One more point worth commenting on to give a true picture rather than the Wiki perspective.

The main differences with Wiki are that I am taking the kWh at the shaft of the electric motor and working on the battery staying within a charge range of 10% to 90%.  Diesel has an energy density of 12.7kWh/kg but it drops to around 4kWh/kg at the shaft of the diesel.  You might not be able to get the last litre but you might die trying in certain circumstances. The battery also has connectors and monitoring wiring.

So 3.2V x 80Ah x 85%efficiency/ 3.4kg gives 64Wh/kg.  The brushed electric motors and controllers were chosen for their high efficiency.  Motors at best point give 92% and the controllers 95%. 85% allows for not being at the ideal point and cable losses.  

If you take the battery out of the working range I have nominated you will dramatically reduce its cycle life; probably not an issue on most boats as the range I have nominated should give 5000 cycles or more.  There has been one cell failure out of 48 cells over 6 years.  I should note that a battery charge test I did at home with  new cell and another 3 years later yielded 110Ah and 108Ah so I got more than I paid for but given a few more years they will likely be less than 100Ah.  It is also worthwhile noting that the nominal cell voltage is lower than you get if operating the battery less than the 0.5C.  

Rick

• Privacy • Unsubscribe • Terms of Use

SPONSORED LINKS