How do you downsize wires?

[BradKW]

I got my panels switched and fused today, and both controllers mounted and half wired.  But realised that my cables to batteries are too big for the controllers.

The Morningstar 60mppt has screw-down connections where you just stick the wire in and tighten screw. The 1 awg almost fit...close enough that if I snipped some strands I could probably get it. But I think I read once I shouldn't do that.

The little controller has little terminals that I need to use the U-clip shaped connectors, and nothing West Marine had was even close to taking 1 awg down to that size. 

Do I figure out what the largest wires I can possibly make fit and then put a busbar close to controllers?  thanks...

 

[Optimistic Paranoid]

A couple of power posts mounted close to the controller would solve the problem:

https://www.amazon.com/Blue-Sea-Sys...76&sr=8-1&keywords=Blue+Sea+Marine+power+post

 

[highdesertranger]

they make step down connectors. either a step down butt connector, or a step down terminal end. would do it. highdesertranger

 

[GotSmart]

Solar controller to batteries?  A short run, right.

Just go to the nearest size (copper)  that will fit.  

1 AWG is massive overkill.

http://www.powerstream.com/Wire_Size.htm

 

[Mobilesport]

Either way would work but if you cut 2 inch strands of wire off you could heat up some heat shrink around it for a much cleaner less cluttered connection.
Less connections!

 

[rvpopeye]

Yes. as close as possible.....

 

[BradKW]

Solar controller to batteries?  A short run, right.

Just go to the nearest size (copper)  that will fit.  

1 AWG is massive overkill.

http://www.powerstream.com/Wire_Size.htm

It's actually not such a short run...maybe 14', so 28' round trip which seems to be how drop is figured. So using 1 awg gets me between +1% - +2% "savings" on voltage drop over say 6 awg, that's at 24v with 10 to 40 amps figured. On a 12v system, that run would see a more dramatic savings. 

Oh, and I have free 1 awg wire leftovers on spool from a job, so figured why not...

 

[BradKW]

Either way would work but if you cut 2 inch strands of wire off you could heat up some heat shrink around it for a much cleaner less cluttered connection.
Less connections!

I was thinking that, but something sticks in my memory about how current travels on the outside perimeter of stranded wire...but I may be making that up, can't recall.

 

[Mobilesport]

I was thinking that, but something sticks in my memory about how current travels on the outside perimeter of stranded wire...but I may be making that up, can't recall.

All the strands are pressed together just like the connectors would be pressed together in a juntion block when its bolted down.
So no difference.

 

[Optimistic Paranoid]

I was thinking that, but something sticks in my memory about how current travels on the outside perimeter of stranded wire...but I may be making that up, can't recall.

If you're thinking about "skin effect", that's only ac current.

 

[GotSmart]

It's actually not such a short run...maybe 14', so 28' round trip which seems to be how drop is figured. So using 1 awg gets me between +1% - +2% "savings" on voltage drop over say 6 awg, that's at 24v with 10 to 40 amps figured. On a 12v system, that run would see a more dramatic savings. 

Oh, and I have free 1 awg wire leftovers on spool from a job, so figured why not...

Then just trim a couple strands until it fits.  You will never get to the amperage level of "needing" a 1 AWG wire.  Not with solar at 12Volt. The trimming "rule" is for high voltage systems. 

1 awg will handle 119 amps.  That is enough to jump start a whale.  (or instantly drain your batteries. ) 

Free is free.

 

[MrNoodly]

When I set up my system, I went to Northern Arizona Wind & Sun to get cables. After looking at my hardware, they gave me some short big-ass cables to connect the batteries to each other, some more cables to run from the solar panel to the controller, a couple of in-line fuse holders and some 10 gauge cable to run from the controller to the batteries.I figure they know what they're doing.

 

[BradKW]

So to refresh my memory, where and why is it people use 4/0 and 2/0 wiring? thanks...

edit: I was also planning to use the 1 awg for inverter run of 22ft (11 + 11)

 

[GotSmart]

So to refresh my memory, where and why is it people use 4/0 and 2/0 wiring? thanks...

From the alternator to the battery when charging from the engine. and to tie the batteries together.

 

[Trebor English]

Can you get the inverter closer to the battery than 11 feet?  Two feet would be better.  Then the distance can be covered at 120 volts and one tenth the current.  A 600 Watt coffee pot is 5 amps at 120 volts, 50 amps to feed the inverter at 12 volts.  A high voltage transmission line saves energy, that's why electric companies do it.

Beware of #10 wire.  https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

 

[BradKW]

I could, and did consider getting it closer, but it would have caused other design problems for me. Since it's a 24v bank + 24v inverter, and using 1 awg, I ran the numbers and feel I can side-step that rule of thumb without any negative results...

 

[Mobilesport]

I could, and did consider getting it closer, but it would have caused other design problems for me. Since it's a 24v bank + 24v inverter, and using 1 awg, I ran the numbers and feel I can side-step that rule of thumb without any negative results...

You could keep the invertor close to the battery and then only extend the invertors on/off switch .

 

[Spaceman Spiff]

The Morningstar 60mppt has screw-down connections where you just stick the wire in and tighten screw. The 1 awg almost fit...close enough that if I snipped some strands I could probably get it. But I think I read once I shouldn't do that.

Best practice is to use the correct size wire.  Next best would be to use step-down terminals.  Snipping off some wire strands is OK (you are basically reducing wire size for a short distance); it affects the current carrying capacity of the whole wire length (called ampicity, no problem for your application) but will have almost no effect on voltage drop.

If you're thinking about "skin effect", that's only ac current.

You sure of your factoid?  I thought in any current flow the electrons will try to separate themselves.  It is just that with higher voltages there is more energy to push them as far apart as possible.

 -- Spiff

 

[SternWake]

Thick wire can put a lot of stress on the solar controller terminals.  Take measures to keep vibration related issues from forming.

Here is the terminals on my Bluesky SB2512i after 5 years of use.  I am not sure how the 'rust' appeared on the PV- terminal.  Could be the salty surfboard on the ceiling.  The wire was Ancor tinned marine wire, just Split and crushed under screw, no Dielectric grease.  Dooh.

This was my solution to 'crush stranded wire under set screw and plate' when i moved Controller closer to batteries over thicker wire and added more wattage.  There are 10 and 8 awg ring terminals whose ends I filed down so they would fit stacked, under the screws provided.  The larger modified ring terminals BAT+ and batt- are for 4awg wire. 8 awg from my framed kyocera 130 watt panel, 10 awg from the unisolar 68 watt stick on panel. 4AWG goes to 500 amp 50Mv Deltec Shunt(for battery monitor), and to the Common Stud on a Blueseas 6007M manual 1/2/both/0ff switch.  I have a 30 amp lever type circuit breaker in between Switch and controller, but it is a POS and causing too much voltage drop.  It gets warm at noon.  Going to a maxi fuse at some point.

Stereo shops sell offset reducers for stuffing thick copper where it was not designed to be stuffed.
I'll try and find some

Good crimping and good heatshrink, and I've not looked at it in 4 years




https://www.droppinhzcaraudio.com/p...-car-audio-1-0-to-4ga-wire-gauge-reducer-pair

File down the tangs so they fit flat and then drill a hole for the screw.

 

[SternWake]

perhaps an option too:
https://commerce.ilsco.com/e2wShoppingCatalog.aspx?parentId=3100012329

I have on some other projects more recent, 4awg soldered stranded wire solid and then filed, dremelled and drilled it, Which, if filed to fit the surface's mounting area carefully for maximum surface areas mating, is likely the method presenting the least resistance.