New to Forum

rnjpinzrnjpinz Posts: 5Registered Users
I am new to Solar Power so please bear with my ignorance.

I am going to outfit my sailboat with solar panels to help charge my 12 volt, gel battery banks. This is important because I am planning on traveling on this vessel and will not only be off shore for days at a time, but plan to be at anchor for weeks at a time with no onshore power. I have researched putting 2- Kyrocera 135Watt panels wired in parallel. This seems to be what everyone recommends.

My question is this. Why wouldn't I want to go with 2- 235 Watt panels? Is big not better? And if I did, is there an easy way to invert power from 24volt to 12volt. Any recommendations or suggestions would be appreciated.



  • WandermanWanderman Posts: 180Solar Expert ✭✭✭
    Re: New to Forum

    I am far from an expert on this subject, but I would say if you had the space for larger wattage panels than take advantage of that and install them. Bear in mind you should check for shadowing and the like before you install them.

    As for battery charging, you will want some kind of a charge controller. This device will take the voltage and current your panels are supplying and provide your battery bank with the correct values. You can easily charge a 12v bank with 24 volt panels with a controller. I recommend an MPPT controller, this will likely give you a percentage increase in efficiency.

    Do a search on this forum for MPPT for MANY discussions about that type of setup.

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: New to Forum

    The Number One question is: how big is the battery bank? If you intend to use solar panels as the sole charge source you will need sufficient PV's to recharge them in a reasonable amount of time. This will generally be based on the "20 hour" Amp hour rating of the batteries.

    In addition to the potential shading issues Wanderman mentioned, there is also a problem with getting correct angle for insolation on boats, as you never know quite what latitude and direction you'll be docked at. If at all possible, some adjustability of mounting can help increase the efficiency and reduce the size of panels necessary. This is not always possible of course.
  • BB.BB. Posts: 28,136Super Moderators, Administrators admin
    Re: New to Forum

    We have several sailboat threads:

    Also, conservation will be critical to extending your time on solar power.

    Led running lights, low power equipment, etc.

    There are several solutions for 24 to 12 volt conventions. Do you want to charge a 12 volt battery out without a battery. And what is the size of 12 volt loads?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rnjpinzrnjpinz Posts: 5Registered Users
    Re: New to Forum

    I have 2 banks of batteries on board. One consists of 2 12 volt gel batteries, the second 3 12 volt gels. I also have a kiss wind generator on board. The controller for the wind generator is a Xantrex trace C-40. That will stay in place.

    I am in the process of adding up my Amps per appliance. As always, conservation on a boat is a must. That being said, when you have a refridgerator, radio, GPS, lights at night, etc. amps add up quickly. Thats why I am thinking more is better.

    I have been looking at the Morningstar-Tristar MPPT 45. Wondering if this is over kill for 2- Kyocera 235's.
  • WandermanWanderman Posts: 180Solar Expert ✭✭✭
    Re: New to Forum

    OK. 5 batteries total...what size??

    I will have 450 watts of panels (36v) feeding around 25ish amps into a Morningstar TS-45-MPPT controller this feeds 3 130a/hr batteries (290amp/hrs, Wet cell) I average about 60 amp/hrs each night, sometimes as high as 80 per night inthe winter. This gives me a comfortable margin for recharging each day. I believe the MPPT controller will give me slightly extended hours of charging my 12v bank as I have 36v panels that generate sufficiently in less light to begin a recharge.

    Without knowing your total amp/hrs of storage and how much you use it is difficult to estimate panel wattage needed to charge your bank.

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: New to Forum

    Working backwards through your post ....

    Two 235 Watt panels = 470 Watts. They will actually produce less than that due to various factors like heat and angle. But at most: 470W / 14.2 Volts charging = 33 Amps. Well within the range of the Tristar MPPT 45.

    Yes the Amps, and more importantly the Watt hours, add up fast. Leave one thing on for too long ... everything shuts down. :cry:

    It is the Amp hour rating of the batteries that is needed to know if the panels can supply sufficient charging - or indeed too much. No sense being able to harvest 3000 Watt hours if you can only store 300.

    It sounds as though you have two separate banks. Most charge controllers can not charge separate banks, so some accommodation will have to be made there.
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