Runabout conversion

[RoughRiver]

Being the marine forum I thought I'd run this by you all. I picked up this aluminum runabout last week. What I plan on doing is running 2 Minn Kota 40lb trolling motors with solar and lithium iron batteries (the Evinrude is coming off). Being that the Minn Kota's run at 42 amps a piece at max power (84 total) any idea on what would be a good battery to use?

 

[FilterGuy]

The first question is "How long do you want the motors to run assuming full speed?" Your batteries will need to be ~84 AH per hour you want to run at full throttle. As an example if you have 2 100Ah 12V LifePO4 batteries, you would get ~200/84=2.4 hours. If you build a 12v Battery out of the popular 270AH cells, you would get 270/84=3.2 hours. Obviously, if you are going slower you will have more running time.

The next question is "Build your own" or "Prepackaged" ? Build your own will be cheaper, but you will want to take care to get a good case that is water tight and can take the abuse that it will get in the boat.

If you decide to go prepackaged, SOK might be a good choice for the price, but I do not know how water tight they are.

The best place to put the batteries is be protected area at the bow of the boat (Away from the sun and water), but from a weight point of view, they should probably be at the Stearn. That boat is designed for the big heavy engine in the back so with only the small electric motors it is already going to be bow-heavy.

 

[RoughRiver]

The first question is "How long do you want the motors to run assuming full speed?" Your batteries will need to be ~84 AH per hour you want to run at full throttle. As an example if you have 2 100Ah 12V LifePO4 batteries, you would get ~200/84=2.4 hours. If you build a 12v Battery out of the popular 270AH cells, you would get 270/84=3.2 hours. Obviously, if you are going slower you will have more running time.

The next question is "Build your own" or "Prepackaged" ? Build your own will be cheaper, but you will want to take care to get a good case that is water tight and can take the abuse that it will get in the boat.

If you decide to go prepackaged, SOK might be a good choice for the price, but I do not know how water tight they are.

The best place to put the batteries is be protected area at the bow of the boat (Away from the sun and water), but from a weight point of view, they should probably be at the Stearn. That boat is designed for the big heavy engine in the back so with only the small electric motors it is already going to be bow-heavy.

I'm thinking most of the time I'll be running at 12-15 amps per motor since cruise will get me an estimated 3.5-4 mph VS full power (42 amps) giving me 5.5-6. Whatever battery I end up with it will hopefully go in a watertight repurposed cooler to protect it from water and temperatures since as you have guessed it will probably need to be in the back of the boat (I'm thinking behind the front seats). On the other hand I'm hoping the solar cells can be configured in such a way they will work as a bimini top of sorts to provide cover for both me and the batteries, hopefully working to keep us both cool.