# scapped ev to boat retrofit



## Duncan (Dec 8, 2008)

Hi 
The problem is not the power but the duration,
How big is your diesel tank? and what is your burn rate? 

With an 80Kw motor and a 24Kwhr battery you will have 18 minutes at full power - actually less than that as completely discharging the battery is not a good idea

At half power that would be 30 minutes - 

If you are only using the motor to get out of the Marina and can then rely completely on the sails that may be enough but it leaves nothing for emergencies


----------



## Coulomb (Apr 22, 2009)

Plus, an EV motor is not designed for continuous operation. It could well overheat. Though liquid cooled motors may be OK, with an adequate cooling system. A 6.3 L diesel can chug along at high power (in electric car terms) for as long as you have fuel.


----------



## Duncan (Dec 8, 2008)

Just to add to the point about continuous power
That Cummins engine with a different fuel system and turbocharger will happily produce 300+Hp and keep running all day
At 120Hp it is just coasting


----------



## Karter2 (Nov 17, 2011)

Very true Duncan, but no matter how much power you put into a sailboat, it will never go faster than its limiting hull speed, and you dont need a huge amount of power to get a 52' yacht up to a "cruising" or manouvering speed.
4bhp/ tonne is considered a very safe maximum to allow for adverse winds and currents etc, and possibly a fraction of that for normal manouvering, motorsailing, etc.
So 80 bhp max , (60kw) should be sufficient for this sailboat.
But yes, you are also correct , range is the issue,. 
24 kWhr isnt enough for safe offshore use.


----------



## rmltcob (Sep 3, 2016)

Thanks for the comments here.

Range anxiety and energy storage / regenration even more a consideration with off shore sailing versus EVs, even with huge investment in li-lion cells/best solar panels/wind reneragtion etc.... 

Simply not enough power density for long range motoring or in emergency circumstances as tech stands versus large diesel and e.g.1000l fuel tank.

Until e.g. li-air cells come online and thin solar film in sails developed at scale and cost, a Gen 1-type system like I was proposing is a pipe dream for power requirements in these cicumstances.

Best can hope for then is covering all non-motoring energy requirements with renewables - in this case c.1.5kw energy supply and maybe 3kwhr of battery capacity.


----------



## Karter2 (Nov 17, 2011)

Well, if you have the enthusiasm, you could consider a "Hybrid" type set up.
Keep the diesel for long distance /emergency back up, but install the Edrive in parallel ( same propshaft) for instant power, in port manouvering, short trips, etc.
Depending on your type of use, those short (<1hr) motor runs are usually what you would do most.


----------



## Sunking (Aug 10, 2009)

Duncan said:


> With an 80Kw motor and a 24Kwhr battery you will have 18 minutes at full power - actually less than that as completely discharging the battery is not a good idea
> 
> At half power that would be 30 minutes -
> 
> If you are only using the motor to get out of the Marina and can then rely completely on the sails that may be enough but it leaves nothing for emergencies


Duncan I think that is a bit optimistic. Although Lithium batteries and Mr Peukert get along with each other better than Mr Pb. Mr Peukert still collects his taxes above 1C discharge rates. Compound that interest with a maximum limit of 80% DOD, and you end up way less in practice than on paper.


----------

