I was at the boat show yesterday, and took a look at the new electric drive systems available, and was wondering if anyone has installed one on one of our boats?  While I have been less then enthusiastic about them in the past, the seem to be improving dramatically!  I would love to hear any comments.  Thanks...

I remember that article.  I was just begining to consider repowering TAMZIN and thought electric propulsion should be something to consider.  After a bit of research I contacted one of the companies (lost the name when I changed computers) for a estimate.  They came back with a figure on the order of $35,000.  The final tally for a complete engin room redo (tanks, engin, fuel system ect) via Bud and Beta was $15,003.  Possibly the price has come down a bit but between the cost and performance issues I don't think we're quite there yet with electric propulsion.

Bret:

I have been using a hybrid for about 4 years (car) and here are some points to think about.
A.) when in Hawaii I got about 21 miles/gal  ?  yes if you do not run your hybrid more than  6+ miles a week you will only charge the batteries. = NO gain only losses.
B.) I now get an average of 31.2 +/- miles /gal in Oregon. = longer trips more use.
C.) is it worth it ? in about another 5 years I will tell you.

Now for the why; batteries leak off while sitting!, maybe only 0.00125 to 0.005 / day.  but the chemistry wants to balance (go to 0). So unlike diesel in a sealed tank which (tech. note: loss is in the 0.0000001/day range = in 28000 years it will be all gone) you are losing power all the time with the battery, which means you have to make up for the losses. The issues in Hawaii for me was that the car set for a week at a time = it took 8+ miles of driving = 15 min to complete the loss of 2% of the bat's power = extra gas used to recharge the battery.  

Think about this, your system sucks up power (controller + losses = 0.2 amps) this is not to bad but in 24 hours you need to make up 5 Amp hours of loss, and in one week that is 34 amp hours without as much as one prop spin. So for that gen set;  you need to run it 30 min every week to just make up for the battery and control losses.   (need a bigger fuel tank not smaller) 

Next usage = the new controllers (PWM's are pretty good but you only get 88% of what was in the battery) the gen set has losses putting it into the batteries maybe 85% eff. So in the end you are getting 88% of 85% = 75% of what the gen set put out + you need to cover the battery and static controller loses noted above; + we all have lights etc.

That is why a Hybrid would be a better choice:  direct driving the prop gains 3 to 5% from not using the transmission, but the other losses would all be there, less the fact you could power at 4.3 or 4.5 kts while using less fuel from a better matched motor.  A third point of power savings would be the diesel engine heat up (like in and out of an anchorage) this is big! somewhere around 0.15 gal on my 40 - 45hp diesel. So turning the thumper on and off 3 times a day uses almost a half gal of dino + what is needed to do the work.   For a hybrid you could do it less often, but for longer = only 1/10 near coast and 1/2 off shore startups.
Also you could dump the alternator and starter.

BIG NOTE: INCORRECT PROP SIZING IS MORE THAN 5% loss and could be as high as 30% loss.

All in all, until you have a power source:  elec. drive is a no go.  Cats and fast boats can regen but you lose miles when dragging the prop, which means extra days at sea = more food, more water, more light power, and less safety.

    

I'm in the process of converting to an electric motor with a small diesel DC generator. The motor is the 20.0 from electric yacht. They are also putting together the generator, which will be delivered at the end of June. The motor and batteries(300ah at 48V) are installed, but I don't have any performance data yet other than it runs. :) I plan to do a writeup once the generator is installed this summer.

Norm,