Thank you for an abundantly clear explanation, the water & plumbing metaphor for electricity works well for visualizing the flow of this mysterious stuff electric power which unfortunately we can't see. you answered another question I had about controllers, about whether they had a chip that had a complex program running "deciding" where power went.
Ken, do you happen to know, off the cuff, what the loss % is, in power charged into a battery vs power used at a later time when battery is discharged to run the motor? That is, if you had 1000 watts power produced in your solar panels for one hour and sent directly to the motor, we know how much work that KWhr would do expressed in how far/fast your boat would travel...but.if instead we had 1000watts going to charge a depleted battery bank for an hour, how much power is typically lost when we run the motor later, using that stored power? do you get 1/2 a KWhr back out for a full KWhr put in? more? less?. I'm curious what the loss ratio is typically.
I intend to install a circut I can switch on that cuts out batteries and sends power from panels directly to my motor, Aesthetically, I just want to feel and experience the boat moved by sun power alone, have the boat slow when a cloud passes overhead and speed up when I adjust a panel directly towards the sun ....kind of like trimming a sail, only, its catching photons, instead of wind.
As a side note, I installed an inexpensive meter from Missouri wind power available on e-bay for $20. its just wired directly into the circuit as a through wire going to the motor. The digital screen display refreshes every few seconds telling me exactly how many volts/amps/ watts are going to the motor. This is really great info for figuring out efficiency of power used / speed / time / distance. There is a sweet spot in your motor/prop/hull speed that maximizes battery power reserves used to travel a given distance.
The other amazing item I bought for $15. on e-bay, is a 3000 watt PWM motor controller that one dials up power to the motor with. I am running a 36volt 1 KW motor at 50 volts, the pulse wave controller lets it operate at less than 100 watts for slow trolling speed, then I've dialed it up to near 2000watts (approx 3hp) just to see what happens....there is no over heating or over reving- just smooth power.
the PWM controller hooked with the Watt meter lets me see where effeciency lays, Its a waste to drive the 21 ft sailboat hull at speeds approaching 85-90% "hull speed". I would estimate the difference of doubling my power expended from 900watts to 1800watts, only yeilds about 20% more speed. and anything past 2kw is just wasted power thrown against "the wall", a displacement boat hull creates a wave it can't climb over, that "hull speed" is the limit of how fast you can go unless you lift the boat out of the water and plane like a 100hp motor boat.
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Posted by: billhopen@yahoo.com
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