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DrWatson

Electric Drive H28

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Did anyone else note the Electric drive H28 which was up for sale on TM a few months back (might be 8-9 months, can't clearly remember).

 

If so, does anyone have any info on that particular setup?

 

Cheers

 

R

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Not sure of that particular set up, but have a look at:

http://www.thunderstruck-ev.com/electri ... -kits.html

This is the system I've used on my electric boats over there. It is an obvious option to change to. Also try locally http://www.earthling.co.nz/marine-environ.html

It makes a lot of sense on a yacht, when you can regenerate power once you're sailing...

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TimC, I had a look at those links, the exciting bit to me was the drive unit with a variable pitch prop. I love the idea of regenerating while sailing but still be able to get rid of the drag once the batteries are full.

But there wasn't a lot of info there. Do you know how many hours sailing for how many hours motoring? And they talk of a variable pitch prop but show a picture of a folding one (would that even work?)

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I'm no expert but seems 500 watts per ton to drive to 70 % of hull speed so mine is 10 ton and hull speed is 7.2 knots so at 5 knots would draw 5000 watts so at 48 volt a ten kilowatt lithium type batteries may go for 2 hours.

In regards to re generation. May be good when there's enough wind to get to hull speed but when doing say 5 knots and having used the motor I'd be really keen to re charge so I think mostly a pain that is reducing my already slow light wind sailing speed.

I see Lithium batteries have come down in price so its tempting but still would need a diesel generator to ensure a charge is available. The immense power demands make a mockery of solar and wind generation I feel. Great for just going out and back from the marina but I think still hard to justify for cruising. That quiet is so appealing though!

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To me it seems they might be ideal for getting in and out of a bay or marina. But for serious work like getting you off a lee shore or fighting into a strong wind or chop the small power of one of these installations won't cut it. So I'd want a boat which was very reliable sailing to windward.

 

I wonder how the powers that be would see one of these for meeting offshore rating requirements?

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Correct Bogan. 500W/tonne maybe enough to propel you along in ideal conditions, or in and out of the Marina, but that',s about it. You need at least 2200W/tonne. At least.

BBay, the other thing to think about is how long it takes to get all that energy back into the Bank.

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Depends on your expectations there Wheels.There are quite a few boats out there with electric drives and they are getting better.

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Can't talk with any actual experience Wheels but have read that electric drives are pretty potent at least more than the shaft horsepower indicates probably due to high torque output. If just going daysailing and moored with 240 volts alongside then I believe these would be ideal and you would not need a huge amount of battery. You could have a genny onboard to enable slow motoring for longer distances as needed. At very slow speeds they don't draw a lot of current. I believe they are great for sneaking past your mates in light air! :D

Another aspect is that with the rather large batteries aboard the house loads become insignificant. Also, all those batteries will have to be supported well, would not like to be wrestling them in a storm.

I worked out that for 800 amp hours at 48 volts in lithium batteries would need a space 600 by 600 by 600mm. These batteries are getting smaller and much lighter. :thumbup:

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Just to qualify my stand on Electric, my views are slowly changing over time, as they should due to advances in technology and it will continue to improve. But there are still some points that need to be clearly understood by anyone looking at Electric. The main point that will never change is that Power is Power. What goes out must go back in. The charging times have greatly improved. The batteries have become lighter, smaller and charge faster. But you still have to get the energy back in. We all know the pluses and minuses of the various generation methods, but few understand, or at least consider the time required. The time a prop would need to be dragged for, or a Wind gen spun, or a genset run for.

Re the Hp required. The benifits of Electric is that it has high torque over a wide range of RPM. The current drawn is in direct proportion to the load. So apart from the power required to turn the motor on it's own, the power is in direct relation to the load of pushing the boat. Where as a combustion engine will use a great deal of fuel just to run, with ruffly a 20% increase in consumption under load for a diesel and 80% increase for Petrol. Electric thus is the most economical for power required to load placed.

But Hp is Hp (or Kw's) and the figure of 3-5Hp per tonne is based on the requirement needed to safely control your boat in whatever situation. Torque is useless with out referenced to Hp. Hp is useless without reference to Torque. The both give you the actual power available to do something.

By the way, the electric saildrive and batteries are all listed for sail on trademe last night. Not bad for price actually. I was pleasantly surprised, especially the relative cheapness of the batteries. Pretty much on par with a really good quality deep cycle Lead Acid.

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