Solar Powered Pontoon Boat

I have information I hope will help anyone looking to power a 48V Motor on a Pontoon Boat. I did this a couple of years ago, and just blogged this to assist someone in making their own.

Good Luck!!!


  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Powered Pontoon Boat

    i think that pv would be quite a bit shy on being able to charge the batteries if properly sized. in fact, you don't even state the ah rating of the batteries that i suspect are on the short end of capacity that would be proper for the motor. i do suspect you come quite close to killing the batteries often and that severely compromises battery life. if i'm wrong then please point this out to me. nice idea though, but i just feel you fell short with the batteries and pvs.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Solar Powered Pontoon Boat

    Here is the motor:

    They suggest that you use 4 group 31 batteries. They claim 2 hour cruise time and 8 hours troll time (3hp) A search for group 31 batteries give me ~ 95 ah each, so you would have a total of 95ah into 48 vdc,

    Using the rule of thumb for charging lead/acid batteries one would desire a charging rate of between 4.75 and 14.25 amps at 48 vdc. If for example you had 4 100 watt 12 volt panels feeding a controller, you might be able to get a charge rate of ~ 8 amps into 48 volts.

    Assuming (and I am just guessing here) that the motor draws 10 amps, and you only wanted to draw the batteries down to a max of 50% you could draw ~40 ah out, or ~ 4 hours. (That is the easy part)

    The to put that same 40 ah back into the battery will require a minimum of ~48ah of charge. To get that out of your 8 amps you would need a MINIMUM of ~ 6 hours of PERFECT sun, plus a bit more for other system loses.

    So if my math is nearly correct, (and many have found it not to be!) you would need more than 400 watts of panel to do this every day. probably closer to 800 watts. If you only ran the boat to 50% a couple of days a week the panels could be smaller,, but much smaller and they begin to fall below the minimum charging rate suggested for flooded batteries.

    It is a fine idea,, but be aware of the limitations. (If you give us a better idea of the current draw of the motor we could get a closer approximation.

    Also I would suggest that you read the following links regarding batteries:

    This will give you some pretty good information regarding "care and feeding" of batteries and of particular interest, suggestions as to how to maximize "deep cycle" life. Contrary to popular perception, batteries are not boxes in which you can pour out electricity to use, and then pour it back in to charge. It is much more complicated than that.

    Good luck,