Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 18-06-2019, 14:22   #1
Registered User
 
u4ea32's Avatar

Join Date: Nov 2009
Location: Los Angeles and Maine
Boat: Olson 40
Posts: 298
Propellor for charging batteries using electric motor

I am extremely happy that I removed my diesel and all the associated parts, complication, and unreliability.

My electric motor (a 10kw air cooled motor, controller, throttle, motor mounts, etc. by ElectricYacht) is magical: so much easier to get in and out of the marina and raise or lower sails, or use the motor instantly, that it is a transformational experience. We use less than 5% of battery capacity on a given day sailing.

I want to also use the motor to charge the batteries underway.

What are peopleís experiences?

My prop is old and poorly balanced Martec folding elliptical. It is creating the only vibration in the drive train, so I am going to replace it.

Any experience in other low-drag props and regeneration?
__________________

u4ea32 is offline   Reply With Quote
Old 19-06-2019, 04:27   #2
Registered User
 
ranger42c's Avatar

Join Date: Aug 2012
Location: Maryland, USA
Boat: 42' Sportfish
Posts: 3,868
Re: Propellor for charging batteries using electric motor

Quote:
Originally Posted by u4ea32 View Post
We use less than 5% of battery capacity on a given day sailing.

I want to also use the motor to charge the batteries underway.

Unless it's really easy and you don't plug in to shorepower after a day sail... why bother?

-Chris
__________________

__________________
Selby Bay, South River, Chesapeake Bay, USA.
ranger42c is offline   Reply With Quote
Old 19-06-2019, 05:01   #3
Registered User

Join Date: Jan 2018
Posts: 578
Re: Propellor for charging batteries using electric motor

This one has always been tough for me to understand. Especially for someone that just goes out from the dock for a day sail.

Why would you want to slow your boat down?
Chotu is offline   Reply With Quote
Old 19-06-2019, 05:37   #4
Registered User
 
denverd0n's Avatar

Join Date: Jun 2008
Location: Tampa, FL
Posts: 4,404
Images: 6
Re: Propellor for charging batteries using electric motor

In light air it will slow the boat down. But if the breeze is enough that you are hitting hull speed anyway, then it will not make any significant difference.
denverd0n is offline   Reply With Quote
Old 19-06-2019, 05:52   #5
Registered User

Join Date: Jan 2018
Posts: 578
Re: Propellor for charging batteries using electric motor

Quote:
Originally Posted by denverd0n View Post
In light air it will slow the boat down. But if the breeze is enough that you are hitting hull speed anyway, then it will not make any significant difference.
Which is almost never in my years of boat ownership. LOL Always wishing for more wind. Until five minutes later you have a Gale. Ha ha ha.
Chotu is offline   Reply With Quote
Old 19-06-2019, 05:59   #6
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 25,494
Re: Propellor for charging batteries using electric motor

If you fit a fixed prop, itís going to slow the boat down whether you use regen or not.
Think about this, most will agree that a fixed prop you lose .5 to 1kt on average over a folding / feathering prop.
Thatís without taking any power from it, thatís just from letting the prop autorotate, take much power from that prop and youíll likely at least double or triple the drag.
There just isnít any such thing as a free lunch.

Enjoy your electric motor, your itís best use case in my opinion, but donít go and spend time and money making your boat a dog, for very little if any gain.
But it would be interesting for someone to do it, and measure the speed loss per watt of power, over and above the prop drag of course
a64pilot is offline   Reply With Quote
Old 19-06-2019, 06:03   #7
KTP
Registered User

Join Date: Mar 2010
Posts: 317
Re: Propellor for charging batteries using electric motor

We were out the other day and I saw about 30 watts of regen when we were sailing at 4 kts, climbing to 70 watts at 4.5 kts. I played around with taking it in and out of regen and saw zero difference in speed, but then again 70 watts isn't much. If we had had enough wind to get to 6 or 6.5 kts, I imagine things would have been different.
KTP is offline   Reply With Quote
Old 19-06-2019, 07:09   #8
Registered User

Join Date: Jan 2017
Posts: 11,214
Re: Propellor for charging batteries using electric motor

I guess advancing the community's knowledge of science from a user's POV is a noble cause.

But this would be of **practical** use only for extended times away from shore power, and

actually sailing at a decent speed for many hours per day, IOW likely passage making.

In which type of use case, having electric propulsion **only** would usually be considered impractical, even dangerous

unless a massive genset is also aboard

in which case the reduction in genny runtime and fuel consumption would likely be extremely insignificant.

And then toss in the speed reduction, which would also mean an increased risk of missing weather windows. . .
john61ct is offline   Reply With Quote
Old 19-06-2019, 07:18   #9
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 25,494
Re: Propellor for charging batteries using electric motor

Quote:
Originally Posted by KTP View Post
We were out the other day and I saw about 30 watts of regen when we were sailing at 4 kts, climbing to 70 watts at 4.5 kts. I played around with taking it in and out of regen and saw zero difference in speed, but then again 70 watts isn't much. If we had had enough wind to get to 6 or 6.5 kts, I imagine things would have been different.


70 watts isnít a whole lot, but itís 5 amps at 14V, enough to run a fridge.
Thatís about 1/10 of a HP, roughly.

What would be needed is a folding / feathering prop that can be locked into either unfolded or unfeathered so that you could regen when wanted, and feathered or folded when not.

I believe some feathering props you can do that?
a64pilot is offline   Reply With Quote
Old 19-06-2019, 07:52   #10
KTP
Registered User

Join Date: Mar 2010
Posts: 317
Re: Propellor for charging batteries using electric motor

Actually passage making is probably the area where we would least likely need an electric motor. If you figure a 3000 mile passage, you are going to run out of fuel on a diesel with 2500 miles to go...if you carry a massive fuel tank.

It is coastal cruising where I see the need to carry a small generator for emergency....the eu2200i will do perfectly and is 47 pounds....not really "massive".
KTP is offline   Reply With Quote
Old 19-06-2019, 08:03   #11
Registered User

Join Date: Jul 2016
Location: Alameda, California
Boat: Islander 36
Posts: 68
Re: Propellor for charging batteries using electric motor

I think it is very interesting what could be done with electric power on a sailboat, although I assume the user base is not large enough to really develop it.

I'm thinking it's a hybrid system (wind and electricity), with a computer balancing all the needs of the boat.

Maybe prop drag could be eliminated by turning the prop just enough to neutralize it. Or the prop could be spun just enough to hold the boat over a spot against wind or current while the skipper is reading the anchor to drop.

Re-gen could be used to slow the boat when desired, like when waiting for a boat to pass your bow, or when the boat is approaching max speed.

Power could be goosed on (and off) to make tacking a simple, easy operation.

Maybe heavy lead acid batteries could be a engineered part of a sailboat's keel.
smith8273 is offline   Reply With Quote
Old 19-06-2019, 08:32   #12
Registered User
 
AKA-None's Avatar

Join Date: Oct 2013
Location: Lake City MN
Boat: C&C 27 Mk III
Posts: 570
Re: Propellor for charging batteries using electric motor

I think more use cases will come up as people play around with this type of technology
__________________
Special knowledge can be a terrible disadvantage if it leads you too far along a path that you cannot explain anymore.
Frank Herbert 'Dune'
AKA-None is offline   Reply With Quote
Old 19-06-2019, 08:52   #13
Registered User

Join Date: Jan 2018
Posts: 578
Re: Propellor for charging batteries using electric motor

Quote:
Originally Posted by KTP View Post
Actually passage making is probably the area where we would least likely need an electric motor. If you figure a 3000 mile passage, you are going to run out of fuel on a diesel with 2500 miles to go...if you carry a massive fuel tank.

It is coastal cruising where I see the need to carry a small generator for emergency....the eu2200i will do perfectly and is 47 pounds....not really "massive".
What are you getting at with the EU 2000? Iím not following this. Are you suggesting that little thing could power a boat? Something more than a canoe? Or a dinghy?
Chotu is offline   Reply With Quote
Old 19-06-2019, 09:04   #14
Registered User

Join Date: Dec 2016
Posts: 43
Re: Propellor for charging batteries using electric motor

Taking 600 watts out of the sailsí power (from using a Watt & Sea unit) costs us around 1 knot at 8 knots STW and half a knot at 11 knots STW. I cannot see why the maths would be much different using the prop (which I cannot do since I have a saildrive) for regen charging.

However, the use case for a boat like us would be to have a Diesel engine for motoring, regen charging on a shaft drive and no diesel generator for electric loads and solar panels for charging at anchor.
Telesail is offline   Reply With Quote
Old 19-06-2019, 09:23   #15
Registered User

Join Date: Sep 2017
Location: Langley, WA
Boat: Nordic 44
Posts: 730
Re: Propellor for charging batteries using electric motor

The Maxprop manual says that to use their prop for generating electricity run the engine in reverse before shutting down - I will not feather from this position. So you can have both a low drag solution and the option to generate electricity. But for the price of a Maxprop you could buy a small portable generator that would produce a lot more power.
__________________

stormalong is offline   Reply With Quote
Reply

Tags
batteries, charging, electric, electric motor, motor, rope

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
charging both batteries A+B using solar OZ-Sailor Electrical: Batteries, Generators & Solar 21 06-11-2018 19:53
Charging Bow Thruster Batteries from House Batteries Streetcar Electrical: Batteries, Generators & Solar 2 15-07-2017 00:47
Propellor BC Mike Engines and Propulsion Systems 25 27-01-2007 04:07
Hundstadt propellor Alan Wheeler Propellers & Drive Systems 4 29-10-2006 20:29



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 05:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.