T-Pain Is On A Boat: Re: [Electric Boats] Adding an electric motor to existing diesel

Saturday, January 18, 2014

Re: [Electric Boats] Adding an electric motor to existing diesel - try before you buy.

I'm converting my 30' Beneteau First30 at the moment. Of course, I'm simply replacing the diesel which had the courtesy to wait until after winter haulout for the engine block to split open. But my "in-n-out of the slip" lithium pack is a 48v 100ah pack I am building from 16 100ah cells at a cost of ~$1800 ( plus shipping, customs, duties and taxes which I'll find out later...) and a few hundred more for the BMS (from Elecyr). The charger is an Elcon PFC1500 for about $600. And I'm changing the prop to a larger diameter, much more aggressive pitch -- a few more hundred...

That said, you can do things much cheaper. But I would caution you about spending money and effort for a half measure that, should you decide you like it and to rip out the diesel and go for the full measure, you'll have to replace your half measure solution as well. If you're handy, like to tinker, and have the money and time to do things twice, then by all means, go for it. But if you are looking to save money and sit on the fence about going electric or not, I would suggest that you are not yet ready. Especially if your diesel is still giving good service.

For a parallel hybrid, which is what you are thinking of here, you need some way of having the diesel spin the prop, the electric motor spin the prop or have both spin the prop. Let's not get into the other operational modes here:

- use diesel to spin the motor only in order to act as a genset.

- use the motor as a Diesel engine starter

- let the prop spin the motor to act as a generator.

If you simply place a pulley on the shaft between the Hurth and the shaft seal, then whenever your diesel spins the prop, you are spinning the electric motor. You'll need to do something with the power thus generated -- absorb it into your batteries or a dump load (electric water heater?) or you'll need a clutch on the pulley.

If you spin the electric motor to turn the prop, you are spinning the Hurth transmission (in neutral, of course). You'll need to ensure that it can freewheel without damage. Or you'll need to install another clutch between the Hurth and the shaft.

All of this costs money and takes some engineering and fabrication. As well as trial and error to get things sized right. Is all this worthwhile just so as not to disturb your existing underpowered diesel? It's your decision, and your money...

There is a company (Steyr, if I recall) that makes a parallel transmission that only requires 6" of space. It attaches between the diesel transmission and the prop shaft and has an input for an electric motor. It allows for all the above-mentioned use cases. No idea as to pricing and availability, but rest assured, it ain't cheap. I also think they're intended for larger boats than our little 30s...

Read through the archives. This topic has been dealt with before, but not in the past year, I think.

Good luck, and happy research!

/Jason

On Jan 18, 2014, at 13:10, oak <oak_box@yahoo.com> wrote:

Peter,

I started with a finicky Atomic 4, and very much identify with what you're going through!!!

However, trying to add an electric motor that swaps out with the existing diesel is probably not practical. A big enough motor won't fit in the engine space along side your diesel.   And you might need a motor 2X what you would normally need to overcome the drag of the engine and transmission.   Then there's the question of the transmission - there's all sorts of religious arguments about whether it's better to leave the transmission in reverse or neutral when sailing. ACTIVELY spinning the back side of the transmission with the transmission in nuetral for an extended period of time might not be a good idea (even if you can overcome the force).

My solution was EXPENSIVE, but seemed to be the simplest to implement.
I mounted an outboard motor bracket on the back of the boat, and the bought a Torqeedo 4.0, that's rated at 10HP. Added 4 deep cycle batteries, and I'm done.   I now have electric power to get me home if my gas engine decides not to start.

Ok, well, not quite done yet.....

Here's the brutal truth:

The Torqeedo 4.0R is about $3800. You may or may not spend more on an installed motor setup.
The battery is a whole other issue....

I started with 4 deep cycle 12V batteries. They work. Unfortunately, they just aren't made for taking the high current loads of an electric motor for an extended period of time.   I upgraded to AGM batteries, and am in the process of upgrading my charging system.

Ultimately, you really probably need to spend the money on Lithium batteries - and a LOT of them to get 48V. Suggestions of at least a 200Ah bank seem about right. Eight 200Ah Lithium batteries runs another $1800. And then you need a good charger designed for lithium batteries - at least another $500.

Performance:

The Torqeedo motor is a very nice outboard. Lots of power (for what it is).   On the C-30, it's still marginal.
I boat on a relatively flat, relatively protected inland lake. The Torqeedo will push the boat forward at decent speed (up to 4mph at around 1000 watts).   You won't get there fast, but it's a great backup for getting into the marina. Unfortunately, if I have a STRONG wind pushing me into the slip, the Torqeedo doesn't have enough power to back me out of the slip into a strong wind (over 15mph).

So, an outboard mounted Torqeedo is fine for "backup", but won't REPLACE the need for the main engine.

Feel free to email me off list if you have any questions.

John

From: edilist <no_reply@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Saturday, January 18, 2014 1:04 AM
Subject: [Electric Boats] Adding an electric motor to existing diesel - try before you buy.

Hello,
I'm new to the list and thinking seriously about a conversion of my own. I have an older Catalina 30 sailboat with an underpowered and finicky Universal 11 HP diesel, w/ a Hurth transmission. The good news is that it's a sailboat, and so most of my engine time is the 10-15 minutes to and from the slip each trip.

I really like the idea of electric, but am non-commital about pulling out the existing diesel. Has anyone thought of adding an electric motor to their existing diesel?   I'm envisioning something like a gear or pulley system connecting an add-on electric motor to the exsiting propshaft. Maybe just one 4D battery to start. Throw the transmission into neutral and turn on the electric motor. If the electric set-up doesn't work for some reason, I disengage it from the prop shaft and start up the diesel.

Of course a set-up like this would have lots of compromises, prop would be underpowered, extra weight, but none of that is a big deal for me. I'm not a racer, not a cruiser, just a localized pleasure boater, and a fair-weather one at that.

If it works even a quarter as well as I hope then I can look at yanking the diesel and going all electric in a season or two. Anyone thought of something like this or better yet actually tried it out?

Thanks,
Peter