The Elco plan was a failure. Apart from the BMS (Battery Management System) being a total disaster, the 144 Volt Battery charger was useless.

Next we found that we couldn't get the RPM or the power that we needed from recommended number of batteries. We would have had to fill the yacht with three times as many batteries including batteries under the bunks in the saloon and then we wouldn't be able to charge them with a single 144 Volt charger as that would require three phase A/c power. The cost would have been over US$100,000 and the weight excessive, so the Elco EP100 is going on E-Bay. 

Although it means going back to smelly old diesel we need that for the genset anyway and it is probably "greener" than batteries in the long run.

My advice to anyone thinking of changing to an electric motor is:

I. Get a diesel electric hybrid that serves as a generator and the main engine.  

https://betamarine.co.uk/he-hybrid-propulsion/

2. Go for a 46 Volt system, not 144 Volts, then the batteries can be charged from shore power.