Electric in one hull, diesel in the other, refit.

[almex]

I am buying a Catana 39 with original 32 year old Volvo 18hp 2002 diesels. I am considering replacing one of the engines with a 10kw electric motor attached to the saildrive and adding a 10 -20kw Lifepo4 battery bank, 2kw of solar, use the electric motor as a hydro generator and a 400w wind generator. I test sailed the boat, it could sail at about 5kts in 5-6 kts of wind at about 40 degrees so I don't think I will have to motor often? The displacement is listed as 4-5 tons, the current set up is very minimal and light with an spinnaker and a screecher, should sail well in light winds.

My wife want's air conditioning and we will almost never stay in a marina as we won't be cruising full time, the large battery bank is needed for the air conditioning so I though swapping one of the smelly engines for electric could save weight to help offset the battery weight. The engine room in this boat is not sealed well and having one hull without the smell would be amazing.

My plan is to start with a 10kw battery and one 10kw motor which together weigh about the same as one of the diesel motors. and will use the boat in the sea of cortez and Mexican west coast for a year or so and if I don't use the diesel often I will take the other diesel motor out and put in another 10kw motor and add 10kw to the battery bank. If I end up using the diesel motor often I will replace it with new more powerful diesel motor.

I assume this approach has been taken often but I can't find many examples.. Does anyone know of any? Any issues I probably haven't considered?

[Johan Leopard51]

I def want to watch this!

My thinking was we ditch the gennie and in its space put a large (with room to expand) LifePO4 battery bank.

Keep all 12V as is with 48:12 bridge to existing house bank. But upscale the battery inverter to say 15/20kW to be able to run all AC loads off the 48V bank.

I’d been thinking Integrel on both big Yanmar, but this idea is interesting. With enough solar I could maybe go Integrel on only one motor and replace the other motor with an electric motor. We travel chill speed, and often cruise on only one motor (twin 370Hp powercat). I’ll try lookup the electrical motor size needed to propel us on one electrical motor at say 7 knots. With a lot of solar and occasionally run the big Yanmar while electric rests - might work?

We had to replace one Yanmar (about $40K) and for $40k one can get a lot of battery and electrical motor if the starboard motor goes south. I really doubt that if the Northern Lights gennie goes I would replace it. I really hate gensets on a vessel.

[barnakiel]

Can be done.


But you will be better of renting a condo next to the marina and buying a plain boat without complications of mods and cons.


Condos have better aircon than boats. Wife to be happy at all times.


b.

[leecea]

This article might be helpful: https://www.gonewiththewynns.com/air...ning-sailboat/

[fxykty]

Originally Posted by Johan Leopard51

I def want to watch this!

My thinking was we ditch the gennie and in its space put a large (with room to expand) LifePO4 battery bank.

Keep all 12V as is with 48:12 bridge to existing house bank. But upscale the battery inverter to say 15/20kW to be able to run all AC loads off the 48V bank.

I’d been thinking Integrel on both big Yanmar, but this idea is interesting. With enough solar I could maybe go Integrel on only one motor and replace the other motor with an electric motor. We travel chill speed, and often cruise on only one motor (twin 370Hp powercat). I’ll try lookup the electrical motor size needed to propel us on one electrical motor at say 7 knots. With a lot of solar and occasionally run the big Yanmar while electric rests - might work?

We had to replace one Yanmar (about $40K) and for $40k one can get a lot of battery and electrical motor if the starboard motor goes south. I really doubt that if the Northern Lights gennie goes I would replace it. I really hate gensets on a vessel.

Lots of solar and a big LFP house bank (and/or EP bank) works great when the sun shines, until it doesn’t. What do you do when a low system brings a week of clouds? Or you decide to cruise somewhere that doesn’t have 14 hours of sunshine a day? An Integral system on one or both of your propulsion engines can generate a lot of power, but it does mean running a propulsion engine much more than what’s needed for propulsion alone. We have high output alternators on our engines and 2.6KW solar, but we are about to install a new NL generator shortly because the year we’ve spent in SE Asia has had way less sun than we expected and running our relatively noisy and old propulsion engines for generating purposes really does suck.

[Johan Leopard51]

Originally Posted by fxykty

Lots of solar and a big LFP house bank (and/or EP bank) works great when the sun shines, until it doesn’t. What do you do when a low system brings a week of clouds? Or you decide to cruise somewhere that doesn’t have 14 hours of sunshine a day? An Integral system on one or both of your propulsion engines can generate a lot of power, but it does mean running a propulsion engine much more than what’s needed for propulsion alone. We have high output alternators on our engines and 2.6KW solar, but we are about to install a new NL generator shortly because the year we’ve spent in SE Asia has had way less sun than we expected and running our relatively noisy and old propulsion engines for generating purposes really does suck.

Our boat is based in Seychelles - 4 degrees off equator so plenty sunshine. There are weather systems that come through but irradiance is excellent on average. On twin cat we can fit a lot of solar on the flybridge.

Our motors are very quiet compared to the NL gennie.

I don’t expect that we will be cruising mostly electric, but if we can cruise 50% electric…. Eg leave an atoll on motor, between it and solar the big 48V bank is fully charged by time get to a dropoff we want to target game fish on, then trawl 6-7 knots electric for a few hours, and motor back to atoll for the evening.

I need to go find the electric motor size needed to match the Hp of the Yanmar at 7 knots. That will tell me what size motor and how long it can run on what size battery bank.

[CAT-SAIL]

Originally Posted by almex

I am buying a Catana 39 with original 32 year old Volvo 18hp 2002 diesels. I am considering replacing one of the engines with a 10kw electric motor attached to the saildrive and adding a 10 -20kw Lifepo4 battery bank, 2kw of solar, use the electric motor as a hydro generator and a 400w wind generator. I test sailed the boat, it could sail at about 5kts in 5-6 kts of wind at about 40 degrees so I don't think I will have to motor often? The displacement is listed as 4-5 tons, the current set up is very minimal and light with an spinnaker and a screecher, should sail well in light winds.

My wife want's air conditioning and we will almost never stay in a marina as we won't be cruising full time, the large battery bank is needed for the air conditioning so I though swapping one of the smelly engines for electric could save weight to help offset the battery weight. The engine room in this boat is not sealed well and having one hull without the smell would be amazing.

My plan is to start with a 10kw battery and one 10kw motor which together weigh about the same as one of the diesel motors. and will use the boat in the sea of cortez and Mexican west coast for a year or so and if I don't use the diesel often I will take the other diesel motor out and put in another 10kw motor and add 10kw to the battery bank. If I end up using the diesel motor often I will replace it with new more powerful diesel motor.

I assume this approach has been taken often but I can't find many examples.. Does anyone know of any? Any issues I probably haven't considered?

I am considering a similar approach on a 38 foot sailing cat, only I am not concerned about using airconditioning.

After reviewing different solutions, I would encourage you to look into Kräutler electric saildrives (link / details below). They manufacture drop-in electric saildrives which will fit the bolt pattern of your Yanmar. They manufacture the saildrive in saltwater resistant materials. I did look at different types of POD drives, but I prefer having the electric motor above sea level, inside the boat, just in case something goes wrong (fishing line, leak etc).

KRÄUTLER ELEKTROMASCHINEN GMBH
Hohenemser Strasse 47
A-6890 Lustenau
AUSTRIA

www.kraeutler.at

[motion30]

This summer I installed a 12 volt air conditioner supplied by the boss Marine air-condition. Now distribute by Mike at sea pro watermaker. I am in the southern part of Florida and it was a game changer. It is a variable speed unit at the lowest speed it draws 31 amps and it high speed which I never used to draw 61 amps. We had a cold front move through and I ran it on heat last night for the first time it does a really good job warming up the cabin

[Dockhead]

This is a fun engineering problem. I always thought that 3 diesel engines on board inherently weight-sensitive cats made no sense at all.

Different variations are possible:

1. Single diesel propulsion engine with large alternator charging a large 48v LiFePo4 bank (plus solar of course), electric motor in the other hull. You will not be able to use max power continuously, but with battery assist, long enough for those times when you need emergency propulsion power. You have to use the single propulsion engine for generator duty. No redundancy. Cost and weight benefits.

2. One diesel propulsion engine, one electric motor in the other hull, one diesel generator set, 48v LiFePo4 bank.

You add weight and complexity of multiple engines, but you gain redundancy and you gain the ability to use the electric motor continuously (within the limitations of the genset capacity). You gain dedicated genset for aircon. This will be roughly similar in weight and cost to conventional cat setup (less than conventional cat twin diesels plus genset) but much better functionality. I like it.

3. One larger diesel genset and two electric motors.

Let us know how this project evolves.

[mcarthur]

Originally Posted by Dockhead

This is a fun engineering problem. I always thought that 3 diesel engines on board inherently weight-sensitive cats made no sense at all.

Different variations are possible:

1. Single diesel propulsion engine with large alternator charging a large 48v LiFePo4 bank (plus solar of course), electric motor in the other hull. You will not be able to use max power continuously, but with battery assist, long enough for those times when you need emergency propulsion power. You have to use the single propulsion engine for generator duty. No redundancy. Cost and weight benefits.

2. One diesel propulsion engine, one electric motor in the other hull, one diesel generator set, 48v LiFePo4 bank.

You add weight and complexity of multiple engines, but you gain redundancy and you gain the ability to use the electric motor continuously (within the limitations of the genset capacity). You gain dedicated genset for aircon. This will be roughly similar in weight and cost to conventional cat setup (less than conventional cat twin diesels plus genset) but much better functionality. I like it.

3. One larger diesel genset and two electric motors.

Let us know how this project evolves.

Good summary!
Add 3.5: two diesel gensets, one per hull, and two electric motors. This option allows for gensets of differing size to cater for different needs - a larger for long low/mid-speed propulsion, a smaller set for non-propulsion but low solar days needing aircon, and of course both together.

Another benefit of the genset route - one or two - is that you should be far less limited in where they can be housed since they aren't connected to the prop shafts.

[Johan Leopard51]

One complicating factor for us would be that at the moment the Yanmar systems are integrated to the Raymarine systems. Would maybe just mean that have a separate start and speed throttle for the electric side - on flybridge and in saloon. Rudders would stay same, we’d keep both fuel tanks as starboard can pump over to port tank. I think the 12V systems would stay the same except have to program out the system monitors that were expecting data from the starboard diesel. Adding a much larger 48v battery inverter that supplies the AC side should be simple enough - it can probably sit with the 48V bank in the NL gennie enclosure but it and the battery system would need a way to circulate airflow. May as well if there is space keep the current 12V battery inverter as backup but disconnect it from AC.