charge controller question

SystemSystem Posts: 2,511 admin
My installation (brand new) is on a sailboat. I have two 135W Kyocera panels with a Morningstar SunSaver-20 controller (PWM type) and two pairs of 6v golf cart batteries wired in series, for a 12v 220 amp-hour house battery bank. My concern is that after initial installation, with the batteries fully charged, the battery monitor (a linc-10 unit) showed 14.4 to 14.5 volts ALL DAY LONG in sunny southern California. My concern is that this will lead to overcharging and excessive gassing of the flooded batteries, with reduced lifespan and safety issues due to the gassing in an enclosed space. This initial run was at the slip, with the shore power connected and full batteries. I intend to use the PV system at anchor or cruising, off the grid, and I'm sure the dynamics would be different, but I'm still concerned about the above issues. Tech support inquiry from Morningstar was not too helpfull ("buy a MPPT controller"). Hey, I just bought the SunSaver for $100, and I'd like not to just junk it. So, any advice or suggestions for my situation?

Comments

  • mike95490mike95490 Solar Expert Posts: 8,431 ✭✭✭✭✭
    Re: charge controller question

    I've got somewhat the same problem, no loads, and the batteries on float, are bubbeling away. June, I will be setting some custom setpoints in the morningstar controller with a laptop.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 29,639 admin
    Re: charge controller question

    A three stage charge controller would enter the "float" and hold the voltage around 13.6 volts or so---But this controller does not have that option.

    About all I could suggest is put the jumper back in and have it charge at 14.1 volts---You should use less water... If you wanted, you could wire up a switch and use "sealed" battery mode when the boat is in storage--and set the switch to flooded when you are on board using power (the higher voltage will more quickly bring the battery back to near 100% charge during the day).

    You could also disconnect (cut-out switch) for one of the pairs of panels and reduce available charging current when in storage...

    Other than a different controller, I am not sure what else to do.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: charge controller question

    being you will be present when the batteries attain full charge there may be a work around for it if you have a bit of electronics knowledge. you could switch in 2 high current diodes in series rated at least as high as the total short circuit current of the pvs with a good dc switch rated for those current levels. that means the 14.4v setting will be used to charge the batteries and when you know them to be full (ammeter would show the small current rate as the controller would shrink the current) then switch it through the 2 diodes and the voltage drop will be about 1-1.5v or so. if that's too much of a drop then use the 14.1v setting on the controller and go through 1 diode to give a .5-.75v drop.
    this would essentially be a manually activated float charge setting.
  • System2System2 Posts: 6,290 admin
    Re: charge controller question

    Thanks for your recommendations. I think I will wire in a switch to the controller jumper, so I can manually switch from 14.1v (sealed setting) to 14.4v (flooded), depending on battery status and whether or not I'm away from shore power. That I can easily handle. I'm a little unclear about the diode. Where do I wire that in? In the output hot wire to the battery? With a switch, so I can bipass it to get the full charging current when desired? Also, can I wire in a switch in the solar panel lead (from both panels) so as to simply shut off the panel flow to the controller when I'm on the shore power charger or under power (motoring) with high output alternator turning and the solar panels are not needed? The panel connectors have a warning "do not disconnect under load."
  • BB.BB. Super Moderators, Administrators Posts: 29,639 admin
    Re: charge controller question

    If you have alternative power sources at times (like shore power)--I would just flip the charge controller to "sealed" battery setting. Keep it simple. I am not sure I would bother switching when motoring... I would guess that time on the motor is a relatively rare event (at most few hours just getting into / out of port?).

    The chargers will not "fight" each other--just who ever is set to the highest voltage (and has the current/power to "back it up") will set the final battery voltage. Your alternator is probably set between 13.8 to 14.4 volts (14.2 would be typical).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: charge controller question

    seeing you questioning of the diodes i will say do not try it as you lack sufficient knowledge of it. the switch on the jumper will allow for lower voltage, but is still on the high side for any prolonged (more than a day) use as a float charge.
  • System2System2 Posts: 6,290 admin
    Re: charge controller question

    Thanks, Neil, I'll do the switch thing on the jumper terminals. One last question; can I wire in a switch on the PV panel input line to simply shut off the panels if on shore power or motoring with alternator for prolonged times (it does happen when the wind dies!). The panels (Kyocera 135w X 2) say not to disconnect under load (warning on the connector terminals). That would solve my conundrum of running the panels when there's plenty of charging power coming in from other sources. Thanks, Skip (KF6VTJ)
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: charge controller question
    Thanks, Neil, I'll do the switch thing on the jumper terminals. One last question; can I wire in a switch on the PV panel input line to simply shut off the panels if on shore power or motoring with alternator for prolonged times (it does happen when the wind dies!). The panels (Kyocera 135w X 2) say not to disconnect under load (warning on the connector terminals). That would solve my conundrum of running the panels when there's plenty of charging power coming in from other sources. Thanks, Skip (KF6VTJ)

    hi skip,
    i guess your name can have a double connotation to it.;)8)
    now i would've thought it to be alright to switch it off, but before i say anything like that can you tell me where you saw that and give the link if you can so that i can read it too just to be sure of where they are coming from with this. i know i've shut mine off without incident or problems and i think it odd as being able to disconnect whether loaded or not is a must according to many local codes. to my knowledge there shouldn't be any damage to the pv and the switch has to be able to handle the current. maybe they are worried of the switch or connection arcing? i don't know.
  • BB.BB. Super Moderators, Administrators Posts: 29,639 admin
    Re: charge controller question

    I would avoid "plugging" the MC3/MC4 connectors under load--the "pin" is very thin and probably could be damaged if subjected to an arc...

    Of hand, I cannot think why not to put a switch in-line between the panel and the controller (charge controllers turn on and off all the time to control the rate of charge--PWM--Pulse Width Modulation).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: charge controller question

    Thank you, Niel and Bill, for your suggestions. The warning on my panels (Kyocera 135w) is etched on the side of the connection terminals (the MC3/MC4 ones), and I do think that's to prevent arcing if disconnected under load. I bought these panels from No. Arizona Wind and Sun, and their website is quite robust in the information therein. I'll check with them (via phone) and make sure, but I think that the best option for me would be to simply wire in a switch to take the panels offline if I'm on the charger at the slip with shore power or motoring with the alternator doing the charging (a high-output one that goes up to 85amps). Incidentally, my system is installed on a 34ft. sloop, located in San Diego, and I'm fitting it out to cruise Mexico the tail end of this year. I'm hoping that I can be energy independant at anchor, with the PV system handling the refer, small stereo and lights (LED's) at night. I estimate that my energy needs will run about 80-90 amp-hours per day. In a pinch I can run the engine at anchor to top up the batteries. Thanks again, this is a great forum.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: charge controller question

    ok, i think bill and i would agree for you to not pull the mc connectors while under load, but i think you can put a switch inline.
  • CorbinKaleCorbinKale Registered Users Posts: 21
    Re: charge controller question
    niel wrote: »
    ok, i think bill and i would agree for you to not pull the mc connectors while under load, but i think you can put a switch inline.

    That answers a question that was nagging me, too. This is a great forum!
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