Electric/Solar Dinghy Up and Running

[Peregrine1983]

I promised I would post once I got my little solar electric dinghy up and running. I've been using it every few days for about two weeks now and just finally got around to installing the solar panel and charge controller as the battery voltage was finally starting to dip. I shot another little video this morning.

The electric dink works great for my purposes (traveling to/from my boat on its mooring and traveling to/from docks or beaches in an anchorage). Top speed is about 4 knots and the 55lb trolling motor is much more efficient with the battery than I imagined. Take it down off top speed and battery life increases drastically, but speed drops to about 3 kts.

My final cost (55lb motor, 105 AH AGM battery, cheap charge controller, and 50w flex panel) ended up being a little over $500 as I opted for a sealed AGM battery over a FLA.

I think this setup would be great for other folks who don't need the speed of a Torqueedo or the range of a gas outboard, and who are also on a budget.

I'm happy because unlike my gas outboard, this thing starts every time.

https://www.youtube.com/watch?v=JjFsin0jZ68

[a64pilot]

Probably not as likely to be stolen as a gas outboard either

[Peregrine1983]

Fingers crossed!

[Peregrine1983]

The other thing I wanted to note was that while it's no speed demon at 4-5 kts, this top speed didn't decrease much with a load of bags and provisions on board like I thought it would.

The motor has more torque than I expected, and I guess since it is propped to move a much larger boat, loading doesn't seem to affect it as much as I thought it would.

[anacapaisland42]

Roughly what range...distance?/time?.. ..do you expect to get ....recognising new battery etc etc
Tx
Bill

Originally Posted by Peregrine1983

The other thing I wanted to note was that while it's no speed demon at 4-5 kts, this top speed didn't decrease much with a load of bags and provisions on board like I thought it would.

The motor has more torque than I expected, and I guess since it is propped to move a much larger boat, loading doesn't seem to affect it as much as I thought it would.

[Peregrine1983]

From a 105AH battery I'm looking at 2 hours run time at full throttle - so about 8 nautical miles at full throttle. If you were trying to cover a long distance, you could conserve the battery a great deal by not going full throttle. There is a big difference in power (and battery consumption) between speed settings 3 and 4 (or 4 and 5... I can't remember).

It took about 7 round-trip runs over the course of two weeks at full throttle out and back to my boat (about 400 yards each way) and some tooling around the bay before the battery meter went down from 4 lights (100%) to 3 lights (75%). At that point, I put on the solar panel and charge controller. Now it just charges up on the days I don't use it.

[Peregrine1983]

But I have yet to see what kind of charge performance I get out of this setup. I currently have a 50 watt panel on there and may swap it for a 100 watt depending on how it does.

[medic1957]

Great idea for short and mid length travels. But I would think that you would have to be very careful as ppl with hot hands would take batteries and solar panels too. Sad but true

[Peregrine1983]

Thanks. This is true, but the motor was only $199 and the panel $100. If they grow legs that will certainly suck, but it's not going to kill me. The battery was the most expensive item at $270... but it also weighs 74lbs, so I like to think a thief might take an accidental dip trying to get it out of my dink on the sly.

My old outboard was worth almost $2k... so in that sense, I have a lot less to lose.

[Scout 30]

I like it!

[medic1957]

Very true good on you. Thanks for posting the info sounds like a very good option and like you say cheaper in initial cost and no fuel costs lol.

[mitiempo]

Originally Posted by Peregrine1983

From a 105AH battery I'm looking at 2 hours run time at full throttle....

Not really. At a 50 amp draw your battery is about 70 AH due to Peukert. You also do not want to drain the battery totally although the motor will shut down if the voltage drops too much anyway.

Looks like a good arrangement though and you can get pretty good speed.

[Peregrine1983]

Originally Posted by mitiempo

Not really. At a 50 amp draw your battery is about 70 AH due to Peukert. You also do not want to drain the battery totally although the motor will shut down if the voltage drops too much anyway.

Looks like a good arrangement though and you can get pretty good speed.

Thanks yes this is an important clarification. You'd never want to draw your batt all the way down.

[Peregrine1983]

Originally Posted by medic1957

Very true good on you. Thanks for posting the info sounds like a very good option and like you say cheaper in initial cost and no fuel costs lol.

Thanks! My wife is sick of me chewing her ear off about this little project, so it's cool to get some feedback on CF.

[ski69sail]

Hi There

Yes I love your idea. Sounds like a great result from a simple marriage of ideas.
But I was wondering if there is any option to connect to the yachts power via a lead. ???

Thanks Ray