Tue, 19 Dec 2017 17:14:26 GMT
Hi, I have a 25ft sailboat at Ukraine and installed an electric motor this year. I used a lithium polymer batteries that assembled from 3,6V 37Ah cells into two 48V 75Ah batteries. Batteries have a sealed case, smart BMS inside with lot of cells protection systems. Using these batteries, I can motor at 4 knots for 8 hrs until depleting them. This is LiPo cells, not a LiFePO4 cells, but work fine for me. I have a BLDC 3 kW motor inboard, all electric system with propeller shaft was created from scratch. Electric system made by me, shaft - I have hired other people to do this. At 1 kW of power I can motor 4 knots at calm water, at 2 kW - 5.5 knots at calm water. Against 12-15 m/s wind at 2 kW I achieve a 3.5 knots. Never run it at full power (3 kW) yet.
Consider for LiPo batteries (this type used at Nissan Leaf electric car) - they are good enough for our purposes and lighter and cheaper than LiFePO4. But do not skimp on BMS - it is your protection from undesirable consequences related to Lithium type battery overcharge or short circuit due water in the boat.