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Solar Trickle Charger

Wanted to share this with the FS Forum community:

My boat is stored at a facility that charges an additional $25.00 per month for electrical use on top of the storage fees. That to me is cost prohibitive, so my batteries 'were' only charged when I was able to get out and use the boat. Over the last 2 years, my batteries became weak and there was a degree of sulfation that had occurred. After looking around online I discovered there are a lot of options using solar energy to keep the batteries at full charge 24/7, and at a very reasonable cost.

This is for those out there who are in the same situation as I am or who have no power available at all where their boat is stored.

I purchased a 30 watt solar panel (20 watt will do just fine) for about $60. You will also need a Charge Controller. I found one for $15. - all purchased on Amazon.

I made two 'legs' using EMT tubing that bolt to the solar panel frame along the sides with a 45 degree bend. The protruding bent legs are spaced to slip into my rod holders on my T-top. Done!
I mounted the charge controller to a piece of Starboard, ran the wiring to alligator clips which power it from the 2 batteries (initially) - and a quick connector that plugs the solar panel into the system. That's it. When I go fishing, it literally takes less than one minute to remove the whole system and store it in my truck. Putting it back up takes about the same amount of time. I have a hard T-top and have thought about permanently mounting the solar panel to the top. I could then mount the controller inside my radio box, and wire it directly into the system from there. So, there would be solar power constantly available. There are many options.

The solar panel puts out about 21 volts. There is no 'load' attached to the system, so all the energy created goes into charging the batteries. When they reach the desired voltage the system goes into trickle mode keeping them at full charge. At night time, it automatically prevents voltage from back feeding into the solar panel and during the day, the charge controller prevents the panel from overcharging and cooking the batteries keeping them right at about 13 volts.

So far, it's been working like a charm. :grin

If anyone out there needs help or advice making one of these systems for themselves feel free to PM me.

Pura Vida!

Replies

  • century7century7 Posts: 2,410 Captain
    Very cool and you are saving the environment

    Sent from my SM-G900V using Tapatalk
    It works 60% of the time all the time......
  • silentfaithsilentfaith Posts: 362 Deckhand
    not sure you need a big panel,,,,all you need to keep a charge is a 5watt panel.
  • Flight RiskFlight Risk Posts: 2,491 Captain
    not sure you need a big panel,,,,all you need to keep a charge is a 5watt panel.

    I'm sure it's over kill. I didn't do any research on what the minimum equipt would be to maintain the charge. If it works out, I may mount it semi-permanently to the T-Top to use as a backup power source.

    I do have a cheap Harbor Freight panel that puts out 1.5 watts - just to experiment with. I knew a sailboat owner that used one to keep a 12 v car battery charged with the el cheapo.

    Pura Vida!
  • JIMinPBJIMinPB Posts: 1,875 Captain
    The number of watts needed depends on the condition of the batteries. As batteries get older, sulfates forms inside them & that increases the self discharge rate. Leaving the batteries sit discharged will increase the rate at which the sulfates form. The charging rate needs to be above the self discharge rate, or else the batteries don't charge.

    The watt rating on solar panels is specified under perfect conditions, with 100% sunlight strength & the panel pointed directly at the sun. A fixed mount panel is not pointed directly at the sun very often. Tuscon AZ is the benchmark for 100% sunlight. South Florida is a bit less.

    The bottom line is this: If the controller shuts off the current that goes to the batteries part of the time, then the charging system is big enough.

    For a system with a pair of group 27 batteries, I would want at least a 10 watt system as a minimum (10 watts @ 12vdc = .833amps, but that is at 100% sun light with good panel alignment). I don't think that 30 watts is overkill. I think that 30W is a good choice.

    Some people might favor duel solar systems for the two batteries. That way, if one battery has a self-discharge rate that is greater than the charge rate, the bad battery will not be able to drag the other battery down with it. A diode system can also isolate one battery from the detrimental effects of the other.

    I didn't realize that the price of solar equipment had come down that far. I may look into this for my own use pretty soon. Thanks for the info Bill.
  • Flight RiskFlight Risk Posts: 2,491 Captain
    JIMinPB wrote: »
    The bottom line is this: If the controller shuts off the current that goes to the batteries part of the time, then the charging system is big enough.
    Thanks Jim - As I said, I did not do any math on estimating power needs. Just read reviews and went from those.

    It actually goes into pulse (trickle mode) within a half hour of connecting the controller. Of course, the batteries are fresh, as you know.

    So far I'm pleased with everything. :grin

    Pura Vida!
  • LMKLMK Posts: 596 Officer
    Very cool post and great information, thank you!!!!
  • Plane Fish nPlane Fish n Posts: 6,439 Admiral
    My boat is stored at a facility that charges an additional $25.00 per month for electrical use on top of the storage fees. That to me is cost prohibitive,

    You need to stop going on those 1 to 2 month cruises and then the $25 monthly charge would be more palatable. :grin:grin:grin :wink:wink:wink

    I'm around next week if you want to do lunch.

    Talk later.

    Cheers

    Eric
    PLANE FISH N
  • Flight RiskFlight Risk Posts: 2,491 Captain
    You need to stop going on those 1 to 2 month cruises and then the $25 monthly charge would be more palatable. :grin:grin:grin :wink:wink:wink

    Guilty! Cost me a couple dead batteries. (Not any more though!)
    Will give you a call.

    Pura Vida!
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