Monday, February 27, 2012

Re: [Electric Boats] Prop size for 10500lbs 30 ft. coronado sailboat

 

kinda forgot to mention.. oh heck yeah a PWM type controller will do wonders regarding efficiency and runtime for that 1/2 to 2/3 to 3/4 throttle speeds! it can be an upgrade later maybe.. where the drive could be dialed in with the mechanical for a while.
again I agree, DONT not have an extinguisher handy!
--- On Mon, 2/27/12, Andrew Gilchrist <andrew@fastelectrics.com> wrote:

From: Andrew Gilchrist <andrew@fastelectrics.com>
Subject: Re: [Electric Boats] Prop size for 10500lbs 30 ft. coronado sailboat
To: electricboats@yahoogroups.com
Date: Monday, February 27, 2012, 10:00 AM

 
I'll be matter of fact here - it sound dangerous to me

the proposition your float is essentially a motor used to push 1500 lbs with short term usage, spikes dropping down rapidly to a very low average amperage and lots of cooling time, will now propel 7 times the mass at 50% more voltage than previously, through a underrated old  tech speed control, through liquid.

the load could be 10.5 times that of the buggy; and its long term 100% duty cycle instead of the short time light load of the buggy 

Establish the amp draw of the controller  - but things don't look great a 36v  controller being run at 48v and probably a much higher load than the cart could create if it is a resistive coil set up ditch it its dangerous and wasteful

and a 10hp motor - is that max power or continuous power

whats the kv - the the torque per amp and the efficiency levels

* first  make sure your charger is correct type for that battery type and you have a battery management system on it.
* Make sure everything is well insulated
* establish the motor kv, peak rpm,  92% of peak rpm and amp draw at max efficiency
* get your prop pitch and use it to establish how fast the prop will try to push the boat at 92% of peak rpm; if its 20 knots you are barking up the wrong tree all round - if its 2-3 knots that may be survivable
 * ditch the electro mechanical controller and well overrated  PWM type

if you persist with the current setup try running it at the dock and so you can observe the controller directly - if it is electromechanical it will probably glow red hot - unworkable -  have fire suppression ready

At the very least you need an overrated PWM controller

Andrew


On 2/27/2012 11:21 PM, Robert Jorgenson wrote:
 
48v battery supply
36 v controller
10 hp General electric DC motor

can the golf cart controller handle the load?

what size Prop will be most efficient????????

fire hazzard lithion ion batteries =factory sealed 24 v battery packs in heavy alluminun box.

what size prop should work well??
I realize I will have to experiment but i need a starting place.

was not getting consistent voltage even though the battery cells read fully charged.

battery terminals factory sealed with foam.

removed foam from top of connectors
two of the nuts on top of batteries required a 360 degree turn to bring them to he same torque as the other 14 9/16 nuts.

this is why I have had an electrician guide me thur such a simple p
ocess as battery instalation.

Capt. Bob 435 678 3436
Shockwave
Golf of Mexico

Equal opportunity Crew openings with Drivers licens Mpving 30 ft Coronado from blanding, Utah 84511
to Houston Texas, one ton Chevy stick shift

Individuals will be incouraged to cruise for a couple of weeks in golf of Mexico
What tourque should the 9/16 nuts on the battery terminals be set at????????



--  AJ Gilchrist Fastelectrics 0419 429 201

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