AWG gauge for 12V panel to 12V inverter (150 foot run)

MyPrepperLife · February 2017

What gauge wire would I need to connect a 12V panel to a 12V inverter 150 feet away from the panel? (I'm concerned about voltage drop.)

Estragon · February 2017

There is a voltage drop table on sponsor web page under learning center you can use to get voltage drop for various size wire. Obviously bigger wire is better. 8 gauge maybe?

dennis461 · February 2017

Hold on, you have GOT to get a higher voltage to run 150 feet.
#8 gauge wire, two conductors, 10 amps will start out at 12.0 VDC and end up as 10.2 VDC.

Voltage drop calculations, either your own or another persons, will vary slightly depending on the values used for resistance, and temperature. But only slightly. For example, wires in conduit heat up more than wires hanging from utility poles, so the wire resistance is different.

Bottom line, (no pun intended) to run 150 feet, you should use higher voltage.

Estragon · February 2017

@dennis461

We don't know what he's trying to accomplish beyond the question. Assuming 18Vmp panel he will need some voltage drop to run a 12v inverter anyway. Why he wants to do such a thing I dunno.

On a cold morning the inverter may overvolt. A cloud rolls by and it undervolts. Hopefully the inverter handles such things gracefully.

MyPrepperLife · February 2017

dennis461 said:

Hold on, you have GOT to get a higher voltage to run 150 feet
...
Bottom line, (no pun intended) to run 150 feet, you should use higher voltage.

I did the research a few months ago and ended up thinking that what dennis461 said is the right way to go, but I wasn't on this forum back then, so I thought I'd ask the question again here.

I already own four 12V panels and four 12V inverters, and I currently have a 50 ft. 10 AWG cable connecting each 12V panel to one of the 12V inverters. This setup is working beautifully, but what I'd really like to do is put the panels in a different location that is about 150 feet from the inverters.

Why do I have four panels and four inverters, you ask? Long story. I have my reasons. If anybody really would like to know, I will explain.

(BTW - in case anybody recognizes my username from some other threads on this forum - I just want to mention that my four 12V panels and four 12V inverters have nothing to do with the solar-electric system I've been discussing on this forum prior to today)

Estragon · February 2017

@MyPrepperLife - then the short answer is you're going to have to spend some time with voltage drop calculators and some money on heavy wire. There may be better and/or cheaper ways to do what you want to do, but we don't know what that is.

westbranch · February 2017

OK, so you have 4 ''12\v ''panels... Are they all the same brand and specs?
If different, please give us the specs from the data tag on the back of the panels....
What are the objectives for the power? just a few lights or a small cabin, etc?Brand and \model of the inverter you plan on using is useful too...
Bow that you know you will be sending more than 12 V down the larger AWG line , which CC are you thinking of using? It WILL have to be a MPPT to max out the conversion to 12V for the inverter to work happily with......

BB. · February 2017

Are you trying to drive the 12 VDC inverters directly from "12 volt" (typical Vmp~18 volts) and not use a battery bank?

Anyway, here is a very simple voltage drop calculator. You enter the numbers and play with the wire gauge.

For example. say 15 amps @ 150 feet @ 18 volts Vmp and you want a maximum drop of 3%:

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.4066&voltage=18&phase=dc&noofconductor=1&distance=150&distanceunit=feet&amperes=15&x=58&y=12

1 AWG cooper cable:
Voltage drop: 0.56
Voltage drop percentage: 3.11%
Voltage at the end: 17.44

As you can see--That is a lot of copper. Your better bet would be to put the inverter next to the panels and run your 120 VAC (or whatever) from the inverter to the loads.

As above but 120 VAC and 1.5 amps (10x the voltage, then 1/10x the current for same power):

14 AWG (about the smallest you would want to bury):
Voltage drop: 1.14
Voltage drop percentage: 0.95%
Voltage at the end: 118.86

-Bill

Photowhit · February 2017

Are these the NOT LEGAL, inverters? ...for back feeding the grid?

MyPrepperLife · February 2017

Ok, obviously I need to provide more detail.

First: I said I need to connect a 12V panel to a 12V inverter, but actually that isn't an accurate description of the situation, because a charge controller is involved.

Here is the scenario.

I moved into my off-grid house last fall. I live in a cold climate, and winter was fast approaching. Rather than rush to put in place the solar-electric system I really need and want, I decided to use some "plug-and-play" technology to build a small solar-electric system - smaller than what I will need eventually.

Doing things this way was't a particularly good use of money, but it made sense because I knew I could do it myself and get it done before winter.

What I have is four setups like this:

- Grape Solar 12V 160W monocrystalline solar panel

- Goal Zero Yeti 400 portable power station

- Mighty Max 35AH SLA Battery

- Two 50 ft. 10AWG cables - each cable has a male MC4 connector on one end and a female MC4 connector on the other end.

- Various other cables and adapters.

The Goal Zero Yeti 400 is a box containing a 12V 33AH battery, a PWM charge controller, and a 300W pure-sine-wave inverter. The Yeti 400 has several output ports: two 110 AC output ports, a 12V cigarette-lighter-style output port, and two USB ports. It also has an input port, of course, and there are three ways to charge the it: solar panel, 110V AC, 12V DC.

I am charging with a solar panel. The panel is connected to the Yeti 400 via the two 50 AWG cables.

To double the storage capacity of the Yeti 400, I have "chained" the Mighty Max battery to it. The chaining is in effect a parallel connection between the battery inside the Yeti 400 and the MightyMax battery, so the chained setup has 70AH (840WH), as opposed to 35AH (420WH), which is what I can store in the un-chained Yeti 400.

(NOTE: Actually, this isn't quite accurate, because the battery inside the Yeti 400 is 12V 33AH and the MightyMax battery is 12V 35AH, which I just noticed while writing this post. Chaining the 35AH battery to the 33AH battery probably isn't ideal, but that is the situation.)

Anyway, to get power out of the Yeti 400, I just plug things into its various output ports.

Here are the electrical specs for the panel:

Max System Voltage (IEC/UL): 1000V/600V

Maximum Power Pmax: 160 W (-5%, +5%)

Cell Type: Mono silicon

Voltage at Maximum Power Point Vmpp: 18.5 V

Current at Maximum Power Point Impp: 8.65 A

Open Circuit Voltage Voc: 22.2 V

Short Circuit Current Isc: 9.46 A

Module Efficiency (%): 16.4%

Temperature Coefficient of Voc: -0.38% /ºC

Temperature Coefficient of +0.05% /ºC

Temperature Coefficient of Pmax: -0.50% /ºC

NOTE: This system is totally off grid. My house does not have grid power.

mcgivor · February 2017

You are the Frankenstein of the solar world, all in good humor of course. You are going to learn a lot, play safe.

MyPrepperLife · February 2017

mcgivor said:

You are the Frankenstein of the solar world, all in good humor of course.

I am totally aware of it.

I will use this small, oddball system even after I build the new, better system. The small system will power a fridge and a freezer.

As I said in an earlier post, everything is working fine. It wouldn't kill me to leave the panels in their present location, which is about 50 feet away from the Yeti 400's, but I'd kind of like to put the panels in a different place that is about 150 away from the Yeti 400's. Hence this thread.

Estragon · February 2017

@MyPrepperLife

Thanks for the detail. Is the new panel location 150' away the same location as you would want your panels for the enlarged system?

mcgivor · February 2017

Consider using aluminum cable, go one gauge larger than copper, use Penetrox or a similar anti oxididant on all splices, will save $$, your monster will grow and always use the correct over current protection, fuses or circuit breakers appropriate for the installation.

MyPrepperLife · February 2017

Estragon said:

@MyPrepperLife

Is the new panel location 150' away the same location as you would want your panels for the enlarged system?

Not exactly the same location, but close. The tentative new location for the four 12V panels is the south-sloping roof of a shed I want to build to enclose the wellhead for my well. The panel array for the larger system will be on a pole mount about 80 feet southwest of the shed. (The larger panel array will likely cast a shadow on the smaller panel array for a short time each day, but I can live with that.)

MyPrepperLife · February 2017

mcgivor said:

Consider using aluminum cable, go one gauge larger than copper, use Penetrox or a similar anti oxididant on all splices, will save $$, your monster will grow and always use the correct over current protection, fuses or circuit breakers appropriate for the installation.

Thanks mcgivor, but I don't really have a good understanding of what you are saying.

RE <<Considr using aluminum cable>> your monster will grow

Why use aluminum - to save money?

RE <<go one gauge large than copper.>>

Yeah, well I'm trying to figure out what gauge the copper should be.

RE <<your monster will grow>>

???

RE << use the correct over current protection, fuses or circuit breakers appropriate for the installation.>>

Is that so the PWM charge controller won't receive too much power from the panels?

Estragon · February 2017

To get a 5% drop in V @12v/8a will take 2ga wire according to NAWS chart. Putting the Yetis in the shed and running smaller wire at 120Vac makes more sense.

I don't think these units will sync AC, so 4 separate circuits. Also not sure about running fridge/freezer off them (300w 600surge ). Are you doing this now?

MyPrepperLife · February 2017

Estragon said:

To get a 5% drop in V @12v/8a will take 2ga wire according to NAWS chart. Putting the Yetis in the shed and running smaller wire at 120Vac makes more sense.

I don't think these units will sync AC, so 4 separate circuits. Also not sure about running fridge/freezer off them (300w 600surge ). Are you doing this now?

I don't mind spending the big bucks for the cable. In fact, let me make the point that I'm not concerned about costs at all; I just want to be able to do what I want to do.

Yes, I would need four separate cable runs. I would put all four in the same conduit. Right now the cables are just coming in through a window, but regardless of where the panels are ultimately located the cables will be in conduit, and the conduit will come into the basement through the house's rim joist.

I'm powering my fridge with a Goal Zero Yeti 400 as I write this. It is a 12V fridge - very energy efficient. It is this one:

http://www.solarpanelstore.com/solar-power/appliances/sundanzer/dcr165/info/1.html?gclid=CNuuwOXknNICFUxLDQodXGAEKA

Here is the spec sheet for the fridge:

http://www.solarpanelstore.com/pdf/sddcfridgefreeze.pdf

Putting the Yeti's in the shed wouldn't work out because it gets too cold here in winter.

Estragon · February 2017

I use similar dc reefer units in my heavily insulated site built fridge and freezer boxes. Yes, they are efficient and also don't need a big surge capability to start. I run directly off DC to avoid DC-AC-DC conversion losses.

If you can live with panels where they are for now, maybe wait until you're ready to do permanent systems? The yeti looks like a great thing for portable power but I doubt it will last long with daily cycling. You could add a charge controller for series wired 12v array to batteries near the loads and run them at native 12v. You could probably use one of the yetis for small AC load circuit like night lighting so you have the option of turning off a bigger inverter overnight.

MyPrepperLife · February 2017

Estragon said:

The yeti looks like a great thing for portable power but I doubt it will last long with daily cycling. You could add a charge controller for series wired 12v array to batteries near the loads and run them at native 12v. You could probably use one of the yetis for small AC load circuit like night lighting so you have the option of turning off a bigger inverter overnight.

The batteries in the Yeti 400's are replaceable and are fairly inexpensive, so I might be able to keep them going for a long time.

However, I have thought about wiring the four 12V panels in series and running the 48 volts to a different charge controller and inverter, as you suggest. (I would have a different battery bank too, of course.) I believe the 48 volts would be enough to push through the 150-foot cable run without using a huge cable and without much voltage drop.

mike95490 · February 2017

In fact, let me make the point that I'm not concerned about costs at all;

Then here's my suggestion:
Move all the panels (5?) to the sunny area. Wire in series (22v x 5 =110Voc)
How cold does it get? That coldness makes the Voc go up, and you may exceed the common 150Voc of many controllers
Get a MPPT controller, Morningstar Mppt-60 or Magnum/Sensata Power Track-100 (PT-100) MPPT if you need the higher input voltage
Run wire rated for 10A (you will be pushing 9A at about 95V for your cable run,
4ga copper gets you 4% voltage drop, you could use 2ga aluminum to save $ (remember, you are buying 300' of this stuff)
MPPT controller will give you 750W , at 12V that will be 60 charging amps
I'd run that to a pair of 6V golf cart batteries wired in series, and then hook the yeti inverters up to that battery. (12V @ 200ah)
You may need to set the controller current limit down a bit to not boil the battery with too much power
But that's the way I'd run 150' of cable.

Estragon · February 2017

The 4 panels in series would be ~72v, easily in the zone for lots of nice charge controllers. If you wanted, you could use a couple of L16 type batteries for ~350ah@12v. I'm guessing your fridges run around 20-30ah@12v/day each so that would give you maybe 5 days autonomy on those loads.

Good that the Yeti batteries are replaceable and reasonably priced. Maybe a standard AGM motorcycle battery or something. You'll want to replace the extra parallel ("chained") battery at the same time and with the same type as the internal one. Leaving an old one with a new one will just make the new one age prematurely.

Estragon · February 2017

@mike95490

I'm not so sure about hooking up GC batteries to a Yeti. It would be in parallel with a 35ah AGM internal battery.

MyPrepperLife · February 2017

Thanks, everybody, for all the suggestions and especially for all the detailed information about wiring the panels in series and moving to a different charge controller, inverter, and battery bank. I have been entertaining that idea for awhile now, and ultimately I might do things that way. At this point in my thought process, though, I'm trying to stick with the Yeti's.

At one point in this thread, I said it gets too cold here to keep the Yeti's in the shed with the panels on the roof. Somebody asked how cold. It's not unusual to have temperatures of -25 F or so. At times it gets as cold as -40F.

In case I haven't been clear already about this, let me just say that I am well aware of the fact that the the setup I have is very unconventional and is not cost-effective. In fact, it's probably about the worst way to go about building a solar-electric system, and I knew that before I started. I just did things that way to get some power to the house before winter last year. I was confident that I could do it quickly with my limited skills and abilities.

MyPrepperLife · February 2017

Estragon said:

@mike95490

I'm not so sure about hooking up GC batteries to a Yeti. It would be in parallel with a 35ah AGM internal battery.

If I ended up using golf-cart batteries, the Yeti's would be out of the picture. I would have a new charge controller and a new inverter.

mike95490 · February 2017

mike95490 said:.....and then hook the yeti inverters up to that battery. (12V @ 200ah).......

I said just hook the inverters. not the battery pack, but no biggie, Not sure why the yeti batteries can't get cold, AGM (if they are truly sealed AGM) can even survive being frozen, thawed and then recharged,

Estragon · February 2017

At those temps you would lose a lot of capacity, and those batteries are pretty small to begin with. If the shed gets as cold as that, keeping batteries there probably wouldn't work well.

I also get temps like that but my batteries are in an unheated but enclosed crawlspace which moderates the temps. I lose some capacity but not like -40 would cause.

MyPrepperLife · February 2017

Estragon said:

At those temps you would lose a lot of capacity, and those batteries are pretty small to begin with. If the shed gets as cold as that, keeping batteries there probably wouldn't work well.

Right. I plan to keep them in my unheated basement, which is usually about 40F in winter.

Estragon · February 2017

Good plan. Being a bit cooler than room temp and fairly stable day/night can help longevity of both batteries and electronics.

AWG gauge for 12V panel to 12V inverter (150 foot run)

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