Replacing an Existing Flexible Solar System on a Boat

Hello All - First....I am a newby so bear with me.

I have a solar system on our sailboat that doesn't keep up with charging and am planning to increase the system I have (at least 6 years old) with Renogy Flex Panels. So here's what I have:
2 Solbian CP125 feeding into
1 BlueSky 2512iX Controller
1 30A fuse
1 IPN Pro monitor
3 AGM batteries rated at 540ah.

My plan is to remove the Solbians and replace with:
6 Renogy 100W Flex Panels
add 2 more Blue Sky Controllers (they network with the IPN PRO)
and will probably replace the 3 AGM's with 3 more that will rate at over 600ah.

As I put these together am I going to need blocking diodes? Additional fuses? What else am I missing? Any diagrams out there that can illustrate better?



  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    For the price of 2 more BlueSky units you could by a MARINE MidNite KID controller, be a bunch of money ahead and have a modern CC (read latest technology) never mind that you could add more panels for the same total $$$
    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
  • BB.BB. Super Moderators, Administrators Posts: 30,488 admin
    What are you loads?

    600 Watts of solar panels is about 6% rate of charge--Not a lot of charging current for that large of battery bank:
    • 600 Watts * 0.77 panel+controller derating * 1/14.4 volts charging = 35.4 amps typical maximum.
    Boats are always a bit difficult with solar panels--The boat may swing at answer, problems with rigging (if sail boat) casting shadows on panels, etc.

    As Westbranch says--Take a look at a better/larger capacity MPPT charge controller. The Kid is only rated to 30 amps--But if your battery bank where 24 volts (and not 12 volt), it would be a nice solution (a bit small for a 600 watt array on 12 volt battery bank--But it will work).

    Others make larger MPPT controllers (MorningStar makes a 45 Amp TS MPPT controller).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kspellman02kspellman02 Registered Users Posts: 6
    Sorry for the slow response...been getting ready for hurricane Danny. So our expected daily output would be 286 Amps (today). I started looking at the Ouback Controller since I have a friend who shared with me that he has 4 250W panels on his boat that run through one and keeps things pretty much charged up here in the Caribbean, on a daily basis. He runs an inverter (which I dont have) that covers the standard AC fridge and Air Conditioning (used very little) plus the DC charge gear he has. I just installed the 3 new AGMs (old ones crashed) for a total of 660AH capacity. I was originally looking at the flex panels but am beginning to re-think based on longetivity and efficiency. More research to do on the panels and Controllers. Also, I agree with you both....the boat provides a more difficult problem with movement, sail, and boom coverage of the panels so I'll also be looking at poly panels. From the advice I have been given and from what I see on the site, I should probably look at roughly 1000W of panels, run those through a high capacity MPPT controller such as the outback, put a large (80a) fuse between the panels and controller, and another one between the controller and the battery (total of 2 fuses). Panels would be wired in series into the single controller. Am I on the right track here?
  • BB.BB. Super Moderators, Administrators Posts: 30,488 admin
    The details matter... Depending on the solar panel Vmp rating--A typical 30 volt Vmp panel--You can put 3 of them in series for a Vmp-array ~ 90 VDC. It is possible that you could put 4 in series for Vmp~120 volts--But on cold days, the Voc-cold of the array could exceed the charge controller's maximum input voltage.

    So assuming a 12 volt battery bank, I would suggest two panels in series (Vmp-array 60 volts) and 2 parallel strings would be better--The higher the Vmp-array, the (slightly) less efficient the MPPT controller. If 12 volt battery bank and Vmp~30 panels, putting only one panel in series and 4x in parallel is usually the most efficient for the MPPT charge controller (Vmp-array ~2x battery charging voltage).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kspellman02kspellman02 Registered Users Posts: 6
    Well...our cold days get into the low 80's so that may not be an issue. I am seeing that most of the poly panels I am looking at are slightly below 30Vmp. at this point I could go with 4 panels (you guys have the REC 255's) with two serial, two parallel. I have a hard-top where two will get unobstructed sun from high-noon on....while the other two could be obstructed by sail/boom. Is there a preference as to which are parallel and which would be serially connected?
  • BB.BB. Super Moderators, Administrators Posts: 30,488 admin
    I would suggest that you do 2 serial x 2 parallel strings. Any shading on a solar panel pretty much kills its output (or the output of the string). In some cases, it may be OK to connect 4 in series--But I would test and see what works best for you. The MPPT controller (assuming you don't over volt it) would not care and just adjust to the array/conditions.

    Note, that while the forum is hosted and paid for by Northern Arizona Wind & Sun, pretty much everyone here (including the moderators) are volunteers. If you have specific business related questions, please contact NAWS directly.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Solar is not rocket science although sometimes it feels like it.

    On a boat you are space constrained. Hence start from the solar panels. It would be worth comparing the sunpower felxible panels with their 22% effciency. Keep the string length down to minimize shading losses.

    But assuming 600Wp, then then get the right controller. Bluesea, Outback, dont go just stabbing at names. You need a controller that will cope with the load, have the lowest tare, and be reasonably efficient, but most of all reliable. Your system is now less than trivial, and 12v systems are really disadvantageous there. Using a 24V system will give you fewer parallel batterys, less cabling, less charge controller, less inverter issues. Ok, so boats for legacy reasons have a lot of 12v gear, but that rarely alters my view on this. (eg my motorhome has 24v start and house banks, and uses DC converters for lower voltage gear). The midnite kid will do 700W at 24V, has a 0.5W tare (compared to 3-5W for the full size controllers), and comes from a stable of long standing thoroughbred of US manufacturing/R&D. You need to understand the significance of the low tare if you dont want to just burn away the power that you have hard won.

    Then batteries, you can go one of two ways. Get the ideal solar only charge rate for long life and happy batteries, 0.1C (ie 10% of the Ah capacity eg 600Wp= 20A= 200Ah= 0.1C) for lead acid generally, 0.2C for AGM, 0.5C for thin plate pure lead and about the same for LiFePO4. OR, try to max the battery out to reduce genset runtime interval. Bulk with genset and absorb with solar. In which case, stack them up but watch the weight. The better quality AGMs (TPPL= enersys,odyssy.northstar etc), and the LiFePO4s allow you to genset charge at higher rates (1C) to reduce genset runtime. So definately consider the lithiums, as thats the cutting edge in boats right now (1/5th the weight), can be a real game changer as they dont need to be kept at high states of charge. However you do need to learn to care for them, so not advised for newbies.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,

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