Re: [electricboats] Recommendation for 48 v inboard motor + generator.

Are you saying you can hold 4.8 knots at 2200 watts (2000+200)?  What are the boat specs?  Have you measured actual output from generator and solar? 

On 2023-06-04 5:28 pm, reesekc wrote:

I'm presently using a 2kw generator (Harbor Freight) and a 48vdc golf cart charger. Also have 200 watts of solar power (12vdc in series for 24vdc with a boost controller to 48vdc). All of that is pretty cheep. But I can hold 4.8 knots all day long with the sun shining. 

On Sun, Jun 4, 2023, 6:03 PM Dan Pfeiffer <dan@pfeiffer.net> wrote:

Is this a commercially available unit or something you put together?  That is a reasonable power output for continuous cruise on about a 10,000 lb monohull I think.

On 2023-06-01 11:23 am, jeremy baker via groups.io wrote:

I have a 4.5Kw, 48 volt, alternator powered by a 8hp propane fueled engine. But no boat yet. Sigh 

 

On Thursday, June 1, 2023, 10:17 AM, Dan Pfeiffer <dan@pfeiffer.net> wrote:

I have not built the genset yet.  It was suggested to me by one of the engineers at Thunderstruck that I could do it with the ME1616 with a rectifier and regulator.  But I have not researched it any further. 

I have a 3cyl 12kW Kubota diesel that was a removal from a new excavator converted to all electric.  It is not a marinized engine and I will need to sort that out but it doesn't seem too difficult.  Mostly to do with the heat exchanger and associated pumps and plumbing.  I may also need a belt drive to better match RPM's to get the desired output.  Direct drive would be preferred and the ME1616 is rated at 38.46 rpm/v so that's is in the ball park (57.2V @ 2200rpm).  Have to consider voltage drop through rectifier stages to get proper charging voltage input to regulator?  More research needed...

BUT, after running my electric drive for two seasons I don't know that I need such a large genset (10kW).  I could probably do with 5 or 6kW rather that 10.  See my reasoning here:
http://dan.pfeiffer.net/10m/diesel_genset.htm

Perhaps as a general rule of thumb the genset capacity needed for reasonable continuous cruise at 75 to 85% of hull speed (for a monohull) you can do with 65 to 75% of the motor kW capacity needed to get to hull speed.  So if you need 10kW to get to hull speed that would be 5.5 to 6.5 kW gen set for reasonable continuous cruise.  By continuous cruise I mean maintaining desired speed without drawing down batteries.  For me that's 5.5 to 6 knots cruise.  From my observations I can do that at about 5kW.  But I always want to consider having sufficient headroom that I am not running any of the components at 100% to get the desired performance.   That gets me to 6 or 7kW genset?  But 5kW would get me at a comfortable continuous cruise at 5 to 5.5 knots with headroom. 
http://dan.pfeiffer.net/10m/electric_drive_performance.htm


My boat is a 12,500lb monohull with a 28.3ft waterline. 
My boat is a 5,700 kg monohull with a 8.6m waterline.

More details on my electric drive conversion here:
http://dan.pfeiffer.net/10m/electric_drive.htm


Dan Pfeiffer

On 2023-06-01 10:01 am, Robert McArthur wrote:

Dan (and anyone else who wants to explain!),

Delving back a little...

On Fri, 24 Mar 2023, 3:03 am Dan Pfeiffer, <dan@pfeiffer.net> wrote:

I got a 2nd 12kW motor to use as a generator with a 3cyl Kubota diesel I have (18hp) but have not built the genset yet.  The diesel is very compact and I figured I could get a 10-12kW 48VDC generator from the combo.  After 2 seasons of use I think a smaller genset would do fine.  Maybe 5-6kW.  I could motor at decent cruising speed with that.   Your use may be different.   Genset info:

http://dan.pfeiffer.net/10m/diesel_genset.htm

 

I just got a quote from one of the few marine DC genset places, and unfortunately it matches what I could find from the others - a new 16kW continuous 48V DC genset is about AU$28,000 or US$18,500. Not installed. Ouch!!

 

I see above Dan you thought about getting around it with a self-marinised bobtail, connected to a ME1616.

I'm thinking of similar, but perhaps an already marinised Beta 20 connected to the ME1616 (another of which will be propulsion) since I am not particularly mechanically minded to self marinise.

 

Could you explain to a layman why, if using the ME1616, you would need rectifier or regulator? I thought the ME1616 already put out 48V DC (I presumed an actual 54V or so) with controller. Or would you replace the usual Thunderstruck kit controller with the rectifier and reg for the genset?

 

Since a brand new marinised kubota (Beta 20) could be less than US$8000, and the ME1616 is about US$1500, it looks about half the cost of buying a named brand 48V DC marine genset! Thoughts?

 

Another option for marinised is a Yanmar 3YM20. Neither though are a perfect rpm match for the ME1616 which is only (!) 12kW. But if I can spend US$10,000 for 12kW vs $18,500 for 16Kw then it seems a big win.

 

Rob