I was fortunate to get Kevin’s notes from going electric on his 48′ cruising cat.
“Hey Kurt thought you’d be interested in my notes from my first tests with electric motors. Overall pleased so far, but this is not for most people. The complication is high and needs to be self installed to understand. Actually the motors are easy…Its just the entire system integration that’s hard. I’m off to Europe for a month so won’t get any more info for a while.
nitial testing motors: All needs redo….Got amps wrong on both motors, need smaller pulleys.
Boat is very light with little equipment and no water etc. Clean paint.
Approx. 14-18knts breeze.
Motoring out into breeze on batts only 7.5knts easy to achieve. Uncertain of total amp draw as port motor not reading shunt. She felt much stronger into the breeze than my old 16hp diesels which I attribute also to the 3blade 18” props vs old 16” 2blades props.
STBD motor (alone) once set is running at power setting 50 achieving 1500rpm @ 250A
Was possible to run 300A+ but dialed down to spec. Scott I screwed up on this one. I had 250A in my head— not 350A per manual. That said, I think I will need the smaller pulley to get the numbers . This highlighted sentence skews all the rest of the numbers on this page of course since everything is based on 250A for starboard and 125A port
Port motor (alone) on power setting 95 got 1300rpm @ 123A (using clamp on amp meter). Scott I guess I need the smaller pulley for this motor to get my 1700rpm and 175A
Running STBD alone at 23A (just above idle) perpendicular to breeze got around 3.3knts which should get just under 10hours on batts alone. But this was in strong cross wind….
Top speed with both motors was 9-9.3knts at 375A…roughly 18.5KW (50v x375a)
So should have about 36m of full power available. This exceeds battery output specs so wouldn’t do this without genset backup. Adding the full 250A from the genset should allow 1.8hrs of full speed before that batts give up. Scott are the motors ok with this if for some unusual reason I wanted to use them this hard? (This question to be adjusted to 350A…)
Did not test amps vs. speed vs. 1motor vs 2motor yet to create efficiency chart.
I suspect 100A on one motor, vs split between 2 motors, will yield higher speed in flat calm but the opposite will be true into a breeze or chopped water. Too be tested.
On the delivery run, when motors were not dialed in, I ran the genset for an hour with the boat cruising at 7.5knts into 10-12knt headwind and saw no voltage drop on the batts. On my old diesels I could have achieved 7knts in the same conditions but they would have been working hard. More typically I cruised at 6.5knts. So very happy with this result but haven’t compared fuel yet.
Setting regen at 100 allowed the props to stop spinning! No shaft brakes needed so far.
This is a big deal for fast boats like mine.
It is very easy to loose settings while adjusting on display. I do not love the displays! Running both motors on one display pointless. Two is much better.
Started testing with 53.5v. Motored out into trades then did 5 or 6 runs back an forth across bay at various speeds. Returned to mooring with 52.5v still in the tank.
Shifting is very different than diesels. Slower response. This makes maneuvering a boat like mine onto the mooring in breeze challenging. I have plenty power but it takes much longer to from forward to reverse. Something to adapt to
Reverse has too much power on both motors! Would like to decrease reverse power. Just a tiny bit of throttle way revs up! Scott any options here? It will be worse with smaller pulleys.
Scott’s performance predictions graph indicate 19kw [my current max output, depending on whether one uses 50v or 53.5v x (123A port + 250A starboard) will push the boat at 8.2knts. Actual speed seems to be 9knts on initial test.
So Scott seems right or better on speed.
Distance, however is poorly predicted simply because 300AH is bad input. Actual available power is only 225AH because batts only receive 90% top charge and cut out at 15%DOD.
My numbers above, 3.3knts @ 23A with 225AH available, indicate a 32 mile range vs. 41 miles on Scott’s chart (corrected for actual AH available). But test was with strong cross wind and run over short distance so better numbers needed.
At 9knts range would be something like 4.5 miles which is very close to roughly 5.25 miles on Scott’s chart corrected for 225AH.
If I had gone with 2x QT10’s I would have had 13kw of max power. Estimating from the chart vs. current actual speed I think my top speed would have been 8knts and somewhat less authority at lower speed.
2x QT20’s probably would scrape a weak 10knts top speed.
Speeds will probably not change much when I load the boat as I have found this doesn’t slow her down much accept in acceleration.
Holo Holo Charters
physical: 4353 Waialo Rd. Ste 5A, Ele’ele HI 96705
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