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Forum Index : Solar : PV cable runs 4mm x 2 cables?
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| rgormley Senior Member  Joined: 22/02/2006 Location: AustraliaPosts: 245 |
Quick question: sort of... I have access to 4mm (56/0.30) twin olex versolex 0.6-1kv 90 deg flexible cable. twin brown+blue The specs show it as having as a current capacity of 25 amps. Vdrop of 12Mv per A/m The question: would it be acceptable to run two runs of this cable. to achieve current capacity of 50AMPS (i only need in theory a max of around 40-45 amps.) cable run length of 7~8 meters. 24v system. I was thinking to have my 6 panels split into two cable runs and then combine on a 24V buss bar next to the Regulator. So the basic questions: A: Is it ok to have two runs of 4mm twin. B: Should i run the cable paralleled at both ends or split the PV panels/cables into two runs and recombine on a local buss next to the regulator. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah thats perfectly acceptable. Only parallel them up at one end, or you can have problems with current loops. I would parallel them up at the local bus. This will let you isolate one group of panels if needed, at the bus. On my panels I run 3.2mm wire from each pair of panels. There are 12 panels, each panel is 24v, I have a 48v system, so each pair of panels in series has its own cable feed to my junction box, 6 in total. This means I can isolate panels, which has proved handy from time to time. My regulator also works a little differently to most. The panels are wired in a way that the regulator can switch then in and out individually to adjust the power fed into the battery bank. Basically the regulator can count up or down in binary, switching in and out panels, to give 6 "steps" in power. Its a much more gentle system than PWM the whole solar array. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
cool, that`s my Sat morning job coming up! |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
just had a think about how i`m going to wire this. total of 6 panels (3 strings of 2 panels in series) hhhmmm only have 2 cables.... will have to get a third cable to bring the 3 strings down evenly, or i will have to double the current in one cable if i use the 2 cables panels 1,2 going to cable one (two wires) panels 3,4 + 5,6 going to cable two (two wires) or i run a third cable panels 1,2 going to cable one (two wires) panels 3,4 going to cable two (two wires) panels 5,6 going to cable three (two wires) then combine downstairs to a 24 bus next to the regulator *does this make sense? |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
got home from work early, so did the PV cabling. ended up running 3 separate runs of 4mm twin and combined next to the regulator. see what happens when the suns up in the morning.. will be interesting the theoretical watts v real world.. noted while up on the roof my panels need a clean  |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
hhmmm.... panels in full sun, very small amount of high cloud 11:45am from panels: 4.2 amps per string at 43 volts x 3 (12.6 amps at 43 volts=541.8 Watts) into batts from MPPT: 22amp at 26 volts (22amps at 26 volts=572 watts) watts in v`s watts out match, but was hoping for more as i have 6 x 180 watt PV will get up and clean them..... |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
UPDATE: 12:45pm cleaned the obviously impenetrable sun barrier from the panels (used diluted CT-18 truck wash) now i`m seeing peaks of 33 Amps into the batts! .... much better 
averaging 25 amps |
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
You might consider installing a 20A ampmeter in each cable run before the common bus, which would give you an idea how each panel pair is performing. I have 5 separate 4mm sq cable runs, one from each of 5 pairs of panels. The panels are spread over the house & shed roof and those meters tell me at a glance if one lot is not up to scratch. Klaus |
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| rgormley Senior Member Joined: 22/02/2006 Location: AustraliaPosts: 245 |
I can very easily add these (or via the "SAK-C10" terms disconnect any string and put a meter across the plugs via banana jacks. when i was on the roof connecting the cables to the PV`s i pulled each "MC" connector apart. they looked ok, but it did make me wonder if a soldered connection would provide a better connection. there is not much current flowing on each series connection but hey, if i can reduce any bad connection/voltage drop point... all the better... but i decided to leave them. as the "MC" connectors are world proven.... in many solar installs... oh this afternoon whne the sun was full and bright and better angles i hit some peaks of 38 amps (edge effect on some high cloud?)... and at the time was averaging 32 amps... the tracer i thought was running a little hot so i put a computer fan on it. the Tracer had the panels at 40~43 volts... is this ok??? |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
I have PMed you. Dave |
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