120ft wire run

dnaisbitt

Hello I have read a lot and I kind of understand some of it but it's confused me a lot more than it would have when I was younger.
So I have Three 405 Watt Canadian solar panels; https://www.ecodirect.com/Canadian-Solar-405W-BiHiKu-Bifacial-Solar-Panel-p/canadian-solar-cs3w-405pb-ag.htm
Unfortunately, I placed them before I realized how bad it is to run direct current long distances, and I really don't want to move the panels now.  I have read if I hook them up in series they will run higher voltage, will that higher voltage be enough voltage to run wires 120 ft to my house? 
I currently have this controller but I could return it if it won't work right or I should get something different; https://www.amazon.com/gp/aw/d/B07JLVPVGR?ref=ppx_pt2_mob_b_prod_image
My setup is really for just in case all heck brakes loose. I have a mini refrigerator and freezer that runs off of 12 or 24 volts DC, and I need to keep my medicine in the refrigerator . But my mini fridge only uses 40watts, and I want to be able to just run random little appliances. I already have a good inverter and I thought I was all set up until I learned that the run was a problem.  Will it work to run wires 120 ft at the voltage of these three solar panels combined? If so what gauge wire would I need?
I currently just have four lead acid batteries but I am planning on getting two more batteries for a total of six.
I do also have a small wind turbine but that's running alternating current so it's easy to run to my house, I have a separate controller for the wind turbine that came with it.

Photowhit

Before you do anything... Stop buying stuff until you make a plan!

dnaisbitt said:

Unfortunately, I placed them before I realized how bad it is to run direct current long distances, and I really don't want to move the panels now.  I have read if I hook them up in series they will run higher voltage, will that higher voltage be enough voltage to run wires 120 ft to my house? 

Yes, generally speaking it's NOT running DC long distances, but running low voltage long distances.
Unfortunately, strings of 3 high voltage panels usually don't work with typical MPPT type charge controllers.

Looks like you purchased an MPPT type charge controller. That's good, I'll look for spec's for it. Could you tell us the VMP, and VOC of the panels you have?  I can look those up as well, but if you have time invested, you might respect the information more.

 I may also need the system voltage, How your battery bank is wired, is it 12 volt or 24 volt?

mike95490

panels : Open Circuit Voltage (VOC)     47.4 V   Max Power Voltage (VMPP)     38.9 V

Not Good.  to use all three panels, you would need a 200V rated  MPPT controller.
Can you obtain one more panel, then you could run 2S2P and use your existing controller and run either a 48V or 24V battery.

Photowhit

I looked at the charge controller. I couldn't find a manual on line for it. From owner pic's and Amazon description, I don't know if it would work with your system. Then again every thing inexpensive will be a bit 'iffy'. Your situation is that 3 of your panels in series will have a VOC of around 47.4volts x3= 142.2. When the panels are very cold this voltage could go up enough to fry your controller in much of the US. I also don't know your max low temperature...

In addition owner photos like this;

Would seem to indicate there is a max input voltage of 60v for a 12 volt system and 100v for a 24 volt system, as well as a max input wattage, which better charge controllers would self limit and/or have a higher level.

softdown

mike95490 said:

panels : Open Circuit Voltage (VOC)     47.4 V   Max Power Voltage (VMPP)     38.9 V

Not Good.  to use all three panels, you would need a 200V rated  MPPT controller.
Can you obtain one more panel, then you could run 2S2P and use your existing controller and run either a 48V or 24V battery.

Sounds like a great plan. Add a panel and run 2S2P. 

If that is impossible, then two panels should power those minimal needs. Far better to add a panel if possible. If the SHTF real badly then ~three people may be needed for security issues. 

dnaisbitt

Thank you for all the responses. I should be able to obtain another panel but does it have to be the exact same panel? And then will that voltage be high enough to run wire 120ft to my house?
I was planning to have it be a 24-volt system.  I thought I had it all planned out but I obviously didn't understand a lot.  
Would it be better for me to just buy a different controller? Or should I get a different controller and another solar panel? Sorry I have studied this a lot but I obviously dont understand it well enough.

BB.

How much do you want to pay for a higher voltage MPPT controller? You are looking for a ~140+ VDC Vpanel input controller which is north of $300 pretty much... And ~400+ VDC ones are much more expensive.

Also, what is the size of battery bank (AH rating) are you looking for? And do you have a maximum solar array you are looking for?

Long cable runs are difficult at lower voltages (need heavy copper cable to keep voltage drop down)... A quick look at what things would look like and how to do the calculations.

First 3 panels in parallel (405 Watts @ 38.9 volts Vmp @ 10.4 amps estimated). 120 Feet and 3% voltage drop. 3x10.4Imp=31.2amps Imp-array:

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.5127&voltage=38.9&phase=dc&noofconductor=1&distance=120&distanceunit=feet&amperes=31.2&x=52&y=15

Playing around with the wire gauge--2 AWG gives a 3% drop:

Voltage drop: 1.17
Voltage drop percentage: 3.01%
Voltage at the end: 37.73

Say you want 2s x 2p array... 2*38.9Vmp=77.8Vmp-array; 2*10.4Imp=20.8Imp-array

https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&voltage=77.8&phase=dc&noofconductor=1&distance=120&distanceunit=feet&amperes=20.8&x=57&y=12

A larger array (4 panels), and you only need 6 AWG cable (less than 1/2 the size of copper cable) for a 33% larger (wattage) array:

Voltage drop: 1.97
Voltage drop percentage: 2.53%
Voltage at the end: 75.83

You need to identify your desired system (battery bank voltage/AH rating), your daily loads (Watt*Hours), and your minimum rate of charge (5% for weekend, sunny weather, emergency backup system, 10% for full time off grid system, and 13%+ for lots of solar power during the day and less genset usage) and rough location (for hours of sun per day by season--No shading by trees/buildings/etc... Almost any shade kills solar panel output).

Once you have the basic back of the envelope calculations, then you can start finding MPPT charge controllers that may meet your needs (input voltage, output current, features) and solar panels that match the controller(s) specifications.

This is sort of jumping in the middle of the design process without any design info.

-Bill

dnaisbitt

I was really just trying to make a cheap system that will run a 40watt fridge and freezer for emergency (with the hope that I would have a little extra power to run other small appliances if needed).  But now I've spent enough that I need to make it work whether or not I need to spend more.  I was originally planning on six 12v deep cycle batteries (Three 24v battery banks).
So if I get another solar panel and run 2s2p (that is just running 2 sets of 2 panels right? And I can do the 120ft run with 6awg copper wire?  And them my controller will work? 

I did not realize that the number of batteries would have any effects on the panels and controller, I was thinking that I could start with 6 and add more later if desired?

Photowhit

dnaisbitt said:

I was really just trying to make a cheap system that will run a 40watt fridge and freezer for emergency 

Well this doesn't make sense. Fridges don't normally run a 'set' wattage. they turn on and off with a thermostat...
Do you know the energy star rating of the fridge? from that you can make some rough calculations as to the amount of energy they will use each day.

dnaisbitt said:

 I was thinking that I could start with 6 and add more later if desired?

Never a good idea of adding new batteries to old, or having multiple strings of batteries. I would suggest limiting to 2 strings. Before we get there... "Marine" batteries are rarely true deep cycle batteries. Usually the best value in true deep cycle batteries for a small system are golfcart batteries. Typically they are 6 volt 210-230amp hour batteries.

dnaisbitt said:

I did not realize that the number of batteries would have any effects on the panels and controller, I was thinking that I could start with 6 and add more later if desired?

Basically you want a balanced system. Batteries self discharge a bit and you will want to deliver about 5% of their capacity for weekend/emergency use. For daily use around 10-13%

So if you have a string of 2 Golf cart batteries with a battery bank capacity of 210 ah at 12 volts. Then you want to be able to deliver about 5% of that or 10.5 ah. I say deliver since there's another thing we haven't discussed and that is the difference between the solar panel's STC ratting (Standard Test Condition) and their NOCT value (Normal Operating Cell Temperature) which runs about 75% of STC.

Did you receive a manual for your charge controller? What does it say about system voltage and maximum input voltage and wattage?

Another viable option is to have an outside power center, place the charge controller, batteries and inverter outside and run the higher voltage AC current to your home. ALL of my home systems have been done this way! Yu do have some minor reduction in capacity in the winter and is unacceptable for lithium batteries.

As an example I ran an under counter fridge/freezer that used about 1kWh a day with a system with 4 golfcart batteries and a 1300 watt array along with a laptop, lighting and fans. I likely could have done it on a smaller array, but had it setup for some minimal air conditioning during the summer.


The bottom right photo is my 'power center' it has 4 golf cart batteries in the section on the right and charge controller, inverter and breakers/fuses in the upper section on the left. Much like my current system below, though the battery bank is to the left on it.

dnaisbitt

Thank you so much for all your help.  I like your setup I think I will just copy that idea and have a power center right by it outside.
I actually have this fridge and another one that is basically the same; https://www.amazon.com/gp/aw/d/B07WGHKHRY/ref=ppx_yo_mob_b_track_package_o0_img?ie=UTF8&psc=1
So if I put my power center right by it outside will what I have work or do I still need a fourth panel? 

706jim

I think you should just run your three panels in parallel to charge your 24 volt system. Yes there will be some line loss but not so much that the system won't charge. My system has two groups of three similar panels running through probably 80' of wire to the charge controller and works quite well. I agree with others here that your batteries should be of approximately the same age to work properly. As for a different type of panel there will be no problem running it in parallel so long as the open circuit voltage is approximately the same as your 405 watt panels. If you were to connect a panel with a lower open circuit voltage than the 405's you would get the system back charging the lower voltage panel with the system approaches float. (Ask me how I know...)

Photowhit

dnaisbitt said:

Thank you so much for all your help.  I like your setup I think I will just copy that idea and have a power center right by it outside.
I actually have this fridge and another one that is basically the same; https://www.amazon.com/gp/aw/d/B07WGHKHRY/ref=ppx_yo_mob_b_track_package_o0_img?ie=UTF8&psc=1
So if I put my power center right by it outside will what I have work or do I still need a fourth panel? 

Well...

It appears this is a DC compressor type fridge or freezer. It likely will work nicely off the battery bank if it accepts 24 volt.

I always hate when you can't find correct info in the description. but here's a review, and if you look at the items supplied, the AC adapter has a wall wart;

This freezer/cooler has great cooling...works well thus far...24 hours. Problem is, it isn't really optimized for storage. I like the compressor on top. It claims 13.2 gallons or 50 liters...I can tell you, unless you just fill it with water, it won't hold 13.2 gallons. An example, if you used gallon milk jugs, you might fit 6 inside with some space around the edges for other stuff. Looks to me more like 10-11 gallons at best. Also, the cooler I got wasn't made by Cho sports. It was some company named Massimo. Anyway, so far for what it holds, it works.
edit: It has no interior light either...using A/C power, when compressor is on it uses between 48 and 82 watts (it goes up and down), when the compressor is off it uses 1.2 watts.
After a few days there is a slight frost layer on the interior walls, that layer was there after 24 hours and hasn't gotten thicker 2 days after that. Frost is often caused by opening and closing the door frequently.

edit: 07/29/2020 - Freezer still going strong on 24/7 in our place. We can't even hear the compressor unless we are next to it and everything else is off. So far, so good.

So there might be a reason to run the DC to the home, I would be fine with running it off AC though.

I would think it would be better to run 2x2 solar array, mostly because the charge controller will likely work best with around double the charging voltage. But that still could be a problem on a couple levels. The sticker above says max input voltage should be 100 volts for a 24 volt system, which could still be a problem if it gets very cold in your location. 

It does say "24V System best mppt working voltage range (36V-72V)" but the VMP (operating voltage) will drop a bit in use and be right at the bottom edge of this range. It should work down very close to the charging voltage(around 29-30 volt normal and 31-32 volts equalizing) but in a less efficient mode. I would say hook them all up in parallel and run the three and if you have to change up later do that... 3 panels in parallel will require a combiner box, while 2 strings would not. so if you can get another panel and lives somewhere warm, then it would make more sense to buy another panel than the combinerbox and have a larger amount of energy to deal with.

The basic rule is that if you have 2 panels or strings of panels 1 can't over power the other and there's no fire risk. If you have 3 it's okay in some instances, Usually this is when the string fuse/breaker rating is more than double the IMP current, which is true in your case, <11 IMP and a Max. Series Fuse Rating 25 A. I never got to the point that I understood this completely. Not sure if any regular person here would understand this unless Bill has followed up on this... We just use the more than 2 strings and go from there normally.

mike95490

If you run your 3 panels in parallel. 38.9v may not be enough for for the MPPT to operate,  MPPT usually wants 1.3x max battery voltage.  With a 24V system, 30V could be needed when charging,

Photowhit

I built the power center out of scraps after I built my cabin.

It was designed with a knock out front, so I could put in a forklift battery, which I actually did fr the last year of service.

Once the inverter and charge controllerer/breakers are installed it's quite tipsy without batteries in the battery section. It was quite easy to build with 2x4 construction, building the bottom 'box' and then build the upper section. 

Would change the design slightly and make the lid not hinge at the back of the power center, but run a 2x4 support aross the bac of the power center to give a better place to hinge the lid. And run the roof of the power center so that water hit past the hinged section...

Shed roof design is simple if you keep a single reference angle to cut all your angles...

dnaisbitt

Again thank you so much for all your help, Let me make sure I'm understanding all the comments and suggestions correctly I do not have a problem buying another panel so I think since most people are suggesting that I will just buy a fourth panel (it will probably be good for me to have extra power anyway).  I should use 6 AWG copper wire to run the 120 ft to my house? 
With the controller I just barely bought it from Amazon (easy to return) so if someone thinks there's a better controller let me know cuz I can easily return this one, or do you guys think this controller will work well? 
It seemed like I was getting mixed information on that?
Some people did ask how cold it gets the average cold temperature where I live is in January and it is 21° f the lowest recorded temperature Ever is -34° f (but of course that's very rare) but it does get to be like -4° f Periodically.

Photowhit

The voltage drop for 120 volts over 120 feet will vary by the load. So look at your high demand items and run them through a voltage drop calculator. If you are running a microwave at 1200 watts you would use 10 amps the voltage drop would be about 2% on a 10 gauge wire. Understand that the total might be more depending on what else is running.


Link to calculator;
https://www.calculator.net/voltage-drop-calculator.html

I would just use 10 gauge direct bury wire, if you are unlikely to dig things up in the area. 

The temperature thing has to do with what your manual says about max voltage. if it indeed says 100volts like the sticker says and implies it's any 100 volts as in VOC (volts open circuit) then I'd run the minimum temperature through Midnite's string calculator for your panels and minimum temperature. I think they will give you a max voltage.

There are certainly better charge controller out there, but they cost more. Not sure if a Renolgy 60 amp wouldn't be in your range and still have a 150 volt upper limit. I haven't checked around... I use Midnite classic (2) other brands would be Outback, Schneider, MorningStar. Renolgy has a more moderate price and likely would be fine. Since you would be close to the battery, you could also run all 3 in parallel and use a cheaper PWM charge controller. Same issues apply as to wanting to run a combiner box. a VMP of 38.5 is a good range for a PWM type charge controller, charging a 24 volt battery bank.

Midnite string calculator;

http://www.midnitesolar.com/sizingTool/

dnaisbitt

Awesome thank you for all your help!

Photowhit

A PWM charge controller does limit you to expansion, and you might find a bit less production than MPPT type, but your MPPT type will likely only be using a PWM mode if wired in parallel and produce less and use more energy. A bit long to explain. That's what I used with the cabin above, but that's pretty much all that was available in 2004.

dnaisbitt

after reading your comments about regular deep cycle batteries not being good enough I started studying battery options and found the old Nissan leaf batteries.  Seems like a cheap way to get a lot of amp hours. Would this be a good option for my system? I was thinking about getting two of them so I'd have three kilowatt hours; https://www.google.com/amp/s/www.techdirectclub.com/amp/24-volts-nissan-leaf-battery-g1-module-lithium-ion-1-5-kwh-66-amh-lot-of-3/
Would I need to change anything or would they work just like the other battery options we talked about?
Here is the link to the wind turbine I have; https://www.ebay.com/itm/24V-Charge-Controller-8000W-Max-Power-5Blades-Wind-Turbines-Generator-DC-Charge-/174394375586?_trksid=p2349624.m46890.l49292
I know it says 8000 Watts but I know it's a cheap knockoff so I think I'll be lucky if I get 300 watts out of it on average. I would prefer to hook the two battery packs together in parallel and hook both the solar and the wind charge controllers to charge the same battery packs combined. I read online that you can do that but I figured I should ask you, would that work right? Would I be better off getting a different more expensive controller? I would rather not spend more money but I've been working on this forever and have got nowhere overall 😫 so I would rather spend money and get it working well at this point.

Dave Angelini

You get what you pay for in power systems. If you buy from the store here, they will support you quite a bit. Most of the items (used loosely) on EBAY are not supported and often inferior to what Wind and Sun sells. Used batteries from cars are for the qualified or folks who have learned and researched. Not DIY in my opinion. It is good you are asking but you really need to know the answers for offgrid.

However, everyone is different. I have clients living 200+ miles from town in Alaska that tell me they will use candles and take cold showers if something bad happens. Others with 2 back-ups to everything in the home.   Good Luck

Photowhit

dnaisbitt said:

"after reading your comments about regular deep cycle batteries not being good enough...."

I never saw this in this thread? are you referring to another thread? They've been good enough for me for my 25-30 years of having solar electric systems.

Lithium batteries create some other issues. They can't be charged when below freezing (30 degrees), and I've read can have issues charging below 40 degrees. I would think you would want a BMS (Battery management system) usually used with lithium batteries, but understand others have gotten by with "bottom balancing(?)" but it's not my end of the pool.

dnaisbitt

Hello again everyone, so I did change things.  I moved my setup closer so it is now only 80ft.  I have it hooked up and it is working great, but currently I am only using 2 of the solar panels.  I have the ability to get a FREE used panel that 270watts.  It has an open current voltage of 38.2 vs my 47.4.  could I use this other panel to hook to my unused panel to have the 2s2p run?  
Thanks again for all the help!  The fridge for the medicine is working flawlessly.

BB.

Just to be exact, what vmp.imp of the other 3x panels?.

Do you still have a own controller, or an appt controller now?

Bill "no guessing here" B.

dnaisbitt

Here are the stats on the other 3 panels;
Watts (STC) 405 W

Max Power Voltage (VMPP) 38.9 V

Max Power Current (IMPP) 10.42 A

Open Circuit Voltage (VOC) 47.4 V

Used Panel I can get free;

Watts 270
Max Power voltage 31.2
Max Power current 8.71
Open Circuit Voltage  38.2

dnaisbitt

sorry I forgot to post this I am still using this controller that I bought before;

https://www.amazon.com/gp/aw/d/B07JLVPVGR?ref=ppx_pt2_mob_b_prod_image

BB.

That is very close to being >10% difference between the two parallel strings:

• A = 38.9 + 38.9 = 77.8 Volts Vmp-array-A
• B = 38.9 + 31.2 = 70.1 Volts Vmp-array-B

And Current:

• A = 10.7 amps per panel
• B = 8.71/10.42 amps = 0.84 or >10% current difference...

Look at the series protection fuse--Should be 15 amps (guess)?

It is less than an ideal array match--But it is hard to ignore a "free" 270 Watt panel... Try it and see if it works (do you get more current/harvest with the second mixed string? If you get almost no "boost" or even less than the single "A" string power (current), then the MPPT controller is tracking the "wrong" Vmp-array voltage (which can happen with "mixed" arrays).

You are running this on a 24 volt battery bank (12 volt bank is 60 Volts max solar input voltage)?

-Bill

dnaisbitt

Yes I have a 24-volt battery bank.

Thank you for the help I will give it a try.