RE: [Electric Boats] Re: Paint for ME0913(Think inside the box)

 

Sure, watts are watts.

 

And while you’re taking your watts this far out of the box, you need to take this a step further.  You’re talking about turning the motor continuously enough to generate 60watts of heat.  Let’s look at this number.  Pretty much every motor controller we use on these boats is around 95% efficient and many or most of our motors are between 80 and 90% efficient, even more so at the very low current end of things.  Combined, you’re looking at, say, 90% efficiency or better in converting energy from controller power to mechanical energy out of the motor.  And so, you propose that we run the motor to lose 60watts to heat.  But unless you are talking about highly loading your motor, you need to draw 600watts from your batteries continuously to lose 60 watts to heat.  Please tell me how this is not a waste and how the power delivered to the prop wouldn’t try to push my boat up on the dock.

 

Maybe I didn’t get something in what you were suggesting here, but as I see it, unless you have something highly loading the motor shaft to bring the efficiency down a LOT, the motor and controller just aren’t going to be generating 60watts of heat.  It’s interesting: An ETEK motor is so efficient at low power that I was able to turn the prop on my outboard by powering my motor with a single D-cell battery---IIRC, it was 1.5v @ 2amps and the prop was turning…

 

-Myles

 

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Kevin Pemberton
Sent: Sunday, December 02, 2012 7:10 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Re: Paint for ME0913(Think inside the box)

 

 

Folks,

Watts is Watts. Any and all watts not converted to motion, in our case(work), is heat energy that we look at as waste. A light of any sort will have waste energy emitted. Why waste energy? because we are looking for light(used as a heater the waste energy is the light). If we loose 100w of power to produce light, we have 100w of heat energy to get rid of or use. A simple carbon resistor, a simple FET drive circuit, or any other item we feed power into will have some waste energy emitted. Why? because we have no perfect devices, or circuits.

To the point! We have electric boats! Electric boats have excess waste energy. we keep wondering how to get rid of the heat. Is any one with me yet! Electricians are in charge of turning motors before the job is released to the customer, even before it is installed. This is to save the bearings by keeping the grease in motion so it will not harden and it is believed that it will keep the balls and race free of flat spots. If your boat is in a slip, or... well if you are going to run a light bulb for 100w of heat. Why not run the drive enough to produce 60w of direct heat? It will keep the circuits warm, so condensate will not form on them. It will keep the batteries on float - slow charge. It will keep the motor slowly turning and keep the bearings moving, the motor warm enough to stop condensate. An added benefit it should reduce chaff on the lines.

You will not be wasting energy, and money on any other heating element, and applying heat where wanted. You will be keeping all electrolyte capacitors with a charge in them. The bearings worked, to keep the grease and balls moving(no bearing replacement because the grease has hardened the bearing balls and races will be better off because of it. If your motor has brushes the wear will be minimum because we are not talking moving the boat, just rotating the shaft(make a box for over the prop if you feel it is needed I would not, think of moving water as a discouragement for ice formation around the boat). Not to mention that seals with lube all the time, do seem to last longer.

If you have limited resource(power) you can set up a timer to cycle the drive. We are talking about parts count here(timer) that will be more expensive than a few light fixtures, for each location you are worried about condensation, but one item located some place on the boat should not change things as much as you prepare for a launch into the drink (using light fixtures would likely add much more time).

Kevin Pemberton

On 11/28/2012 07:22 PM, Reid wrote:

Pat,

I am intrigued.  Are you saying that we have been wrong all these years trying to get the kids to turn out the lights?  When the house is heated by electricity, it will cost the same whether you leave all the incandescent lights on or not?  Of coarse some of the light escapes through the windows, so this is a loss.  And there is no loss of conversion from heat to light and back to heat?  Interesting.

Thanks,

--- In electricboats@yahoogroups.com, "greenpjs04" <forums@...> wrote:

Just a comment about light bulbs...  Incandescent bulbs (ie, not florescent, CFL, LED, etc) are a pure resistive load.  In other words, they are not indictive or capacitive.  Therefore they make pretty good heaters for enclosed spaces.  A 100 watt bulb, will supply 100 watts of heat to an enclosed space.  Some of that (more than you might guess) is directly produced as heat while the rest of comes away from the bulb as light.  That light, however, then gets absorbed by "stuff" in the space and gets converted to heat.

I would still recommend buying parts designed to be used as heaters such as the one you recommended because light bulbs can easily get broken and they burn out, but light bulbs do work as heaters.

Pat

--- In electricboats@yahoogroups.com, "Reid" <axius@> wrote:

Jim,

That is the perfect part for the job.  Most people don't seem to >realize that you want a pure resistive load to generate heat, not a >light bulb.

-- 

Committing murder in exchange for lifestyle

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