Comment On New RV Solar Setup (Please)

gdoty · May 2012

Will be buying a 38’ 5th wheel Dec. or so & have been studying solar and would like to be mostly independent for boondocking. Here’s what I’m looking at so far:
• 5 - Kyocera 140 w panels ( Vmp – 17.7/Imp – 7.91 / Isc – 8.68 )
• Mounting syst. with tilt
• #8/3 wire (max 20’ run) to junction box on roof to keep voltage loss less than 3% (3rd wire for gnd)
• #6/3 down to controller & ground (10’ to 12’)
• Morningstar TS MPPT60 controller, w/heat sensor and remote monitor (or Trimetric 2025RV meter)
• 6 T-105 Batteries w/ Hydrocaps & #4 interconnecting wire (& wire from controller - less than 3’)
• 50 Amp (house AC type double fuse box) to run solar down wire thru one fuse & controller out wire
• thru 2nd fuse (quick disconnect for solar system)

Correct me if I’m wrong…. This setup will give me 700w with 17.7 Vmp to the controller and should charge up 675 Ah batteries at a good rate. I plan on running panels in parallel – keeps the shadow problem to a minimum and keeps the Vmp closer to the MPPT output (more efficient?). Everyone uses #10/2 on the panels, but to keep the voltage drop to 3% or less on runs longer than 15’ or 20’ I’d rather use #8. I will pull out whatever 12v batteries come with the unit & just attach all the wires to the new battery setup. Would like to use them but not a good idea to have a couple of 12w bats with a couple of T-105 6v bats. May use one of them in the truck to run a 300w inverter there…

Question: If the unit comes with an inverter (I’m assuming it will be small so they can keep the cost down) and I replace it with a 2000w pure sine inverter, what issues will I have besides replacing fuses with ones that are higher amp? Any other thoughts or suggestions would be appreciated. I have a laptop and TV on most of the day, and I understand that a microwave (among other things) will run better on a pure sine inverter. Also have cell phones, ipads, elect. razor etc to charge up. Might have to run one of the AC units for an hour or two as well, but that would probably be better off a gen. (would rather stay off a gen. if possible).

Comments & suggestions appreciated. Great forum by the way - just joined. Will be sifting through everything for quite a while.

ywhic · May 2012

Re: Comment On New RV Solar Setup (Please)

Each panel will need a fuse or breaker.. before or when combing in the JUNCTION BOX..

Down and dirty would be this.. for 12v panels (aka 17.x v)..

10ga wire comes in from the right from each panel.. and goes to a lug/fuse..

8ga wire exits on the left to the controller inside the RV..

Thats a double gang box with outdoor cover.. YMMV..

Some people use inline fuse holders inside a small outdoor POLY box and then fuse the hot lead inside the box..

Many are on YTube..

Then you can bring the 8AWG down inside from the roof mounted junction box..

Amp rating for the battery bank/inverter will vary per the inverter.. 12v system and 2000 watt inverter.. 250 amp breaker/fuse needed..

Figure 1 1/2 x the inverter output.. 1000w = 150 amp , 1500w = 200 amp, etc..

You will need either 2 AWG or 0 AWG wire for the inverter to be safe..

Others will be along.. I got the same setup starting.. mines off grid and not RV

niel · May 2012

Re: Comment On New RV Solar Setup (Please)

welcome,
those pvs will give you almost 40a imp and a charge rate roughly at about 5.9% if everything goes ideal. now if it isn't a case of room that you chose those pvs then why not get higher wattage pvs with better bang for the buck seeing as how you are going with an mppt controller anyway? having vmp ratings at 30v or so will certainly not harm a thing and efficiency will be very close to the lower vmp's efficiency.

as to putting in a larger inverter i don't see the harm just as long as any and all wires and fusing is proper.

gdoty · May 2012

Re: Comment On New RV Solar Setup (Please)

niel wrote: »

welcome,
those pvs will give you almost 40a imp and a charge rate roughly at about 5.9% if everything goes ideal. now if it isn't a case of room that you chose those pvs then why not get higher wattage pvs with better bang for the buck seeing as how you are going with an mppt controller anyway? having vmp ratings at 30v or so will certainly not harm a thing and efficiency will be very close to the lower vmp's efficiency.

as to putting in a larger inverter i don't see the harm just as long as any and all wires and fusing is proper.

Panel size is a space thing. Didn't think I could drop down to a MPPT 45, but would that be more efficient? The MPPT rating of 45 would be for the Isc, correct? Those panels would put it afully close (43.4) to the max. Isn't there a fudge factor % you should leave in there? How do you figure efficiency of panels compared to MPPT specs?

gdoty · May 2012

Re: Comment On New RV Solar Setup (Please)

ywhiz
Thanks for the inverter info - had planned on upping the wire to the #2 you recommended. Didn't realize each panel was individually fused. Thought I could put the whole array on one large fuse in the elect. compartment to keep from going up on the roof to replace the fuse. BUT - I'd have to go up there anyway to see what made the fuse blow. DUH. I saw that suggestion from someone else but just realize their stupidity. Do people usually just have an inline fuse at each PV panel? If I wanted to run #8 instead of #10, can you get connectors with that wire or do you have to splice it in? Thanks for the pic also. Saw those fuse blocks somewhere doing my solar research. Those are auto fuses, right?

CATraveler · May 2012

Re: Comment On New RV Solar Setup (Please)

If you can mount 3 230W panels you would save a lot of money. Otherwise you're stuck with the smaller panels.

You should definitely look at a serial connection (which you can do with the 230W panels or serial/parallel. Serial is easier/cheaper to wire.

It's popular belief that parallel is more shade tolerant. A lot of this has to do with older panels and tradition. For modern panels with bypass diodes serial may be more shade tolerant. I said may be because I'm unable to find any apples to apples comparison between serial and parallel. I started a thread on these boards asking about testing. I'll get you the link, but there apparently aren't any such tests. There is a thread on rv.net on exactly that subject and contains much information. But the parallel/serial comparison wasn't correct IMHO. I'll get that link for you. There is no set answer on this subject and your shade and my shade are probably different.

Example: Partial shade on a serial panel and you might lose 1/3 panel only due to the bypass diodes. Same shade on a parallel panel and you might lose most of the panel.

For serial instead of the AC fuse box use a AC switch box to disconnect the panels and batteries. A fuse is not needed for the panels and the controller should be fused at the battery.

I sized 690W at 10' CC to the battery and concluded that 4 ga wire would be best for me (but I like to reduce loss). I haven't checked those numbers recently.

Buy the 10ga UV resistant wire for the panels. If you do go parallel run them to 1 or 2 combiner boxes as required. All roof wire needs to be UV resistant or covered.

You might consider a small 300W more efficient inverter for basic daytime usage and a 2K unit for big loads.

You will NOT be running an AC off of your proposed system. The startup surge will get you and even then the run time will be short. Let's say the AC takes 12A AC. That's about 132A DC. At 340AH (50%) you'll have 2+ hours of AC and then the batteries will need heavy recharge. Solar and ACs don't mix unless the solar is very large.

CATraveler · May 2012

Re: Comment On New RV Solar Setup (Please)

Handy Bob is FT with 300W+ solar and no gen. Apparently he has adequate AC power for his tools, DW sewing machine, toaster, etc. He is a BIG fan of 12V panels and PWM controller. Need more power then add another panel – cheaper than mppt. Read his RV Battery Charging Puzzle doc. Lots of information.

Here’s the serial/parallel thread. The initial posts are for covered cells while later in the thread there was a serial test with a shadow from 1’ away. http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25983904/srt/pa/pging/1/page/1

Here’s the NAWS thread http://forum.solar-electric.com/showthread.php?15635-Shading-Tests-Serial-vs-Parallel-Panels&p=116686#post116686

CATraveler · May 2012

Re: Comment On New RV Solar Setup (Please)

gdoty wrote: »

Panel size is a space thing. Didn't think I could drop down to a MPPT 45, but would that be more efficient? The MPPT rating of 45 would be for the Isc, correct? Those panels would put it afully close (43.4) to the max. Isn't there a fudge factor % you should leave in there? How do you figure efficiency of panels compared to MPPT specs?

Isc is short circuit. Use Imp (maximum power). Vmp is for max power also. Voc open circuit is very important as you don't want to exceed the controller maximum.

All of this is for ballpark estimating. Use the Morningstar String Calculator and it will consider temp, battery voltage, etc and let you know what serial/parallel configurations are OK for your panels. I've been using 11.5-15.5V and 0-200F.

ywhic · May 2012

Re: Comment On New RV Solar Setup (Please)

Most panels come with 10 or 12 ga MC4 wire hanging off them with about 3' of wire.. FleaBay may have some selling 8 AWG wire leads that till plug onto the 10 or 12 ga on the panels.. you can also buy 8 AWG solar UV wire and crimp them your self.. (crimper is like $45 though)..

You could use a simple ATC single fuse holder with a 10 or 15 amp auto fuse.. run them all thru that double gang box I posted.. and just have the fuse holders in that..

Get 2 busbars.. 1 for the NEG lead and 1 for all the positives you just fused (as above).. then from each busbar bring down your 6 awg wire feed (1 ps and 1 neg) into the RV and to your charge controller..

Like I said plenty on line how to's.. look up solar combiner box on YTube..

The best/correct option thought is to get a MidNite Solar 6 model.. which is outdoor rated and can go right on the roof.. this takes DC breakers.. bring it all to that and THEN 1 + and 1 - down to your controller.. its about $120 for the bare box..

The 2nd class and good option is to get a QO612L100RB breaker box (outdoor 3R rated) $36 at Lowes or HDepot or MillsFleetFarm (online).. and buy 15 AMP QO breakers $6/each (Lowes or HD) for how ever many panels you got.. max of 6 unless you buy TANDEM 15 Amp breakers at $15/each.. then you can get 12 panels into that same box...

This is the option I am using in my cabin.. the QO breakers are good for upto 48VDC each.. (& A/C rated also..)

Some of the online solar places sell them for $70-80 for the bare box.. LoL..

My 'combiner' QO box is due in tommorrow and I'll be wiring it.. I'll put a pic in this thread for you..

niel · May 2012

Re: Comment On New RV Solar Setup (Please)

actually i'm thinking 3 240w solarworld poly. it would up the wattage by 20w over the 5 kc140 pvs and be a tad more efficient due to lower v drops through the wires more than making up for the very small efficiency loss in the cc going to a higher vmp. each pv will need to be fused unless you put all 3 in series and then you would not need any, but i would put a disconnect in. 3 in series would be a higher efficiency loss to the cc, but less loss in wires for v drop too. even though the sw240w pvs are more expensive than the sw230 pvs you are still paying $500 less than 5 of the kc140 pvs so if you feel bold then go for the 250w and still save over your present proposed kc140 system. the sw pvs will be about 7in longer, but would take up about 14 or 15in less in total side by side area than the kc140s side by side.

ywhic · May 2012

Re: Comment On New RV Solar Setup (Please)

@gdoty..

Heres a link to my post in this same forum on the QO combiner box with pics and video..

http://forum.solar-electric.com/showthread.php?15793-Using-a-Square-D-QO-Load-Center-for-Combiner-Box-pics-and-video

Teaser pic..

Comment On New RV Solar Setup (Please)

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