Re: [electricboats] Throttle control head

Your gut is correct. 2x12kw at 48v is fine. Your top speed will likely be around 7.5 knots. There are some efficiency gains at 72 or 96v but definitely not worth the hassle, especially on a sailboat.  You will need a reduction gear/belt with that motor. 

Now that you will have multiple voltages on board start thinking and speaking in watt hours. Amp hours is meaningless without also stating the voltage. 

You will want to reconfigure your solar and generator to charge the 48v bank. 

If you already have a large lithium setup at 12 volts, you can use a bi-directional DC-DC. Otherwise step down the 48v bank to charge the 12. Over time as equipment needs to get replaced, replace it with a 48 volt version. 

Your generator speed will be about 4.5 knots if you max out its charging capabilities. 

Matt Foley 

Sunlight Conversions

Perpetual Energy, LLC

201-914-0466

sunlightconversions.com

instagram.com/sunlightconversions/

youtube/sunlightconversions

ABYC Certified Marine 

Electrical Technician 

On Saturday, March 9, 2024 at 09:49:10 AM EST, Eric via groups.io <sailawayvlog=yahoo.com@groups.io> wrote:

[Edited Message Follows]

Okay, I'm just going to keep spinning off my original thread with another tangential question...hope that's okay.  This question is regarding the motor "size" to go with...really just the voltage.  My boat is a 48' cat at about 15 tons fully loaded.  When I consulted Thunderstruck, not having gotten to calculating exact hull speed numbers or anything yet, they were suggesting x2 of the 24kw kits at 96v.  That seems like serious overkill to me - after all this isn't a motor yacht, it's still a sailboat.  From info on this forum and a few other sources, my gut tells me that the 12kw kit (x2) running at 48v would do the trick.  Their description even suggests that this kit is used for boats up to 15 tons - mine is twice that (probably not quite actually), two pretty efficient hulls, and of course I would be using 2 motors, so it seems logical that the 12kw would work. I also have no interest or need to achieve my "hull speed" which is probably over 9 knots.  If we get 6-7 knots full out and 3-5 knots at a more efficient power band, that's perfect. 

The middle option would be sizing up to 72v (all kits run the same Me1616 motor, kit price is the same) for 18kw per side.  A 72v pack seems fairly manageable, though maybe not as easily as 48v.  For the same money it would have to be less amp hours than a 48v pack.

So my question is - assuming the 12kw 48v motors are strong enough and the 18kw 72v motors aren't strictly necessary, is there still some benefit to going that route, but with less amp hours, money definitely being an object?  

Thanks...I'm probably overthinking it.  But I've definitely gotten into more trouble in my life underthinking things.  Lol.

Additional note - as mentioned somewhere above, we'll be running about 2000w of solar and a 6kw generator as well.