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# 208035 24-Jan-2017 12:03
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I have a few things I want to do:

 

     

  1. Connect my three 30AH SLA batteries in parallel so that the solar panel controller charges them all at the same time.
  2. Move my 40W 12V (which actually puts out more like 20V) solar panel into my greenhouse (easy) or onto my greenhouse roof (more difficult), which will mean a longer cable run. I probably have enough proper solar cable with connectors attached do this, I think.
  3. Have my solar panel and batteries run a 12V DC fan in my greenhouse that I got from ebay, using a timer I also got from ebay.

 

 

 

For these I'll need the following

 

     

  1. Four 0.5m lengths of cable (not sure what type / thickness) and appropriate lugs to fit to the battery screw terminals.
  2. I might need additional cable to go from the solar panel to the controller. I guess this has to be proper solar cable? How about if the cable isn't exposed to the outdoors, can I use a cheaper cable?
  3. 5-10m of cable that can run a 20W fan for periods of up to a few hours. Cable can be subject to sunlight and temperatures up to 40 degrees, and maybe the weather, depending if I drill a hole or go via the eaves.
  4. Small lengths of cable to connect things, like the timer to the fan.

 

I'm currently using 2.5mm, 2 core solar cable, at $4.50 per meter, from sustainable solutions. I wonder if I can get a suitable cable cheaper. I got the fan and timer from ebay cheap, buying in NZ it looks like the cable could be more expensive than the things they'll power!

 

Can anyone help refine the requirements to the type and size of cables / connectors I need, and where to buy them in NZ? I have found electrical direct, which has reasonable prices for cable, but no lugs as far as I can see. Particularly the lugs, something like this from Jaycar. This is a little side project so I don't want to spend a bunch of money. If it's too expensive I won't bother.


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  # 1708638 24-Jan-2017 13:09
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For the lugs, have you tried somewhere like Repco or Supercheap Auto?


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  # 1708644 24-Jan-2017 13:13
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Surplustronics have some quite meaty red and black twin cables sold as speaker cable that I am using for ELV DC stuff, they also have quite a few more terminals than what is on their website in store too.





Richard rich.ms

 
 
 
 


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  # 1708672 24-Jan-2017 13:38
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For (2) in your list: According to BlueSeas circuit wizard (I use this for my boat and find it very reliable) you would choose 14AWG cable to keep your voltage drop below <3%.  Marine cable (tinned) is a good choice for outdoors or humid environments.  It's also heat tolerant (usually 90*C insulation).  It's often available in sheathed twin core, which is physically durable.  If you shop around you will find a deal somewhere.  I normally wait until what I want is on special at marine deals.

 

For (1) in your list 40W at ~20VDC is lower amperage, you could also used the 14AWG cable for that.

 

For your lugs, most specialist auto-electrical places sell adhesive-heat-shrink, crimp terminals.  These make a robust connection.

 

To select the right terminals you need to know your cable gauge and the diameter of the screw posts.

 

The standard crimp terminals at Repco and SCA aren't as good.

 

 





Mike



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  # 1708738 24-Jan-2017 14:08
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Thanks for the thoughts so far. 14AWG at 1.6mm square is the kind of gauge that tables have told me as well, at the low end - some have said up to 5mm2.

 

Lugs still seem problematic.  The Jaycar ones I linked to look ok, but it'd be nice to have heat shrink built in - I have some thick heat shrink tape but it'd be overkill. Surplustronics have some, but they look a bit small, and I'm in Wellington so can't go to stores. SCA lugs seem ok, but I'd have to take a look.

 

Looks like a few places have lugs - I wouldn't have considered car places. I guess the question could be is there one good place to get decent 14AWG cable (or slightly thicker perhaps) along with matching size lugs?


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  # 1708894 24-Jan-2017 18:36
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Head in to your local electrical wholesaler such as ideal electrical or JA Russel will have everything u need.

 

what about using 2.5mm TPS or Flex(HD extension leads)


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  # 1708930 24-Jan-2017 19:25
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SuperCheap Auto will have the cable e.g. http://www.supercheapauto.co.nz/Product/Auto-Cable-10-Amp-3mm-7m-Yellow/376694

 

Probably a good first stop - hopefully you'll get everything there, otherwise move onto Jaycar in Taranaki St or electrical wholesaler (customer experience can be a bit variable for non-tradies)


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  # 1708964 24-Jan-2017 20:43

Try your local friendly auto electrician.




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  # 1708966 24-Jan-2017 20:43
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I think the 3mm is a bit thin. The 4mm is good, but at $2.50 per meter is just over half the cost of really high quality solar cable. If I can get it less than $2/meter I'd probably go for cheaper cable, otherwise I'll just get the proper solar stuff. If I go past I'll call in for a look though. Electrical wholesaler might be worth a shot, but they probably sell in bulk and wouldn't be too keen on retail.


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  # 1709095 25-Jan-2017 00:33
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Definitely JA Russel or other electrical wholesaler for the lugs. Massive range can choose almost any combination of hole size and cable size. They are also made of tinned copper. So after crimping I also solder as well. As you are more likely to get corrosion with DC than AC. Since you only want to run 12V go to the scrap dealer and buy some cables bought in by the local sparkie. Scrap dealers normally only charge slightly more than what they would have originally paid.

Make sure you put fuses on your batteries. As lead acid batteries deliver massive currents if they get shorted. The combined for your 3 could easily be over 1000 Amps.







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  # 1709117 25-Jan-2017 07:23
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JA Russel just bought Stewarts, I have a Stewarts not far from me. Will they sell to the public? They might have cable worth getting as well.


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  # 1709232 25-Jan-2017 10:32
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You have quite low amperages going through those cables. 

 

  You will be able to find crimpable lugs to suit.  If you want heat shrink adhesive terminals you normally have to go to a specialist auto-electrial shop.

 

I don't think you need to go to heavy soldered battery lugs. Unless you prefer solder?

 

If so then see SCA may sell solder slugs for their lugs. You put them in the lug (held by a vice) turn on the blow torch and when the solder is liquid enough you stick the stripped wire in (held with pliers) and hold in place while it cools.





Mike



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  # 1709235 25-Jan-2017 10:36
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It's 12V to 25V, up to 4A, so not trivial power but not extreme either. I don't much care what kind of lugs I use, whatever's easier. I'd probably tend to throw some solder on to help reinforce a mechanical connection. 


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  # 1709251 25-Jan-2017 11:00
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timmmay:

 

It's 12V to 25V, up to 4A, so not trivial power but not extreme either. I don't much care what kind of lugs I use, whatever's easier. I'd probably tend to throw some solder on to help reinforce a mechanical connection. 

 

 

The ampacity of 14AWG wire is 15A - 25A.

 

Even with quite long periods of use it will cope with 4A no problem.  The only advantage of heavier wire would be less voltage drop.

 

I have up to 5.5A continuous on 16AWG circuits on my boat and they never even get warm.





Mike



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  # 1709264 25-Jan-2017 11:18
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Ah great. I looked at a few different tables and some seem to recommend much heavier wire for that current.


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  # 1709307 25-Jan-2017 12:23
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I comes down to tolerable voltage drop. When you only have 12 then every bit lost matters.




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