Inboard Electric Motor?

[maxum247]

Would it be possible to repower my 20ft v bottom fiberglass boat, weight about 1700 lbs with a single deep cycle battery and a dc electric motor useing an automobile altenator run off a pulley on the electric motor to keep the battery charged as the boat is being used?
What kind of speed and power could I expect from that sort of set up if it were possible?
Would I be able to have forward and reverse with throttle control thru the electric motor?
I understand I could use parts from a golf cart but would have to have a charger and recharge I think 6 batteries after each trip out.

Thanks!

max

 

[Bifflefan]

Re: Inboard Electric Motor?

Would it be possible to repower my 20ft v bottom fiberglass boat, weight about 1700 lbs with a single deep cycle battery and a dc electric motor useing an automobile altenator run off a pulley on the electric motor to keep the battery charged as the boat is being used?
What kind of speed and power could I expect from that sort of set up if it were possible?
Would I be able to have forward and reverse with throttle control thru the electric motor?
I understand I could use parts from a golf cart but would have to have a charger and recharge I think 6 batteries after each trip out.

Thanks!

max

I think a trolling motor will do the trick.
Golf carts have 6 or more batts, and are more than 12 volts i believe. 36 come to mind but im not sure of this.
I supose if your are talking about a total redesign then sure, you can build one that should move as good as a gas engine. There are electric cars that kick the crap out of a Ferrari.
If you build it id be very interested in how it turns out.

 

[Silvertip]

Re: Inboard Electric Motor?

Ummm -- perpetual motion has not been invented yet. If you don't understand the concept, it takes power to generate power. I'll get to that in a second. First - electric power on a 20 foot 1700# boat requires not one battery but a boat load of them if you want to go very far. You would need at least a 48 volt system and a "biiigggg" electric motor. Now then, back to the alternator for charging. You see, getting power from an alternator means you need to put power into it. That power comes from the electric motor. So that electric motor, which is sucking juice from the batteries like crazy to propel the boat needs to now suck more juice so it can power an alternator that CONSUMES more power than it GENERATES. So you see, that is a losing proposition all the way around. In otherwords, you would consume more electrical energy trying to charge the batteries than you have power available. If you forget the charging business and use an on-board charger that you plug into AC power at the dock, then a 36 or 48 volt motor would move the boat but again, it would never get on plane.

 

[maxum247]

Re: Inboard Electric Motor?

Thanks for the reply's!
I sort of figured that it would be something like that but needed for someone to lay it out for me as electricity isn't something that I understand readily.

Thanks again!

max

 

[bassboattech]

Re: Inboard Electric Motor?

now solar powered runabout would be cool, you would probably not want conventional deep cycles

 

[Chris1956]

Re: Inboard Electric Motor?

To amplify Silvertips response. Electric motors and generators are about 99% efficient, which is good news. The bad news is that the devices used to power generators (usually steam turbines) are only 33% efficient. So 2/3 of the energy needed to generate the electricity is wasted during generation. That is why electricity costs so much more that oil or gas to heat your home.

OK, one horsepower is 746 Watts of electricity. if you wanted a one hundred HP electric motor, it would take about 74,600 Watts/hour of electricity to power it. At 48 volts that is 1554 Amps, which is about 16 group 24 car batteries(4 sets of 4 in series). So you could run the motor for about an hour, and then recharge all the batteries. A gallon of gas contains about 36KWatts, so 16 batteries equals 2 gallons of gasoline, roughly.

 

[maxum247]

Re: Inboard Electric Motor?

What about useing a 48 volt set up from a golf cart? 1700# boat 20ft long.
What boat speed and running time would I be looking at roughly?

max!

 

[Silvertip]

Re: Inboard Electric Motor?

You seem hell bent on trying to get blood out of a turnip. What are your expectations with this 1700# boat? How big a lake are we talking about? How long do you "expect" it to run, and how fast do you "expect" it to go, and how many people would be in this boat at the time? We don't have any data to work with other than you have a 1700 pound boat. 1) The boat will not plane so it will be limited to displacement speed and any attempt to get above that will simply drain batteries quicker. 2) Most efficient speed will likely be in the 3 -4 MPH range but that depends on the efficiency of the motor controls used in the golf cart electronics and the power of the motor. 3) Run time would likely be an hour or so but again that depends on how hard you push the boat. 4) Installing a watt meter or ammeter would help you determine the optimum operating conditions. 5) Depending on the size of the motor you may also need some sort of gear reduction unit. 6) then there is the cost element. I hope you have deep pockets. Golf car batteries (4 or 8 of them) are not cheap, nor is the 48 volt charger, and then there is the golf car motor and electronics. 7) About weight. Add the weight of 4 or 8 batteries, a heavy motor, some electronics, and a drive system and you now have more weight than a 70 HP two stroke outboard that would actually get the boat on plane. See why there aren't any electric boats in the runabout
category. Down the road there may be a hybrid something, or a fuel cell something, but right now, electric power in a cruiser is not practical. If you are after true electric power put one troller on the bow and two on the stern. Add a boat full of batteries and away you go -- at displacement speed max.

 

[bruceb58]

Re: Inboard Electric Motor?

You probably need to go do some research in other places. Here, for example, is an electric outboard. You can see that you will need a bunch of batteries. In this case you would have 4 HP which would require 8 6V golf cart batteries.

http://www.qis.net/~jmgraham/resrun.htm

http://www.qis.net/~jmgraham/rr500spc.htm

Running at full speed would get you a couple hours of run time. You are not going to go very fast! with a 1700# boat you might get 3 MPH

 

[4JawChuck]

Re: Inboard Electric Motor?

Why re-invent the wheel, btw its not cheap.

http://www.torqeedo.com/us/hn/products/cruise-r.html

 

[maxum247]

Re: Inboard Electric Motor?

Thank you all for your time! Much appreciated!

max!

 

[Lyle29464]

Re: Inboard Electric Motor?

now solar powered runabout would be cool, you would probably not want conventional deep cycles

The power generated by the largest solar panel you could fit on the boat might keep the batteries charged if they were all in top condition. "with out any load on them". The weight of the panel would offset the benefit of it. If you ran the motor off the panel with out batteries you could count the rpm by watching the prop turn.

 

[theboatwire]

Re: Inboard Electric Motor?

Hey you guys I am on the same course. I have done a lot of research here and have not yet finished. The main consideration is the use of the boat. For fishing the idea is totally OK, but for planing, the comments are quite correct, the batteries would sink the boat.

I am going to solve the question one way or the other. But my option at the moment is for trimtab mounted electric motors, either twin 80 or 110lb thrust, double bank of batteries, and a generator to keep me going on those long weekends.

Much cheaper than repairing the cracked mercruiser 120hp in my 18ft sangster. The maximum thrust of a gale force wind on the side of the boat is 100lbs, the power required to move the boat efficiently is 80lbs.

I am putting together a web site currently at http://theboatwire.shoutthenoiz.com will be soon http://theboatwire.com

Hope to keep it updated and good luck maxum247

 

[Silvertip]

Re: Inboard Electric Motor?

Let's see -- you will use a pair of 80 to 110# thrust motors and a dual bank of batteries. Since 80# motors are 24 volt and 110 should be 36V that amounts to four to six 12 volt batteries (big deep cycles). Depending on what you buy, that could be nearly $600 bucks alone. Now you need a generator to keep up with that load. Since generators do have a 12 volt charging capability, that output is not up to the task of charging six big deep cycles. So your next option is a big 110V charger which would work but remember, you have batteries in series so with two banks you need two very large, three bank (three outputs per charger) to keep the batteries charged. Those are about $200 or more (each) so you are at the $1000 level. Now you need the two trollers which will set you back in the area of $1000 each (maybe $750 if you find them at a Pawn Shop or E-bay). This puts you very near $3000 and you still need to wire the whole mess, not to mention the cost of the generator. If you wonder why I question the wisdom of this effort you can buy a new short block for half that and have a real boat again. Just being the devils advocate in this effort. Unless you will have this boat on a very small lake, I think you will be very sad how long that bank of batteries will last if you need to rely on them to get around anything other than a small puddle.

 

[Bondo]

Re: Inboard Electric Motor?

You seem hell bent on trying to get blood out of a turnip.

Ayuh,... Current technology don't/ Won't allow these hairbrained Ideas to work....

Finding,+ rebuilding the 120hp motor would also be Way Cheaper....

 

[ENSIGN]

Re: Inboard Electric Motor?

I heard on the news this morning that there is a electric powered boat at the baltimore boat show.There story said it will run all day on a 14hr charge.I'll have to check it out this weekend and I'll let you know.