[48v alternators]

It would appear that you are correct.  Found this on wikipedia...  uses a belt-driven integrated starter/generator-motor (BiSG); which is in essence a starter motor, alternator, and propulsion motor in one.

[48v alternators]

Don't know if this is relevant but Ford put 48V alternators on their 1.0L hybrid cars (ecoboost I think).  Plenty of used ones on Ebay for £200 - £300.

 

Couldn't be asked to read all the pages on this thread so this may have already been pointed out.  🙂

[Electric boats - the future???]

2 hours ago, peterboat said:

We tend to use Lifepo4s on boats that dont do the above. The batteries you suggest are big heavy expensive and very slow charging, not long lived in a traction situation. I have lifepo4s on my boat which have worked well for 3 years, they are second life and were not expensive 

 

[Electric boats - the future???]

I know this is an old thread now but surely we don't need to use Lithium batteries on boats.  As far as I can see Carbon AGM batteries would be almost as good at a much lower price.  Weight, on most boats, is not an issue.

Also lithium has a nasty habit of doing this if something is amiss....

I guess insurance could become an issue.