Rob

Comparing the price for electric drive with the price for the outboard as you have below is not apples to apples.

With the single outboard you will need a house battery.  Cheap lead/acid last 3 years and expensive deep cycle last maybe 7 years.  Peter’s original Li batteries are now more than 7 years old and still strong.

DC-DC converters are low cost and appear very reliable.  That means the 48V pack can double as a large capacity house bank as well.  A 48V, 300Ah Li battery would be equivalent to  something like a 2500Ah 12V deep cycle lead/acid in terms of reliable, available energy.  Peter’s proa has a converter supplied from each battery.  There is a 12V battery used to strat the diesel and run the anchor winch.  The diesel needs to be run when hauling the anchor as the winch motor sucks about 120A under load.  

Running an outboard to charge batteries is very expensive so it would make sense to have solar panels irrespective of the means of motoring.  

In terms of performance, the submersible pods could be operated effectively in any sea condition in either direction.  The outboard would be next to useless in waves over 1m.  Two drives gives the ability to manoeuvre in tight spots.  One outboard, with limited turning range is hopeless for getting in and out of tight spots.  The single outboard set up that Nol eventually worked out for Compean (aka Blind Date) was effective in calm conditions using the big rudders as brakes.  But his motor mount permitted about 180 degree rotation enabling him to go sideways if needed.  By playing with rudders he could almost spin on the spot.

The only thing I would add to the electrical system is a portable generator and a charger capable of about 1kW.  The generator is handy for power tools on deck as well.  I would also split the battery to have a battery for each drive.  That reduces the electrical fault level and gives a measure of redundancy.   

A real issue with electric drives in a remote location is the inability of most people to repair them.  Outboards are far more common and many people tinker with them.  Electric propulsion is becoming more common but still at the bleeding edge of development.

Rick

On 14 Aug 2019, at 9:19 am, harryproa@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:

Thanks Rick.  I took your advice and contacted All4Solar about the Krautler for the prototype cargo ferry.  $AUS17,000 for the set up on p2 of http://www.all4solar.com.au/ALL4SOLAR_KR4_8_PODS.pdf, plus solar panels.  For 2 smaller motors (one on the tender, one on a rotating tube under the bridgedeck, the quote was:

 Two motorsysteems   AUD$  17000.00

(Induction motor PODs 5 KW, high end curtis controllers, lever, switches)

Battery bank 48 V DC 300 Ah  including terminals & main cables,

fuse and switches  AUD$ 3500.00

3.2 KW solar system with MPPT (2 units)  cables, breakers, fuses AUD  4600.00