Solar on a boat

I'm happy to find a forum like this. Thanks to the knowlegeable and thoughtful posters here.

I live aboard a sailboat, and have relied on solar power for most of my dc needs for almost 4 years. Recently, I have noticed a serious decline in output, at least as indicated by my charge control display. Also, my house batteries are not being charged as normal.

System is:
2- KC120 panels, purchased new in 2004. They are bolted to the cabin top of my boat.

Morningstar PS-15M charge control purchased at the same time.

Panels are wired in parallel to a terminal block using separate runs of 8ga duplex wire.

Charge control is right next to the terminal block, and charge inputs are wired to the terminal block with short runs of 10ga wire. Charge control outputs are 8ga duplex wire directly to the house battery with a 20Amp fuse in the +.

Hope that's not too confusing an explanation.

In full sun at noon I'm accustomed to seeing 9-11 amps on the display. Recently, I get 1.2Amps, sometimes 3-4Amps. Yesterday I was reading .7 amps at noon. I disconnected one of the sets of panel leads and saw the display jump to 4.5Amps. I attached a voltmeter to the disconnected leads and read 20 volts, 6Amps. It would seem that the panel is puttng out near rated power, but the controller does not indicate it.

Any and all help with diagnosing the problem will be greatly appreciated.



  • BB.BB. Super Moderators, Administrators Posts: 30,522 admin
    Re: Solar on a boat

    Check with Kyocera and see if they are part of the recall (2001 panels are--when you purchased them may be different than the date code on the back--if present).

    Otherwise, clean and check all of the connections?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Solar on a boat

    Thanks very much, BB.
    That link was very helpful. I'll check the dates on the panels to see if they are from that period.

    It's interesting that defective panels can show normal when disconnected from load.

    Again, Thanks!
  • BB.BB. Super Moderators, Administrators Posts: 30,522 admin
    Re: Solar on a boat

    On a saltwater research vessel, we had to take all the external fittings apart, clean and preserve, wrap with tape/self vulcanizing tape, about once a year to keep everything working well...

    Normally, a Voc and Isc should be enough to check a panel out--there was one person here (at least) that found a "good" panel from these first two checks did not do well when checked under operating load (Vmp and Imp).

    Also, you can get connections (outside or inside the panel) where it takes >12 volts and >1 amp to punch through oxides of the connections--so just the act of testing them can case things to work again (if sometimes, only for a while).

    So, frequently, it is helpful to have two people... One monitoring your power/current meter while the other rotates a connection or taps on a panel/connector to find the intermittent component/connection.

    When one person "checks" everything at once--it is difficult or impossible to locate the actual weak component/connection.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Solar on a boat

    I get your point on checking the connections.
    I've pulled one panel off the deck and opened the juction box and I find shiny tinned wire and tight terminal screws. The panel boxes are well made and there is no apparent corrosion.
    The terminal block in the boat is spotless and the posts are 1/4-28 high grade stuff with nylock nuts and tight. All wire terminations are crimped and soldered. Where the wires have to be shoved into the terminals on the charge control, they are soldered and the wire is all Ancor tinned.

    I recently called Morningstar and told them of my problem. To their credit, they immediately sent a replacement charge control. The problem persists with the new controller in place.

    FWIW, the serial number on the panel I pulled is 97849194, 1997.8.

    Thanks again for your replies.

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar on a boat

    i concur that it is probably the pv and you won't always see the problem right off as it is in the cell connections. kyocera has been good on replacing these bad pvs that were of the vintage you have. exacting serial numbers i don't know where it began or left off of, but you should contact kyocera and tell them of this. if they deem the pv to be defective, they will most likely give you 2 kc130s to replace them with even if only one of them is defective.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,962 ✭✭✭
    Re: Solar on a boat

    I'd bet the bypass diodes have shorted on the panel that is pulling down the other. Simple test on the KC-120 is to just remove the diodes as they are only held in place by two screws and measure the voltage in the Sun.

    The diodes can be had at radio shack if it is the issue for about 5 dollars, its a common failure as sitting in the Sun with no ventilation on a boat the backside cooks the diodes and diodes fail shorted when over heated.

    Also, you are a perfect canidate for the new MorningStar SunSaver Mppt. a pair of KC120's is a perfect match for a 12Volyt system and the Mppt can handle frequent changes, like when a sail shadows a panel.
Sign In or Register to comment.