My cheap electric dinghy experiment

[Peregrine1983]

I am working out the specifics of my little electric dinghy experiment...

I have no need to go fast (I am usually in no-wake zones on my dink anyway), I don't go long distances (never more than a few hundred yards from my boat to the dock, or the boat to the beach) and I'm sick of fighting with my gas outboard (ethanol woes etc), so I'm now giving this a whirl. I also don't use the dink super often (about 4 times a week at most to go a couple hundred yards each time). I also have oars should things go wrong. This whole new motor and solar setup will cost less than $500 US.

I wanted to throw this setup out to the group and their infinite wisdom...

My dink is a lightweight Takakat inflatable catamaran.

My plan:

Newport Vessels 12v 55lb trolling motor $199 - https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1

100AH AGM deep cycle batt $159 (in a nice commercial battery box) - https://www.amazon.com/gp/product/B0...4IXVZNRN&psc=1

50watt solar panel $85 - https://www.amazon.com/ACOPOWER-Blac...ar+panel&psc=1

A basic amazon charge controller $20 - https://www.amazon.com/gp/product/B0...GR6V2Z8F&psc=1

I plan to remove the motor from the dink after each use - it's only 22 lbs and I will store it in a cockpit locker or in my car. I want the battery, panel, and controller to live on the dink.

My first challenge is finding a suitable container that's out of the elements, but also ventilated for the charge controller.

Any thoughts appreciated.

[David M]

If a high weight to stored energy ratio is okay, you don't need great range and you don't need great speed then you will be fine.

Also consider a Torquedo.

[Peregrine1983]

The plan is to go cheap for now, so Torqueedo is kind of out of the question. I plan to track and report my findings about range and speed here with different loads when I get it up and running.

[David M]

There are also much less expensive electric motors than Torquedos...used a lot by bass fishermen. Typically, they do not have as much thrust as a Torquedo.

[Peregrine1983]

Exactly. The 55-lb trolling motor is essentially that. Mounted on an inflatable dinghy, I think it will move pretty well even with the wife, dogs and some gear... We shall see.

[seandepagnier]

This setup you propose will surely work well.

Consider that you could improve it greatly by using an outrigger canoe. In this setup it is also possible to sail.

[SecondBase]

I've seen that setup in use and used it myself (without the solar) on a 10 foot dink. Electric is much more polite to the rest of us than spraying outboard acid gas residue across pristine coral reefs.

You need a mounting point for the panel. I've seen flexible panels mounted to a bench seat. You could mount the hard panel you picked out to top of the bucket with the battery and controller inside as well.

You can of course drill vents into most any plastic container.

White 5 gallon containers are available from restaurants. If your battery would sit flat in the bottom that's an option.

Maybe a hunters box from Cabelas (but pricey). Or maybe best of all is pick out a decent plastic cooler and use that as a durable "box" for your setup. Size to hold your selected panel. Drill plenty of vents in an upward 45 degree angle. Will have a strong enough handle for the rare occasions you pull the whole kit out of the dink. Will also have UV protection. The more I think about it the more I like the cooler option. Let's see what else comes in...

[Peregrine1983]

Thanks guys. I do like the cooler idea. With so many holes, I'd just think water might drip in when it rains.

One of my thoughts was to get a over-sized (sized close to the size of the panel), well-ventilated battery box and put both the battery and the charge controller inside one box... however it may be a bad idea to have the battery and controller in an enclosed space? Not exactly sure.

[SecondBase]

Battery box can work. Cooler - I was thinking holes in the sides drilled upward on 45 degrees to keep the rain out.

[GILow]

How would the cost be effected if you put a small lithium battery setup in the dink? I ask because the weight of the battery is the only downside that I can see to what you propose.

[Peregrine1983]

Originally Posted by SecondBase

Cooler - I was thinking holes in the sides drilled upward on 45 degrees to keep the rain out.

I like it...

[Peregrine1983]

Originally Posted by GILow

How would the cost be effected if you put a small lithium battery setup in the dink? I ask because the weight of the battery is the only downside that I can see to what you propose.

I think I'm basically weight neutral here compared to my Tohatsu 9.8 and fuel tank. That was nearly 100lbs. This setup is basically a 65lb battery and a 22lb motor, so I'm close.

I love the idea of less weight, but since I'm looking at over $1000US for for a 100AH lifepo, I wonder how much I'll have to sacrifice in terms of range. For a 35AH I think I'm looking at over $400. I don't know if it makes sense to lose all that range for lithium. Maybe someone can enlighten me.

[GILow]

When you clarify the weights there I see that the weight of a conventional battery is not so bad in the grand scheme of things.

Costs do get a bit eye watering with lithium. Not to forget the solar reg would likely cost more plus some kind of battery protection feature to prevent over-discharge.

Still, if money were no object I would absolutely set up my smaller dink with lithium, solar and an electric trolling motor.

[Peregrine1983]

Originally Posted by GILow

Costs do get a bit eye watering with lithium. Not to forget the solar reg would likely cost more plus some kind of battery protection feature to prevent over-discharge.

Still, if money were no object I would absolutely set up my smaller dink with lithium, solar and an electric trolling motor.

Agreed. A lithium-solar dink would be a pretty sweet rig!

[a64pilot]

Keep speed down and you will be surprised at the range.
When I was in the Army you could rent little 12' or so Jon boats for nearly nothing. I was fishing with my Daughter and we started out with a two stroke weedeater type of outboard, horribly noisy and had little to no thrust then the speedometer cable that drove the prop broke, took it back to Sears and swapped it for a small trolling motor, deep cycle battery and charger. It would move us around slowly for hours. Now I'm talking slow paddling speed, but still astonishing to me. That was a completely charged group 31 battery to nearly dead.