diy solar

diy solar

1st post, interest in a solar runabout boat

RoughRiver

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Aug 25, 2021
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Hi, first post on the boards. I've done a search of the forum and read up on solar boating questions asked but I do have specific questions to a project I'd like to start. I've been watching Will Prowse's videos on youtube for some time now with an interesting in building a solar powered boat. As some background my wife and I live on a 5000 acre lake in Kentucky, I'd like to spend more time on the lake and less time at the marina putting gas in a boat so I'm looking at converting a small boat to run on solar. I have an older 14 foot aluminum runabout I think could be ideal converted to solar although this would be my first solar system of any kind.

I'm not worried too much about speed, 5-8 kns would do, of course the faster the better. I'd like to at some point move up to a small electric outboard but at first I'd like to do some testing with a trolling motor. As far as batteries go I'm definitely going lithium although I'm not sure of the size needed, I'd like to run off the panels as much as possible but the boat is smallish in size and I don't know if I can hang enough panels to do that so there may be some need to run off panels + batteries which isn't a big deal (this is purely 100% recreational).

At this point this is what I'm thinking:
40-50lb 12v trolling motor pulling 40amps max, I could go with a 24v motor if that helps overall. Anyone have advice on good boat motors that work with solar systems? From what I read a trolling motor is limited to 5mph although this can be increased some by use of aftermarket props, anyone ever try these?

A minimum of 4 solar panels, these would need to be at least 3 maybe 4 feet above the boat so weight is a factor. At this point I'm thinking some of the flexible type since they weigh less. I would make a frame either of painted PVC pipe or aluminum tubing.

Batteries, I would hope a 100ah lithium iron battery would work, although I'm not against a 24v system and running 2 if that helps. I've been reading up on the Chinns and SOK batteries as being the best, although I not sure about the 40amp draw requirement. Also being in a boat would I need low temp protection, this is going to be a summer/warm weather project so I'm not planning on sub zero sailing. Is it worth the extra money for this feature?

Anything else a novice is forgetting? :) Thanks and I hope to get this project started this winter if at all possible.
 
I'm fairly clueless but think it best to include a battery. I don't know if you can run a trolling motor off a solar charge controller and definitely not on a cloudy day.

I looked at these panels: https://www.amazon.com/dp/B099F4VL8...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Sounds like something I'd like to try. I've been kept off the water because of a bad back and can't paddle my canoe for any length of time.

I'd start with the 400w set of panels and see how it goes with what battery you are already using before going for an expensive LiFePo4 battery. Add another set of panels if it can't keep the battery charged. A LiFePo4 battery would be nice but if you can keep a deep cycle battery from being discharged less than 50% while cruising around the lake I would stick with a AGM deep cycle and save a bit of $.


Electric outboard motors look like they're out. I did see a 24v for $4000 but it needed 2000w input (2 hour use at full speed, 10 hours slow speed) That I'm afraid is far more wattage that I can install on a canoe
https://www.westmarine.com/buy/torq...PdfgoCMGpDvy2Xm2Ewc3tjLqImOdrzzRoC6o4QAvD_BwE

others I saw were cheaper, less powerful andbut needed 48v
 
Just some quick math:
You trolling motor, 12.8V x 40A = 512W

100Ah / 40A = 2.25 hour theoretical runtime. But drawing power at .4C, probably less than 2 hours.
I am not sure what 4 solar panels you have in mind. But to break even, you’d need over 500W, probably closer to 700-800W.

I would be concerned about flexible panels in a windy environment without firm backing. And even then, their durability has a bad reputation. You are right about the weight of big panels, it will be important to keep weight lower to Center of gravity.

Thinking outside the box…having a shore solar charging station and extra “easily swappable batteries” might be easier.
Or maybe pull a dinghy/raft that is covered in panels. Just a thought.
 
Thanks for the replies, I am sure I will need a battery. I think at first I'll see what a 100ah battery along with the solar cells will do, I figure at worse I'll have to monitor the battery to cut short trips if need be (although I'll just be cruising so it should not be a biggie).
 
This is the boat I picked up, $675 with a new 40lb trolling motor thrown in. My idea is to buy another 40lb trolling motor and then run dual motors off the transom. Now to find a battery that can handle the amperage draw (84 amps total/42 amps a piece at max draw).IMG_1003 (1).jpg
 
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