27' Owens Full Electric Conversion Feasibility

This thread is for me to research the feasibility of converting my 1967 27' Owens Concorde to plug in electric propulsion power. Current power comes via 350 cid Chevy engine with Borg Warner velvet drive transmission(I believe a 1.34-1 gear ratio). Electric head, fridge and 2 burner cook top. 1 rather large (66"x32")solar panel can be fitted to the hard top without affecting the appearance of the boat. 3 additional while possible on the cabin top would affect the use and looks of the boat enough to be less desirable.

Our current use of the boat is mostly day trips of less than 30 miles out and back, however overnight and multi-day trips are in our future. Protected inland waterways with moderately slow tides are the norm rather than the exception in my cruising area. Assume no more than 3 days away from the dock. If longer trips are desired a small generator may need to be compromised into the equation.

I imagine the design will incorporate the use of LiFePO4 battery cells for power storage. The amount of storage needed will need to be determined. The horsepower of the motor would ideally provide for up to 10 kn of speed but 7 or less would be acceptable too. All interior and exterior lighting will be LED.

How close to reality are my expectations to the current state of electric propulsion and battery storage technology? For our purposes here let us assume future resale value is of no concern to me.

Thank you

 

No chance, no way. The power demands for this boat would far outstrip the ability of a battery bank to provide power.

Lets just assume that you were willing to eliminate planning speeds completely, so you dropped a 25hp motor in, which would probably get you to 6kn or so. This would use roughly 18.5kwh. Since you want to go a total of 60nm, this would work out to about 5hours of run time. So figure you need a usable power storage of 1,500amps per hour... So for the weekend you need a 9,000amp hour usable bank, so minimum size would be 18,000 amp hours. Figure that means 72 large 8d batteries weighing in at 180lbs/battery. So figure you have to install just under 13,000lbs of batteries.

This far exceeded the load capacity of the boat, ignoring the cost (about $47,000).

 

IIRC- LiFePO4 batteries cost 3-4x that of lead acid based on kwh...

 

Thank you for your replies.

I see the error I made in the original post. My statement above of "less than 30 miles out and back" should have read "less than 30 miles total trip". The mistake is mine and I apologize for that. This 30 miles represents the absolute maximum this boat will see as it is for protected inland use, not long range coastal use.(think bathtub like sea state) Also note the actual typical trip this boat makes is less than 20 miles in any given day. 8 mile trip to anchorage returning the next day. The 30 mile maximum expressed is a data point for reference only.

Please also note that nowhere in the spec is there a "planing" requirement. The desired absolute maximum is no more than 10 Kn with 7 Kn or less considered ideal. 5 Kn would be completely acceptable too.

I have no interest in pursuing the project with lead based batteries, LiFePO4 will be the spec battery for this proposed project bringing the weight of the pack down significantly. With LiFePO4 there is also more usable amp hours and the 50% maximum draw down of lead batteries does not apply either.

The only reason for any solar on this boat is to augment charging ability while away from the dock and supplement house load. "Plug in charging only" would be the "ideal" arrangement, however we live in the real world along with the rest of you hence a DC generator to augment charging away from the dock is acceptable. Making this a hybrid boat which is the section of the forum we are currently in.

Also, budget is not discussed in the OP on purpose as cost to bring the project to fruition is yet unknown. This project has nothing to do with making economic sense. Economic sense is to not own a pleasure boat in the first place. This project is about what motivates everyone on this forum, a pure passion for boats.

 

It would be much cheaper for you to sell your Owens and build a boat that is more appropriate for low power. For example, a low displacement catamaran.

 

I appreciate that sentiment, spoken like a true engineer

A multi hull makes complete sense but the problem with that is one of looks. Aesthetically the common complaint I hear is that electric powered boats look too futuristic with hyper efficient hulls and visible solar equipment. Traditional boats look well, traditional. The concept is to see what can be done to electrify an old school classic with modern electric propulsion to hopefully overcome some of the stereotypes.

Ultimately a different donor hull may be sourced possibly a small displacement hull with natural classic style and character but the Owens is the horse I have in the race right now.

 

With a somewhat relaxed speed target and inland use, the power requirements drop significantly and the project is feasible from an engineers point of view.
But although you have not set a budget, the financial side cannot be omitted completely.

If you could obtain the battery pack, charging circuit and power train of an electric vehicle, the conversion surely can be feasible. I would not limit the storage options to lithium-iron because with that technology every individual cell must be monitored both during charging and discharging if life expectancy is a consideration. Using an existing lithium-ion pack that has all the electronics already built in would be my preferred choice.

 

A wrecked hybrid car could be an option.

 

stumble's post had it laid out.
25hp~18kw
6 knots, 30 miles = 5h.
5h*18kw=90kwh with no reserve capacity. so lets be ultra optimistic and round up to 100kwh

http://www.evsroll.com/Electric_Car_Battery_Cost.html

Lets use the cost of $400/kwh (which is ultra optimistic if you think cells vs. functional pack with management and everything)

~$40,000

that is very very optimistic price for the batteries. Now maybe you only need half the power (but what if you need to come back against wind?). but even at $20k for just teh pack its pointless. (imo)

There are place where electric starts to kind of make sense - but that usually means purpose built low power applications. Now you are taking a boat that uses big power (V8, 150-200hp?) and not at all optimal for low power slow cruising.

And how about those multi day trips? how will you charge your batteries?

Why not put a 20hp gas outbboard. That will do everything the electric system would but not be range limited and it would have resale value (and used ones are available too). I would think trying to sell your LiFePO4 pack used will not get you very good dollar.

 

Your problem is the OWens hull shape...not good for low power.

A low power boat needs a hull form like that of a sailboat.

 

The other problem is that gas is still really cheap, and when use for comparison it makes it hard to justify the modification. Also, after being modified, the boat will be hardly usable. With the added weight the capacity will be greatly reduced and the hull design handles horribly at low speeds.

 

That Owens will have a 200 to 250 HP V8, which will push it into the mid 30's pretty easily. She'll need most of this to get over her hump and she'll start leveling out around 15 to 17 MPH, where HP requirements will drop. Being a warped bottom, she'll need to have enough to reach 20 MPH just to overcome chop, windage and reasonable efficiency underway. So, 100 KW isn't all that unreasonable, though this is a lot of juice to carry around. How many 160 pound, 8D's is this at $600 bucks a crack?

 

Lets assume for a moment that you make the switch to a very efficient hull form, and reduce required range to 30nm. As for hull form you are pretty much going to make the switch over to a sailboat hull. Cut the keel off, and replace the lead with batteries it would probably be a wash... So what does this look like?

A 30' sailboat will generally hit 5kn at around 20hp used. Again, at 30km you have 6 hours of run time. So...

6 hours
20hp ~= 15kwh
Required available power = 90kwh.

To store that at 12v means you need 90,000/12=7,500amps

A quick look indicated that a 12v 100amp lifepo4 battery would run about $1,200 and weigh 30lbs. And has a volume of .42 cubic foot.

We need 75 of them so, to put this pack together:

Cost - $86,400
Weight - 2,160lbs
Take up - 30.25 cubic foot

Assuming its worth it to you, it is possible, but very expensive.



A solar panel would be meaningless in terms of propulsion. You couldn't carry enough solar panels to generate a meaningful amount of poet.

Just as a FYI... With a 55amp battery charger, assuming 100% absorption it will take five and a half days to recharge, and the battery charger alone will require a 50amp power plug.

Technically it is just possible... Practically I just don't see it.

 

Thank you all for the responses. They all are valuable to me and each one knits itself into the tapestry of my concept. I'm the first to admit that nothing proposed is either cheap, easy or even economically practical. This proposed project will be a one off and no delusions of mass marketing this is at all envisioned by me. While some may think me crazy for trying something like this, I also recognize that working with the compromise that is a boats nature is important.

I appear to be stuck trying to make what essentially would be a mono hull sailboat have the appearance of an old school cabin cruiser. Thoughts of the All Weather brand boat comes to mind immediately but lacks the cabin aesthetics desired. Scout remakes of the old Elko design trunk cabin would be another desirable look as the replacement for the Owens.

Putting aside the economic reality of the hardware cost for a moment as well as the technical aspects of pulling this off. If you where to pick an existing mono hull cabin cruiser less than 30 feet in length to attempt a project such as this on which one would you choose? Low speed classic lines that are generally aesthetically pleasing. Commercially available on the used market for a refit. Efficient hull design with low drag.

 

Cabin cruisers are basically a pointy wide box. I can't think you are describing a cabin cruiser but most likely a double ended sailboat hull.