6AWG directly into Solar Panels

jdubs714

Advice needed here.. I am experiencing some issues with my circuit breakers tripping when the charge controller goes into Boost mode to charge the battery bank at full potential. I have an 80A 200V max EPever off grid charge controller, and 2 panels that are 305 watt sunpower in series. They came with the standard 10AWG wire with MC4, but after exhausting attempts to get an answer from EPsolar, I have decided to apply what I think I know and upgrade the cables from 10AWG to 6AWG with 60A circuit breakers instead of the 30A ones that I am using now. I speak in plural because I have 3 arrays and 3 controllers all the same. All 3 trip at about the same time when the bank is low and the sun hits the panels. The question I have is, do I need to attach the 6AWG directly into the junction boxes on the backs of the panels, or can I cut the 10AWG 2 inches out, strip and butt connect to it with 6AWG. Any advice on reconfiguring is appreciated, but I am trying to create a system that can run the 6k btu AC/Heat pump off primarily solar charging into the 14 battery storage bank I have made up of 6v batteries in series/parallel to give me 1485 Amp Hours available. Thanks in advance, and I apologize for any mistakes as I am new to forums, including this one. Please advise of any information needed to help me answer this question. 

jdubs714

Pleasure to meet all of you by the way, I am Joshua, and I have a trailer I built that I am still working out the bugs. I'm a General Contractor, live in AZ and work in Cali. Although right now, I am on holiday (stay at home orders). Thank you guys for this forum and any help you can provide!

mike95490

STOP !
Don't alter the factory wires on the panels, you will instantly (and needlessly) void the warranty,

How about post a pic of the label on the back of the panel, or tell us what the:
Voc
Vmp
Iss
Imp
series fuse
values for your panels are.  Also how many wired in a string, how many strings paralleled into the Combiner and the location of the breaker that keeps opening.
I assume with your large loads, you are using a 48V battery bank, but fourteen 6V batteries makes no sense.

In a series string of panels, the amps stay the same, I'm guessing the series fuse spec is less than 20A, so maybe a sketch of the way things are wired is going to be needed too.

jdubs714

Thank you, I have read that it voids the warranty. I purchased the panels from a company that liquidates solar farms. They were made in 2017, and dont have a lot of use on them. My bank is 12V because I use a lot of 12V appliances, lighting, etc.. and I was still beating the learning curve when I started. My ambitions have grown some since then, but my main drive is still the same; to be able to operate my AC 24/7 if needed, hence the large bank. I use the Xantrex freedom XC2000 inverter Charger as well on my system. And everything seemed to be working well, until I ran the Air all night and in the morning when all panels woke up is when I realised I had a problem. I will get that info right now and post it in a few minutes. I wanna thank you for your time and for responding, I appreciate it. Stand by for the info...

jdubs714

Solar panels:
6 of them in 3 arrays (2 per array, wired in series)

Sunpower

Model: SPR-305-WHT-U
Peak Power: 305 W
Voltage: 54.7 V
Current: 5.58 A
Open Circuit Voltage: 64.2 V
Short Circuit Current: 5.96 A
Max Series Fuse: 15 A

3 strings:
610 W per string going to their own 80A charge Controller, model "EPever Tracer 6420an" and in between the panel and charge controller, there is a 10A DC fuse and a 30A DC circuit breaker on one, and 30A fuses and 30A DC breakers on the other two (I've been experimenting with the fuses). I will post a pic in a second... 

jdubs714

Keeps failing to upload a 3mb pic.. 

jdubs714

Here you go

jdubs714

I will do a sketch and post it. It's pretty simple by the book, but the weird thing is, when the controllers start to ramp up, I can see on the display the PV amps start to raise, and they go way up over what the panels state. My series wiring is cut and dry (pos + from panel 1 goes to controller PV pos input, neg - from panel 1 connects to pos + from panel 2, and neg - from panel 2 goes to controller PV neg input). All the manufacturer could tell me was that the cabling from the panels needs to be bigger (6AWG).. so that's where I made the decision to upgrade the cabling... just not sure how exactly to go about it. I can access the panels junction and plug into the terminals directly, but they dont quite accomodate 6 guage, so that's why I thought I could cut and splice. Not sure if that small amount of 10AWG will create a pinch point and get hot. I can always plug the old 10 guage leads with MC4s back into the box if needed....

littleharbor2

I think your problem is the breakers themselves. Are they rated for 12 volt usage? You're running 109 Vmp. into them and they probably aren't designed to handle that kind of voltage. You're only putting 11 amps or so into them so why would going to 60 amps from 30 do anything? As previously mentioned, Don't cut the leads on the panels, they are fine. You have no need to increase the wire size either.

MarkC

Note that the manufacturer recommends the larger wire (4 or 6 AWG) IF you have many parallel strings of panels - would be more than 8 strings per controller to reach the rated 60 amps - after a combiner?    It is also stated that the max input voltage is around 90 VDC from the panels.  With 2 in series or your panels, this could be your issue.  Note that I'm simply looking at your 60 amp controller installation manual - pages 6,  9 and 11.

Also, the wiring diagram shows a fuse on battery bank terminal (+).  If this breaker/fuse is not sized for your system load, it will likely open.  Note that this is an observation based on the recommended wiring diagram of your controller - and may NOT BE YOUR ISSUE.  If you can trace your entire wiring/fuse/breaker installation and give us a sketch, it will be helpful.    

mike95490

With those high voltage panels, I'd only place 2 in series , and then use a combiner box to parallel the strings. After the panels are paralled, you use a larger wire gauge.  And if you use a larger breaker, you have to use wire rated for the value of the breaker. That's $$ and pointless

Those breakers look like automotive breakers and not rated for continuous solar duty,

Have your ever blown your 10A fuse ?   It would be real hard to do unless you have very cold conditions, reflective snow on the ground and bright sun .  the panels suggest no larger than 15A in a series string.

With full sun, your controllers will each output over 40A to the batteries, and the wire from the controllers to the batteries needs to be rated for 60A and a 60A breaker on the battery OUTPUT of the controller

jdubs714

Thank you guys for your input, I highly appreciate it all. I started a sketch to upload and will finish it and upload tonight. I'm in AZ and the cell service here is awfu . I dont get good coverage between 10am and 6pm for some reason, but that's another issue. So, you are all correct and that's what they were trying to tell me, but they were saying I need to use 6AWG all the way from the panel to the controller on each array to each controller. I have 2 panels going to each 60A controller, 3 controllers/3 arrays. I think it also could be the breaker itself, thanks for that input. I will get that sketch done and upload some more pics this evening. Thank you little harbor, Mark, and Mike, I REALLY appreciate your help on this. 4 heads are way better than 1 and you guys know this stuff through and through. Stand by for the drawings, I am putting my bumper together today and its burning hot out here! Talk in a bit, thanks again!

jdubs714

I am still working on my truck, but had a quick thought.. Mike mentioned the wiring from the controller to the bank.. that is the same size (10AWG) as the wire from the panels... do you guys all agree, that I should change the 10G wire with 15A breakers from the controllers to the bank to 6AWG with 60A breakers? As a GC who mostly works with residential wiring, I think I made a mistake and ran the same wire going into the controllers out of them. But wouldnt that have made those 15A inline fuses blow instead of the breaker before the controller? Well, I am gonna upload my sketch tonight for you guys to look over, and then change the output wiring to 6 guage, and also shop online for some 60A DC solar breakers. Again.. I cannot thank you guys enough for helping me work through this! Talk later this eve. 

jdubs714

Something like this .. maybe 150VDC

mike95490

You don't really need the expensive 300V rating, the 150VDC rating would be fine.

jdubs714

Hey guys, heres a drawing.. I'm not the best artist.. it shows one of the 3 identical arrays/controllers, all wired the same... I think you guys may have figured it out for me, I am ordering 3 breakers that are 15A 150VDC and going to put a panel with the solar cables going into them before the controllers and also replace the 10AWG wire from controllers to the bank with 6AWG and 60A breakers. I think that will do it. I will report back to you after I do that. Please comment any thoughts you have or advice, I will keep checking in here. If this works, I will be ecstatic! Thanks again... here you go... and THANK YOU FOR SAVING ME THE WORK OF REPLACING THE PANEL WIRING, OMG! THANK YOU THANK YOU THANK YOU, HAHAHA. 

BB.

You really do not need the 15 amp fuse in the solar + wiring with one or two parallel solar panels. If you have three or more parallel strings of solar panels, then a 15 amp fuse/breaker per string is probably appropreate (need to check the array series fuse protection requirement to ensure that 15 amps is correct). The 30 amp breaker is just being used as an "on/off" switch at this point (not a bad thing).

The output of the charge controller--Rough maximum output for sizing breaker/wiring with present array:

• 2 * 305 Watt panels * 1/12 volt charging * 1.25 NEC derating = 63.5 Amps

Since your controller is a 60 amp controller... I would have suggested the minimum wiring+breaker to be for each MPPT controller to battery bank/bus:

• 60 amp MPPT controller * 1.25 NEC derating = 75 Amp branch circuit ~ 80 amp breaker + wiring

So, the 15 Amp fuse/breaker and 10 AWG cable is too small... You can use this simplified NEC wire AWG table to pick the wiring:
https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

But 4 AWG to 2 AWG would not be a bad choice (depending on insulation class).

12 volt @ 1,485 AH? That is a big bank for a 12 volt system.... Eventually, you may wish to revisit and look at a 24 volt or 48 volt battery bank (much more than 800 AH on a battery bank, it is usually a good idea to go to the next higher bus voltage 12/24/48 volts, etc.).

Just to size "what can be expected" from your system... The typical average peak current from each 610 Watt array+controller (a few times a year, discharged battery bank, very good cool/sunny day):

• 610 Watts * 0.77 panel+controller derating * 1/14.5 volts nominal charging = 32.4 Amps nominal best case charging current

When dealing with solar, this big drops in "expected" harvest are normal, and part of the "fun" of solar. Variations in sky, temperature, battery bank voltage, angle of panels, etc. all affect harvest vs the "ideal system".

Lets say you are around Scottsdale AZ, with your 1,830 Watt array mounted flat to the roof of your RV:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Scottsdale
Average Solar Insolation figures

Measured in kWh/m2/day onto a horizontal surface:

Jan	Feb	Mar	Apr	May	Jun
3.21	4.01	5.47	6.87	7.70	7.76
Jul	Aug	Sep	Oct	Nov	Dec
6.94	6.20	5.73	4.60	3.56	2.97

• 1,830 Watt array * 0.52 off grid system eff for AC power * 4.0 hours of sun per day (A/C season) = 3,806 WH per average "warm day" minimum

From your battery bank, assuming 2 days of storage and 50% maximum discharge:

• 1,485 AH * 12 volts * 0.85 AC system eff * 1/2 days storage * 0.50 max planned batt discharge = 3,787 WH per day from battery bank

The basic math looks doable... The right AC inverter (not too large, not too small), the right A/C unit (inverter based mini-split or LG inverter based window unit, or similar) are usually pretty solar friendly. And picking a cooling method that works for you (suggested possibly running A/C on low during day to pre-cool, vs running on high in evening when you get back from work, etc.). A well insulated RV and keeping heat from coming in windows (awnings, insulation, heavy curtains, etc.)... all help too.

Your thoughts?

-Bill