hey Bruce, sorry mate. I just didn't understand the comment about channel nine news. It implied there was a safety issue which I couldn't see, anyway never mind. And I didn't like being referred to as Frank from that crap limey show. I must admit I can be a little hot headed when someone has a crack at me, must be my Scottish/Irish bloodlines, or perhaps it's from having to put up with the sergeants and warrant officers for years. So sorry Bruce, and you too Glenn, I know you didn't create this site so we could act like little bitches in the playground. Electronics is an area which I know very little about, that's why I ask you guys for help, which I'm grateful for. I've learned a lot from you guys, thanks and it's been fun. Central Victorian highlands |
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| windman Newbie Joined: 02/12/2006 Location: Posts: 19 |
viva the crimp |
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