I believe that there is some confusion in this discussion. There has been a misconception by some regarding the wattage that our electric motors use.
The amp draw is times the rated nominal voltage of the motor. It is not times the recorded state of charge (SOC) of the batteries. Therefore if you have a 48v system and are pulling 10amps out of the motor it is 480watts. If your SOC at that time is 50v it is still 10amps times 48v or 480 watts of power from the motor. It is not 10amps time 50v. SOC is going to be inaccurate in most of our boats as there is draw from the battery bank and only when the battery is in a quiet state is it spot on accurate. You likely all notice how the battery bank pops back up so quickly after you turn off the motor.
If you have been incorrect in your usage of amperage and voltage, you should do a new calculation and you will likely see a marked improvement in your slow speed powering. At the higher draws (amps) the batteries SOC is normally a little lower than at the very low draws. This is a fact of life that we all deal with when we use lead acid based batteries and which I believe is not as misleading with LiFePO4 batteries. Its the chemistry and physics that we are dealing with.
That will bring me to my final comment. We are all students and can learn from each other. We are all teachers and can teach each other. Therefore the collegial sharing of information should be encouraged and corrected when necessary. This is how we all learn.
Mike
Electric Yachts of Southern California
Posted by: mike@electricyachtssocal.com
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