Using two 15KW 48VDC motors

[EllisElectric]

Can they be powered from one generator, say 30KW @48V. Are there even such thing as a 48VDC generator? Also probably have six LiPo batteries 24VDC 200AH connected in series to obtain 48VDC for running motor in the short term.

[marshmat]

From a very general, architectural standpoint, yes. You can set your main bus voltage at 48 V, and then have any number of 48 V loads (eg. motors) combined with any number of 48 V sources (eg. generators, solar panels) and a 48 V battery pack.


The devil is in the details.


30 kW @ 48 V is 625 amps continuous. At that point, you're way beyond the end of the standard marine wire gauge table; you're looking at conductors on the order of 1500 kcmil. That's not wire, that's a 1-1/4" solid copper bar. Even the 48 V "mild hybrid" systems the carmakers are working on don't go much over 10 kW; if they need more than that, they change the whole architecture to one that uses hundreds of volts.


Regulation and control for all of this will be non-trivial. The power electronics definitely exist, but they are not plug-and-play. The system will need to be engineered, and all the control logic figured out and programmed. Safety precautions will also be non-trivial. Not because of the voltage (which is quite reasonable) but because of the current that a LiPo pack like that could put out in a fault condition.


It's definitely possible, but doing it safely and reliably for under $50k would be tricky and I could easily see it spiralling to $100k once you factor in engineering and design labour.


What's the application? Is this a case where you can get 95% of the way there at 15%-25% of the cost with a conventional engine, shaft, & prop for high speed, a nice big alternator & LiFePO4 battery, and a retractable Torqeedo for low speed?

[EllisElectric]

The 100K is about what it cost to ship a vessel from China, so I better spend that amount on something I can keep.
Yeah I'm looking for an advanced electrical system that can be published about.

[StuM]

On your 1 tonne displacement Seaward 22?

[EllisElectric]

Originally Posted by StuM

On your 1 tonne displacement Seaward 22?

55 foot cat

[marshmat]

Is "can be published about" the goal?


Spending that kind of money on a lithium & serial hybrid system doesn't exactly get you on the front page of ProBoat these days. Serial hybrids just don't make sound engineering sense with the house load vs. propulsion load mix and daily / weekly usage profile you get on a boat like that. And I'd not want to be caught out in a 55' cruising cat with only 30 kW to play with if the wind picks up and there's a lee shore.


If you wanted to come up with a system where you can choose to either use a pair of 40 hp engines directly driving the props, or clutch in some 3 kW golf cart motors with the diesels disengaged & shut down, that might be both more practical and more manageable. Still a lot of engineering effort, though.

[sailingchiro]

625 amps. Holy Moly. And I have trouble bending 200 amp wire.
Hope to never smell smoke on that vessel because it will go quick.
Yeah, I haven't seen any good way to drive electric motors without a good sized gen set which would be diesel any way. Why pull your hair out trying to figure it out. This is the same as trying to run air conditioning 24/7 off solar and battery. We are getting closer with Lifepo4 but not there yet.
I have seen some transparent film that is solar may offer promise to coat the entire deck. It is nice to say, hey my boat is powered by the sun. Until you really need the power and it isn't there. Currently it is a worm hole. You start on that quest and before you know it, you have exceeded $70,000 or more. Then you tell yourself, new engines and transmissions were only $14k-20k. Dang.

[moseriw]

marshmat: THANK YOU FOR FIGURING IT OUT!

I hope the stupid - Ohh I go electric - tasks end here!!!
Again << 2 tons on a lake to go in and out it'll be ok but definitively not for bluewater cruising if you take security as a serious concern.

[RaymondR]

Another example of all the trouble and bother this anti diesel, pro electric and "green" movement causes us in obliging us to redirect our fellow yatchies back onto the path of sensible propulsion systems.

[sailingchiro]

How about nuclear??

[Takamoana]

The Torqeedo Deep Blue system may give some insights

[sailingchiro]

I love the youtube video of the couple that can't make the last mile to the dock because of an out going tide and have to ride out a storm at night because of low batteries.

[NaClyDog]

Originally Posted by RaymondR

Another example of all the trouble and bother this anti diesel, pro electric and "green" movement causes us in obliging us to redirect our fellow yatchies back onto the path of sensible propulsion systems.

I don't think it's an anti-diesel, pro-electric movement.


You need to think much bigger picture as in anti-fossil fuel, pro-environment movement.


It's just a different way of thinking required to ensure that generations that come after us (personally, none of this will affect me as I'm a crusty old man who will die long before the planet does). We know the status quo is killing the planet and some change is needed. We should be encouraging the search for the change so the people down the line can get their fair shake just like most of us got.

[GordMay]

Originally Posted by RaymondR

Another example of all the trouble and bother this anti diesel, pro electric and "green" movement causes us in obliging us to redirect our fellow yatchies back onto the path of sensible propulsion systems.

Unlike outright climate denial, "climate delay" might acknowledge the reality of a changing climate, and the role of carbon emissions from human activity in climate change. But, instead of actively working to deal with the issue, it seeks to create a debate about what should be done (& how), who is responsible, and how we should allocate costs and benefits.
It is an effective strategy to significantly delay action to reduce emissions.

[smac999]

Your 600ah 48v battery bank would run A 30kw motor for less then an hour...

Running a 30kw genny to power a 30kw electrical motor doesn’t Help the planet...