Designing a space-constrained PV system for a boat. Advice needed.

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Comments

  • SOMFSOMF Registered Users Posts: 18 ✭✭
    The boat is in Mexico and I am not so I can't check the breaker but from the above posts it sounds too small. If I have it right the 550w set up if it works should have 60 amp breaker?
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,296 ✭✭✭✭✭
    A 40 amp breaker should be fine if it the wires out of the fm-60 it is protecting are around  #8. You do lose about 25% of the nameplate power of a solar panel so keep that in mind.
    3 or more parrallel strings need to have a 10 amp breaker/fuse on each panel but this often gets fudged on boats. If I was leaving the boat unattended I would use only 2 panels to protect against a bad panel causing problems or fuse them and be safe.
    Adding the panels should be fine as the Vmp is pretty close.

    San Carlos or Mazatlan where the boat is? Fair Winds!

    "we go where power lines don't" Sierra Nevada mountain area
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    SOMF said:
    my boat currently has 3 135w Kyocera panels with the following specs Vmp17.7 Imp7.63 Voc22.1 Isc8.37

    I want to add 2 smaller panels in to the mix Everbright 80w specs Vmp17.2 Imp4.65 Voc21.6 Isc5.17.

    The plan is to run all panels parallel into an Outback FM60 feeding 4 Trojan L16h batteries totaling 870ah. Will the FM60 handle the variances in the panels?
    I think you would be better off with a PWM controller.   The Outback, like most MPPT controllers, needs more voltage headroom than does a PWM controller.  When your panels heat up, their 17 volt output will drop by a couple of volts.  If you need 15 volts going to the batteries you may not be able to get it with an MPPT controller.   Of course, if you have an even number of matched panels you could put them two in series (string Vmp = about 35 volts) and use an MPPT controller.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    edited September 2016 #35
    you have it right, PARALLEL is the ONLY way to hook up those 5 panels....  I assume you already have the FM60... other wise as long as you are not going to expand the number of panels, a Midnight KID mppt CC would be a good fit.... for those new panels (80W) use the CB size posted on the panel... the reason is to protect the panel from a back feed generated by the other PVs that could possibly start a fire.  
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Thanks everyone for the input. First the boat is in Puerto Vallarta for the moment, soon to be headed back in to the Sea Of Cortez, 2nd yes I already have the FM60, wish I would have checked the forum first hope it works OK. It's replacing a Bluesea 2000i that was only rated to 25 amps. That controller worked great for 4 years but didn't allow for any added amps. And lastly, if I am understanding correctly I should have a 40amp CB between the last panel and the Outback, 10amp fuses between each panel except the fuses between to two 60w panels and the others should be 5amp is all of this right?
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,296 ✭✭✭✭✭
    edited September 2016 #37
    PV is one of the best towns. Have not been there in 10 years and I can imagine the changes. Paradise Village was nice then and we did many of those time share sales tours for free bottles of whiskey, until they found out we were boaters...

    The 40 amp needs to protect the wiring from your battery to the fm-60. It will be fine as I assume you have DC refrigeration and probably rarely get close to 14V let alone 15V.  
    "we go where power lines don't" Sierra Nevada mountain area
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Dave, PV has changed unbelievably, they average 4 cruise ships a week during the season which makes the Malecon a zoo. My boat is in La Cruz, about 20 miles North of downtown PV. Much more laid back. Actually I have an apartment sized refrigerator that is amazingly efficient, it's a Samsung "inverter" model, all lighting on the boat is LED now and a typical night starting with full batteries shows a 10% discharge on an 880ah bank. Before I replaced the old fridge I struggled to keep the bank above 70% in the morning so i am really happy with this fridge. That said will the 40amp CB still be correct between the batts and the controller? Also is the 5amps fuses between the 80w panels and the 10amp fuses between the larger panels correct or should they get progressively larger down the line?
  • BB.BB. Super Moderators, Administrators Posts: 32,921 admin
    edited September 2016 #39
    The question is "what is the average/peak current expected", size the wire to manage those currents (and size to minimize voltage drop--if needed), and then size the fuses/breakers to protect the installed wiring. Details matter (exposed wiring, vs wiring in conduit, ambient temperatures--on deck under sun, vs inside/shaded, temperature rating of insulation, etc.).

    In general, the wiring from the charge controller to the battery bank should be sized for low voltage drop (say 0.05 to 0.10 maximum for a 12 volt battery bank) to insure that the charge controller "reads" the voltage of the battery bank accurately. That will probably suggest a larger AWG cable--And would allow you to use a larger rated fuse/circuit breaker.

    For example, say you use 40 Amps. And using the NEC table and deratings:
    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm
    • 40 amps * 1.25 NEC derating for wiring and fuses = 50 Amps
    • From table, 8-6 AWG would be indicated
    • Choose 6 AWG and based on insulation, you can use 55-75 Amp rated breaker
    Now--Lets say you have 5 feet from charge controller to battery bank and want at most 0.1 volt drop at 40 amps, using a simple voltage drop calculator:
    http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&voltage=12&phase=dc&noofconductor=1&distance=5&distanceunit=feet&amperes=40&x=73&y=7
    6 AWG:
    Voltage drop: 0.16
    Voltage drop percentage: 1.33%
    Voltage at the end: 11.84

    Which is "too high" (in my humble opinion) for voltage drop... So try another AWG:

    4 AWG:
    Voltage drop: 0.099
    Voltage drop percentage: 0.83%
    Voltage at the end: 11.901

    At 4 AWG, the voltage drop meets my minimum, and if you go to the NEC table, you can use a 70-95 Amp rated breaker. You have to look at the Outback manual to see if they have a maximum wire AWG (what fits the holes) and a maximum output breaker--Lets say 60 amps maximum output current:
    • 60 amps * 1.25 NEC deratring = 75 Amps maximum (guess) breaker) ~80 amps (next standard size)
    From the above (using my guesses), you would have a choice of ~50 to 80 amps for your breaker choice (depending on if you choose 6 or 4 AWG wiring).

    For the panels--The fuses/breaker are there to protect the panel and the panel's jbox+attached wiring. Usually, panels have a series fuse rating (larger panels have a larger series fuse ratings vs smaller panels). If the panel does not have a series fuse rating, I would suggest a 1.25*1.25=1.56 derating over the Imp rating minimum (to prevent false trips). Say you have an Imp=5 amps:
    • 5 amp Imp * 1.56 derating = 7.8 amp ~ 8-10 amp recommended fuse/breaker for that panel string (and wiring rated for 8-10 amps minimum).
    You do not need a fuse/breaker on the combined input string of the Outback... Just that the wiring the carries all of the combined current be ~1.56x higher than Imp for the array. It would be assumed that the array will never be able to output more than 1.56x Imp (really 1.25 peak solar output current x 1.25 NEC wiring/breaker derating)--So no single input master breaker is needed. Although, many people like this so they can easily shut down the array for charge controller/wiring maintenance (a single breaker/switch easier to get at versus having to pull fuses/turn off breaker at the array).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,296 ✭✭✭✭✭
    And since none of us know what size the battery to CC wire is I picked 40 amps to be safe. Do you remember? Bill has good points if the wire is sized right.

    La Cruz was just an anchoage then but I had heard that a marina went in. Do they still have the Tigers at paridise village. The Dolphin swim experience?


    "we go where power lines don't" Sierra Nevada mountain area
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Looks like I will use a 2 awg feed from the CC to the battery bank with a 60 amp breaker. Now my biggest bottle neck is the light gauge wire, as in 10ga wiring from panel to panel over some long runs simi-shaded but still on deck and no conduit. The distances are roughly 6' from 1st parallel panels, 4' between next panels, 16' to the next panel and the 10' to the deck thru gland and another 5' to the CC. I could conceivably go to an 8 or possibly 6 AWG all of the way except at the through deck spot. Using the calculator from above it would appear that I should only be seeing 9.5 volts at the CC input but this system has kept my old 6v golf carts (880ah) going for 4 years now so I must be looking at something wrong. What I don't know about electricity is shocking. By the way the batteries are going on their 8th year, just added solar 4 years ago. But I am replacing them with 4 L16H Trojans. Oh yeah, dolphin show is still there but I don't believe the Tigers are...
  • BB.BB. Super Moderators, Administrators Posts: 32,921 admin
    You need to be specific now... Exactly what solar panels (brand/model number / Vmp/Imp) do you want to use (and how many of each).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    September 9 edited September 9 #31
    Wow, quite a bit to consider. I have a similar situation, my boat currently has 3 135w Kyocera panels with the following specs Vmp17.7 Imp7.63 Voc22.1 Isc8.37 I want to add 2 smaller panels in to the mix Everbright 80w specs Vmp17.2 Imp4.65 Voc21.6 Isc5.17. The plan is to run all panels parallel into an Outback FM60 feeding 4 Trojan L16h batteries totaling 870ah. Will the FM60 handle the variances in the panels? I already have all of the above and will be heading South in a few weeks to start putting it together so if this won't work the alternative is to make some other cruiser happy with a couple of 80w panels for sale. If it will work what would be the recommended circuit breaker, I believe it's 25 amp currently.
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    The above are the panels and CC I have.
  • BB.BB. Super Moderators, Administrators Posts: 32,921 admin
    Normally, I would suggest that you put identical panels in series (2x) and run a Vmp~35 volt array. That would let you reduce the wire AWG a lot.

    But, you have 3x of one panel--So, unless you "dumped" one 135 Watt panel (or got 1x more 135 watt panel to match--2x in series x 2x parallel strings)--That won't work.

    Also--If the panels have different shading (shadows from lines, different sides of a deck house, etc.)--The pairs of panels will not work for you either--Blocking/shading part of one panel will kill the output from the entire 2x series string.

    How long of cable run from the array to the Outback controller?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    A close estimate is 41'. I am thinking of running a second 10/2 cable and tieing 2 of each conductors together, from what I've found on the Internet this should roughly equate to 7awg wire? I know it's not perfect but it should help the voltage drop.
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    I am also thinking about removing the existing 10/2 and going to a 6/2. Not sure if the increase from 7awg to 6awg is worth the additional cost.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭

    SOMF said:
    I am also thinking about removing the existing 10/2 and going to a 6/2. Not sure if the increase from 7awg to 6awg is worth the additional cost.
    the cost effectiveness is up to you... almost any up-sizing from 10 AWG is a good move...

    What are your numbers from a Voltage loss calculator for the different wire sizes?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Well, I guess that settles it. The calculator doesn't have a 7awg option so I used 8awg and 6awg and got the following:
    8awg = 11.7% drop and a 2v drop, 6awg = 7.3% drop and a 1.26v drop so worth the extra $$ and work to go to 6awg, the double 10awg would be equal to a 7awg which would be a slight improvement over a single 10awg but I might as well get everything I can. Thanks
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Now this generates a 2nd question. How do I go about connecting the 6 awg to the panels? My old Kyocera panels have an M box which has screw terminals so I should be able to use a 6awg ring terminal but the new 80w everbright panels have MC4 connectors, not sure how to accomplish that. 
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Sorry for all of the posts but I need to get everything sorted before I head down to the boat in Mexico. Would the voltage loss be affected much if I use 10awg from the two 80w panels to the Kyocera panels since they are at the far end of the 40' run then use the 6awg from that poin on? It would be approximately 8' from the 80w to the Kyoceras the 6awg the rest of the way.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    the double 10awg would be equal to a 7awg        One is always better than two...

    How do I go about connecting the 6 awg to the panels?    Use a junction block... like these 2 ...http://www.shining.com.tw/1EN/ENterminal_blocks_stud.htm

    or  https://www.google.ca/search?q=junction+block+stud+type&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwie0Kzv94_PAhVs74MKHSORDpAQsAQIHQ&biw=1024&bih=635#imgrc=Jshgwjs7kJXspM:

    for example,.... lots of choice

    for the MC4 just order up some short MC4 cables from here https://www.solar-electric.com/100fomc4so2e.html

    and cut them in 1/2 and place an end  connector of your choice...

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SOMFSOMF Registered Users Posts: 18 ✭✭
    Well that makes it simple, I thought the idea was to get the 10awg out of the system as much as possible but leaving a foot or so at each panel and going up and down from 6awg to 10awg makes it very easy. I'll just cut the ends off of the MC4 cables (not worried about warranty) and attach a block so I can put 2 wires on each terminal to make my parallel connections. Lot's of great help on this site. Thanks!
  • grizzzmangrizzzman Registered Users Posts: 18 ✭✭
    Simply trim a few strands of the 6 AWG wire to fit the MC4 connector. Adding yet another connection to the run will only add more resistance/failure points. Remember its the distance that causes the voltage drop. Besides the wire from the panels are no more then 10 AWG (or less)
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 100AH LIFEPO4 2P4S
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