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

Hello Rob,

I went the easier (but more expensive route) of buying a DC genset (I settled on a Fischer Panda AGT 18000 --> 18KVA). I am running at 96VDC, and that was a 5% premium on top of their 48VDC catalog price.

The larger price tag compared to an equivalent power AC genset makes sense to me, as the rectifier box is an additional piece of equipment provided in the system. The rectifier diodes are water cooled (connected to the sea water circuit of the generator). If you were to go this path, you need to account for the space requirement for the rectifier box, and how you will route not only the electric wire, but the water cooling circuit.

As you described, running the output of an AC generator to a DC charger is not practical for 10kW+, due to the lack of battery charger designed for that much power.

 

The advantage of the DC genset I see is that the output of the generator feeding the rectifier box is 3 phases AC. That means that the output of the rectifier box is a quite stable voltage. If you were to rectify a single phase AC, your DC voltage would drop to 0V around 120 times per second, so the current would do the same (when the rectified DC voltage is less than the battery voltage, no current flows from the generator to the battery or to the load).

Regarding your question on the ME1616 motor, it is not a DC motor. The ME1616 is a 3 phase AC motor. In traction mode, we use a motor controller that we feed DC to, and the controller creates the 3 phase AC to drive the motor at the RPM specified to the controller.

Cheers,

Jerome

On Thu, Jun 1, 2023 at 5:01 PM Robert McArthur <rjmcarthur@gmail.com> 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

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