Re: [electricboats] Electric motor size for 48' cat

The ME1616 will REQUIRE cooling at anything over 125 amps.  So without cooling you max out at 6000 watts at 48V (12,000 at 96V).  For me that's about 5.5 to 6 knots depending on conditions (waves, wind, etc).   Do NOT plan your system without cooling.  I have a sea water heat exchanger and plan to add a radiator type heat exchanger so I have 2 stages of cooling.  The radiator (basically a heater core from a car) should be fine up to 85% of hull speed.  If I need to push harder for any length of time (battery capacity limited) I will kick in the sea water system. 

Note on my cooling system
http://dan.pfeiffer.net/10m/electric_drive_cooling.htm

Dan Pfeiffer

On 2023-10-21 10:17 am, Eric via groups.io wrote:

Hey Dan and Randy,

Thanks so much and very nice to meet you.  That's very helpful and definitely gives me a place to start.  Dan I'll definitely go take a look at your FB page.  I had noticed that the motors are the same, just battery config and programming to step up to 72 or 96v which at least leaves some flexibility.  Again, just from a very general standpoint, for a sailing cat our size (around 26,000 to 28,000 lbs) and purpose, it sounds like the 48v x2-12Kw setup would likely be just fine.  Our Volvo MD-22's are 50hp, but even when both were running their power output wasn't strong and it was just fine for this boat.  I always figured a pair of good running 40hp Yanmars would be better.  Our hull speed is theoretically somewhere around 9 knots, but I have no need to ever see that with the motors.  If we can max out at 6-7 when needed and cruise at 3-5 that would be perfect.  The 12Kw kits have an option for the water cooled pieces and parts, which I assumed I'd do, plus a blower setup in the compartment.  I love the idea of merging these batteries with some new ones, but with them being close to 9 months old now, I'd be concerned about trying to do that.  We likely will just put together a decent bank for the motor(s), about 400 amp hours at 48V to run eventually 2 motors and stick with the hearty house bank using DC-DC to charge the house, plus direct charging ability from the genny if needed.

Okay, I'm getting excited!  It's looking more and more like Davy Jones might receive an offering of an old seized up MD-22 sometime soon. ;-). Now I just need to slow my roll slightly and curb my obsession since I won't be in a position to really dig into this until maybe January.  But I'm sure I'll come up with lots more questions up til then.

Eric Dove