Running a 240vac Motor off 48vdc Battery Bank

[Dame.n.Jess]

I will be converting my yacht to electric (yes I know its wrong and diesel is mans best friend, blah blah blah) I have been looking at a number of kits which all seem to be based on 24-48v DC motors. When you want to add re-generation into the mix most add an additional unit which will do this (you guessed it, at an additional cost). Plus with DC you have Brushes to factor in.

So I started looking at what the electric car guys are doing, a large number appear to be moving towards 180-240v AC motors. Paraphrasing them - AC delivers more re-gen and has less maintenance due to the lack of brushes.

I have found a local supplier of 240v AC motors to suit my boat. The engine is 5.5kw with an operating rpm of 1450.

I have measured by available space and can fit 12x6V/210AH batteries to run the motor.

This is where my knowledge starts to run thin, I am aware I will need to convert the DC to AC for this I have tracked down some large inverters on eBay. See the link below.

18000WATT PEAK 48V PURE SINEWAVE INVERTER 70A CHARGER - eBay Batteries, Electrical, Parts, Accessories, Boats, Watercraft, Cars, Bikes, Boats. (end time 08-Jun-10 20:00:50 AEST)

I need to know if this type/size inverter would be up to it.
If AC is indeed the better option, or if I should return to DC
What additional gear will I need, ie; some type of throttle would be handy

I'm sure more questions will come of this discussion, and I still open as to what I do with the total set-up (except going back to diesel, my wife is highly allergic to it)

[Dockhead]

You kill any efficiency you might have gained with that motor by trying to power it through an inverter. Rube Goldberg lives!

You should have the entire system designed -- as a system -- by a qualified engineer. Don't attempt to do it on your kitchen table.

Better yet, just buy one of the hybrid drive systems for yachts which are coming available -- you get the benefit of some actual R&D done on other people's boats.

It will be 5 times the expense and 10 times the problems of a conventional drive system, but whatever -- if it turns you on, go for it. Personally, I prefer tried and true, utterly conventional, and very well proven systems for propulsion on my own yacht. Your life may depend on your propulsion system at sea. In my opinion that is no place at all for a science experiment, but -- whatever.

[Dame.n.Jess]

I realise this is not the conventional way of powering a boat but as my wifes organs start to shut down when she goes inside our boat due to the diesel/oil vapors so my only option is think outside the box or dont cruise.

Option two is not one I take lightly, therefore im not really interested in the im a fool for wanting to not have deisel type of responses.

But I would realy enjoy a conversation from some open minded to the possibilty of electric power.

[senormechanico]

AC brushless drive systems use variable frequency and voltage drives.
They're not all that expensive and are what you want.
Trying to make a standard inverter do what you want will not work.

[sigmasailor]

Originally Posted by Dame.n.Jess

I will be converting my yacht to electric (yes I know its wrong and diesel is mans best friend, blah blah blah) I have been looking at a number of kits which all seem to be based on 24-48v DC motors. When you want to add re-generation into the mix most add an additional unit which will do this (you guessed it, at an additional cost). Plus with DC you have Brushes to factor in.

I think you should talk to Gideon. Did you read this topic?: http://www.cruisersforum.com/forums/...est-37969.html.
Lost of info in the article alone.

[Opie91]

Originally Posted by Dame.n.Jess

I realise this is not the conventional way of powering a boat but as my wifes organs start to shut down when she goes inside our boat due to the diesel/oil vapors so my only option is think outside the box or dont cruise..

Are these fumes all the time or just when the engine is running? Maybe some more ventilaton? Fix a few oil leaks or the sort.

[fishwife]

I can understand you wish to avoid diesel. Is your wife also allergic to petrol? If not, I'd suggest that you sail for most of the time and use an outboard for when you really need power. Using inverted power from a battery for propulsion is going to waste a great deal of your amp hours. As already suggested, have a look at the Green eMotion's postings.

P.

[Dame.n.Jess]

Originally Posted by Opie91

Are these fumes all the time or just when the engine is running? Maybe some more ventilaton? Fix a few oil leaks or the sort.

I did try cleaning the engine and sealing the compartment. The engine bay is air tight (with a vent to get air into the engine when running)

I spent 4 weekends scrubbing the engine with dish washing liquid and a toothbrush.

It would be great if simple solutions worked but I think that time has pasted.

I do like the fundamental efficiency of electric, I realize its not that simple but neither is my wifes condition and we are both cruisers so we will find a way.

[LiFeTech Energy]

Originally Posted by Dame.n.Jess

I did try cleaning the engine and sealing the compartment. The engine bay is air tight (with a vent to get air into the engine when running)

I spent 4 weekends scrubbing the engine with dish washing liquid and a toothbrush.

It would be great if simple solutions worked but I think that time has pasted.

I do like the fundamental efficiency of electric, I realize its not that simple but neither is my wifes condition and we are both cruisers so we will find a way.

Really, it is that simple going electric!!
Just stick with any of the reputable manufacturers of high efficiency electric boat motors (either inboard or outboard). The major manufacturer's such as Torqeedo, Belman, Thoosa/Asmo Marine, etc.are all good choices depending on the type of motor you want and your particular requirements.

Like yourself I am also in Sydney so I would be pleased to meet up and answer any questions you might have about converting your yacht to electric drive and the pros and cons of AC motors, DC motors and any questions you may have.

A good starting point is the EBAA website here- http://www.electricboats.org.au/

I have been asked to provide a presentation and talk on converting a boat to electric drive at the August meeting of the Sydney Cruising Yacht Club. You might be interested to come along.

[LiFeTech Energy]

Originally Posted by Dame.n.Jess

But I would realy enjoy a conversation from some open minded to the possibilty of electric power.

Feel free to call me at anytime if you have questions you would like answered. My number is 0420 948757.