trickle charging sailboat batteries 4D with solar?

I have been told I cannot charge my large 4D marine batteries with a 10 watt solar charger or any solar charger. My batteries are about 200 AmHr each and are too big and weigh about 150 lbs each to take out my boat over the winter hence my quest to use a solar charger and keep them charged in freezing Montana. Since there are two batteries I thought I would plug the solar charger into the boats DC outlet, switch the batteries to "both" and go to AZ for the winter. Anyone out there have any ideas if all this would work and if not why not and what I could do to make it work without plugging into AC? Thanks! Sailor Pat

Comments

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: trickle charging sailboat batteries 4D with solar?

    Welcome to the forum Sailor Pat.

    How many of these 4D batteries have you got? It doesn't take much to keep batteries charged as opposed to charging them up to begin with. At 200 Amp hours each putting a couple of (regulated) Amps to them will suffice to prevent self-discharge from doing them in over Winter. One nice thing about cold temps; it slows down the battery chemistry and thus the self-discharge rate.

    So if you had two in parallel and want to put 4 Amps to the pair you'd need about 70 Watts of panel & a small controller to do it with.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: trickle charging sailboat batteries 4D with solar?

    i'm confused by your statement that you can't charge the 4d battery with any solar charger as you can if it will supply at least 1-2% of the capacity leaning the latter. 200ah x 2% = 4a. a 10w pv will not supply enough current so that much is true. if you have 2 of these identical batteries you would need 8a. there are pvs out there that can certainly supply this kind of current. do not mix a different battery with the 4d. for different batteries you would need 2 different solar float chargers or have the ability to isolate them which gets tricky.
  • EnduranceEndurance Posts: 40Solar Expert
    Re: trickle charging sailboat batteries 4D with solar?

    A solar panel is a great way to keep boat batteries charged while you're away for the winter. I do it on my houseboat every winter. If you end the boating season with full batteries and disconnect them from any loads, it doesn't take much to make up for the batteries' self-discharge.

    Like you, I looked at a really small panel that some vendors sell without a charge controller. Their theory is that the charge is so small that you can't do much overcharging damage. I rejected that theory and bought a 100 watt 12v panel and a little Morningstar SS-10 controller. I figured that the larger panel would gather more sun in the short winter hours and make up for any days with snow cover or clouds. The 100 watt panel would actually bring up the level of charge in my battery bank if I gave it a couple of weeks. I also liked that the controller prevents overcharging.

    Just this spring, I replaced the single 100w panel with a 1740 watt solar array so I won't be using my old system this winter. But it worked very well for the three years I used it.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: trickle charging sailboat batteries 4D with solar?
    So if you had two in parallel and want to put 4 Amps to the pair you'd need about 70 Watts of panel & a small controller to do it with.

    Sailor Pat, Do you need any help picking out a controller or panel?

    One small detail... consider mounting the panel vertical (pointing south). In the winter that will help keep ice and snow off the panel. Quite a bit of sunlight reflects off snow or water, and you may get just as much power from a vertical panel as one that is tilted towards the sun. If you intend to mount it on a mast (or any other vertical pole) search for a "side of pole" mount.

    Also, you should know that any shadows (even from a rope or antenna) will be devastating to your solar output.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: trickle charging sailboat batteries 4D with solar?

    endurance,
    even though you don't have the ss10 float charging any longer i should point out that the ss10 does not have a float setting as it only has 14.4v and 14.1v outputs. if you had to choose between the two it would be the 14.1v setting for float, but it should've been even lower. you could've placed a diode in line to drop another .5v or .6v that is of the current rating of the pv. imo you were slowly frying your battery. only savings grace may have been the inclimate weather and snow being accumulated for many days.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: trickle charging sailboat batteries 4D with solar?

    Niel; according to the manual Morningstar's SunSaver 10 Amp controller has four stage charging. Float Voltage is given as 13.7 on 12 Volt models. It even does EQ every 28 days for 3 hours @ 14.9, although I'm not so sure I'd want it to.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: trickle charging sailboat batteries 4D with solar?

    i stand corrected then as they have since upgraded the ss10 to include more stages. glad to hear of it.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: trickle charging sailboat batteries 4D with solar?
    niel wrote: »
    i stand corrected then as they have since upgraded the ss10 to include more stages. glad to hear of it.

    I think that's the case indeed as I have the same recollection of it being a 2-stage charger originally.
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